ace-dent/kolibrios-gitea
1
0
Fork 0
forked from KolibriOS/kolibrios
Code Pull Requests Activity
9ebd703865
kolibrios-gitea/drivers/ddk/malloc/malloc.c
Sergey Semyonov (Serge) 1070204c9a drivers: udpate ddk 
git-svn-id: svn://kolibrios.org@3297 a494cfbc-eb01-0410-851d-a64ba20cac60
2013-03-01 06:44:14 +00:00

3210 lines
124 KiB
C
Raw Blame History

/*
This is a version (aka dlmalloc) of malloc/free/realloc written by
Doug Lea and released to the public domain, as explained at
http://creativecommons.org/publicdomain/zero/1.0/ Send questions,
comments, complaints, performance data, etc to dl@cs.oswego.edu
* Version 2.8.6 Wed Aug 29 06:57:58 2012 Doug Lea
Note: There may be an updated version of this malloc obtainable at
ftp://gee.cs.oswego.edu/pub/misc/malloc.c
Check before installing!
* Quickstart
This library is all in one file to simplify the most common usage:
ftp it, compile it (-O3), and link it into another program. All of
the compile-time options default to reasonable values for use on
most platforms. You might later want to step through various
compile-time and dynamic tuning options.
For convenience, an include file for code using this malloc is at:
ftp://gee.cs.oswego.edu/pub/misc/malloc-2.8.6.h
You don't really need this .h file unless you call functions not
defined in your system include files. The .h file contains only the
excerpts from this file needed for using this malloc on ANSI C/C++
systems, so long as you haven't changed compile-time options about
naming and tuning parameters. If you do, then you can create your
own malloc.h that does include all settings by cutting at the point
indicated below. Note that you may already by default be using a C
library containing a malloc that is based on some version of this
malloc (for example in linux). You might still want to use the one
in this file to customize settings or to avoid overheads associated
with library versions.
* Vital statistics:
Supported pointer/size_t representation: 4 or 8 bytes
size_t MUST be an unsigned type of the same width as
pointers. (If you are using an ancient system that declares
size_t as a signed type, or need it to be a different width
than pointers, you can use a previous release of this malloc
(e.g. 2.7.2) supporting these.)
Alignment: 8 bytes (minimum)
This suffices for nearly all current machines and C compilers.
However, you can define MALLOC_ALIGNMENT to be wider than this
if necessary (up to 128bytes), at the expense of using more space.
Minimum overhead per allocated chunk: 4 or 8 bytes (if 4byte sizes)
8 or 16 bytes (if 8byte sizes)
Each malloced chunk has a hidden word of overhead holding size
and status information, and additional cross-check word
if FOOTERS is defined.
Minimum allocated size: 4-byte ptrs: 16 bytes (including overhead)
8-byte ptrs: 32 bytes (including overhead)
Even a request for zero bytes (i.e., malloc(0)) returns a
pointer to something of the minimum allocatable size.
The maximum overhead wastage (i.e., number of extra bytes
allocated than were requested in malloc) is less than or equal
to the minimum size, except for requests >= mmap_threshold that
are serviced via mmap(), where the worst case wastage is about
32 bytes plus the remainder from a system page (the minimal
mmap unit); typically 4096 or 8192 bytes.
Security: static-safe; optionally more or less
The "security" of malloc refers to the ability of malicious
code to accentuate the effects of errors (for example, freeing
space that is not currently malloc'ed or overwriting past the
ends of chunks) in code that calls malloc. This malloc
guarantees not to modify any memory locations below the base of
heap, i.e., static variables, even in the presence of usage
errors. The routines additionally detect most improper frees
and reallocs. All this holds as long as the static bookkeeping
for malloc itself is not corrupted by some other means. This
is only one aspect of security -- these checks do not, and
cannot, detect all possible programming errors.
If FOOTERS is defined nonzero, then each allocated chunk
carries an additional check word to verify that it was malloced
from its space. These check words are the same within each
execution of a program using malloc, but differ across
executions, so externally crafted fake chunks cannot be
freed. This improves security by rejecting frees/reallocs that
could corrupt heap memory, in addition to the checks preventing
writes to statics that are always on. This may further improve
security at the expense of time and space overhead. (Note that
FOOTERS may also be worth using with MSPACES.)
By default detected errors cause the program to abort (calling
"abort()"). You can override this to instead proceed past
errors by defining PROCEED_ON_ERROR. In this case, a bad free
has no effect, and a malloc that encounters a bad address
caused by user overwrites will ignore the bad address by
dropping pointers and indices to all known memory. This may
be appropriate for programs that should continue if at all
possible in the face of programming errors, although they may
run out of memory because dropped memory is never reclaimed.
If you don't like either of these options, you can define
CORRUPTION_ERROR_ACTION and USAGE_ERROR_ACTION to do anything
else. And if if you are sure that your program using malloc has
no errors or vulnerabilities, you can define INSECURE to 1,
which might (or might not) provide a small performance improvement.
It is also possible to limit the maximum total allocatable
space, using malloc_set_footprint_limit. This is not
designed as a security feature in itself (calls to set limits
are not screened or privileged), but may be useful as one
aspect of a secure implementation.
Thread-safety: NOT thread-safe unless USE_LOCKS defined non-zero
When USE_LOCKS is defined, each public call to malloc, free,
etc is surrounded with a lock. By default, this uses a plain
pthread mutex, win32 critical section, or a spin-lock if if
available for the platform and not disabled by setting
USE_SPIN_LOCKS=0. However, if USE_RECURSIVE_LOCKS is defined,
recursive versions are used instead (which are not required for
base functionality but may be needed in layered extensions).
Using a global lock is not especially fast, and can be a major
bottleneck. It is designed only to provide minimal protection
in concurrent environments, and to provide a basis for
extensions. If you are using malloc in a concurrent program,
consider instead using nedmalloc
(http://www.nedprod.com/programs/portable/nedmalloc/) or
ptmalloc (See http://www.malloc.de), which are derived from
versions of this malloc.
System requirements: Any combination of MORECORE and/or MMAP/MUNMAP
This malloc can use unix sbrk or any emulation (invoked using
the CALL_MORECORE macro) and/or mmap/munmap or any emulation
(invoked using CALL_MMAP/CALL_MUNMAP) to get and release system
memory. On most unix systems, it tends to work best if both
MORECORE and MMAP are enabled. On Win32, it uses emulations
based on VirtualAlloc. It also uses common C library functions
like memset.
Compliance: I believe it is compliant with the Single Unix Specification
(See http://www.unix.org). Also SVID/XPG, ANSI C, and probably
others as well.
* Overview of algorithms
This is not the fastest, most space-conserving, most portable, or
most tunable malloc ever written. However it is among the fastest
while also being among the most space-conserving, portable and
tunable. Consistent balance across these factors results in a good
general-purpose allocator for malloc-intensive programs.
In most ways, this malloc is a best-fit allocator. Generally, it
chooses the best-fitting existing chunk for a request, with ties
broken in approximately least-recently-used order. (This strategy
normally maintains low fragmentation.) However, for requests less
than 256bytes, it deviates from best-fit when there is not an
exactly fitting available chunk by preferring to use space adjacent
to that used for the previous small request, as well as by breaking
ties in approximately most-recently-used order. (These enhance
locality of series of small allocations.) And for very large requests
(>= 256Kb by default), it relies on system memory mapping
facilities, if supported. (This helps avoid carrying around and
possibly fragmenting memory used only for large chunks.)
All operations (except malloc_stats and mallinfo) have execution
times that are bounded by a constant factor of the number of bits in
a size_t, not counting any clearing in calloc or copying in realloc,
or actions surrounding MORECORE and MMAP that have times
proportional to the number of non-contiguous regions returned by
system allocation routines, which is often just 1. In real-time
applications, you can optionally suppress segment traversals using
NO_SEGMENT_TRAVERSAL, which assures bounded execution even when
system allocators return non-contiguous spaces, at the typical
expense of carrying around more memory and increased fragmentation.
The implementation is not very modular and seriously overuses
macros. Perhaps someday all C compilers will do as good a job
inlining modular code as can now be done by brute-force expansion,
but now, enough of them seem not to.
Some compilers issue a lot of warnings about code that is
dead/unreachable only on some platforms, and also about intentional
uses of negation on unsigned types. All known cases of each can be
ignored.
For a longer but out of date high-level description, see
http://gee.cs.oswego.edu/dl/html/malloc.html
* MSPACES
If MSPACES is defined, then in addition to malloc, free, etc.,
this file also defines mspace_malloc, mspace_free, etc. These
are versions of malloc routines that take an "mspace" argument
obtained using create_mspace, to control all internal bookkeeping.
If ONLY_MSPACES is defined, only these versions are compiled.
So if you would like to use this allocator for only some allocations,
and your system malloc for others, you can compile with
ONLY_MSPACES and then do something like...
static mspace mymspace = create_mspace(0,0); // for example
#define mymalloc(bytes) mspace_malloc(mymspace, bytes)
(Note: If you only need one instance of an mspace, you can instead
use "USE_DL_PREFIX" to relabel the global malloc.)
You can similarly create thread-local allocators by storing
mspaces as thread-locals. For example:
static __thread mspace tlms = 0;
void* tlmalloc(size_t bytes) {
if (tlms == 0) tlms = create_mspace(0, 0);
return mspace_malloc(tlms, bytes);
}
void tlfree(void* mem) { mspace_free(tlms, mem); }
Unless FOOTERS is defined, each mspace is completely independent.
You cannot allocate from one and free to another (although
conformance is only weakly checked, so usage errors are not always
caught). If FOOTERS is defined, then each chunk carries around a tag
indicating its originating mspace, and frees are directed to their
originating spaces. Normally, this requires use of locks.
------------------------- Compile-time options ---------------------------
Be careful in setting #define values for numerical constants of type
size_t. On some systems, literal values are not automatically extended
to size_t precision unless they are explicitly casted. You can also
use the symbolic values MAX_SIZE_T, SIZE_T_ONE, etc below.
WIN32 default: defined if _WIN32 defined
Defining WIN32 sets up defaults for MS environment and compilers.
Otherwise defaults are for unix. Beware that there seem to be some
cases where this malloc might not be a pure drop-in replacement for
Win32 malloc: Random-looking failures from Win32 GDI API's (eg;
SetDIBits()) may be due to bugs in some video driver implementations
when pixel buffers are malloc()ed, and the region spans more than
one VirtualAlloc()ed region. Because dlmalloc uses a small (64Kb)
default granularity, pixel buffers may straddle virtual allocation
regions more often than when using the Microsoft allocator. You can
avoid this by using VirtualAlloc() and VirtualFree() for all pixel
buffers rather than using malloc(). If this is not possible,
recompile this malloc with a larger DEFAULT_GRANULARITY. Note:
in cases where MSC and gcc (cygwin) are known to differ on WIN32,
conditions use _MSC_VER to distinguish them.
DLMALLOC_EXPORT default: extern
Defines how public APIs are declared. If you want to export via a
Windows DLL, you might define this as
#define DLMALLOC_EXPORT extern __declspec(dllexport)
If you want a POSIX ELF shared object, you might use
#define DLMALLOC_EXPORT extern __attribute__((visibility("default")))
MALLOC_ALIGNMENT default: (size_t)(2 * sizeof(void *))
Controls the minimum alignment for malloc'ed chunks. It must be a
power of two and at least 8, even on machines for which smaller
alignments would suffice. It may be defined as larger than this
though. Note however that code and data structures are optimized for
the case of 8-byte alignment.
MSPACES default: 0 (false)
If true, compile in support for independent allocation spaces.
This is only supported if HAVE_MMAP is true.
ONLY_MSPACES default: 0 (false)
If true, only compile in mspace versions, not regular versions.
USE_LOCKS default: 0 (false)
Causes each call to each public routine to be surrounded with
pthread or WIN32 mutex lock/unlock. (If set true, this can be
overridden on a per-mspace basis for mspace versions.) If set to a
non-zero value other than 1, locks are used, but their
implementation is left out, so lock functions must be supplied manually,
as described below.
USE_SPIN_LOCKS default: 1 iff USE_LOCKS and spin locks available
If true, uses custom spin locks for locking. This is currently
supported only gcc >= 4.1, older gccs on x86 platforms, and recent
MS compilers. Otherwise, posix locks or win32 critical sections are
used.
USE_RECURSIVE_LOCKS default: not defined
If defined nonzero, uses recursive (aka reentrant) locks, otherwise
uses plain mutexes. This is not required for malloc proper, but may
be needed for layered allocators such as nedmalloc.
LOCK_AT_FORK default: not defined
If defined nonzero, performs pthread_atfork upon initialization
to initialize child lock while holding parent lock. The implementation
assumes that pthread locks (not custom locks) are being used. In other
cases, you may need to customize the implementation.
FOOTERS default: 0
If true, provide extra checking and dispatching by placing
information in the footers of allocated chunks. This adds
space and time overhead.
INSECURE default: 0
If true, omit checks for usage errors and heap space overwrites.
USE_DL_PREFIX default: NOT defined
Causes compiler to prefix all public routines with the string 'dl'.
This can be useful when you only want to use this malloc in one part
of a program, using your regular system malloc elsewhere.
MALLOC_INSPECT_ALL default: NOT defined
If defined, compiles malloc_inspect_all and mspace_inspect_all, that
perform traversal of all heap space. Unless access to these
functions is otherwise restricted, you probably do not want to
include them in secure implementations.
ABORT default: defined as abort()
Defines how to abort on failed checks. On most systems, a failed
check cannot die with an "assert" or even print an informative
message, because the underlying print routines in turn call malloc,
which will fail again. Generally, the best policy is to simply call
abort(). It's not very useful to do more than this because many
errors due to overwriting will show up as address faults (null, odd
addresses etc) rather than malloc-triggered checks, so will also
abort. Also, most compilers know that abort() does not return, so
can better optimize code conditionally calling it.
PROCEED_ON_ERROR default: defined as 0 (false)
Controls whether detected bad addresses cause them to bypassed
rather than aborting. If set, detected bad arguments to free and
realloc are ignored. And all bookkeeping information is zeroed out
upon a detected overwrite of freed heap space, thus losing the
ability to ever return it from malloc again, but enabling the
application to proceed. If PROCEED_ON_ERROR is defined, the
static variable malloc_corruption_error_count is compiled in
and can be examined to see if errors have occurred. This option
generates slower code than the default abort policy.
DEBUG default: NOT defined
The DEBUG setting is mainly intended for people trying to modify
this code or diagnose problems when porting to new platforms.
However, it may also be able to better isolate user errors than just
using runtime checks. The assertions in the check routines spell
out in more detail the assumptions and invariants underlying the
algorithms. The checking is fairly extensive, and will slow down
execution noticeably. Calling malloc_stats or mallinfo with DEBUG
set will attempt to check every non-mmapped allocated and free chunk
in the course of computing the summaries.
ABORT_ON_ASSERT_FAILURE default: defined as 1 (true)
Debugging assertion failures can be nearly impossible if your
version of the assert macro causes malloc to be called, which will
lead to a cascade of further failures, blowing the runtime stack.
ABORT_ON_ASSERT_FAILURE cause assertions failures to call abort(),
which will usually make debugging easier.
MALLOC_FAILURE_ACTION default: sets errno to ENOMEM, or no-op on win32
The action to take before "return 0" when malloc fails to be able to
return memory because there is none available.
HAVE_MORECORE default: 1 (true) unless win32 or ONLY_MSPACES
True if this system supports sbrk or an emulation of it.
MORECORE default: sbrk
The name of the sbrk-style system routine to call to obtain more
memory. See below for guidance on writing custom MORECORE
functions. The type of the argument to sbrk/MORECORE varies across
systems. It cannot be size_t, because it supports negative
arguments, so it is normally the signed type of the same width as
size_t (sometimes declared as "intptr_t"). It doesn't much matter
though. Internally, we only call it with arguments less than half
the max value of a size_t, which should work across all reasonable
possibilities, although sometimes generating compiler warnings.
MORECORE_CONTIGUOUS default: 1 (true) if HAVE_MORECORE
If true, take advantage of fact that consecutive calls to MORECORE
with positive arguments always return contiguous increasing
addresses. This is true of unix sbrk. It does not hurt too much to
set it true anyway, since malloc copes with non-contiguities.
Setting it false when definitely non-contiguous saves time
and possibly wasted space it would take to discover this though.
MORECORE_CANNOT_TRIM default: NOT defined
True if MORECORE cannot release space back to the system when given
negative arguments. This is generally necessary only if you are
using a hand-crafted MORECORE function that cannot handle negative
arguments.
NO_SEGMENT_TRAVERSAL default: 0
If non-zero, suppresses traversals of memory segments
returned by either MORECORE or CALL_MMAP. This disables
merging of segments that are contiguous, and selectively
releasing them to the OS if unused, but bounds execution times.
HAVE_MMAP default: 1 (true)
True if this system supports mmap or an emulation of it. If so, and
HAVE_MORECORE is not true, MMAP is used for all system
allocation. If set and HAVE_MORECORE is true as well, MMAP is
primarily used to directly allocate very large blocks. It is also
used as a backup strategy in cases where MORECORE fails to provide
space from system. Note: A single call to MUNMAP is assumed to be
able to unmap memory that may have be allocated using multiple calls
to MMAP, so long as they are adjacent.
HAVE_MREMAP default: 1 on linux, else 0
If true realloc() uses mremap() to re-allocate large blocks and
extend or shrink allocation spaces.
MMAP_CLEARS default: 1 except on WINCE.
True if mmap clears memory so calloc doesn't need to. This is true
for standard unix mmap using /dev/zero and on WIN32 except for WINCE.
USE_BUILTIN_FFS default: 0 (i.e., not used)
Causes malloc to use the builtin ffs() function to compute indices.
Some compilers may recognize and intrinsify ffs to be faster than the
supplied C version. Also, the case of x86 using gcc is special-cased
to an asm instruction, so is already as fast as it can be, and so
this setting has no effect. Similarly for Win32 under recent MS compilers.
(On most x86s, the asm version is only slightly faster than the C version.)
malloc_getpagesize default: derive from system includes, or 4096.
The system page size. To the extent possible, this malloc manages
memory from the system in page-size units. This may be (and
usually is) a function rather than a constant. This is ignored
if WIN32, where page size is determined using getSystemInfo during
initialization.
USE_DEV_RANDOM default: 0 (i.e., not used)
Causes malloc to use /dev/random to initialize secure magic seed for
stamping footers. Otherwise, the current time is used.
NO_MALLINFO default: 0
If defined, don't compile "mallinfo". This can be a simple way
of dealing with mismatches between system declarations and
those in this file.
MALLINFO_FIELD_TYPE default: size_t
The type of the fields in the mallinfo struct. This was originally
defined as "int" in SVID etc, but is more usefully defined as
size_t. The value is used only if HAVE_USR_INCLUDE_MALLOC_H is not set
NO_MALLOC_STATS default: 0
If defined, don't compile "malloc_stats". This avoids calls to
fprintf and bringing in stdio dependencies you might not want.
REALLOC_ZERO_BYTES_FREES default: not defined
This should be set if a call to realloc with zero bytes should
be the same as a call to free. Some people think it should. Otherwise,
since this malloc returns a unique pointer for malloc(0), so does
realloc(p, 0).
LACKS_UNISTD_H, LACKS_FCNTL_H, LACKS_SYS_PARAM_H, LACKS_SYS_MMAN_H
LACKS_STRINGS_H, LACKS_STRING_H, LACKS_SYS_TYPES_H, LACKS_ERRNO_H
LACKS_STDLIB_H LACKS_SCHED_H LACKS_TIME_H default: NOT defined unless on WIN32
Define these if your system does not have these header files.
You might need to manually insert some of the declarations they provide.
DEFAULT_GRANULARITY default: page size if MORECORE_CONTIGUOUS,
system_info.dwAllocationGranularity in WIN32,
otherwise 64K.
Also settable using mallopt(M_GRANULARITY, x)
The unit for allocating and deallocating memory from the system. On
most systems with contiguous MORECORE, there is no reason to
make this more than a page. However, systems with MMAP tend to
either require or encourage larger granularities. You can increase
this value to prevent system allocation functions to be called so
often, especially if they are slow. The value must be at least one
page and must be a power of two. Setting to 0 causes initialization
to either page size or win32 region size. (Note: In previous
versions of malloc, the equivalent of this option was called
"TOP_PAD")
DEFAULT_TRIM_THRESHOLD default: 2MB
Also settable using mallopt(M_TRIM_THRESHOLD, x)
The maximum amount of unused top-most memory to keep before
releasing via malloc_trim in free(). Automatic trimming is mainly
useful in long-lived programs using contiguous MORECORE. Because
trimming via sbrk can be slow on some systems, and can sometimes be
wasteful (in cases where programs immediately afterward allocate
more large chunks) the value should be high enough so that your
overall system performance would improve by releasing this much
memory. As a rough guide, you might set to a value close to the
average size of a process (program) running on your system.
Releasing this much memory would allow such a process to run in
memory. Generally, it is worth tuning trim thresholds when a
program undergoes phases where several large chunks are allocated
and released in ways that can reuse each other's storage, perhaps
mixed with phases where there are no such chunks at all. The trim
value must be greater than page size to have any useful effect. To
disable trimming completely, you can set to MAX_SIZE_T. Note that the trick
some people use of mallocing a huge space and then freeing it at
program startup, in an attempt to reserve system memory, doesn't
have the intended effect under automatic trimming, since that memory
will immediately be returned to the system.
DEFAULT_MMAP_THRESHOLD default: 256K
Also settable using mallopt(M_MMAP_THRESHOLD, x)
The request size threshold for using MMAP to directly service a
request. Requests of at least this size that cannot be allocated
using already-existing space will be serviced via mmap. (If enough
normal freed space already exists it is used instead.) Using mmap
segregates relatively large chunks of memory so that they can be
individually obtained and released from the host system. A request
serviced through mmap is never reused by any other request (at least
not directly; the system may just so happen to remap successive
requests to the same locations). Segregating space in this way has
the benefits that: Mmapped space can always be individually released
back to the system, which helps keep the system level memory demands
of a long-lived program low. Also, mapped memory doesn't become
`locked' between other chunks, as can happen with normally allocated
chunks, which means that even trimming via malloc_trim would not
release them. However, it has the disadvantage that the space
cannot be reclaimed, consolidated, and then used to service later
requests, as happens with normal chunks. The advantages of mmap
nearly always outweigh disadvantages for "large" chunks, but the
value of "large" may vary across systems. The default is an
empirically derived value that works well in most systems. You can
disable mmap by setting to MAX_SIZE_T.
MAX_RELEASE_CHECK_RATE default: 4095 unless not HAVE_MMAP
The number of consolidated frees between checks to release
unused segments when freeing. When using non-contiguous segments,
especially with multiple mspaces, checking only for topmost space
doesn't always suffice to trigger trimming. To compensate for this,
free() will, with a period of MAX_RELEASE_CHECK_RATE (or the
current number of segments, if greater) try to release unused
segments to the OS when freeing chunks that result in
consolidation. The best value for this parameter is a compromise
between slowing down frees with relatively costly checks that
rarely trigger versus holding on to unused memory. To effectively
disable, set to MAX_SIZE_T. This may lead to a very slight speed
improvement at the expense of carrying around more memory.
*/
#include <ddk.h>
#include <mutex.h>
#include <syscall.h>
/* Version identifier to allow people to support multiple versions */
#ifndef DLMALLOC_VERSION
#define DLMALLOC_VERSION 20806
#endif /* DLMALLOC_VERSION */
/*
malloc(size_t n)
Returns a pointer to a newly allocated chunk of at least n bytes, or
null if no space is available, in which case errno is set to ENOMEM
on ANSI C systems.
If n is zero, malloc returns a minimum-sized chunk. (The minimum
size is 16 bytes on most 32bit systems, and 32 bytes on 64bit
systems.) Note that size_t is an unsigned type, so calls with
arguments that would be negative if signed are interpreted as
requests for huge amounts of space, which will often fail. The
maximum supported value of n differs across systems, but is in all
cases less than the maximum representable value of a size_t.
*/
/*
free(void* p)
Releases the chunk of memory pointed to by p, that had been previously
allocated using malloc or a related routine such as realloc.
It has no effect if p is null. If p was not malloced or already
freed, free(p) will by default cause the current program to abort.
*/
/*
calloc(size_t n_elements, size_t element_size);
Returns a pointer to n_elements * element_size bytes, with all locations
set to zero.
*/
/*
realloc(void* p, size_t n)
Returns a pointer to a chunk of size n that contains the same data
as does chunk p up to the minimum of (n, p's size) bytes, or null
if no space is available.
The returned pointer may or may not be the same as p. The algorithm
prefers extending p in most cases when possible, otherwise it
employs the equivalent of a malloc-copy-free sequence.
If p is null, realloc is equivalent to malloc.
If space is not available, realloc returns null, errno is set (if on
ANSI) and p is NOT freed.
if n is for fewer bytes than already held by p, the newly unused
space is lopped off and freed if possible. realloc with a size
argument of zero (re)allocates a minimum-sized chunk.
The old unix realloc convention of allowing the last-free'd chunk
to be used as an argument to realloc is not supported.
*/
/*
memalign(size_t alignment, size_t n);
Returns a pointer to a newly allocated chunk of n bytes, aligned
in accord with the alignment argument.
The alignment argument should be a power of two. If the argument is
not a power of two, the nearest greater power is used.
8-byte alignment is guaranteed by normal malloc calls, so don't
bother calling memalign with an argument of 8 or less.
Overreliance on memalign is a sure way to fragment space.
*/
#define DEBUG 1
#define assert(x)
#define MAX_SIZE_T (~(size_t)0)
#define CALL_DIRECT_MMAP(s) MMAP_DEFAULT(s)
/* ------------------- size_t and alignment properties -------------------- */
/* The byte and bit size of a size_t */
#define SIZE_T_SIZE (sizeof(size_t))
#define SIZE_T_BITSIZE (sizeof(size_t) << 3)
/* Some constants coerced to size_t */
/* Annoying but necessary to avoid errors on some platforms */
#define SIZE_T_ZERO ((size_t)0)
#define SIZE_T_ONE ((size_t)1)
#define SIZE_T_TWO ((size_t)2)
#define SIZE_T_FOUR ((size_t)4)
#define TWO_SIZE_T_SIZES (SIZE_T_SIZE<<1)
#define FOUR_SIZE_T_SIZES (SIZE_T_SIZE<<2)
#define SIX_SIZE_T_SIZES (FOUR_SIZE_T_SIZES+TWO_SIZE_T_SIZES)
#define HALF_MAX_SIZE_T (MAX_SIZE_T / 2U)
#define USE_LOCK_BIT (2U)
#define USE_MMAP_BIT (SIZE_T_ONE)
#define USE_NONCONTIGUOUS_BIT (4U)
/* segment bit set in create_mspace_with_base */
#define EXTERN_BIT (8U)
#define HAVE_MMAP 1
#define HAVE_MORECORE 0
#define MORECORE_CANNOT_TRIM 1
#define CALL_MMAP(s) MMAP_DEFAULT(s)
#define CALL_MUNMAP(a, s) MUNMAP_DEFAULT((a), (s))
#define CALL_MREMAP(addr, osz, nsz, mv) MFAIL
#define MAX_RELEASE_CHECK_RATE 4095
#define NO_SEGMENT_TRAVERSAL 1
#define MALLOC_ALIGNMENT ((size_t)8U)
#define CHUNK_OVERHEAD (SIZE_T_SIZE)
#define DEFAULT_GRANULARITY ((size_t)128U * (size_t)1024U)
#define DEFAULT_MMAP_THRESHOLD ((size_t)512U * (size_t)1024U)
#define DEFAULT_TRIM_THRESHOLD ((size_t)1024U * (size_t)1024U)
/* The bit mask value corresponding to MALLOC_ALIGNMENT */
#define CHUNK_ALIGN_MASK (MALLOC_ALIGNMENT - SIZE_T_ONE)
/* True if address a has acceptable alignment */
#define is_aligned(A) (((size_t)((A)) & (CHUNK_ALIGN_MASK)) == 0)
/* the number of bytes to offset an address to align it */
#define align_offset(A)\
((((size_t)(A) & CHUNK_ALIGN_MASK) == 0)? 0 :\
((MALLOC_ALIGNMENT - ((size_t)(A) & CHUNK_ALIGN_MASK)) & CHUNK_ALIGN_MASK))
/* -------------------------- MMAP preliminaries ------------------------- */
/*
If HAVE_MORECORE or HAVE_MMAP are false, we just define calls and
checks to fail so compiler optimizer can delete code rather than
using so many "#if"s.
*/
/* MORECORE and MMAP must return MFAIL on failure */
#define MFAIL ((void*)(MAX_SIZE_T))
#define CMFAIL ((char*)(MFAIL)) /* defined for convenience */
#define should_trim(M,s) (0)
/* --------------------------- Lock preliminaries ------------------------ */
/*
When locks are defined, there is one global lock, plus
one per-mspace lock.
The global lock_ensures that mparams.magic and other unique
mparams values are initialized only once. It also protects
sequences of calls to MORECORE. In many cases sys_alloc requires
two calls, that should not be interleaved with calls by other
threads. This does not protect against direct calls to MORECORE
by other threads not using this lock, so there is still code to
cope the best we can on interference.
Per-mspace locks surround calls to malloc, free, etc.
By default, locks are simple non-reentrant mutexes.
Because lock-protected regions generally have bounded times, it is
OK to use the supplied simple spinlocks. Spinlocks are likely to
improve performance for lightly contended applications, but worsen
performance under heavy contention.
If USE_LOCKS is > 1, the definitions of lock routines here are
bypassed, in which case you will need to define the type MLOCK_T,
and at least INITIAL_LOCK, DESTROY_LOCK, ACQUIRE_LOCK, RELEASE_LOCK
and TRY_LOCK. You must also declare a
static MLOCK_T malloc_global_mutex = { initialization values };.
*/
static DEFINE_MUTEX(malloc_global_mutex);
#define ACQUIRE_MALLOC_GLOBAL_LOCK() MutexLock(&malloc_global_mutex);
#define RELEASE_MALLOC_GLOBAL_LOCK() MutexUnlock(&malloc_global_mutex);
/* ----------------------- Chunk representations ------------------------ */
/*
(The following includes lightly edited explanations by Colin Plumb.)
The malloc_chunk declaration below is misleading (but accurate and
necessary). It declares a "view" into memory allowing access to
necessary fields at known offsets from a given base.
Chunks of memory are maintained using a `boundary tag' method as
originally described by Knuth. (See the paper by Paul Wilson
ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a survey of such
techniques.) Sizes of free chunks are stored both in the front of
each chunk and at the end. This makes consolidating fragmented
chunks into bigger chunks fast. The head fields also hold bits
representing whether chunks are free or in use.
Here are some pictures to make it clearer. They are "exploded" to
show that the state of a chunk can be thought of as extending from
the high 31 bits of the head field of its header through the
prev_foot and PINUSE_BIT bit of the following chunk header.
A chunk that's in use looks like:
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of previous chunk (if P = 0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P|
| Size of this chunk 1| +-+
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- -+
| |
+- -+
| :
+- size - sizeof(size_t) available payload bytes -+
: |
chunk-> +- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|
| Size of next chunk (may or may not be in use) | +-+
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
And if it's free, it looks like this:
chunk-> +- -+
| User payload (must be in use, or we would have merged!) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P|
| Size of this chunk 0| +-+
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next pointer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prev pointer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :
+- size - sizeof(struct chunk) unused bytes -+
: |
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of this chunk |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|
| Size of next chunk (must be in use, or we would have merged)| +-+
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| :
+- User payload -+
: |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|
+-+
Note that since we always merge adjacent free chunks, the chunks
adjacent to a free chunk must be in use.
Given a pointer to a chunk (which can be derived trivially from the
payload pointer) we can, in O(1) time, find out whether the adjacent
chunks are free, and if so, unlink them from the lists that they
are on and merge them with the current chunk.
Chunks always begin on even word boundaries, so the mem portion
(which is returned to the user) is also on an even word boundary, and
thus at least double-word aligned.
The P (PINUSE_BIT) bit, stored in the unused low-order bit of the
chunk size (which is always a multiple of two words), is an in-use
bit for the *previous* chunk. If that bit is *clear*, then the
word before the current chunk size contains the previous chunk
size, and can be used to find the front of the previous chunk.
The very first chunk allocated always has this bit set, preventing
access to non-existent (or non-owned) memory. If pinuse is set for
any given chunk, then you CANNOT determine the size of the
previous chunk, and might even get a memory addressing fault when
trying to do so.
The C (CINUSE_BIT) bit, stored in the unused second-lowest bit of
the chunk size redundantly records whether the current chunk is
inuse (unless the chunk is mmapped). This redundancy enables usage
checks within free and realloc, and reduces indirection when freeing
and consolidating chunks.
Each freshly allocated chunk must have both cinuse and pinuse set.
That is, each allocated chunk borders either a previously allocated
and still in-use chunk, or the base of its memory arena. This is
ensured by making all allocations from the `lowest' part of any
found chunk. Further, no free chunk physically borders another one,
so each free chunk is known to be preceded and followed by either
inuse chunks or the ends of memory.
Note that the `foot' of the current chunk is actually represented
as the prev_foot of the NEXT chunk. This makes it easier to
deal with alignments etc but can be very confusing when trying
to extend or adapt this code.
The exceptions to all this are
1. The special chunk `top' is the top-most available chunk (i.e.,
the one bordering the end of available memory). It is treated
specially. Top is never included in any bin, is used only if
no other chunk is available, and is released back to the
system if it is very large (see M_TRIM_THRESHOLD). In effect,
the top chunk is treated as larger (and thus less well
fitting) than any other available chunk. The top chunk
doesn't update its trailing size field since there is no next
contiguous chunk that would have to index off it. However,
space is still allocated for it (TOP_FOOT_SIZE) to enable
separation or merging when space is extended.
3. Chunks allocated via mmap, have both cinuse and pinuse bits
cleared in their head fields. Because they are allocated
one-by-one, each must carry its own prev_foot field, which is
also used to hold the offset this chunk has within its mmapped
region, which is needed to preserve alignment. Each mmapped
chunk is trailed by the first two fields of a fake next-chunk
for sake of usage checks.
*/
struct malloc_chunk {
size_t prev_foot; /* Size of previous chunk (if free). */
size_t head; /* Size and inuse bits. */
struct malloc_chunk* fd; /* double links -- used only if free. */
struct malloc_chunk* bk;
};
typedef struct malloc_chunk mchunk;
typedef struct malloc_chunk* mchunkptr;
typedef struct malloc_chunk* sbinptr; /* The type of bins of chunks */
typedef unsigned int bindex_t; /* Described below */
typedef unsigned int binmap_t; /* Described below */
typedef unsigned int flag_t; /* The type of various bit flag sets */
/* ------------------- Chunks sizes and alignments ----------------------- */
#define MCHUNK_SIZE (sizeof(mchunk))
#if FOOTERS
#define CHUNK_OVERHEAD (TWO_SIZE_T_SIZES)
#else /* FOOTERS */
#define CHUNK_OVERHEAD (SIZE_T_SIZE)
#endif /* FOOTERS */
/* MMapped chunks need a second word of overhead ... */
#define MMAP_CHUNK_OVERHEAD (TWO_SIZE_T_SIZES)
/* ... and additional padding for fake next-chunk at foot */
#define MMAP_FOOT_PAD (FOUR_SIZE_T_SIZES)
/* The smallest size we can malloc is an aligned minimal chunk */
#define MIN_CHUNK_SIZE\
((MCHUNK_SIZE + CHUNK_ALIGN_MASK) & ~CHUNK_ALIGN_MASK)
/* conversion from malloc headers to user pointers, and back */
#define chunk2mem(p) ((void*)((char*)(p) + TWO_SIZE_T_SIZES))
#define mem2chunk(mem) ((mchunkptr)((char*)(mem) - TWO_SIZE_T_SIZES))
/* chunk associated with aligned address A */
#define align_as_chunk(A) (mchunkptr)((A) + align_offset(chunk2mem(A)))
/* Bounds on request (not chunk) sizes. */
#define MAX_REQUEST ((-MIN_CHUNK_SIZE) << 2)
#define MIN_REQUEST (MIN_CHUNK_SIZE - CHUNK_OVERHEAD - SIZE_T_ONE)
/* pad request bytes into a usable size */
#define pad_request(req) \
(((req) + CHUNK_OVERHEAD + CHUNK_ALIGN_MASK) & ~CHUNK_ALIGN_MASK)
/* pad request, checking for minimum (but not maximum) */
#define request2size(req) \
(((req) < MIN_REQUEST)? MIN_CHUNK_SIZE : pad_request(req))
/* ------------------ Operations on head and foot fields ----------------- */
/*
The head field of a chunk is or'ed with PINUSE_BIT when previous
adjacent chunk in use, and or'ed with CINUSE_BIT if this chunk is in
use, unless mmapped, in which case both bits are cleared.
FLAG4_BIT is not used by this malloc, but might be useful in extensions.
*/
#define PINUSE_BIT (SIZE_T_ONE)
#define CINUSE_BIT (SIZE_T_TWO)
#define FLAG4_BIT (SIZE_T_FOUR)
#define INUSE_BITS (PINUSE_BIT|CINUSE_BIT)
#define FLAG_BITS (PINUSE_BIT|CINUSE_BIT|FLAG4_BIT)
/* Head value for fenceposts */
#define FENCEPOST_HEAD (INUSE_BITS|SIZE_T_SIZE)
/* extraction of fields from head words */
#define cinuse(p) ((p)->head & CINUSE_BIT)
#define pinuse(p) ((p)->head & PINUSE_BIT)
#define flag4inuse(p) ((p)->head & FLAG4_BIT)
#define is_inuse(p) (((p)->head & INUSE_BITS) != PINUSE_BIT)
#define is_mmapped(p) (((p)->head & INUSE_BITS) == 0)
#define chunksize(p) ((p)->head & ~(FLAG_BITS))
#define clear_pinuse(p) ((p)->head &= ~PINUSE_BIT)
#define set_flag4(p) ((p)->head |= FLAG4_BIT)
#define clear_flag4(p) ((p)->head &= ~FLAG4_BIT)
/* Treat space at ptr +/- offset as a chunk */
#define chunk_plus_offset(p, s) ((mchunkptr)(((char*)(p)) + (s)))
#define chunk_minus_offset(p, s) ((mchunkptr)(((char*)(p)) - (s)))
/* Ptr to next or previous physical malloc_chunk. */
#define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->head & ~FLAG_BITS)))
#define prev_chunk(p) ((mchunkptr)( ((char*)(p)) - ((p)->prev_foot) ))
/* extract next chunk's pinuse bit */
#define next_pinuse(p) ((next_chunk(p)->head) & PINUSE_BIT)
/* Get/set size at footer */
#define get_foot(p, s) (((mchunkptr)((char*)(p) + (s)))->prev_foot)
#define set_foot(p, s) (((mchunkptr)((char*)(p) + (s)))->prev_foot = (s))
/* Set size, pinuse bit, and foot */
#define set_size_and_pinuse_of_free_chunk(p, s)\
((p)->head = (s|PINUSE_BIT), set_foot(p, s))
/* Set size, pinuse bit, foot, and clear next pinuse */
#define set_free_with_pinuse(p, s, n)\
(clear_pinuse(n), set_size_and_pinuse_of_free_chunk(p, s))
/* Get the internal overhead associated with chunk p */
#define overhead_for(p)\
(is_mmapped(p)? MMAP_CHUNK_OVERHEAD : CHUNK_OVERHEAD)
/* Return true if malloced space is not necessarily cleared */
#if MMAP_CLEARS
#define calloc_must_clear(p) (!is_mmapped(p))
#else /* MMAP_CLEARS */
#define calloc_must_clear(p) (1)
#endif /* MMAP_CLEARS */
/* ---------------------- Overlaid data structures ----------------------- */
/*
When chunks are not in use, they are treated as nodes of either
lists or trees.
"Small" chunks are stored in circular doubly-linked lists, and look
like this:
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of previous chunk |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
`head:' | Size of chunk, in bytes |P|
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forward pointer to next chunk in list |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Back pointer to previous chunk in list |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused space (may be 0 bytes long) .
. .
. |
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
`foot:' | Size of chunk, in bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Larger chunks are kept in a form of bitwise digital trees (aka
tries) keyed on chunksizes. Because malloc_tree_chunks are only for
free chunks greater than 256 bytes, their size doesn't impose any
constraints on user chunk sizes. Each node looks like:
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of previous chunk |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
`head:' | Size of chunk, in bytes |P|
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forward pointer to next chunk of same size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Back pointer to previous chunk of same size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pointer to left child (child[0]) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pointer to right child (child[1]) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pointer to parent |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| bin index of this chunk |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused space .
. |
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
`foot:' | Size of chunk, in bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Each tree holding treenodes is a tree of unique chunk sizes. Chunks
of the same size are arranged in a circularly-linked list, with only
the oldest chunk (the next to be used, in our FIFO ordering)
actually in the tree. (Tree members are distinguished by a non-null
parent pointer.) If a chunk with the same size an an existing node
is inserted, it is linked off the existing node using pointers that
work in the same way as fd/bk pointers of small chunks.
Each tree contains a power of 2 sized range of chunk sizes (the
smallest is 0x100 <= x < 0x180), which is is divided in half at each
tree level, with the chunks in the smaller half of the range (0x100
<= x < 0x140 for the top nose) in the left subtree and the larger
half (0x140 <= x < 0x180) in the right subtree. This is, of course,
done by inspecting individual bits.
Using these rules, each node's left subtree contains all smaller
sizes than its right subtree. However, the node at the root of each
subtree has no particular ordering relationship to either. (The
dividing line between the subtree sizes is based on trie relation.)
If we remove the last chunk of a given size from the interior of the
tree, we need to replace it with a leaf node. The tree ordering
rules permit a node to be replaced by any leaf below it.
The smallest chunk in a tree (a common operation in a best-fit
allocator) can be found by walking a path to the leftmost leaf in
the tree. Unlike a usual binary tree, where we follow left child
pointers until we reach a null, here we follow the right child
pointer any time the left one is null, until we reach a leaf with
both child pointers null. The smallest chunk in the tree will be
somewhere along that path.
The worst case number of steps to add, find, or remove a node is
bounded by the number of bits differentiating chunks within
bins. Under current bin calculations, this ranges from 6 up to 21
(for 32 bit sizes) or up to 53 (for 64 bit sizes). The typical case
is of course much better.
*/
struct malloc_tree_chunk {
/* The first four fields must be compatible with malloc_chunk */
size_t prev_foot;
size_t head;
struct malloc_tree_chunk* fd;
struct malloc_tree_chunk* bk;
struct malloc_tree_chunk* child[2];
struct malloc_tree_chunk* parent;
bindex_t index;
};
typedef struct malloc_tree_chunk tchunk;
typedef struct malloc_tree_chunk* tchunkptr;
typedef struct malloc_tree_chunk* tbinptr; /* The type of bins of trees */
/* A little helper macro for trees */
#define leftmost_child(t) ((t)->child[0] != 0? (t)->child[0] : (t)->child[1])
/* ----------------------------- Segments -------------------------------- */
/*
Each malloc space may include non-contiguous segments, held in a
list headed by an embedded malloc_segment record representing the
top-most space. Segments also include flags holding properties of
the space. Large chunks that are directly allocated by mmap are not
included in this list. They are instead independently created and
destroyed without otherwise keeping track of them.
Segment management mainly comes into play for spaces allocated by
MMAP. Any call to MMAP might or might not return memory that is
adjacent to an existing segment. MORECORE normally contiguously
extends the current space, so this space is almost always adjacent,
which is simpler and faster to deal with. (This is why MORECORE is
used preferentially to MMAP when both are available -- see
sys_alloc.) When allocating using MMAP, we don't use any of the
hinting mechanisms (inconsistently) supported in various
implementations of unix mmap, or distinguish reserving from
committing memory. Instead, we just ask for space, and exploit
contiguity when we get it. It is probably possible to do
better than this on some systems, but no general scheme seems
to be significantly better.
Management entails a simpler variant of the consolidation scheme
used for chunks to reduce fragmentation -- new adjacent memory is
normally prepended or appended to an existing segment. However,
there are limitations compared to chunk consolidation that mostly
reflect the fact that segment processing is relatively infrequent
(occurring only when getting memory from system) and that we
don't expect to have huge numbers of segments:
* Segments are not indexed, so traversal requires linear scans. (It
would be possible to index these, but is not worth the extra
overhead and complexity for most programs on most platforms.)
* New segments are only appended to old ones when holding top-most
memory; if they cannot be prepended to others, they are held in
different segments.
Except for the top-most segment of an mstate, each segment record
is kept at the tail of its segment. Segments are added by pushing
segment records onto the list headed by &mstate.seg for the
containing mstate.
Segment flags control allocation/merge/deallocation policies:
* If EXTERN_BIT set, then we did not allocate this segment,
and so should not try to deallocate or merge with others.
(This currently holds only for the initial segment passed
into create_mspace_with_base.)
* If USE_MMAP_BIT set, the segment may be merged with
other surrounding mmapped segments and trimmed/de-allocated
using munmap.
* If neither bit is set, then the segment was obtained using
MORECORE so can be merged with surrounding MORECORE'd segments
and deallocated/trimmed using MORECORE with negative arguments.
*/
struct malloc_segment {
char* base; /* base address */
size_t size; /* allocated size */
struct malloc_segment* next; /* ptr to next segment */
flag_t sflags; /* mmap and extern flag */
};
#define is_mmapped_segment(S) ((S)->sflags & USE_MMAP_BIT)
#define is_extern_segment(S) ((S)->sflags & EXTERN_BIT)
typedef struct malloc_segment msegment;
typedef struct malloc_segment* msegmentptr;
/* ---------------------------- malloc_state ----------------------------- */
/*
A malloc_state holds all of the bookkeeping for a space.
The main fields are:
Top
The topmost chunk of the currently active segment. Its size is
cached in topsize. The actual size of topmost space is
topsize+TOP_FOOT_SIZE, which includes space reserved for adding
fenceposts and segment records if necessary when getting more
space from the system. The size at which to autotrim top is
cached from mparams in trim_check, except that it is disabled if
an autotrim fails.
Designated victim (dv)
This is the preferred chunk for servicing small requests that
don't have exact fits. It is normally the chunk split off most
recently to service another small request. Its size is cached in
dvsize. The link fields of this chunk are not maintained since it
is not kept in a bin.
SmallBins
An array of bin headers for free chunks. These bins hold chunks
with sizes less than MIN_LARGE_SIZE bytes. Each bin contains
chunks of all the same size, spaced 8 bytes apart. To simplify
use in double-linked lists, each bin header acts as a malloc_chunk
pointing to the real first node, if it exists (else pointing to
itself). This avoids special-casing for headers. But to avoid
waste, we allocate only the fd/bk pointers of bins, and then use
repositioning tricks to treat these as the fields of a chunk.
TreeBins
Treebins are pointers to the roots of trees holding a range of
sizes. There are 2 equally spaced treebins for each power of two
from TREE_SHIFT to TREE_SHIFT+16. The last bin holds anything
larger.
Bin maps
There is one bit map for small bins ("smallmap") and one for
treebins ("treemap). Each bin sets its bit when non-empty, and
clears the bit when empty. Bit operations are then used to avoid
bin-by-bin searching -- nearly all "search" is done without ever
looking at bins that won't be selected. The bit maps
conservatively use 32 bits per map word, even if on 64bit system.
For a good description of some of the bit-based techniques used
here, see Henry S. Warren Jr's book "Hacker's Delight" (and
supplement at http://hackersdelight.org/). Many of these are
intended to reduce the branchiness of paths through malloc etc, as
well as to reduce the number of memory locations read or written.
Segments
A list of segments headed by an embedded malloc_segment record
representing the initial space.
Address check support
The least_addr field is the least address ever obtained from
MORECORE or MMAP. Attempted frees and reallocs of any address less
than this are trapped (unless INSECURE is defined).
Magic tag
A cross-check field that should always hold same value as mparams.magic.
Max allowed footprint
The maximum allowed bytes to allocate from system (zero means no limit)
Flags
Bits recording whether to use MMAP, locks, or contiguous MORECORE
Statistics
Each space keeps track of current and maximum system memory
obtained via MORECORE or MMAP.
Trim support
Fields holding the amount of unused topmost memory that should trigger
trimming, and a counter to force periodic scanning to release unused
non-topmost segments.
Locking
If USE_LOCKS is defined, the "mutex" lock is acquired and released
around every public call using this mspace.
Extension support
A void* pointer and a size_t field that can be used to help implement
extensions to this malloc.
*/
/* Bin types, widths and sizes */
#define NSMALLBINS (32U)
#define NTREEBINS (32U)
#define SMALLBIN_SHIFT (3U)
#define SMALLBIN_WIDTH (SIZE_T_ONE << SMALLBIN_SHIFT)
#define TREEBIN_SHIFT (8U)
#define MIN_LARGE_SIZE (SIZE_T_ONE << TREEBIN_SHIFT)
#define MAX_SMALL_SIZE (MIN_LARGE_SIZE - SIZE_T_ONE)
#define MAX_SMALL_REQUEST (MAX_SMALL_SIZE - CHUNK_ALIGN_MASK - CHUNK_OVERHEAD)
struct malloc_state {
binmap_t smallmap;
binmap_t treemap;
size_t dvsize;
size_t topsize;
char* least_addr;
mchunkptr dv;
mchunkptr top;
size_t trim_check;
size_t release_checks;
size_t magic;
mchunkptr smallbins[(NSMALLBINS+1)*2];
tbinptr treebins[NTREEBINS];
size_t footprint;
size_t max_footprint;
size_t footprint_limit; /* zero means no limit */
flag_t mflags;
struct mutex lock; /* locate lock among fields that rarely change */
msegment seg;
void* extp; /* Unused but available for extensions */
size_t exts;
};
typedef struct malloc_state* mstate;
/* ------------- Global malloc_state and malloc_params ------------------- */
/*
malloc_params holds global properties, including those that can be
dynamically set using mallopt. There is a single instance, mparams,
initialized in init_mparams. Note that the non-zeroness of "magic"
also serves as an initialization flag.
*/
struct malloc_params {
size_t magic;
size_t page_size;
size_t granularity;
size_t mmap_threshold;
size_t trim_threshold;
flag_t default_mflags;
};
static struct malloc_params mparams;
/* Ensure mparams initialized */
#define ensure_initialization() (void)(mparams.magic != 0 || init_mparams())
static struct malloc_state _gm_;
#define gm (&_gm_)
#define is_global(M) ((M) == &_gm_)
#define is_initialized(M) ((M)->top != 0)
/* -------------------------- system alloc setup ------------------------- */
/* Operations on mflags */
#define use_lock(M) ((M)->mflags & USE_LOCK_BIT)
#define enable_lock(M) ((M)->mflags |= USE_LOCK_BIT)
#if USE_LOCKS
#define disable_lock(M) ((M)->mflags &= ~USE_LOCK_BIT)
#else
#define disable_lock(M)
#endif
#define use_mmap(M) ((M)->mflags & USE_MMAP_BIT)
#define enable_mmap(M) ((M)->mflags |= USE_MMAP_BIT)
#if HAVE_MMAP
#define disable_mmap(M) ((M)->mflags &= ~USE_MMAP_BIT)
#else
#define disable_mmap(M)
#endif
#define use_noncontiguous(M) ((M)->mflags & USE_NONCONTIGUOUS_BIT)
#define disable_contiguous(M) ((M)->mflags |= USE_NONCONTIGUOUS_BIT)
#define set_lock(M,L)\
((M)->mflags = (L)?\
((M)->mflags | USE_LOCK_BIT) :\
((M)->mflags & ~USE_LOCK_BIT))
/* page-align a size */
#define page_align(S)\
(((S) + (mparams.page_size - SIZE_T_ONE)) & ~(mparams.page_size - SIZE_T_ONE))
/* granularity-align a size */
#define granularity_align(S)\
(((S) + (mparams.granularity - SIZE_T_ONE))\
& ~(mparams.granularity - SIZE_T_ONE))
/* For mmap, use granularity alignment on windows, else page-align */
#ifdef WIN32
#define mmap_align(S) granularity_align(S)
#else
#define mmap_align(S) page_align(S)
#endif
/* For sys_alloc, enough padding to ensure can malloc request on success */
#define SYS_ALLOC_PADDING (TOP_FOOT_SIZE + MALLOC_ALIGNMENT)
#define is_page_aligned(S)\
(((size_t)(S) & (mparams.page_size - SIZE_T_ONE)) == 0)
#define is_granularity_aligned(S)\
(((size_t)(S) & (mparams.granularity - SIZE_T_ONE)) == 0)
/* True if segment S holds address A */
#define segment_holds(S, A)\
((char*)(A) >= S->base && (char*)(A) < S->base + S->size)
/* Return segment holding given address */
static msegmentptr segment_holding(mstate m, char* addr) {
msegmentptr sp = &m->seg;
for (;;) {
if (addr >= sp->base && addr < sp->base + sp->size)
return sp;
if ((sp = sp->next) == 0)
return 0;
}
}
/* Return true if segment contains a segment link */
static int has_segment_link(mstate m, msegmentptr ss) {
msegmentptr sp = &m->seg;
for (;;) {
if ((char*)sp >= ss->base && (char*)sp < ss->base + ss->size)
return 1;
if ((sp = sp->next) == 0)
return 0;
}
}
/*
TOP_FOOT_SIZE is padding at the end of a segment, including space
that may be needed to place segment records and fenceposts when new
noncontiguous segments are added.
*/
#define TOP_FOOT_SIZE\
(align_offset(chunk2mem(0))+pad_request(sizeof(struct malloc_segment))+MIN_CHUNK_SIZE)
/* ------------------------------- Hooks -------------------------------- */
/*
PREACTION should be defined to return 0 on success, and nonzero on
failure. If you are not using locking, you can redefine these to do
anything you like.
*/
#define PREACTION(M) ( MutexLock(&(M)->lock))
#define POSTACTION(M) { MutexUnlock(&(M)->lock); }
/* -------------------------- Debugging setup ---------------------------- */
#if ! DEBUG
#define check_free_chunk(M,P)
#define check_inuse_chunk(M,P)
#define check_malloced_chunk(M,P,N)
#define check_mmapped_chunk(M,P)
#define check_malloc_state(M)
#define check_top_chunk(M,P)
#else /* DEBUG */
#define check_free_chunk(M,P) do_check_free_chunk(M,P)
#define check_inuse_chunk(M,P) do_check_inuse_chunk(M,P)
#define check_top_chunk(M,P) do_check_top_chunk(M,P)
#define check_malloced_chunk(M,P,N) do_check_malloced_chunk(M,P,N)
#define check_mmapped_chunk(M,P) do_check_mmapped_chunk(M,P)
#define check_malloc_state(M) do_check_malloc_state(M)
static void do_check_any_chunk(mstate m, mchunkptr p);
static void do_check_top_chunk(mstate m, mchunkptr p);
static void do_check_mmapped_chunk(mstate m, mchunkptr p);
static void do_check_inuse_chunk(mstate m, mchunkptr p);
static void do_check_free_chunk(mstate m, mchunkptr p);
static void do_check_malloced_chunk(mstate m, void* mem, size_t s);
static void do_check_tree(mstate m, tchunkptr t);
static void do_check_treebin(mstate m, bindex_t i);
static void do_check_smallbin(mstate m, bindex_t i);
static void do_check_malloc_state(mstate m);
static int bin_find(mstate m, mchunkptr x);
static size_t traverse_and_check(mstate m);
#endif /* DEBUG */
/* ---------------------------- Indexing Bins ---------------------------- */
#define is_small(s) (((s) >> SMALLBIN_SHIFT) < NSMALLBINS)
#define small_index(s) (bindex_t)((s) >> SMALLBIN_SHIFT)
#define small_index2size(i) ((i) << SMALLBIN_SHIFT)
#define MIN_SMALL_INDEX (small_index(MIN_CHUNK_SIZE))
/* addressing by index. See above about smallbin repositioning */
#define smallbin_at(M, i) ((sbinptr)((char*)&((M)->smallbins[(i)<<1])))
#define treebin_at(M,i) (&((M)->treebins[i]))
#define compute_tree_index(S, I)\
{\
unsigned int X = S >> TREEBIN_SHIFT;\
if (X == 0)\
I = 0;\
else if (X > 0xFFFF)\
I = NTREEBINS-1;\
else {\
unsigned int K = (unsigned) sizeof(X)*__CHAR_BIT__ - 1 - (unsigned) __builtin_clz(X); \
I = (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT-1)) & 1)));\
}\
}
/* Bit representing maximum resolved size in a treebin at i */
#define bit_for_tree_index(i) \
(i == NTREEBINS-1)? (SIZE_T_BITSIZE-1) : (((i) >> 1) + TREEBIN_SHIFT - 2)
/* Shift placing maximum resolved bit in a treebin at i as sign bit */
#define leftshift_for_tree_index(i) \
((i == NTREEBINS-1)? 0 : \
((SIZE_T_BITSIZE-SIZE_T_ONE) - (((i) >> 1) + TREEBIN_SHIFT - 2)))
/* The size of the smallest chunk held in bin with index i */
#define minsize_for_tree_index(i) \
((SIZE_T_ONE << (((i) >> 1) + TREEBIN_SHIFT)) | \
(((size_t)((i) & SIZE_T_ONE)) << (((i) >> 1) + TREEBIN_SHIFT - 1)))
/* ------------------------ Operations on bin maps ----------------------- */
/* bit corresponding to given index */
#define idx2bit(i) ((binmap_t)(1) << (i))
/* Mark/Clear bits with given index */
#define mark_smallmap(M,i) ((M)->smallmap |= idx2bit(i))
#define clear_smallmap(M,i) ((M)->smallmap &= ~idx2bit(i))
#define smallmap_is_marked(M,i) ((M)->smallmap & idx2bit(i))
#define mark_treemap(M,i) ((M)->treemap |= idx2bit(i))
#define clear_treemap(M,i) ((M)->treemap &= ~idx2bit(i))
#define treemap_is_marked(M,i) ((M)->treemap & idx2bit(i))
/* isolate the least set bit of a bitmap */
#define least_bit(x) ((x) & -(x))
/* mask with all bits to left of least bit of x on */
#define left_bits(x) ((x<<1) | -(x<<1))
/* mask with all bits to left of or equal to least bit of x on */
#define same_or_left_bits(x) ((x) | -(x))
#define compute_bit2idx(X, I)\
{\
unsigned int J;\
J = __builtin_ctz(X); \
I = (bindex_t)J;\
}
/* ----------------------- Runtime Check Support ------------------------- */
/*
For security, the main invariant is that malloc/free/etc never
writes to a static address other than malloc_state, unless static
malloc_state itself has been corrupted, which cannot occur via
malloc (because of these checks). In essence this means that we
believe all pointers, sizes, maps etc held in malloc_state, but
check all of those linked or offsetted from other embedded data
structures. These checks are interspersed with main code in a way
that tends to minimize their run-time cost.
When FOOTERS is defined, in addition to range checking, we also
verify footer fields of inuse chunks, which can be used guarantee
that the mstate controlling malloc/free is intact. This is a
streamlined version of the approach described by William Robertson
et al in "Run-time Detection of Heap-based Overflows" LISA'03
http://www.usenix.org/events/lisa03/tech/robertson.html The footer
of an inuse chunk holds the xor of its mstate and a random seed,
that is checked upon calls to free() and realloc(). This is
(probabalistically) unguessable from outside the program, but can be
computed by any code successfully malloc'ing any chunk, so does not
itself provide protection against code that has already broken
security through some other means. Unlike Robertson et al, we
always dynamically check addresses of all offset chunks (previous,
next, etc). This turns out to be cheaper than relying on hashes.
*/
#if !INSECURE
/* Check if address a is at least as high as any from MORECORE or MMAP */
#define ok_address(M, a) ((char*)(a) >= (M)->least_addr)
/* Check if address of next chunk n is higher than base chunk p */
#define ok_next(p, n) ((char*)(p) < (char*)(n))
/* Check if p has inuse status */
#define ok_inuse(p) is_inuse(p)
/* Check if p has its pinuse bit on */
#define ok_pinuse(p) pinuse(p)
#else /* !INSECURE */
#define ok_address(M, a) (1)
#define ok_next(b, n) (1)
#define ok_inuse(p) (1)
#define ok_pinuse(p) (1)
#endif /* !INSECURE */
#if (FOOTERS && !INSECURE)
/* Check if (alleged) mstate m has expected magic field */
#define ok_magic(M) ((M)->magic == mparams.magic)
#else /* (FOOTERS && !INSECURE) */
#define ok_magic(M) (1)
#endif /* (FOOTERS && !INSECURE) */
/* In gcc, use __builtin_expect to minimize impact of checks */
#if !INSECURE
#if defined(__GNUC__) && __GNUC__ >= 3
#define RTCHECK(e) __builtin_expect(e, 1)
#else /* GNUC */
#define RTCHECK(e) (e)
#endif /* GNUC */
#else /* !INSECURE */
#define RTCHECK(e) (1)
#endif /* !INSECURE */
/* macros to set up inuse chunks with or without footers */
#if !FOOTERS
#define mark_inuse_foot(M,p,s)
/* Macros for setting head/foot of non-mmapped chunks */
/* Set cinuse bit and pinuse bit of next chunk */
#define set_inuse(M,p,s)\
((p)->head = (((p)->head & PINUSE_BIT)|s|CINUSE_BIT),\
((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT)
/* Set cinuse and pinuse of this chunk and pinuse of next chunk */
#define set_inuse_and_pinuse(M,p,s)\
((p)->head = (s|PINUSE_BIT|CINUSE_BIT),\
((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT)
/* Set size, cinuse and pinuse bit of this chunk */
#define set_size_and_pinuse_of_inuse_chunk(M, p, s)\
((p)->head = (s|PINUSE_BIT|CINUSE_BIT))
#else /* FOOTERS */
/* Set foot of inuse chunk to be xor of mstate and seed */
#define mark_inuse_foot(M,p,s)\
(((mchunkptr)((char*)(p) + (s)))->prev_foot = ((size_t)(M) ^ mparams.magic))
#define get_mstate_for(p)\
((mstate)(((mchunkptr)((char*)(p) +\
(chunksize(p))))->prev_foot ^ mparams.magic))
#define set_inuse(M,p,s)\
((p)->head = (((p)->head & PINUSE_BIT)|s|CINUSE_BIT),\
(((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT), \
mark_inuse_foot(M,p,s))
#define set_inuse_and_pinuse(M,p,s)\
((p)->head = (s|PINUSE_BIT|CINUSE_BIT),\
(((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT),\
mark_inuse_foot(M,p,s))
#define set_size_and_pinuse_of_inuse_chunk(M, p, s)\
((p)->head = (s|PINUSE_BIT|CINUSE_BIT),\
mark_inuse_foot(M, p, s))
#endif /* !FOOTERS */
/* ---------------------------- setting mparams -------------------------- */
#if LOCK_AT_FORK
static void pre_fork(void) { ACQUIRE_LOCK(&(gm)->mutex); }
static void post_fork_parent(void) { RELEASE_LOCK(&(gm)->mutex); }
static void post_fork_child(void) { INITIAL_LOCK(&(gm)->mutex); }
#endif /* LOCK_AT_FORK */
/* Initialize mparams */
static int init_mparams(void) {
ACQUIRE_MALLOC_GLOBAL_LOCK();
if (mparams.magic == 0) {
size_t magic;
size_t psize;
size_t gsize;
psize = 4096;
gsize = ((DEFAULT_GRANULARITY != 0)? DEFAULT_GRANULARITY : psize);
mparams.granularity = gsize;
mparams.page_size = psize;
mparams.mmap_threshold = DEFAULT_MMAP_THRESHOLD;
mparams.trim_threshold = DEFAULT_TRIM_THRESHOLD;
mparams.default_mflags = USE_LOCK_BIT|USE_MMAP_BIT|USE_NONCONTIGUOUS_BIT;
/* Set up lock for main malloc area */
gm->mflags = mparams.default_mflags;
MutexInit(&gm->lock);
{
magic = (size_t)&magic ^ (size_t)0x55555555U;
magic |= (size_t)8U; /* ensure nonzero */
magic &= ~(size_t)7U; /* improve chances of fault for bad values */
/* Until memory modes commonly available, use volatile-write */
(*(volatile size_t *)(&(mparams.magic))) = magic;
}
}
RELEASE_MALLOC_GLOBAL_LOCK();
return 1;
}
#if DEBUG
/* ------------------------- Debugging Support --------------------------- */
/* Check properties of any chunk, whether free, inuse, mmapped etc */
static void do_check_any_chunk(mstate m, mchunkptr p) {
assert((is_aligned(chunk2mem(p))) || (p->head == FENCEPOST_HEAD));
assert(ok_address(m, p));
}
/* Check properties of top chunk */
static void do_check_top_chunk(mstate m, mchunkptr p) {
msegmentptr sp = segment_holding(m, (char*)p);
size_t sz = p->head & ~INUSE_BITS; /* third-lowest bit can be set! */
assert(sp != 0);
assert((is_aligned(chunk2mem(p))) || (p->head == FENCEPOST_HEAD));
assert(ok_address(m, p));
assert(sz == m->topsize);
assert(sz > 0);
assert(sz == ((sp->base + sp->size) - (char*)p) - TOP_FOOT_SIZE);
assert(pinuse(p));
assert(!pinuse(chunk_plus_offset(p, sz)));
}
/* Check properties of (inuse) mmapped chunks */
static void do_check_mmapped_chunk(mstate m, mchunkptr p) {
size_t sz = chunksize(p);
size_t len = (sz + (p->prev_foot) + MMAP_FOOT_PAD);
assert(is_mmapped(p));
assert(use_mmap(m));
assert((is_aligned(chunk2mem(p))) || (p->head == FENCEPOST_HEAD));
assert(ok_address(m, p));
assert(!is_small(sz));
assert((len & (mparams.page_size-SIZE_T_ONE)) == 0);
assert(chunk_plus_offset(p, sz)->head == FENCEPOST_HEAD);
assert(chunk_plus_offset(p, sz+SIZE_T_SIZE)->head == 0);
}
/* Check properties of inuse chunks */
static void do_check_inuse_chunk(mstate m, mchunkptr p) {
do_check_any_chunk(m, p);
assert(is_inuse(p));
assert(next_pinuse(p));
/* If not pinuse and not mmapped, previous chunk has OK offset */
assert(is_mmapped(p) || pinuse(p) || next_chunk(prev_chunk(p)) == p);
if (is_mmapped(p))
do_check_mmapped_chunk(m, p);
}
/* Check properties of free chunks */
static void do_check_free_chunk(mstate m, mchunkptr p) {
size_t sz = chunksize(p);
mchunkptr next = chunk_plus_offset(p, sz);
do_check_any_chunk(m, p);
assert(!is_inuse(p));
assert(!next_pinuse(p));
assert (!is_mmapped(p));
if (p != m->dv && p != m->top) {
if (sz >= MIN_CHUNK_SIZE) {
assert((sz & CHUNK_ALIGN_MASK) == 0);
assert(is_aligned(chunk2mem(p)));
assert(next->prev_foot == sz);
assert(pinuse(p));
assert (next == m->top || is_inuse(next));
assert(p->fd->bk == p);
assert(p->bk->fd == p);
}
else /* markers are always of size SIZE_T_SIZE */
assert(sz == SIZE_T_SIZE);
}
}
/* Check properties of malloced chunks at the point they are malloced */
static void do_check_malloced_chunk(mstate m, void* mem, size_t s) {
if (mem != 0) {
mchunkptr p = mem2chunk(mem);
size_t sz = p->head & ~INUSE_BITS;
do_check_inuse_chunk(m, p);
assert((sz & CHUNK_ALIGN_MASK) == 0);
assert(sz >= MIN_CHUNK_SIZE);
assert(sz >= s);
/* unless mmapped, size is less than MIN_CHUNK_SIZE more than request */
assert(is_mmapped(p) || sz < (s + MIN_CHUNK_SIZE));
}
}
/* Check a tree and its subtrees. */
static void do_check_tree(mstate m, tchunkptr t) {
tchunkptr head = 0;
tchunkptr u = t;
bindex_t tindex = t->index;
size_t tsize = chunksize(t);
bindex_t idx;
compute_tree_index(tsize, idx);
assert(tindex == idx);
assert(tsize >= MIN_LARGE_SIZE);
assert(tsize >= minsize_for_tree_index(idx));
assert((idx == NTREEBINS-1) || (tsize < minsize_for_tree_index((idx+1))));
do { /* traverse through chain of same-sized nodes */
do_check_any_chunk(m, ((mchunkptr)u));
assert(u->index == tindex);
assert(chunksize(u) == tsize);
assert(!is_inuse(u));
assert(!next_pinuse(u));
assert(u->fd->bk == u);
assert(u->bk->fd == u);
if (u->parent == 0) {
assert(u->child[0] == 0);
assert(u->child[1] == 0);
}
else {
assert(head == 0); /* only one node on chain has parent */
head = u;
assert(u->parent != u);
assert (u->parent->child[0] == u ||
u->parent->child[1] == u ||
*((tbinptr*)(u->parent)) == u);
if (u->child[0] != 0) {
assert(u->child[0]->parent == u);
assert(u->child[0] != u);
do_check_tree(m, u->child[0]);
}
if (u->child[1] != 0) {
assert(u->child[1]->parent == u);
assert(u->child[1] != u);
do_check_tree(m, u->child[1]);
}
if (u->child[0] != 0 && u->child[1] != 0) {
assert(chunksize(u->child[0]) < chunksize(u->child[1]));
}
}
u = u->fd;
} while (u != t);
assert(head != 0);
}
/* Check all the chunks in a treebin. */
static void do_check_treebin(mstate m, bindex_t i) {
tbinptr* tb = treebin_at(m, i);
tchunkptr t = *tb;
int empty = (m->treemap & (1U << i)) == 0;
if (t == 0)
assert(empty);
if (!empty)
do_check_tree(m, t);
}
/* Check all the chunks in a smallbin. */
static void do_check_smallbin(mstate m, bindex_t i) {
sbinptr b = smallbin_at(m, i);
mchunkptr p = b->bk;
unsigned int empty = (m->smallmap & (1U << i)) == 0;
if (p == b)
assert(empty);
if (!empty) {
for (; p != b; p = p->bk) {
size_t size = chunksize(p);
mchunkptr q;
/* each chunk claims to be free */
do_check_free_chunk(m, p);
/* chunk belongs in bin */
assert(small_index(size) == i);
assert(p->bk == b || chunksize(p->bk) == chunksize(p));
/* chunk is followed by an inuse chunk */
q = next_chunk(p);
if (q->head != FENCEPOST_HEAD)
do_check_inuse_chunk(m, q);
}
}
}
/* Find x in a bin. Used in other check functions. */
static int bin_find(mstate m, mchunkptr x) {
size_t size = chunksize(x);
if (is_small(size)) {
bindex_t sidx = small_index(size);
sbinptr b = smallbin_at(m, sidx);
if (smallmap_is_marked(m, sidx)) {
mchunkptr p = b;
do {
if (p == x)
return 1;
} while ((p = p->fd) != b);
}
}
else {
bindex_t tidx;
compute_tree_index(size, tidx);
if (treemap_is_marked(m, tidx)) {
tchunkptr t = *treebin_at(m, tidx);
size_t sizebits = size << leftshift_for_tree_index(tidx);
while (t != 0 && chunksize(t) != size) {
t = t->child[(sizebits >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 1];
sizebits <<= 1;
}
if (t != 0) {
tchunkptr u = t;
do {
if (u == (tchunkptr)x)
return 1;
} while ((u = u->fd) != t);
}
}
}
return 0;
}
/* Traverse each chunk and check it; return total */
static size_t traverse_and_check(mstate m) {
size_t sum = 0;
if (is_initialized(m)) {
msegmentptr s = &m->seg;
sum += m->topsize + TOP_FOOT_SIZE;
while (s != 0) {
mchunkptr q = align_as_chunk(s->base);
mchunkptr lastq = 0;
assert(pinuse(q));
while (segment_holds(s, q) &&
q != m->top && q->head != FENCEPOST_HEAD) {
sum += chunksize(q);
if (is_inuse(q)) {
assert(!bin_find(m, q));
do_check_inuse_chunk(m, q);
}
else {
assert(q == m->dv || bin_find(m, q));
assert(lastq == 0 || is_inuse(lastq)); /* Not 2 consecutive free */
do_check_free_chunk(m, q);
}
lastq = q;
q = next_chunk(q);
}
s = s->next;
}
}
return sum;
}
/* Check all properties of malloc_state. */
static void do_check_malloc_state(mstate m) {
bindex_t i;
size_t total;
/* check bins */
for (i = 0; i < NSMALLBINS; ++i)
do_check_smallbin(m, i);
for (i = 0; i < NTREEBINS; ++i)
do_check_treebin(m, i);
if (m->dvsize != 0) { /* check dv chunk */
do_check_any_chunk(m, m->dv);
assert(m->dvsize == chunksize(m->dv));
assert(m->dvsize >= MIN_CHUNK_SIZE);
assert(bin_find(m, m->dv) == 0);
}
if (m->top != 0) { /* check top chunk */
do_check_top_chunk(m, m->top);
/*assert(m->topsize == chunksize(m->top)); redundant */
assert(m->topsize > 0);
assert(bin_find(m, m->top) == 0);
}
total = traverse_and_check(m);
assert(total <= m->footprint);
assert(m->footprint <= m->max_footprint);
}
#endif /* DEBUG */
#define CORRUPTION_ERROR_ACTION(m) \
do { \
printf("%s malloc heap corrupted\n",__FUNCTION__); \
while(1) \
{ \
delay(100); \
} \
}while(0) \
#define USAGE_ERROR_ACTION(m, p) \
do { \
printf("%s malloc heap corrupted\n",__FUNCTION__); \
while(1) \
{ \
delay(100); \
} \
}while(0) \
/* ----------------------- Operations on smallbins ----------------------- */
/*
Various forms of linking and unlinking are defined as macros. Even
the ones for trees, which are very long but have very short typical
paths. This is ugly but reduces reliance on inlining support of
compilers.
*/
/* Link a free chunk into a smallbin */
#define insert_small_chunk(M, P, S) {\
bindex_t I = small_index(S);\
mchunkptr B = smallbin_at(M, I);\
mchunkptr F = B;\
assert(S >= MIN_CHUNK_SIZE);\
if (!smallmap_is_marked(M, I))\
mark_smallmap(M, I);\
else if (RTCHECK(ok_address(M, B->fd)))\
F = B->fd;\
else {\
CORRUPTION_ERROR_ACTION(M);\
}\
B->fd = P;\
F->bk = P;\
P->fd = F;\
P->bk = B;\
}
/* ----------------------- Operations on smallbins ----------------------- */
/*
Various forms of linking and unlinking are defined as macros. Even
the ones for trees, which are very long but have very short typical
paths. This is ugly but reduces reliance on inlining support of
compilers.
*/
/* Link a free chunk into a smallbin */
#define insert_small_chunk(M, P, S) {\
bindex_t I = small_index(S);\
mchunkptr B = smallbin_at(M, I);\
mchunkptr F = B;\
assert(S >= MIN_CHUNK_SIZE);\
if (!smallmap_is_marked(M, I))\
mark_smallmap(M, I);\
else if (RTCHECK(ok_address(M, B->fd)))\
F = B->fd;\
else {\
CORRUPTION_ERROR_ACTION(M);\
}\
B->fd = P;\
F->bk = P;\
P->fd = F;\
P->bk = B;\
}
/* Unlink a chunk from a smallbin */
#define unlink_small_chunk(M, P, S) {\
mchunkptr F = P->fd;\
mchunkptr B = P->bk;\
bindex_t I = small_index(S);\
assert(P != B);\
assert(P != F);\
assert(chunksize(P) == small_index2size(I));\
if (RTCHECK(F == smallbin_at(M,I) || (ok_address(M, F) && F->bk == P))) { \
if (B == F) {\
clear_smallmap(M, I);\
}\
else if (RTCHECK(B == smallbin_at(M,I) ||\
(ok_address(M, B) && B->fd == P))) {\
F->bk = B;\
B->fd = F;\
}\
else {\
CORRUPTION_ERROR_ACTION(M);\
}\
}\
else {\
CORRUPTION_ERROR_ACTION(M);\
}\
}
/* Unlink the first chunk from a smallbin */
#define unlink_first_small_chunk(M, B, P, I) {\
mchunkptr F = P->fd;\
assert(P != B);\
assert(P != F);\
assert(chunksize(P) == small_index2size(I));\
if (B == F) {\
clear_smallmap(M, I);\
}\
else if (RTCHECK(ok_address(M, F) && F->bk == P)) {\
F->bk = B;\
B->fd = F;\
}\
else {\
CORRUPTION_ERROR_ACTION(M);\
}\
}
/* Replace dv node, binning the old one */
/* Used only when dvsize known to be small */
#define replace_dv(M, P, S) {\
size_t DVS = M->dvsize;\
assert(is_small(DVS));\
if (DVS != 0) {\
mchunkptr DV = M->dv;\
insert_small_chunk(M, DV, DVS);\
}\
M->dvsize = S;\
M->dv = P;\
}
/* ------------------------- Operations on trees ------------------------- */
/* Insert chunk into tree */
#define insert_large_chunk(M, X, S) {\
tbinptr* H;\
bindex_t I;\
compute_tree_index(S, I);\
H = treebin_at(M, I);\
X->index = I;\
X->child[0] = X->child[1] = 0;\
if (!treemap_is_marked(M, I)) {\
mark_treemap(M, I);\
*H = X;\
X->parent = (tchunkptr)H;\
X->fd = X->bk = X;\
}\
else {\
tchunkptr T = *H;\
size_t K = S << leftshift_for_tree_index(I);\
for (;;) {\
if (chunksize(T) != S) {\
tchunkptr* C = &(T->child[(K >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 1]);\
K <<= 1;\
if (*C != 0)\
T = *C;\
else if (RTCHECK(ok_address(M, C))) {\
*C = X;\
X->parent = T;\
X->fd = X->bk = X;\
break;\
}\
else {\
CORRUPTION_ERROR_ACTION(M);\
break;\
}\
}\
else {\
tchunkptr F = T->fd;\
if (RTCHECK(ok_address(M, T) && ok_address(M, F))) {\
T->fd = F->bk = X;\
X->fd = F;\
X->bk = T;\
X->parent = 0;\
break;\
}\
else {\
CORRUPTION_ERROR_ACTION(M);\
break;\
}\
}\
}\
}\
}
/*
Unlink steps:
1. If x is a chained node, unlink it from its same-sized fd/bk links
and choose its bk node as its replacement.
2. If x was the last node of its size, but not a leaf node, it must
be replaced with a leaf node (not merely one with an open left or
right), to make sure that lefts and rights of descendents
correspond properly to bit masks. We use the rightmost descendent
of x. We could use any other leaf, but this is easy to locate and
tends to counteract removal of leftmosts elsewhere, and so keeps
paths shorter than minimally guaranteed. This doesn't loop much
because on average a node in a tree is near the bottom.
3. If x is the base of a chain (i.e., has parent links) relink
x's parent and children to x's replacement (or null if none).
*/
#define unlink_large_chunk(M, X) {\
tchunkptr XP = X->parent;\
tchunkptr R;\
if (X->bk != X) {\
tchunkptr F = X->fd;\
R = X->bk;\
if (RTCHECK(ok_address(M, F) && F->bk == X && R->fd == X)) {\
F->bk = R;\
R->fd = F;\
}\
else {\
CORRUPTION_ERROR_ACTION(M);\
}\
}\
else {\
tchunkptr* RP;\
if (((R = *(RP = &(X->child[1]))) != 0) ||\
((R = *(RP = &(X->child[0]))) != 0)) {\
tchunkptr* CP;\
while ((*(CP = &(R->child[1])) != 0) ||\
(*(CP = &(R->child[0])) != 0)) {\
R = *(RP = CP);\
}\
if (RTCHECK(ok_address(M, RP)))\
*RP = 0;\
else {\
CORRUPTION_ERROR_ACTION(M);\
}\
}\
}\
if (XP != 0) {\
tbinptr* H = treebin_at(M, X->index);\
if (X == *H) {\
if ((*H = R) == 0) \
clear_treemap(M, X->index);\
}\
else if (RTCHECK(ok_address(M, XP))) {\
if (XP->child[0] == X) \
XP->child[0] = R;\
else \
XP->child[1] = R;\
}\
else\
CORRUPTION_ERROR_ACTION(M);\
if (R != 0) {\
if (RTCHECK(ok_address(M, R))) {\
tchunkptr C0, C1;\
R->parent = XP;\
if ((C0 = X->child[0]) != 0) {\
if (RTCHECK(ok_address(M, C0))) {\
R->child[0] = C0;\
C0->parent = R;\
}\
else\
CORRUPTION_ERROR_ACTION(M);\
}\
if ((C1 = X->child[1]) != 0) {\
if (RTCHECK(ok_address(M, C1))) {\
R->child[1] = C1;\
C1->parent = R;\
}\
else\
CORRUPTION_ERROR_ACTION(M);\
}\
}\
else\
CORRUPTION_ERROR_ACTION(M);\
}\
}\
}
/* Relays to large vs small bin operations */
#define insert_chunk(M, P, S)\
if (is_small(S)) insert_small_chunk(M, P, S)\
else { tchunkptr TP = (tchunkptr)(P); insert_large_chunk(M, TP, S); }
#define unlink_chunk(M, P, S)\
if (is_small(S)) unlink_small_chunk(M, P, S)\
else { tchunkptr TP = (tchunkptr)(P); unlink_large_chunk(M, TP); }
static inline void* os_mmap(size_t size)
{
void* ptr = KernelAlloc(size);
printf("%s %x %d bytes\n",__FUNCTION__, ptr, size);
return (ptr != 0)? ptr: MFAIL;
}
static inline int os_munmap(void* ptr, size_t size)
{
return (KernelFree(ptr) != 0) ? 0 : -1;
}
#define MMAP_DEFAULT(s) os_mmap(s)
#define MUNMAP_DEFAULT(a, s) os_munmap((a), (s))
#define DIRECT_MMAP_DEFAULT(s) os_mmap(s)
/* ----------------------- Direct-mmapping chunks ----------------------- */
/*
Directly mmapped chunks are set up with an offset to the start of
the mmapped region stored in the prev_foot field of the chunk. This
allows reconstruction of the required argument to MUNMAP when freed,
and also allows adjustment of the returned chunk to meet alignment
requirements (especially in memalign).
*/
/* Malloc using mmap */
static void* mmap_alloc(mstate m, size_t nb) {
size_t mmsize = mmap_align(nb + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
if (m->footprint_limit != 0) {
size_t fp = m->footprint + mmsize;
if (fp <= m->footprint || fp > m->footprint_limit)
return 0;
}
if (mmsize > nb) { /* Check for wrap around 0 */
char* mm = (char*)(CALL_DIRECT_MMAP(mmsize));
if (mm != CMFAIL) {
size_t offset = align_offset(chunk2mem(mm));
size_t psize = mmsize - offset - MMAP_FOOT_PAD;
mchunkptr p = (mchunkptr)(mm + offset);
p->prev_foot = offset;
p->head = psize;
mark_inuse_foot(m, p, psize);
chunk_plus_offset(p, psize)->head = FENCEPOST_HEAD;
chunk_plus_offset(p, psize+SIZE_T_SIZE)->head = 0;
if (m->least_addr == 0 || mm < m->least_addr)
m->least_addr = mm;
if ((m->footprint += mmsize) > m->max_footprint)
m->max_footprint = m->footprint;
assert(is_aligned(chunk2mem(p)));
check_mmapped_chunk(m, p);
return chunk2mem(p);
}
}
return 0;
}
/* Realloc using mmap */
static mchunkptr mmap_resize(mstate m, mchunkptr oldp, size_t nb, int flags) {
size_t oldsize = chunksize(oldp);
(void)flags; /* placate people compiling -Wunused */
if (is_small(nb)) /* Can't shrink mmap regions below small size */
return 0;
/* Keep old chunk if big enough but not too big */
if (oldsize >= nb + SIZE_T_SIZE &&
(oldsize - nb) <= (mparams.granularity << 1))
return oldp;
else {
size_t offset = oldp->prev_foot;
size_t oldmmsize = oldsize + offset + MMAP_FOOT_PAD;
size_t newmmsize = mmap_align(nb + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
char* cp = (char*)CALL_MREMAP((char*)oldp - offset,
oldmmsize, newmmsize, flags);
if (cp != CMFAIL) {
mchunkptr newp = (mchunkptr)(cp + offset);
size_t psize = newmmsize - offset - MMAP_FOOT_PAD;
newp->head = psize;
mark_inuse_foot(m, newp, psize);
chunk_plus_offset(newp, psize)->head = FENCEPOST_HEAD;
chunk_plus_offset(newp, psize+SIZE_T_SIZE)->head = 0;
if (cp < m->least_addr)
m->least_addr = cp;
if ((m->footprint += newmmsize - oldmmsize) > m->max_footprint)
m->max_footprint = m->footprint;
check_mmapped_chunk(m, newp);
return newp;
}
}
return 0;
}
/* -------------------------- mspace management -------------------------- */
/* Initialize top chunk and its size */
static void init_top(mstate m, mchunkptr p, size_t psize) {
/* Ensure alignment */
size_t offset = align_offset(chunk2mem(p));
p = (mchunkptr)((char*)p + offset);
psize -= offset;
m->top = p;
m->topsize = psize;
p->head = psize | PINUSE_BIT;
/* set size of fake trailing chunk holding overhead space only once */
chunk_plus_offset(p, psize)->head = TOP_FOOT_SIZE;
m->trim_check = mparams.trim_threshold; /* reset on each update */
}
/* Initialize bins for a new mstate that is otherwise zeroed out */
static void init_bins(mstate m) {
/* Establish circular links for smallbins */
bindex_t i;
for (i = 0; i < NSMALLBINS; ++i) {
sbinptr bin = smallbin_at(m,i);
bin->fd = bin->bk = bin;
}
}
/* Allocate chunk and prepend remainder with chunk in successor base. */
static void* prepend_alloc(mstate m, char* newbase, char* oldbase,
size_t nb) {
mchunkptr p = align_as_chunk(newbase);
mchunkptr oldfirst = align_as_chunk(oldbase);
size_t psize = (char*)oldfirst - (char*)p;
mchunkptr q = chunk_plus_offset(p, nb);
size_t qsize = psize - nb;
set_size_and_pinuse_of_inuse_chunk(m, p, nb);
assert((char*)oldfirst > (char*)q);
assert(pinuse(oldfirst));
assert(qsize >= MIN_CHUNK_SIZE);
/* consolidate remainder with first chunk of old base */
if (oldfirst == m->top) {
size_t tsize = m->topsize += qsize;
m->top = q;
q->head = tsize | PINUSE_BIT;
check_top_chunk(m, q);
}
else if (oldfirst == m->dv) {
size_t dsize = m->dvsize += qsize;
m->dv = q;
set_size_and_pinuse_of_free_chunk(q, dsize);
}
else {
if (!is_inuse(oldfirst)) {
size_t nsize = chunksize(oldfirst);
unlink_chunk(m, oldfirst, nsize);
oldfirst = chunk_plus_offset(oldfirst, nsize);
qsize += nsize;
}
set_free_with_pinuse(q, qsize, oldfirst);
insert_chunk(m, q, qsize);
check_free_chunk(m, q);
}
check_malloced_chunk(m, chunk2mem(p), nb);
return chunk2mem(p);
}
/* Add a segment to hold a new noncontiguous region */
static void add_segment(mstate m, char* tbase, size_t tsize, flag_t mmapped) {
/* Determine locations and sizes of segment, fenceposts, old top */
char* old_top = (char*)m->top;
msegmentptr oldsp = segment_holding(m, old_top);
char* old_end = oldsp->base + oldsp->size;
size_t ssize = pad_request(sizeof(struct malloc_segment));
char* rawsp = old_end - (ssize + FOUR_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
size_t offset = align_offset(chunk2mem(rawsp));
char* asp = rawsp + offset;
char* csp = (asp < (old_top + MIN_CHUNK_SIZE))? old_top : asp;
mchunkptr sp = (mchunkptr)csp;
msegmentptr ss = (msegmentptr)(chunk2mem(sp));
mchunkptr tnext = chunk_plus_offset(sp, ssize);
mchunkptr p = tnext;
int nfences = 0;
/* reset top to new space */
init_top(m, (mchunkptr)tbase, tsize - TOP_FOOT_SIZE);
/* Set up segment record */
assert(is_aligned(ss));
set_size_and_pinuse_of_inuse_chunk(m, sp, ssize);
*ss = m->seg; /* Push current record */
m->seg.base = tbase;
m->seg.size = tsize;
m->seg.sflags = mmapped;
m->seg.next = ss;
/* Insert trailing fenceposts */
for (;;) {
mchunkptr nextp = chunk_plus_offset(p, SIZE_T_SIZE);
p->head = FENCEPOST_HEAD;
++nfences;
if ((char*)(&(nextp->head)) < old_end)
p = nextp;
else
break;
}
assert(nfences >= 2);
/* Insert the rest of old top into a bin as an ordinary free chunk */
if (csp != old_top) {
mchunkptr q = (mchunkptr)old_top;
size_t psize = csp - old_top;
mchunkptr tn = chunk_plus_offset(q, psize);
set_free_with_pinuse(q, psize, tn);
insert_chunk(m, q, psize);
}
check_top_chunk(m, m->top);
}
/* -------------------------- System allocation -------------------------- */
/* Get memory from system using MORECORE or MMAP */
static void* sys_alloc(mstate m, size_t nb) {
char* tbase = CMFAIL;
size_t tsize = 0;
flag_t mmap_flag = 0;
size_t asize; /* allocation size */
ensure_initialization();
printf("%s %d bytes\n", __FUNCTION__, nb);
/* Directly map large chunks, but only if already initialized */
if (use_mmap(m) && nb >= mparams.mmap_threshold && m->topsize != 0) {
void* mem = mmap_alloc(m, nb);
if (mem != 0)
return mem;
}
asize = granularity_align(nb + SYS_ALLOC_PADDING);
if (asize <= nb)
return 0; /* wraparound */
if (m->footprint_limit != 0) {
size_t fp = m->footprint + asize;
if (fp <= m->footprint || fp > m->footprint_limit)
return 0;
}
/*
Try getting memory in any of three ways (in most-preferred to
least-preferred order):
1. A call to MORECORE that can normally contiguously extend memory.
(disabled if not MORECORE_CONTIGUOUS or not HAVE_MORECORE or
or main space is mmapped or a previous contiguous call failed)
2. A call to MMAP new space (disabled if not HAVE_MMAP).
Note that under the default settings, if MORECORE is unable to
fulfill a request, and HAVE_MMAP is true, then mmap is
used as a noncontiguous system allocator. This is a useful backup
strategy for systems with holes in address spaces -- in this case
sbrk cannot contiguously expand the heap, but mmap may be able to
find space.
3. A call to MORECORE that cannot usually contiguously extend memory.
(disabled if not HAVE_MORECORE)
In all cases, we need to request enough bytes from system to ensure
we can malloc nb bytes upon success, so pad with enough space for
top_foot, plus alignment-pad to make sure we don't lose bytes if
not on boundary, and round this up to a granularity unit.
*/
#if 0
if (MORECORE_CONTIGUOUS && !use_noncontiguous(m)) {
char* br = CMFAIL;
size_t ssize = asize; /* sbrk call size */
msegmentptr ss = (m->top == 0)? 0 : segment_holding(m, (char*)m->top);
ACQUIRE_MALLOC_GLOBAL_LOCK();
if (ss == 0) { /* First time through or recovery */
char* base = (char*)CALL_MORECORE(0);
if (base != CMFAIL) {
size_t fp;
/* Adjust to end on a page boundary */
if (!is_page_aligned(base))
ssize += (page_align((size_t)base) - (size_t)base);
fp = m->footprint + ssize; /* recheck limits */
if (ssize > nb && ssize < HALF_MAX_SIZE_T &&
(m->footprint_limit == 0 ||
(fp > m->footprint && fp <= m->footprint_limit)) &&
(br = (char*)(CALL_MORECORE(ssize))) == base) {
tbase = base;
tsize = ssize;
}
}
}
else {
/* Subtract out existing available top space from MORECORE request. */
ssize = granularity_align(nb - m->topsize + SYS_ALLOC_PADDING);
/* Use mem here only if it did continuously extend old space */
if (ssize < HALF_MAX_SIZE_T &&
(br = (char*)(CALL_MORECORE(ssize))) == ss->base+ss->size) {
tbase = br;
tsize = ssize;
}
}
if (tbase == CMFAIL) { /* Cope with partial failure */
if (br != CMFAIL) { /* Try to use/extend the space we did get */
if (ssize < HALF_MAX_SIZE_T &&
ssize < nb + SYS_ALLOC_PADDING) {
size_t esize = granularity_align(nb + SYS_ALLOC_PADDING - ssize);
if (esize < HALF_MAX_SIZE_T) {
char* end = (char*)CALL_MORECORE(esize);
if (end != CMFAIL)
ssize += esize;
else { /* Can't use; try to release */
(void) CALL_MORECORE(-ssize);
br = CMFAIL;
}
}
}
}
if (br != CMFAIL) { /* Use the space we did get */
tbase = br;
tsize = ssize;
}
else
disable_contiguous(m); /* Don't try contiguous path in the future */
}
RELEASE_MALLOC_GLOBAL_LOCK();
}
#endif
if (HAVE_MMAP && tbase == CMFAIL) { /* Try MMAP */
char* mp = (char*)(CALL_MMAP(asize));
if (mp != CMFAIL) {
tbase = mp;
tsize = asize;
mmap_flag = USE_MMAP_BIT;
}
}
#if 0
if (HAVE_MORECORE && tbase == CMFAIL) { /* Try noncontiguous MORECORE */
if (asize < HALF_MAX_SIZE_T) {
char* br = CMFAIL;
char* end = CMFAIL;
ACQUIRE_MALLOC_GLOBAL_LOCK();
br = (char*)(CALL_MORECORE(asize));
end = (char*)(CALL_MORECORE(0));
RELEASE_MALLOC_GLOBAL_LOCK();
if (br != CMFAIL && end != CMFAIL && br < end) {
size_t ssize = end - br;
if (ssize > nb + TOP_FOOT_SIZE) {
tbase = br;
tsize = ssize;
}
}
}
}
#endif
if (tbase != CMFAIL) {
if ((m->footprint += tsize) > m->max_footprint)
m->max_footprint = m->footprint;
if (!is_initialized(m)) { /* first-time initialization */
if (m->least_addr == 0 || tbase < m->least_addr)
m->least_addr = tbase;
m->seg.base = tbase;
m->seg.size = tsize;
m->seg.sflags = mmap_flag;
m->magic = mparams.magic;
m->release_checks = MAX_RELEASE_CHECK_RATE;
init_bins(m);
if (is_global(m))
init_top(m, (mchunkptr)tbase, tsize - TOP_FOOT_SIZE);
else
{
/* Offset top by embedded malloc_state */
mchunkptr mn = next_chunk(mem2chunk(m));
init_top(m, mn, (size_t)((tbase + tsize) - (char*)mn) -TOP_FOOT_SIZE);
}
}
else {
/* Try to merge with an existing segment */
msegmentptr sp = &m->seg;
/* Only consider most recent segment if traversal suppressed */
while (sp != 0 && tbase != sp->base + sp->size)
sp = (NO_SEGMENT_TRAVERSAL) ? 0 : sp->next;
if (sp != 0 &&
!is_extern_segment(sp) &&
(sp->sflags & USE_MMAP_BIT) == mmap_flag &&
segment_holds(sp, m->top)) { /* append */
sp->size += tsize;
init_top(m, m->top, m->topsize + tsize);
}
else {
if (tbase < m->least_addr)
m->least_addr = tbase;
sp = &m->seg;
while (sp != 0 && sp->base != tbase + tsize)
sp = (NO_SEGMENT_TRAVERSAL) ? 0 : sp->next;
if (sp != 0 &&
!is_extern_segment(sp) &&
(sp->sflags & USE_MMAP_BIT) == mmap_flag) {
char* oldbase = sp->base;
sp->base = tbase;
sp->size += tsize;
return prepend_alloc(m, tbase, oldbase, nb);
}
else
add_segment(m, tbase, tsize, mmap_flag);
}
}
if (nb < m->topsize) { /* Allocate from new or extended top space */
size_t rsize = m->topsize -= nb;
mchunkptr p = m->top;
mchunkptr r = m->top = chunk_plus_offset(p, nb);
r->head = rsize | PINUSE_BIT;
set_size_and_pinuse_of_inuse_chunk(m, p, nb);
check_top_chunk(m, m->top);
check_malloced_chunk(m, chunk2mem(p), nb);
return chunk2mem(p);
}
}
// MALLOC_FAILURE_ACTION;
return 0;
}
/* ----------------------- system deallocation -------------------------- */
/* Unmap and unlink any mmapped segments that don't contain used chunks */
static size_t release_unused_segments(mstate m) {
size_t released = 0;
int nsegs = 0;
msegmentptr pred = &m->seg;
msegmentptr sp = pred->next;
while (sp != 0) {
char* base = sp->base;
size_t size = sp->size;
msegmentptr next = sp->next;
++nsegs;
if (is_mmapped_segment(sp) && !is_extern_segment(sp)) {
mchunkptr p = align_as_chunk(base);
size_t psize = chunksize(p);
/* Can unmap if first chunk holds entire segment and not pinned */
if (!is_inuse(p) && (char*)p + psize >= base + size - TOP_FOOT_SIZE) {
tchunkptr tp = (tchunkptr)p;
assert(segment_holds(sp, (char*)sp));
if (p == m->dv) {
m->dv = 0;
m->dvsize = 0;
}
else {
unlink_large_chunk(m, tp);
}
if (CALL_MUNMAP(base, size) == 0) {
released += size;
m->footprint -= size;
/* unlink obsoleted record */
sp = pred;
sp->next = next;
}
else { /* back out if cannot unmap */
insert_large_chunk(m, tp, psize);
}
}
}
if (NO_SEGMENT_TRAVERSAL) /* scan only first segment */
break;
pred = sp;
sp = next;
}
/* Reset check counter */
m->release_checks = (((size_t) nsegs > (size_t) MAX_RELEASE_CHECK_RATE)?
(size_t) nsegs : (size_t) MAX_RELEASE_CHECK_RATE);
return released;
}
static int sys_trim(mstate m, size_t pad) {
size_t released = 0;
ensure_initialization();
if (pad < MAX_REQUEST && is_initialized(m)) {
pad += TOP_FOOT_SIZE; /* ensure enough room for segment overhead */
if (m->topsize > pad) {
/* Shrink top space in granularity-size units, keeping at least one */
size_t unit = mparams.granularity;
size_t extra = ((m->topsize - pad + (unit - SIZE_T_ONE)) / unit -
SIZE_T_ONE) * unit;
msegmentptr sp = segment_holding(m, (char*)m->top);
if (!is_extern_segment(sp)) {
if (is_mmapped_segment(sp)) {
if (HAVE_MMAP &&
sp->size >= extra &&
!has_segment_link(m, sp)) { /* can't shrink if pinned */
size_t newsize = sp->size - extra;
(void)newsize; /* placate people compiling -Wunused-variable */
/* Prefer mremap, fall back to munmap */
if ((CALL_MREMAP(sp->base, sp->size, newsize, 0) != MFAIL) ||
(CALL_MUNMAP(sp->base + newsize, extra) == 0)) {
released = extra;
}
}
}
else if (HAVE_MORECORE) {
if (extra >= HALF_MAX_SIZE_T) /* Avoid wrapping negative */
extra = (HALF_MAX_SIZE_T) + SIZE_T_ONE - unit;
ACQUIRE_MALLOC_GLOBAL_LOCK();
{
/* Make sure end of memory is where we last set it. */
char* old_br = (char*)(CALL_MORECORE(0));
if (old_br == sp->base + sp->size) {
char* rel_br = (char*)(CALL_MORECORE(-extra));
char* new_br = (char*)(CALL_MORECORE(0));
if (rel_br != CMFAIL && new_br < old_br)
released = old_br - new_br;
}
}
RELEASE_MALLOC_GLOBAL_LOCK();
}
}
if (released != 0) {
sp->size -= released;
m->footprint -= released;
init_top(m, m->top, m->topsize - released);
check_top_chunk(m, m->top);
}
}
/* Unmap any unused mmapped segments */
if (HAVE_MMAP)
released += release_unused_segments(m);
/* On failure, disable autotrim to avoid repeated failed future calls */
if (released == 0 && m->topsize > m->trim_check)
m->trim_check = MAX_SIZE_T;
}
return (released != 0)? 1 : 0;
}
/* Consolidate and bin a chunk. Differs from exported versions
of free mainly in that the chunk need not be marked as inuse.
*/
static void dispose_chunk(mstate m, mchunkptr p, size_t psize) {
mchunkptr next = chunk_plus_offset(p, psize);
if (!pinuse(p)) {
mchunkptr prev;
size_t prevsize = p->prev_foot;
if (is_mmapped(p)) {
psize += prevsize + MMAP_FOOT_PAD;
if (CALL_MUNMAP((char*)p - prevsize, psize) == 0)
m->footprint -= psize;
return;
}
prev = chunk_minus_offset(p, prevsize);
psize += prevsize;
p = prev;
if (RTCHECK(ok_address(m, prev))) { /* consolidate backward */
if (p != m->dv) {
unlink_chunk(m, p, prevsize);
}
else if ((next->head & INUSE_BITS) == INUSE_BITS) {
m->dvsize = psize;
set_free_with_pinuse(p, psize, next);
return;
}
}
else {
CORRUPTION_ERROR_ACTION(m);
return;
}
}
if (RTCHECK(ok_address(m, next))) {
if (!cinuse(next)) { /* consolidate forward */
if (next == m->top) {
size_t tsize = m->topsize += psize;
m->top = p;
p->head = tsize | PINUSE_BIT;
if (p == m->dv) {
m->dv = 0;
m->dvsize = 0;
}
return;
}
else if (next == m->dv) {
size_t dsize = m->dvsize += psize;
m->dv = p;
set_size_and_pinuse_of_free_chunk(p, dsize);
return;
}
else {
size_t nsize = chunksize(next);
psize += nsize;
unlink_chunk(m, next, nsize);
set_size_and_pinuse_of_free_chunk(p, psize);
if (p == m->dv) {
m->dvsize = psize;
return;
}
}
}
else {
set_free_with_pinuse(p, psize, next);
}
insert_chunk(m, p, psize);
}
else {
CORRUPTION_ERROR_ACTION(m);
}
}
/* ---------------------------- malloc --------------------------- */
/* allocate a large request from the best fitting chunk in a treebin */
static void* tmalloc_large(mstate m, size_t nb) {
tchunkptr v = 0;
size_t rsize = -nb; /* Unsigned negation */
tchunkptr t;
bindex_t idx;
compute_tree_index(nb, idx);
if ((t = *treebin_at(m, idx)) != 0) {
/* Traverse tree for this bin looking for node with size == nb */
size_t sizebits = nb << leftshift_for_tree_index(idx);
tchunkptr rst = 0; /* The deepest untaken right subtree */
for (;;) {
tchunkptr rt;
size_t trem = chunksize(t) - nb;
if (trem < rsize) {
v = t;
if ((rsize = trem) == 0)
break;
}
rt = t->child[1];
t = t->child[(sizebits >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 1];
if (rt != 0 && rt != t)
rst = rt;
if (t == 0) {
t = rst; /* set t to least subtree holding sizes > nb */
break;
}
sizebits <<= 1;
}
}
if (t == 0 && v == 0) { /* set t to root of next non-empty treebin */
binmap_t leftbits = left_bits(idx2bit(idx)) & m->treemap;
if (leftbits != 0) {
bindex_t i;
binmap_t leastbit = least_bit(leftbits);
compute_bit2idx(leastbit, i);
t = *treebin_at(m, i);
}
}
while (t != 0) { /* find smallest of tree or subtree */
size_t trem = chunksize(t) - nb;
if (trem < rsize) {
rsize = trem;
v = t;
}
t = leftmost_child(t);
}
/* If dv is a better fit, return 0 so malloc will use it */
if (v != 0 && rsize < (size_t)(m->dvsize - nb)) {
if (RTCHECK(ok_address(m, v))) { /* split */
mchunkptr r = chunk_plus_offset(v, nb);
assert(chunksize(v) == rsize + nb);
if (RTCHECK(ok_next(v, r))) {
unlink_large_chunk(m, v);
if (rsize < MIN_CHUNK_SIZE)
set_inuse_and_pinuse(m, v, (rsize + nb));
else {
set_size_and_pinuse_of_inuse_chunk(m, v, nb);
set_size_and_pinuse_of_free_chunk(r, rsize);
insert_chunk(m, r, rsize);
}
return chunk2mem(v);
}
}
CORRUPTION_ERROR_ACTION(m);
}
return 0;
}
/* allocate a small request from the best fitting chunk in a treebin */
static void* tmalloc_small(mstate m, size_t nb) {
tchunkptr t, v;
size_t rsize;
bindex_t i;
binmap_t leastbit = least_bit(m->treemap);
compute_bit2idx(leastbit, i);
v = t = *treebin_at(m, i);
rsize = chunksize(t) - nb;
while ((t = leftmost_child(t)) != 0) {
size_t trem = chunksize(t) - nb;
if (trem < rsize) {
rsize = trem;
v = t;
}
}
if (RTCHECK(ok_address(m, v))) {
mchunkptr r = chunk_plus_offset(v, nb);
assert(chunksize(v) == rsize + nb);
if (RTCHECK(ok_next(v, r))) {
unlink_large_chunk(m, v);
if (rsize < MIN_CHUNK_SIZE)
set_inuse_and_pinuse(m, v, (rsize + nb));
else {
set_size_and_pinuse_of_inuse_chunk(m, v, nb);
set_size_and_pinuse_of_free_chunk(r, rsize);
replace_dv(m, r, rsize);
}
return chunk2mem(v);
}
}
CORRUPTION_ERROR_ACTION(m);
return 0;
}
void* malloc(size_t bytes)
{
/*
Basic algorithm:
If a small request (< 256 bytes minus per-chunk overhead):
1. If one exists, use a remainderless chunk in associated smallbin.
(Remainderless means that there are too few excess bytes to
represent as a chunk.)
2. If it is big enough, use the dv chunk, which is normally the
chunk adjacent to the one used for the most recent small request.
3. If one exists, split the smallest available chunk in a bin,
saving remainder in dv.
4. If it is big enough, use the top chunk.
5. If available, get memory from system and use it
Otherwise, for a large request:
1. Find the smallest available binned chunk that fits, and use it
if it is better fitting than dv chunk, splitting if necessary.
2. If better fitting than any binned chunk, use the dv chunk.
3. If it is big enough, use the top chunk.
4. If request size >= mmap threshold, try to directly mmap this chunk.
5. If available, get memory from system and use it
The ugly goto's here ensure that postaction occurs along all paths.
*/
ensure_initialization(); /* initialize in sys_alloc if not using locks */
PREACTION(gm);
{
void* mem;
size_t nb;
if (bytes <= MAX_SMALL_REQUEST) {
bindex_t idx;
binmap_t smallbits;
nb = (bytes < MIN_REQUEST)? MIN_CHUNK_SIZE : pad_request(bytes);
idx = small_index(nb);
smallbits = gm->smallmap >> idx;
if ((smallbits & 0x3U) != 0) { /* Remainderless fit to a smallbin. */
mchunkptr b, p;
idx += ~smallbits & 1; /* Uses next bin if idx empty */
b = smallbin_at(gm, idx);
p = b->fd;
assert(chunksize(p) == small_index2size(idx));
unlink_first_small_chunk(gm, b, p, idx);
set_inuse_and_pinuse(gm, p, small_index2size(idx));
mem = chunk2mem(p);
check_malloced_chunk(gm, mem, nb);
goto postaction;
}
else if (nb > gm->dvsize) {
if (smallbits != 0) { /* Use chunk in next nonempty smallbin */
mchunkptr b, p, r;
size_t rsize;
bindex_t i;
binmap_t leftbits = (smallbits << idx) & left_bits(idx2bit(idx));
binmap_t leastbit = least_bit(leftbits);
compute_bit2idx(leastbit, i);
b = smallbin_at(gm, i);
p = b->fd;
assert(chunksize(p) == small_index2size(i));
unlink_first_small_chunk(gm, b, p, i);
rsize = small_index2size(i) - nb;
/* Fit here cannot be remainderless if 4byte sizes */
if (SIZE_T_SIZE != 4 && rsize < MIN_CHUNK_SIZE)
set_inuse_and_pinuse(gm, p, small_index2size(i));
else {
set_size_and_pinuse_of_inuse_chunk(gm, p, nb);
r = chunk_plus_offset(p, nb);
set_size_and_pinuse_of_free_chunk(r, rsize);
replace_dv(gm, r, rsize);
}
mem = chunk2mem(p);
check_malloced_chunk(gm, mem, nb);
goto postaction;
}
else if (gm->treemap != 0 && (mem = tmalloc_small(gm, nb)) != 0) {
check_malloced_chunk(gm, mem, nb);
goto postaction;
}
}
}
else if (bytes >= MAX_REQUEST)
nb = MAX_SIZE_T; /* Too big to allocate. Force failure (in sys alloc) */
else {
nb = pad_request(bytes);
if (gm->treemap != 0 && (mem = tmalloc_large(gm, nb)) != 0) {
check_malloced_chunk(gm, mem, nb);
goto postaction;
}
}
if (nb <= gm->dvsize) {
size_t rsize = gm->dvsize - nb;
mchunkptr p = gm->dv;
if (rsize >= MIN_CHUNK_SIZE) { /* split dv */
mchunkptr r = gm->dv = chunk_plus_offset(p, nb);
gm->dvsize = rsize;
set_size_and_pinuse_of_free_chunk(r, rsize);
set_size_and_pinuse_of_inuse_chunk(gm, p, nb);
}
else { /* exhaust dv */
size_t dvs = gm->dvsize;
gm->dvsize = 0;
gm->dv = 0;
set_inuse_and_pinuse(gm, p, dvs);
}
mem = chunk2mem(p);
check_malloced_chunk(gm, mem, nb);
goto postaction;
}
else if (nb < gm->topsize) { /* Split top */
size_t rsize = gm->topsize -= nb;
mchunkptr p = gm->top;
mchunkptr r = gm->top = chunk_plus_offset(p, nb);
r->head = rsize | PINUSE_BIT;
set_size_and_pinuse_of_inuse_chunk(gm, p, nb);
mem = chunk2mem(p);
check_top_chunk(gm, gm->top);
check_malloced_chunk(gm, mem, nb);
goto postaction;
}
mem = sys_alloc(gm, nb);
postaction:
POSTACTION(gm);
// printf("%s %p %d\n", __FUNCTION__, mem, bytes);
return mem;
}
// FAIL();
return 0;
}
/* ---------------------------- free --------------------------- */
void free(void* mem)
{
/*
Consolidate freed chunks with preceeding or succeeding bordering
free chunks, if they exist, and then place in a bin. Intermixed
with special cases for top, dv, mmapped chunks, and usage errors.
*/
// dbgprintf("%s %p\n", __FUNCTION__, mem);
if (mem != 0) {
mchunkptr p = mem2chunk(mem);
#if FOOTERS
mstate fm = get_mstate_for(p);
if (!ok_magic(fm)) {
USAGE_ERROR_ACTION(fm, p);
return;
}
#else /* FOOTERS */
#define fm gm
#endif /* FOOTERS */
PREACTION(fm);
{
check_inuse_chunk(fm, p);
if (RTCHECK(ok_address(fm, p) && ok_inuse(p))) {
size_t psize = chunksize(p);
mchunkptr next = chunk_plus_offset(p, psize);
if (!pinuse(p)) {
size_t prevsize = p->prev_foot;
if (is_mmapped(p)) {
psize += prevsize + MMAP_FOOT_PAD;
if (CALL_MUNMAP((char*)p - prevsize, psize) == 0)
fm->footprint -= psize;
goto postaction;
}
else {
mchunkptr prev = chunk_minus_offset(p, prevsize);
psize += prevsize;
p = prev;
if (RTCHECK(ok_address(fm, prev))) { /* consolidate backward */
if (p != fm->dv) {
unlink_chunk(fm, p, prevsize);
}
else if ((next->head & INUSE_BITS) == INUSE_BITS) {
fm->dvsize = psize;
set_free_with_pinuse(p, psize, next);
goto postaction;
}
}
else
goto erroraction;
}
}
if (RTCHECK(ok_next(p, next) && ok_pinuse(next))) {
if (!cinuse(next)) { /* consolidate forward */
if (next == fm->top) {
size_t tsize = fm->topsize += psize;
fm->top = p;
p->head = tsize | PINUSE_BIT;
if (p == fm->dv) {
fm->dv = 0;
fm->dvsize = 0;
}
if (should_trim(fm, tsize))
sys_trim(fm, 0);
goto postaction;
}
else if (next == fm->dv) {
size_t dsize = fm->dvsize += psize;
fm->dv = p;
set_size_and_pinuse_of_free_chunk(p, dsize);
goto postaction;
}
else {
size_t nsize = chunksize(next);
psize += nsize;
unlink_chunk(fm, next, nsize);
set_size_and_pinuse_of_free_chunk(p, psize);
if (p == fm->dv) {
fm->dvsize = psize;
goto postaction;
}
}
}
else
set_free_with_pinuse(p, psize, next);
if (is_small(psize)) {
insert_small_chunk(fm, p, psize);
check_free_chunk(fm, p);
}
else {
tchunkptr tp = (tchunkptr)p;
insert_large_chunk(fm, tp, psize);
check_free_chunk(fm, p);
if (--fm->release_checks == 0)
release_unused_segments(fm);
}
goto postaction;
}
}
erroraction:
USAGE_ERROR_ACTION(fm, p);
postaction:
POSTACTION(fm);
}
}
// LEAVE();
#if !FOOTERS
#undef fm
#endif /* FOOTERS */
}
View Git Blame Copy Permalink