forked from KolibriOS/kolibrios
126 lines
4.1 KiB
PHP
126 lines
4.1 KiB
PHP
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;; ;;
|
|
;; Copyright (C) KolibriOS team 2013-2022. All rights reserved. ;;
|
|
;; Distributed under terms of the GNU General Public License ;;
|
|
;; ;;
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
$Revision$
|
|
|
|
; Memory management for slab structures.
|
|
; The allocator meets special requirements:
|
|
; * memory blocks are properly aligned
|
|
; * memory blocks do not cross page boundary
|
|
; The allocator manages fixed-size blocks.
|
|
; Thus, the specific allocator works as follows:
|
|
; allocate one page, split into blocks, maintain the single-linked
|
|
; list of all free blocks in each page.
|
|
|
|
; Note: size must be a multiple of required alignment.
|
|
|
|
; Data for one pool: dd pointer to the first page, MUTEX lock.
|
|
|
|
; Allocator for fixed-size blocks: allocate a block.
|
|
; [ebx-4] = pointer to the first page, ebx = pointer to MUTEX structure.
|
|
proc slab_alloc
|
|
push edi ; save used register to be stdcall
|
|
virtual at esp
|
|
dd ? ; saved edi
|
|
dd ? ; return address
|
|
.size dd ?
|
|
end virtual
|
|
; 1. Take the lock.
|
|
mov ecx, ebx
|
|
call mutex_lock
|
|
; 2. Find the first allocated page with a free block, if any.
|
|
; 2a. Initialize for the loop.
|
|
mov edx, ebx
|
|
.pageloop:
|
|
; 2b. Get the next page, keeping the current in eax.
|
|
mov eax, edx
|
|
mov edx, [edx-4]
|
|
; 2c. If there is no next page, we're out of luck; go to 4.
|
|
test edx, edx
|
|
jz .newpage
|
|
add edx, 0x1000
|
|
@@:
|
|
; 2d. Get the pointer to the first free block on this page.
|
|
; If there is no free block, continue to 2b.
|
|
mov eax, [edx-8]
|
|
test eax, eax
|
|
jz .pageloop
|
|
; 2e. Get the pointer to the next free block.
|
|
mov ecx, [eax]
|
|
; 2f. Update the pointer to the first free block from eax to ecx.
|
|
; Normally [edx-8] still contains eax, if so, atomically set it to ecx
|
|
; and proceed to 3.
|
|
; However, the price of simplicity of slab_free (in particular, it doesn't take
|
|
; the lock) is that [edx-8] could (rarely) be changed while we processed steps
|
|
; 2d+2e. If so, return to 2d and retry.
|
|
lock cmpxchg [edx-8], ecx
|
|
jnz @b
|
|
.return:
|
|
; 3. Release the lock taken in step 1 and return.
|
|
push eax
|
|
mov ecx, ebx
|
|
call mutex_unlock
|
|
pop eax
|
|
pop edi ; restore used register to be stdcall
|
|
ret 4
|
|
.newpage:
|
|
; 4. Allocate a new page.
|
|
push eax
|
|
stdcall kernel_alloc, 0x1000
|
|
pop edx
|
|
; If failed, say something to the debug board and return zero.
|
|
test eax, eax
|
|
jz .nomemory
|
|
; 5. Add the new page to the tail of list of allocated pages.
|
|
mov [edx-4], eax
|
|
; 6. Initialize two service dwords in the end of page:
|
|
; first free block is (start of page) + (block size)
|
|
; (we will return first block at (start of page), so consider it allocated),
|
|
; no next page.
|
|
mov edx, eax
|
|
lea edi, [eax+0x1000-8]
|
|
add edx, [.size]
|
|
mov [edi], edx
|
|
and dword [edi+4], 0
|
|
; 7. All blocks starting from edx are free; join them in a single-linked list.
|
|
@@:
|
|
mov ecx, edx
|
|
add edx, [.size]
|
|
mov [ecx], edx
|
|
cmp edx, edi
|
|
jbe @b
|
|
sub ecx, [.size]
|
|
and dword [ecx], 0
|
|
; 8. Return (start of page).
|
|
jmp .return
|
|
.nomemory:
|
|
dbgstr 'no memory for slab allocation'
|
|
xor eax, eax
|
|
jmp .return
|
|
endp
|
|
|
|
; Allocator for fixed-size blocks: free a block.
|
|
proc slab_free
|
|
push ecx edx
|
|
virtual at esp
|
|
rd 2 ; saved registers
|
|
dd ? ; return address
|
|
.block dd ?
|
|
end virtual
|
|
; Insert the given block to the head of free blocks in this page.
|
|
mov ecx, [.block]
|
|
mov edx, ecx
|
|
or edx, 0xFFF
|
|
@@:
|
|
mov eax, [edx+1-8]
|
|
mov [ecx], eax
|
|
lock cmpxchg [edx+1-8], ecx
|
|
jnz @b
|
|
pop edx ecx
|
|
ret 4
|
|
endp
|