diff --git a/.gitignore b/.gitignore
index b9bf3c8..d7b4461 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,4 @@ mkfilepattern
 *.img.lz4
 *.img.info
 t_*.out
+.gdb_history
diff --git a/GPL2.txt b/GPL2.txt
new file mode 100644
index 0000000..d159169
--- /dev/null
+++ b/GPL2.txt
@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+    a) Accompany it with the complete corresponding machine-readable
+    source code, which must be distributed under the terms of Sections
+    1 and 2 above on a medium customarily used for software interchange; or,
+
+    b) Accompany it with a written offer, valid for at least three
+    years, to give any third party, for a charge no more than your
+    cost of physically performing source distribution, a complete
+    machine-readable copy of the corresponding source code, to be
+    distributed under the terms of Sections 1 and 2 above on a medium
+    customarily used for software interchange; or,
+
+    c) Accompany it with the information you received as to the offer
+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
+    received the program in object code or executable form with such
+    an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it.  For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
+control compilation and installation of the executable.  However, as a
+special exception, the source code distributed need not include
+anything that is normally distributed (in either source or binary
+form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component
+itself accompanies the executable.
+
+If distribution of executable or object code is made by offering
+access to copy from a designated place, then offering equivalent
+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices.  Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission.  For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+                            NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/GPL3.txt b/GPL3.txt
new file mode 100644
index 0000000..f288702
--- /dev/null
+++ b/GPL3.txt
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+  The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works.  By contrast,
+the GNU General Public License is intended to guarantee your freedom to
+share and change all versions of a program--to make sure it remains free
+software for all its users.  We, the Free Software Foundation, use the
+GNU General Public License for most of our software; it applies also to
+any other work released this way by its authors.  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
+free programs, and that you know you can do these things.
+
+  To protect your rights, we need to prevent others from denying you
+these rights or asking you to surrender the rights.  Therefore, you have
+certain responsibilities if you distribute copies of the software, or if
+you modify it: responsibilities to respect the freedom of others.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must pass on to the recipients the same
+freedoms that you received.  You must make sure that they, too, receive
+or can get the source code.  And you must show them these terms so they
+know their rights.
+
+  Developers that use the GNU GPL protect your rights with two steps:
+(1) assert copyright on the software, and (2) offer you this License
+giving you legal permission to copy, distribute and/or modify it.
+
+  For the developers' and authors' protection, the GPL clearly explains
+that there is no warranty for this free software.  For both users' and
+authors' sake, the GPL requires that modified versions be marked as
+changed, so that their problems will not be attributed erroneously to
+authors of previous versions.
+
+  Some devices are designed to deny users access to install or run
+modified versions of the software inside them, although the manufacturer
+can do so.  This is fundamentally incompatible with the aim of
+protecting users' freedom to change the software.  The systematic
+pattern of such abuse occurs in the area of products for individuals to
+use, which is precisely where it is most unacceptable.  Therefore, we
+have designed this version of the GPL to prohibit the practice for those
+products.  If such problems arise substantially in other domains, we
+stand ready to extend this provision to those domains in future versions
+of the GPL, as needed to protect the freedom of users.
+
+  Finally, every program is threatened constantly by software patents.
+States should not allow patents to restrict development and use of
+software on general-purpose computers, but in those that do, we wish to
+avoid the special danger that patents applied to a free program could
+make it effectively proprietary.  To prevent this, the GPL assures that
+patents cannot be used to render the program non-free.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                       TERMS AND CONDITIONS
+
+  0. Definitions.
+
+  "This License" refers to version 3 of the GNU General Public License.
+
+  "Copyright" also means copyright-like laws that apply to other kinds of
+works, such as semiconductor masks.
+
+  "The Program" refers to any copyrightable work licensed under this
+License.  Each licensee is addressed as "you".  "Licensees" and
+"recipients" may be individuals or organizations.
+
+  To "modify" a work means to copy from or adapt all or part of the work
+in a fashion requiring copyright permission, other than the making of an
+exact copy.  The resulting work is called a "modified version" of the
+earlier work or a work "based on" the earlier work.
+
+  A "covered work" means either the unmodified Program or a work based
+on the Program.
+
+  To "propagate" a work means to do anything with it that, without
+permission, would make you directly or secondarily liable for
+infringement under applicable copyright law, except executing it on a
+computer or modifying a private copy.  Propagation includes copying,
+distribution (with or without modification), making available to the
+public, and in some countries other activities as well.
+
+  To "convey" a work means any kind of propagation that enables other
+parties to make or receive copies.  Mere interaction with a user through
+a computer network, with no transfer of a copy, is not conveying.
+
+  An interactive user interface displays "Appropriate Legal Notices"
+to the extent that it includes a convenient and prominently visible
+feature that (1) displays an appropriate copyright notice, and (2)
+tells the user that there is no warranty for the work (except to the
+extent that warranties are provided), that licensees may convey the
+work under this License, and how to view a copy of this License.  If
+the interface presents a list of user commands or options, such as a
+menu, a prominent item in the list meets this criterion.
+
+  1. Source Code.
+
+  The "source code" for a work means the preferred form of the work
+for making modifications to it.  "Object code" means any non-source
+form of a work.
+
+  A "Standard Interface" means an interface that either is an official
+standard defined by a recognized standards body, or, in the case of
+interfaces specified for a particular programming language, one that
+is widely used among developers working in that language.
+
+  The "System Libraries" of an executable work include anything, other
+than the work as a whole, that (a) is included in the normal form of
+packaging a Major Component, but which is not part of that Major
+Component, and (b) serves only to enable use of the work with that
+Major Component, or to implement a Standard Interface for which an
+implementation is available to the public in source code form.  A
+"Major Component", in this context, means a major essential component
+(kernel, window system, and so on) of the specific operating system
+(if any) on which the executable work runs, or a compiler used to
+produce the work, or an object code interpreter used to run it.
+
+  The "Corresponding Source" for a work in object code form means all
+the source code needed to generate, install, and (for an executable
+work) run the object code and to modify the work, including scripts to
+control those activities.  However, it does not include the work's
+System Libraries, or general-purpose tools or generally available free
+programs which are used unmodified in performing those activities but
+which are not part of the work.  For example, Corresponding Source
+includes interface definition files associated with source files for
+the work, and the source code for shared libraries and dynamically
+linked subprograms that the work is specifically designed to require,
+such as by intimate data communication or control flow between those
+subprograms and other parts of the work.
+
+  The Corresponding Source need not include anything that users
+can regenerate automatically from other parts of the Corresponding
+Source.
+
+  The Corresponding Source for a work in source code form is that
+same work.
+
+  2. Basic Permissions.
+
+  All rights granted under this License are granted for the term of
+copyright on the Program, and are irrevocable provided the stated
+conditions are met.  This License explicitly affirms your unlimited
+permission to run the unmodified Program.  The output from running a
+covered work is covered by this License only if the output, given its
+content, constitutes a covered work.  This License acknowledges your
+rights of fair use or other equivalent, as provided by copyright law.
+
+  You may make, run and propagate covered works that you do not
+convey, without conditions so long as your license otherwise remains
+in force.  You may convey covered works to others for the sole purpose
+of having them make modifications exclusively for you, or provide you
+with facilities for running those works, provided that you comply with
+the terms of this License in conveying all material for which you do
+not control copyright.  Those thus making or running the covered works
+for you must do so exclusively on your behalf, under your direction
+and control, on terms that prohibit them from making any copies of
+your copyrighted material outside their relationship with you.
+
+  Conveying under any other circumstances is permitted solely under
+the conditions stated below.  Sublicensing is not allowed; section 10
+makes it unnecessary.
+
+  3. Protecting Users' Legal Rights From Anti-Circumvention Law.
+
+  No covered work shall be deemed part of an effective technological
+measure under any applicable law fulfilling obligations under article
+11 of the WIPO copyright treaty adopted on 20 December 1996, or
+similar laws prohibiting or restricting circumvention of such
+measures.
+
+  When you convey a covered work, you waive any legal power to forbid
+circumvention of technological measures to the extent such circumvention
+is effected by exercising rights under this License with respect to
+the covered work, and you disclaim any intention to limit operation or
+modification of the work as a means of enforcing, against the work's
+users, your or third parties' legal rights to forbid circumvention of
+technological measures.
+
+  4. Conveying Verbatim Copies.
+
+  You may convey verbatim copies of the Program's source code as you
+receive it, in any medium, provided that you conspicuously and
+appropriately publish on each copy an appropriate copyright notice;
+keep intact all notices stating that this License and any
+non-permissive terms added in accord with section 7 apply to the code;
+keep intact all notices of the absence of any warranty; and give all
+recipients a copy of this License along with the Program.
+
+  You may charge any price or no price for each copy that you convey,
+and you may offer support or warranty protection for a fee.
+
+  5. Conveying Modified Source Versions.
+
+  You may convey a work based on the Program, or the modifications to
+produce it from the Program, in the form of source code under the
+terms of section 4, provided that you also meet all of these conditions:
+
+    a) The work must carry prominent notices stating that you modified
+    it, and giving a relevant date.
+
+    b) The work must carry prominent notices stating that it is
+    released under this License and any conditions added under section
+    7.  This requirement modifies the requirement in section 4 to
+    "keep intact all notices".
+
+    c) You must license the entire work, as a whole, under this
+    License to anyone who comes into possession of a copy.  This
+    License will therefore apply, along with any applicable section 7
+    additional terms, to the whole of the work, and all its parts,
+    regardless of how they are packaged.  This License gives no
+    permission to license the work in any other way, but it does not
+    invalidate such permission if you have separately received it.
+
+    d) If the work has interactive user interfaces, each must display
+    Appropriate Legal Notices; however, if the Program has interactive
+    interfaces that do not display Appropriate Legal Notices, your
+    work need not make them do so.
+
+  A compilation of a covered work with other separate and independent
+works, which are not by their nature extensions of the covered work,
+and which are not combined with it such as to form a larger program,
+in or on a volume of a storage or distribution medium, is called an
+"aggregate" if the compilation and its resulting copyright are not
+used to limit the access or legal rights of the compilation's users
+beyond what the individual works permit.  Inclusion of a covered work
+in an aggregate does not cause this License to apply to the other
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+                     END OF TERMS AND CONDITIONS
+
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+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
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+
+The hypothetical commands `show w' and `show c' should show the appropriate
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+might be different; for a GUI interface, you would use an "about box".
+
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+if any, to sign a "copyright disclaimer" for the program, if necessary.
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+<https://www.gnu.org/licenses/>.
+
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+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
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diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..7e20d5d
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1 @@
+GPL-2.0-or-later
diff --git a/img/makefile b/img/makefile
index a801271..85bf9ad 100644
--- a/img/makefile
+++ b/img/makefile
@@ -3,10 +3,11 @@ MKFILEPATTERN=../tools/mkfilepattern
 LOOP_DEV=/dev/loop8
 TEMP_DIR:=$(shell mktemp -d)
 
-all: s512_xfs_v4_ftype0.img s512_xfs_v4_ftype1.img s512_xfs_v4_ftype0_xattr.img s512_xfs_v4_files.img s512_xfs_v4_ftype1_btree_dirs.img
+all: s512_xfs_v4_ftype0.img s512_xfs_v4_ftype0_b4k_n2b.img s512_xfs_v4_ftype1.img s512_xfs_v4_ftype0_xattr.img s512_xfs_v4_files.img s512_xfs_v4_files_b4k_n2b.img s512_xfs_v4_ftype1_btree_dirs.img
 
 s512_xfs_v4_ftype0.img:
-	dd if=/dev/zero of=$@ bs=1M count=64
+#	dd if=/dev/zero of=$@ bs=1M count=64
+	fallocate -l 64MiB $@
 	parted --script $@ mktable gpt
 	parted --script --align optimal $@ mkpart primary 1MiB 100%
 	sudo losetup $(LOOP_DEV) --partscan $@
@@ -32,8 +33,37 @@ s512_xfs_v4_ftype0.img:
 	sudo umount $(TEMP_DIR)
 	sudo losetup -d $(LOOP_DEV)
 
+s512_xfs_v4_ftype0_b4k_n2b.img:
+#	dd if=/dev/zero of=$@ bs=1M count=64
+	fallocate -l 64MiB $@
+	parted --script $@ mktable gpt
+	parted --script --align optimal $@ mkpart primary 1MiB 100%
+	sudo losetup $(LOOP_DEV) --partscan $@
+	sudo mkfs.xfs -b size=4k -m crc=0,finobt=0,rmapbt=0,reflink=0 -d sectsize=512 -i maxpct=100 -n size=2b,ftype=0 $(LOOP_DEV)p1
+	sudo mount $(LOOP_DEV)p1 $(TEMP_DIR)
+	sudo chown $(shell whoami) $(TEMP_DIR) -R
+#
+	mkdir $(TEMP_DIR)/sf
+	$(MKDIRRANGE) $(TEMP_DIR)/sf 3
+#
+	mkdir $(TEMP_DIR)/block
+	$(MKDIRRANGE) $(TEMP_DIR)/block 20
+#
+	mkdir $(TEMP_DIR)/leaf
+	$(MKDIRRANGE) $(TEMP_DIR)/leaf 70
+#
+	mkdir $(TEMP_DIR)/node
+	$(MKDIRRANGE) $(TEMP_DIR)/node 520
+#
+	mkdir $(TEMP_DIR)/btree
+	$(MKDIRRANGE) $(TEMP_DIR)/btree 600
+
+	sudo umount $(TEMP_DIR)
+	sudo losetup -d $(LOOP_DEV)
+
 s512_xfs_v4_ftype1.img:
-	dd if=/dev/zero of=$@ bs=1M count=64
+#	dd if=/dev/zero of=$@ bs=1M count=64
+	fallocate -l 64MiB $@
 	parted --script $@ mktable gpt
 	parted --script --align optimal $@ mkpart primary 1MiB 100%
 	sudo losetup $(LOOP_DEV) --partscan $@
@@ -60,7 +90,8 @@ s512_xfs_v4_ftype1.img:
 	sudo losetup -d $(LOOP_DEV)
 
 s512_xfs_v4_ftype0_xattr.img:
-	dd if=/dev/zero of=$@ bs=1M count=64
+#	dd if=/dev/zero of=$@ bs=1M count=64
+	fallocate -l 64MiB $@
 	parted --script $@ mktable gpt
 	parted --script --align optimal $@ mkpart primary 1MiB 100%
 	sudo losetup $(LOOP_DEV) --partscan $@
@@ -83,12 +114,29 @@ s512_xfs_v4_ftype0_xattr.img:
 	sudo umount $(TEMP_DIR)
 	sudo losetup -d $(LOOP_DEV)
 
-s512_xfs_v4_files.img:
-	dd if=/dev/zero of=$@ bs=1M count=64
+s512_xfs_v4_ftype1_btree_dirs.img:
+#	dd if=/dev/zero of=$@ bs=1M count=128
+	fallocate -l 128MiB $@
 	parted --script $@ mktable gpt
 	parted --script --align optimal $@ mkpart primary 1MiB 100%
 	sudo losetup $(LOOP_DEV) --partscan $@
-	sudo mkfs.xfs -m crc=0,finobt=0,rmapbt=0,reflink=0 -d sectsize=512 -i maxpct=100 -n ftype=0 $(LOOP_DEV)p1
+	sudo mkfs.xfs -m crc=0,finobt=0,rmapbt=0,reflink=0 -d sectsize=512 -i maxpct=100 -n ftype=1 $(LOOP_DEV)p1
+	sudo mount $(LOOP_DEV)p1 $(TEMP_DIR)
+	sudo chown $(shell whoami) $(TEMP_DIR) -R
+#
+	mkdir $(TEMP_DIR)/btree
+	$(MKDIRRANGE) $(TEMP_DIR)/btree 293181
+
+	sudo umount $(TEMP_DIR)
+	sudo losetup -d $(LOOP_DEV)
+
+s512_xfs_v4_files.img:
+#	dd if=/dev/zero of=$@ bs=1M count=128000
+	fallocate -l 128MiB $@
+	parted --script $@ mktable gpt
+	parted --script --align optimal $@ mkpart primary 1MiB 100%
+	sudo losetup $(LOOP_DEV) --partscan $@
+	sudo mkfs.xfs -m crc=0,finobt=0,rmapbt=0,reflink=0 -d sectsize=512 -n ftype=0 $(LOOP_DEV)p1
 	sudo mount $(LOOP_DEV)p1 $(TEMP_DIR)
 	sudo chown $(shell whoami) $(TEMP_DIR) -R
 #
@@ -102,21 +150,53 @@ s512_xfs_v4_files.img:
 #
 	$(MKFILEPATTERN) $(TEMP_DIR)/hole_end 65536
 	fallocate -p -o 49152 -l 16384 $(TEMP_DIR)/hole_end
+#
+#	fallocate -l 120GiB $(TEMP_DIR)/btree_l1_no_hole
+	fallocate -l 4KiB $(TEMP_DIR)/btree_l1_no_hole
+#	$(MKFILEPATTERN) $(TEMP_DIR)/btree_l1_no_hole 2097152
+#		fallocate -c -l 64KiB -o  $$((64*$$n))KiB $(TEMP_DIR)/btree_l1_no_hole ; \
+#	dd if=/dev/zero of=$(TEMP_DIR)/btree_l1_no_hole bs=1M count=128
+	for n in $$(seq 1 2000); do \
+		fallocate -i -l 4KiB -o 0KiB $(TEMP_DIR)/btree_l1_no_hole ; \
+		fallocate -z -l 4KiB -o 0KiB $(TEMP_DIR)/btree_l1_no_hole ; \
+	done
+#	$(MKFILEPATTERN) $(TEMP_DIR)/btree_l1_no_hole 134217728
 #
 	sudo umount $(TEMP_DIR)
 	sudo losetup -d $(LOOP_DEV)
 
-s512_xfs_v4_ftype1_btree_dirs.img:
-	dd if=/dev/zero of=$@ bs=1M count=128
+s512_xfs_v4_files_b4k_n2b.img:
+#	dd if=/dev/zero of=$@ bs=1M count=128000
+	fallocate -l 128MiB $@
 	parted --script $@ mktable gpt
 	parted --script --align optimal $@ mkpart primary 1MiB 100%
 	sudo losetup $(LOOP_DEV) --partscan $@
-	sudo mkfs.xfs -m crc=0,finobt=0,rmapbt=0,reflink=0 -d sectsize=512 -i maxpct=100 -n ftype=1 $(LOOP_DEV)p1
+	sudo mkfs.xfs -b size=4k -m crc=0,finobt=0,rmapbt=0,reflink=0 -d sectsize=512 -n size=2b,ftype=0 $(LOOP_DEV)p1
 	sudo mount $(LOOP_DEV)p1 $(TEMP_DIR)
 	sudo chown $(shell whoami) $(TEMP_DIR) -R
 #
-	mkdir $(TEMP_DIR)/btree
-	$(MKDIRRANGE) $(TEMP_DIR)/btree 293181
-
+	$(MKFILEPATTERN) $(TEMP_DIR)/no_hole 65536
+#
+	$(MKFILEPATTERN) $(TEMP_DIR)/hole_begin 65536
+	fallocate -p -o 0 -l 16384 $(TEMP_DIR)/hole_begin
+#
+	$(MKFILEPATTERN) $(TEMP_DIR)/hole_middle 65536
+	fallocate -p -o 32768 -l 16384 $(TEMP_DIR)/hole_middle
+#
+	$(MKFILEPATTERN) $(TEMP_DIR)/hole_end 65536
+	fallocate -p -o 49152 -l 16384 $(TEMP_DIR)/hole_end
+#
+#	fallocate -l 120GiB $(TEMP_DIR)/btree_l1_no_hole
+	fallocate -l 4KiB $(TEMP_DIR)/btree_l1_no_hole
+#	$(MKFILEPATTERN) $(TEMP_DIR)/btree_l1_no_hole 2097152
+#		fallocate -c -l 64KiB -o  $$((64*$$n))KiB $(TEMP_DIR)/btree_l1_no_hole ; \
+#	dd if=/dev/zero of=$(TEMP_DIR)/btree_l1_no_hole bs=1M count=128
+	for n in $$(seq 1 2000); do \
+		fallocate -i -l 4KiB -o 0KiB $(TEMP_DIR)/btree_l1_no_hole ; \
+		fallocate -z -l 4KiB -o 0KiB $(TEMP_DIR)/btree_l1_no_hole ; \
+	done
+#	$(MKFILEPATTERN) $(TEMP_DIR)/btree_l1_no_hole 134217728
+#
 	sudo umount $(TEMP_DIR)
 	sudo losetup -d $(LOOP_DEV)
+
diff --git a/kofu.c b/kofu.c
index ab94df0..f9141d9 100644
--- a/kofu.c
+++ b/kofu.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <stdio.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -11,6 +12,7 @@
 #include <fcntl.h>
 #include <assert.h>
 #include "kolibri.h"
+#include "trace.h"
 
 #define FGETS_BUF_LEN 4096
 #define MAX_COMMAND_ARGS 42
@@ -213,6 +215,7 @@ int main(int argc, char **argv) {
     int fd = open(argv[1], O_RDONLY);
     struct stat st;
     fstat(fd, &st);
+    trace_begin();
     if (!kos_fuse_init(fd, st.st_size / 512, 512)) {
         exit(1);
     }
@@ -237,5 +240,7 @@ int main(int argc, char **argv) {
             printf("unknown command: %s\n", arg[0]);
         }
     }
+
+    trace_end();
     return 0;
 }
diff --git a/kofuse.c b/kofuse.c
index 12ced3b..b4833e2 100644
--- a/kofuse.c
+++ b/kofuse.c
@@ -1,3 +1,21 @@
+/*
+    Kofuse: KolibriOS kernel FS code as FUSE in Linux
+    Copyright (C) 2018  Ivan Baravy <dunkaist@gmail.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #define FUSE_USE_VERSION 31
 
 #include <fuse.h>
diff --git a/kolibri.asm b/kolibri.asm
index 931037e..eb4db0b 100644
--- a/kolibri.asm
+++ b/kolibri.asm
@@ -9,6 +9,19 @@ _malloc fix malloc
 extrn free
 free fix __free
 _free fix free
+
+macro coverage_magic_instruction {
+        nop
+        int3
+}
+
+purge section,mov,add,sub
+purge section,mov,add,sub
+section '.text' executable align 16
+
+coverage_begin:
+public coverage_begin
+
 include 'macros.inc'
 include 'proc32.inc'
 include 'struct.inc'
@@ -26,8 +39,35 @@ struct FILE_DISK
   Logical dd ?  ; sector size
 ends
 
-purge section,mov,add,sub
-section '.text' executable align 16
+public set_eflags_tf
+set_eflags_tf:
+        pushfd
+        pop     eax
+        mov     ecx, [esp + 4]
+        and     ecx, 1
+        shl     ecx, 8  ; TF
+        and     eax, NOT (1 SHL 8)
+        or      eax, ecx
+        push    eax
+        popfd
+        ret
+
+public get_lwp_event_size
+get_lwp_event_size:
+        mov     eax, 0x80000001
+        cpuid
+        bt      ecx, 15
+        jnc     .no_lwp
+        mov     eax, 0x8000001c
+        cpuid
+        and     eax, 1001b
+        cmp     eax, 1001b
+        jnz     .no_lwp
+        movzx   eax, bh
+        ret
+  .no_lwp:
+        xor     eax, eax
+        ret
 
 ;uint32_t kos_time_to_epoch(uint8_t *time);
 public kos_time_to_epoch
@@ -47,7 +87,14 @@ public kos_fuse_init
 kos_fuse_init:
         push    ebx esi edi ebp
 
-        mov     [pg_data.pages_free], (128*1024*1024)/0x1000
+;DEBUGF 1, "coverage begin: 0x%x\n", coverage_begin
+;DEBUGF 1, "xfs_create_partition: 0x%x\n", xfs_create_partition
+;DEBUGF 1, "coverage end: 0x%x\n", coverage_end
+
+        MEMORY_BYTES = 128 SHL 20
+        mov     [pg_data.mem_amount], MEMORY_BYTES
+        mov     [pg_data.pages_count], MEMORY_BYTES / PAGE_SIZE
+        mov     [pg_data.pages_free], MEMORY_BYTES / PAGE_SIZE
 
         mov     eax, [esp + 0x14]
         mov     [file_disk.fd], eax
@@ -66,6 +113,7 @@ kos_fuse_init:
 
 
 public kos_fuse_lfn
+;proc kos_fuse_lfn c, _blah1, _blah2
 kos_fuse_lfn:
         push    ebx
         mov     ebx, [esp + 8]
@@ -77,6 +125,7 @@ kos_fuse_lfn:
         mov     [ecx + 4], ebx
         pop     ebx
         ret
+;endp
 
 
 proc disk_read stdcall, userdata, buffer, startsector:qword, numsectors
@@ -274,6 +323,9 @@ mutex_lock:
 mutex_unlock:
         ret
 
+coverage_end:
+public coverage_end
+
 
 section '.data' writeable align 16
 include_debug_strings
diff --git a/kolibri.h b/kolibri.h
index 04668cf..9d4412b 100644
--- a/kolibri.h
+++ b/kolibri.h
@@ -92,4 +92,9 @@ uint32_t kos_time_to_epoch(uint32_t *time);
 void *kos_fuse_init(int fd, uint32_t sect_cnt, uint32_t sect_sz);
 void kos_fuse_lfn(void *f70arg, f70ret *r);
 
+void set_eflags_tf(int x);
+void coverage_begin(void);
+void coverage_end(void);
+uint32_t get_lwp_event_size(void);
+
 #endif
diff --git a/makefile b/makefile
index e6405ad..3ca7c3e 100644
--- a/makefile
+++ b/makefile
@@ -5,16 +5,31 @@ CFLAGS_32=-m32 -D_FILE_OFFSET_BITS=64
 LDFLAGS=
 LDFLAGS_32=-m32
 
-all: kofu kofuse tools/mkdirrange tools/mkfilepattern
+all: kofu kofuse kolibri.sym kolibri.lst tools/mkdirrange tools/mkfilepattern
 
-kofu: kofu.o kolibri.o
-	$(CC) $(LDFLAGS) $(LDFLAGS_32) $^ -o $@
+kofu: kofu.o kolibri.o trace.o trace_lbr.o trace_lwp.o
+	$(CC) $(LDFLAGS) $(LDFLAGS_32) $^ -o $@ -static
 
 kofuse: kofuse.o kolibri.o
 	$(CC) $(LDFLAGS) $(LDFLAGS_32) $^ -o $@ `pkg-config fuse3 --libs`
 
-kolibri.o: kolibri.asm kolibri.h
-	INCLUDE="$(KOLIBRI_TRUNK)" $(FASM) $< $@
+kolibri.o kolibri.fas: kolibri.asm kolibri.h
+	INCLUDE="$(KOLIBRI_TRUNK)" $(FASM) $< $@ -s kolibri.fas
+
+kolibri.sym: kolibri.fas
+	symbols kolibri.fas kolibri.sym
+
+kolibri.lst: kolibri.fas
+	listing kolibri.fas kolibri.lst
+
+trace.o: trace.c trace.h trace_lbr.h
+	$(CC) $(CFLAGS) $(CFLAGS_32) -c $<
+
+trace_lbr.o: trace_lbr.c trace_lbr.h kolibri.h
+	$(CC) $(CFLAGS) $(CFLAGS_32) -c $<
+
+trace_lwp.o: trace_lwp.c trace_lwp.h kolibri.h
+	$(CC) $(CFLAGS) $(CFLAGS_32) -c $<
 
 kofu.o: kofu.c kolibri.h
 	$(CC) $(CFLAGS) $(CFLAGS_32) -c $<
@@ -31,5 +46,5 @@ tools/mkfilepattern: tools/mkfilepattern.c
 .PHONY: all clean
 
 clean:
-	rm -f *.o kofu kofuse tools/mkdirrange tools/mkfilepattern
+	rm -f *.o kofu kofuse kolibri.fas kolibri.sym kolibri.lst coverage tools/mkdirrange tools/mkfilepattern
 
diff --git a/test/makefile b/test/makefile
index 104056f..7eec74f 100644
--- a/test/makefile
+++ b/test/makefile
@@ -1,7 +1,7 @@
 KOFU=../kofu
 
-all:    t_000_ls_all_dir_types_ftype0 t_001_ls_all_dir_types_ftype1
-.PHONY: t_000_ls_all_dir_types_ftype0 t_001_ls_all_dir_types_ftype1
+all:    t_000_ls_all_dir_types_ftype0 t_001_ls_all_dir_types_ftype1 t_002_ls_all_dir_types_ftype0_b4k_n2b
+.PHONY: t_000_ls_all_dir_types_ftype0 t_001_ls_all_dir_types_ftype1 t_002_ls_all_dir_types_ftype0_b4k_n2b
 
 t_000_ls_all_dir_types_ftype0:
 	$(KOFU) ../img/s512_xfs_v4_ftype0.img < $@ > $@.out
@@ -10,3 +10,7 @@ t_000_ls_all_dir_types_ftype0:
 t_001_ls_all_dir_types_ftype1:
 	$(KOFU) ../img/s512_xfs_v4_ftype1.img < $@ > $@.out
 	cmp $@.ref $@.out
+
+t_002_ls_all_dir_types_ftype0_b4k_n2b:
+	$(KOFU) ../img/s512_xfs_v4_ftype0_b4k_n2b.img < $@ > $@.out
+	cmp $@.ref $@.out
diff --git a/tools/mkfilepattern.c b/tools/mkfilepattern.c
index ec4373d..226a97e 100644
--- a/tools/mkfilepattern.c
+++ b/tools/mkfilepattern.c
@@ -1,6 +1,8 @@
 #include <stdio.h>
 #include <stdint.h>
+#include <inttypes.h>
 #include <stdlib.h>
+#include <stddef.h>
 #include <unistd.h>
 #include <errno.h>
 #include <sys/types.h>
@@ -13,14 +15,14 @@
 int main(int argc, char *argv[])
 {
     uint8_t buf[BUF_LEN + 7];
-    unsigned len;
+    int64_t len;
     char *path;
     if (argc != 3) {
         fprintf(stderr, "mkfilepattern filename size\n");
         exit(1);
     } else {
         path = argv[1];
-        sscanf(argv[2], "%u", &len);
+        sscanf(argv[2], "%" SCNi64, &len);
     }
 
     int fd = open(path, O_CREAT | O_LARGEFILE | O_WRONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
@@ -29,7 +31,7 @@ int main(int argc, char *argv[])
         exit(1);
     }
 
-    for (unsigned pos = 0, count = BUF_LEN; pos < len; pos += count) {
+    for (int64_t pos = 0, count = BUF_LEN; pos < len; pos += count) {
         if (count > len - pos) {
             count = len - pos;
         }
diff --git a/trace.c b/trace.c
new file mode 100644
index 0000000..59876a9
--- /dev/null
+++ b/trace.c
@@ -0,0 +1,19 @@
+#include "trace_lbr.h"
+#include "trace_lwp.h"
+#include "kolibri.h"
+
+void trace_begin() {
+    if (get_lwp_event_size() > 0) {
+        trace_lwp_begin();
+    } else {
+        trace_lbr_begin();
+    }
+}
+
+void trace_end() {
+    if (get_lwp_event_size() > 0) {
+        trace_lwp_end();
+    } else {
+        trace_lbr_end();
+    }
+}
diff --git a/trace.h b/trace.h
new file mode 100644
index 0000000..4456509
--- /dev/null
+++ b/trace.h
@@ -0,0 +1,7 @@
+#ifndef TRACE_H_INCLUDED
+#define TRACE_H_INCLUDED
+
+void trace_begin(void);
+void trace_end(void);
+
+#endif
diff --git a/trace_lbr.c b/trace_lbr.c
new file mode 100644
index 0000000..e6c98dd
--- /dev/null
+++ b/trace_lbr.c
@@ -0,0 +1,84 @@
+#define _GNU_SOURCE
+#include <stdint.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <sched.h>
+#include "kolibri.h"
+
+int covfd, msrfd;
+
+uint64_t rdmsr(uint32_t reg)
+{
+    uint64_t data;
+
+    if (pread(msrfd, &data, sizeof data, reg) != sizeof data) {
+        perror("rdmsr: pread");
+        exit(1);
+    }
+
+    return data;
+}
+
+void wrmsr(uint32_t reg, uint64_t data)
+{
+    int fd;
+    fd = open("/dev/cpu/0/msr", O_WRONLY);
+    if (fd < 0) {
+        perror("wrmsr: open");
+        exit(1);
+    }
+
+    if (pwrite(fd, &data, sizeof data, reg) != sizeof data) {
+        perror("wrmsr: pwrite");
+        exit(1);
+    }
+
+    close(fd);
+    return;
+}
+
+void handle_sigtrap() {
+    uint64_t from = rdmsr(0x1db);
+    uint64_t to = rdmsr(0x1dc);
+
+    if ((from >= (uintptr_t)coverage_begin && from < (uintptr_t)coverage_end) ||
+        (to >= (uintptr_t)coverage_begin && to < (uintptr_t)coverage_end)) {
+        write(covfd, &from, 8);
+        write(covfd, &to, 8);
+    }
+
+    wrmsr(0x1d9, 3);
+}
+
+void trace_lbr_begin() {
+    printf("hello from lbr!\n");
+    struct sigaction action;
+    action.sa_sigaction = &handle_sigtrap;
+    action.sa_flags = SA_SIGINFO;
+    sigaction(SIGTRAP, &action, NULL);
+
+    cpu_set_t my_set;
+    CPU_ZERO(&my_set);
+    CPU_SET(0, &my_set);
+    sched_setaffinity(0, sizeof(cpu_set_t), &my_set);
+    wrmsr(0x1d9, 3);
+    msrfd = open("/dev/cpu/0/msr", O_RDONLY);
+    if (msrfd < 0) {
+        perror("rdmsr: open");
+        exit(1);
+    }
+    covfd = open("coverage", O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
+    set_eflags_tf(1);
+}
+
+void trace_lbr_end() {
+    set_eflags_tf(0);
+    wrmsr(0x1d9, 0);
+    close(msrfd);
+    close(covfd);
+}
diff --git a/trace_lbr.h b/trace_lbr.h
new file mode 100644
index 0000000..a29a1e0
--- /dev/null
+++ b/trace_lbr.h
@@ -0,0 +1,7 @@
+#ifndef TRACE_LBR_H_INCLUDED
+#define TRACE_LBR_H_INCLUDED
+
+void trace_lbr_begin(void);
+void trace_lbr_end(void);
+
+#endif
diff --git a/trace_lwp.c b/trace_lwp.c
new file mode 100644
index 0000000..c048c1d
--- /dev/null
+++ b/trace_lwp.c
@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+void trace_lwp_begin() {
+    printf("hello from lwp!\n");
+}
+
+void trace_lwp_end() {
+}
diff --git a/trace_lwp.h b/trace_lwp.h
new file mode 100644
index 0000000..c6effae
--- /dev/null
+++ b/trace_lwp.h
@@ -0,0 +1,7 @@
+#ifndef TRACE_LWP_H_INCLUDED
+#define TRACE_LWP_H_INCLUDED
+
+void trace_lwp_begin(void);
+void trace_lwp_end(void);
+
+#endif