<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/scripts, branch v4.6-rc5</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>ASN.1: fix open failure check on headername</title>
<updated>2016-04-06T13:06:48+00:00</updated>
<author>
<name>Colin Ian King</name>
<email>colin.king@canonical.com</email>
</author>
<published>2016-04-06T13:06:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=952cca6a724c420a1efb6025e41862dfd2c1edc3'/>
<id>952cca6a724c420a1efb6025e41862dfd2c1edc3</id>
<content type='text'>
The check for a failed open on headername is incorrectly checking
on the out FILE pointer rather than the hdr. Fix this.

Signed-off-by: Colin Ian King &lt;colin.king@canonical.com&gt;
Signed-off-by: David Howells &lt;dhowells@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The check for a failed open on headername is incorrectly checking
on the out FILE pointer rather than the hdr. Fix this.

Signed-off-by: Colin Ian King &lt;colin.king@canonical.com&gt;
Signed-off-by: David Howells &lt;dhowells@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild</title>
<updated>2016-03-25T02:42:50+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2016-03-25T02:42:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=70c5eb84738cba88e08526fa14e06418cb2bd473'/>
<id>70c5eb84738cba88e08526fa14e06418cb2bd473</id>
<content type='text'>
Pull kbuild misc updates from Michal Marek:
 "The non-critical part of kbuild for v4.6-rc1:

   - coccinelle cleanup and a new patch
   - make tags rule for kprobe helpers
   - make rpm fix to avoid spurious grub2 entries
   - make rpm support for %postun script (Fedora only at the moment)"

* 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild/mkspec: clean boot loader configuration on rpm removal
  kbuild/mkspec: fix grub2 installkernel issue
  Coccinelle: Add api/setup_timer.cocci
  coccinelle: bugon: reduce rule applicability
  Coccinelle: pm_runtime: reduce rule applicability
  Coccinelle: array_size: reduce rule applicability
  Coccinelle: reduce rule applicability
  scripts/tags.sh: add regex to map kprobe helpers
  scripts/coccinelle: modernize &amp;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull kbuild misc updates from Michal Marek:
 "The non-critical part of kbuild for v4.6-rc1:

   - coccinelle cleanup and a new patch
   - make tags rule for kprobe helpers
   - make rpm fix to avoid spurious grub2 entries
   - make rpm support for %postun script (Fedora only at the moment)"

* 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild/mkspec: clean boot loader configuration on rpm removal
  kbuild/mkspec: fix grub2 installkernel issue
  Coccinelle: Add api/setup_timer.cocci
  coccinelle: bugon: reduce rule applicability
  Coccinelle: pm_runtime: reduce rule applicability
  Coccinelle: array_size: reduce rule applicability
  Coccinelle: reduce rule applicability
  scripts/tags.sh: add regex to map kprobe helpers
  scripts/coccinelle: modernize &amp;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'kconfig' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild</title>
<updated>2016-03-25T02:39:28+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2016-03-25T02:39:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=3a1ef0e03eee4c5ac30d19bb1b88e57924295810'/>
<id>3a1ef0e03eee4c5ac30d19bb1b88e57924295810</id>
<content type='text'>
Pull kconfig updates from Michal Marek:
 "Just two kconfig commits this time:

   - kconfig Makefile fix for make 3.80

   - Fix calculating symbols so that KCONFIG_ALLCONFIG=... does not
     disable CONFIG_MODULES silently"

* 'kconfig' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  unbreak allmodconfig KCONFIG_ALLCONFIG=...
  scripts/kconfig: allow building with make 3.80 again
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull kconfig updates from Michal Marek:
 "Just two kconfig commits this time:

   - kconfig Makefile fix for make 3.80

   - Fix calculating symbols so that KCONFIG_ALLCONFIG=... does not
     disable CONFIG_MODULES silently"

* 'kconfig' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  unbreak allmodconfig KCONFIG_ALLCONFIG=...
  scripts/kconfig: allow building with make 3.80 again
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild</title>
<updated>2016-03-25T02:26:47+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2016-03-25T02:26:47+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2162b80fcadf5b0afff08b540bd141f8a5ff5ed1'/>
<id>2162b80fcadf5b0afff08b540bd141f8a5ff5ed1</id>
<content type='text'>
Pull kbuild updates from Michal Marek:

 - make dtbs_install fix

 - Error handling fix fixdep and link-vmlinux.sh

 - __UNIQUE_ID fix for clang

 - Fix for if_changed_* to suppress the "is up to date." message

 - The kernel is built with -Werror=incompatible-pointer-types

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild: Add option to turn incompatible pointer check into error
  kbuild: suppress annoying "... is up to date." message
  kbuild: fixdep: Check fstat(2) return value
  scripts/link-vmlinux.sh: force error on kallsyms failure
  Kbuild: provide a __UNIQUE_ID for clang
  dtbsinstall: don't move target directory out of the way
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull kbuild updates from Michal Marek:

 - make dtbs_install fix

 - Error handling fix fixdep and link-vmlinux.sh

 - __UNIQUE_ID fix for clang

 - Fix for if_changed_* to suppress the "is up to date." message

 - The kernel is built with -Werror=incompatible-pointer-types

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild: Add option to turn incompatible pointer check into error
  kbuild: suppress annoying "... is up to date." message
  kbuild: fixdep: Check fstat(2) return value
  scripts/link-vmlinux.sh: force error on kallsyms failure
  Kbuild: provide a __UNIQUE_ID for clang
  dtbsinstall: don't move target directory out of the way
</pre>
</div>
</content>
</entry>
<entry>
<title>parisc: Use generic extable search and sort routines</title>
<updated>2016-03-23T15:00:46+00:00</updated>
<author>
<name>Helge Deller</name>
<email>deller@gmx.de</email>
</author>
<published>2016-03-23T15:00:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=0de798584bdedfdad19db21e3c7aec84f252f4f3'/>
<id>0de798584bdedfdad19db21e3c7aec84f252f4f3</id>
<content type='text'>
Switch to the generic extable search and sort routines which were introduced
with commit a272858 from Ard Biesheuvel. This saves quite some memory in the
vmlinux binary with the 64bit kernel.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Switch to the generic extable search and sort routines which were introduced
with commit a272858 from Ard Biesheuvel. This saves quite some memory in the
vmlinux binary with the 64bit kernel.

Signed-off-by: Helge Deller &lt;deller@gmx.de&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ubsan: fix tree-wide -Wmaybe-uninitialized false positives</title>
<updated>2016-03-22T22:36:02+00:00</updated>
<author>
<name>Andrey Ryabinin</name>
<email>aryabinin@virtuozzo.com</email>
</author>
<published>2016-03-22T21:27:45+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=dde5cf39d4d2cce71f2997c37210dd624d0e4bf6'/>
<id>dde5cf39d4d2cce71f2997c37210dd624d0e4bf6</id>
<content type='text'>
-fsanitize=* options makes GCC less smart than usual and increase number
of 'maybe-uninitialized' false-positives. So this patch does two things:

 * Add -Wno-maybe-uninitialized to CFLAGS_UBSAN which will disable all
   such warnings for instrumented files.

 * Remove CONFIG_UBSAN_SANITIZE_ALL from all[yes|mod]config builds. So
   the all[yes|mod]config build goes without -fsanitize=* and still with
   -Wmaybe-uninitialized.

Signed-off-by: Andrey Ryabinin &lt;aryabinin@virtuozzo.com&gt;
Reported-by: Fengguang Wu &lt;fengguang.wu@intel.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
-fsanitize=* options makes GCC less smart than usual and increase number
of 'maybe-uninitialized' false-positives. So this patch does two things:

 * Add -Wno-maybe-uninitialized to CFLAGS_UBSAN which will disable all
   such warnings for instrumented files.

 * Remove CONFIG_UBSAN_SANITIZE_ALL from all[yes|mod]config builds. So
   the all[yes|mod]config build goes without -fsanitize=* and still with
   -Wmaybe-uninitialized.

Signed-off-by: Andrey Ryabinin &lt;aryabinin@virtuozzo.com&gt;
Reported-by: Fengguang Wu &lt;fengguang.wu@intel.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>scripts/gdb: account for changes in module data structure</title>
<updated>2016-03-22T22:36:02+00:00</updated>
<author>
<name>Jan Kiszka</name>
<email>jan.kiszka@siemens.com</email>
</author>
<published>2016-03-22T21:27:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=ad4db3b24a93e52a92ad8f9b0273a9416f202c23'/>
<id>ad4db3b24a93e52a92ad8f9b0273a9416f202c23</id>
<content type='text'>
Commit 7523e4dc5057 ("module: use a structure to encapsulate layout.")
factored out the module_layout structure.  Adjust the symbol loader and
the lsmod command to this.

Signed-off-by: Jan Kiszka &lt;jan.kiszka@siemens.com&gt;
Reviewed-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt;
Tested-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt; (qemu-{ARM,x86})
Cc: Rusty Russell &lt;rusty@rustcorp.com.au&gt;
Cc: Jiri Kosina &lt;jkosina@suse.cz&gt;
Cc: Jason Wessel &lt;jason.wessel@windriver.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[4.4+]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Commit 7523e4dc5057 ("module: use a structure to encapsulate layout.")
factored out the module_layout structure.  Adjust the symbol loader and
the lsmod command to this.

Signed-off-by: Jan Kiszka &lt;jan.kiszka@siemens.com&gt;
Reviewed-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt;
Tested-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt; (qemu-{ARM,x86})
Cc: Rusty Russell &lt;rusty@rustcorp.com.au&gt;
Cc: Jiri Kosina &lt;jkosina@suse.cz&gt;
Cc: Jason Wessel &lt;jason.wessel@windriver.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[4.4+]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>scripts/gdb: add cmdline reader command</title>
<updated>2016-03-22T22:36:02+00:00</updated>
<author>
<name>Kieran Bingham</name>
<email>kieran.bingham@linaro.org</email>
</author>
<published>2016-03-22T21:27:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=72bf92ec29ac052e950dcb2cc7f8820a2e1f0a02'/>
<id>72bf92ec29ac052e950dcb2cc7f8820a2e1f0a02</id>
<content type='text'>
lx-cmdline Report the Linux Commandline used in the current kernel

[jan.kiszka@siemens.com: remove blank line from help output and fix pep8 warning]
Signed-off-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt;
Signed-off-by: Jan Kiszka &lt;jan.kiszka@siemens.com&gt;
Cc: Jason Wessel &lt;jason.wessel@windriver.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
lx-cmdline Report the Linux Commandline used in the current kernel

[jan.kiszka@siemens.com: remove blank line from help output and fix pep8 warning]
Signed-off-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt;
Signed-off-by: Jan Kiszka &lt;jan.kiszka@siemens.com&gt;
Cc: Jason Wessel &lt;jason.wessel@windriver.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>scripts/gdb: add version command</title>
<updated>2016-03-22T22:36:02+00:00</updated>
<author>
<name>Kieran Bingham</name>
<email>kieran.bingham@linaro.org</email>
</author>
<published>2016-03-22T21:27:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2d061d999424efd99e30fa4115c7dced07533223'/>
<id>2d061d999424efd99e30fa4115c7dced07533223</id>
<content type='text'>
lx-version Report the Linux Version of the current kernel.

Add a command to identify the version specified by the banner in the
debugged kernel.

This lets the user identify the kernel of the running kernel, and will
let later scripts compare the banner of the attached kernel against the
banner in the vmlinux symbols files to verify that the files are
correct.

[jan.kiszka@siemens.com: remove blank line from help output and fix pep8 warning]
Signed-off-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt;
Signed-off-by: Jan Kiszka &lt;jan.kiszka@siemens.com&gt;
Cc: Jason Wessel &lt;jason.wessel@windriver.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
lx-version Report the Linux Version of the current kernel.

Add a command to identify the version specified by the banner in the
debugged kernel.

This lets the user identify the kernel of the running kernel, and will
let later scripts compare the banner of the attached kernel against the
banner in the vmlinux symbols files to verify that the files are
correct.

[jan.kiszka@siemens.com: remove blank line from help output and fix pep8 warning]
Signed-off-by: Kieran Bingham &lt;kieran.bingham@linaro.org&gt;
Signed-off-by: Jan Kiszka &lt;jan.kiszka@siemens.com&gt;
Cc: Jason Wessel &lt;jason.wessel@windriver.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>kernel: add kcov code coverage</title>
<updated>2016-03-22T22:36:02+00:00</updated>
<author>
<name>Dmitry Vyukov</name>
<email>dvyukov@google.com</email>
</author>
<published>2016-03-22T21:27:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=5c9a8750a6409c63a0f01d51a9024861022f6593'/>
<id>5c9a8750a6409c63a0f01d51a9024861022f6593</id>
<content type='text'>
kcov provides code coverage collection for coverage-guided fuzzing
(randomized testing).  Coverage-guided fuzzing is a testing technique
that uses coverage feedback to determine new interesting inputs to a
system.  A notable user-space example is AFL
(http://lcamtuf.coredump.cx/afl/).  However, this technique is not
widely used for kernel testing due to missing compiler and kernel
support.

kcov does not aim to collect as much coverage as possible.  It aims to
collect more or less stable coverage that is function of syscall inputs.
To achieve this goal it does not collect coverage in soft/hard
interrupts and instrumentation of some inherently non-deterministic or
non-interesting parts of kernel is disbled (e.g.  scheduler, locking).

Currently there is a single coverage collection mode (tracing), but the
API anticipates additional collection modes.  Initially I also
implemented a second mode which exposes coverage in a fixed-size hash
table of counters (what Quentin used in his original patch).  I've
dropped the second mode for simplicity.

This patch adds the necessary support on kernel side.  The complimentary
compiler support was added in gcc revision 231296.

We've used this support to build syzkaller system call fuzzer, which has
found 90 kernel bugs in just 2 months:

  https://github.com/google/syzkaller/wiki/Found-Bugs

We've also found 30+ bugs in our internal systems with syzkaller.
Another (yet unexplored) direction where kcov coverage would greatly
help is more traditional "blob mutation".  For example, mounting a
random blob as a filesystem, or receiving a random blob over wire.

Why not gcov.  Typical fuzzing loop looks as follows: (1) reset
coverage, (2) execute a bit of code, (3) collect coverage, repeat.  A
typical coverage can be just a dozen of basic blocks (e.g.  an invalid
input).  In such context gcov becomes prohibitively expensive as
reset/collect coverage steps depend on total number of basic
blocks/edges in program (in case of kernel it is about 2M).  Cost of
kcov depends only on number of executed basic blocks/edges.  On top of
that, kernel requires per-thread coverage because there are always
background threads and unrelated processes that also produce coverage.
With inlined gcov instrumentation per-thread coverage is not possible.

kcov exposes kernel PCs and control flow to user-space which is
insecure.  But debugfs should not be mapped as user accessible.

Based on a patch by Quentin Casasnovas.

[akpm@linux-foundation.org: make task_struct.kcov_mode have type `enum kcov_mode']
[akpm@linux-foundation.org: unbreak allmodconfig]
[akpm@linux-foundation.org: follow x86 Makefile layout standards]
Signed-off-by: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Reviewed-by: Kees Cook &lt;keescook@chromium.org&gt;
Cc: syzkaller &lt;syzkaller@googlegroups.com&gt;
Cc: Vegard Nossum &lt;vegard.nossum@oracle.com&gt;
Cc: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: Tavis Ormandy &lt;taviso@google.com&gt;
Cc: Will Deacon &lt;will.deacon@arm.com&gt;
Cc: Quentin Casasnovas &lt;quentin.casasnovas@oracle.com&gt;
Cc: Kostya Serebryany &lt;kcc@google.com&gt;
Cc: Eric Dumazet &lt;edumazet@google.com&gt;
Cc: Alexander Potapenko &lt;glider@google.com&gt;
Cc: Kees Cook &lt;keescook@google.com&gt;
Cc: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Cc: Sasha Levin &lt;sasha.levin@oracle.com&gt;
Cc: David Drysdale &lt;drysdale@google.com&gt;
Cc: Ard Biesheuvel &lt;ard.biesheuvel@linaro.org&gt;
Cc: Andrey Ryabinin &lt;ryabinin.a.a@gmail.com&gt;
Cc: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Cc: Jiri Slaby &lt;jslaby@suse.cz&gt;
Cc: Ingo Molnar &lt;mingo@elte.hu&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: "H. Peter Anvin" &lt;hpa@zytor.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
kcov provides code coverage collection for coverage-guided fuzzing
(randomized testing).  Coverage-guided fuzzing is a testing technique
that uses coverage feedback to determine new interesting inputs to a
system.  A notable user-space example is AFL
(http://lcamtuf.coredump.cx/afl/).  However, this technique is not
widely used for kernel testing due to missing compiler and kernel
support.

kcov does not aim to collect as much coverage as possible.  It aims to
collect more or less stable coverage that is function of syscall inputs.
To achieve this goal it does not collect coverage in soft/hard
interrupts and instrumentation of some inherently non-deterministic or
non-interesting parts of kernel is disbled (e.g.  scheduler, locking).

Currently there is a single coverage collection mode (tracing), but the
API anticipates additional collection modes.  Initially I also
implemented a second mode which exposes coverage in a fixed-size hash
table of counters (what Quentin used in his original patch).  I've
dropped the second mode for simplicity.

This patch adds the necessary support on kernel side.  The complimentary
compiler support was added in gcc revision 231296.

We've used this support to build syzkaller system call fuzzer, which has
found 90 kernel bugs in just 2 months:

  https://github.com/google/syzkaller/wiki/Found-Bugs

We've also found 30+ bugs in our internal systems with syzkaller.
Another (yet unexplored) direction where kcov coverage would greatly
help is more traditional "blob mutation".  For example, mounting a
random blob as a filesystem, or receiving a random blob over wire.

Why not gcov.  Typical fuzzing loop looks as follows: (1) reset
coverage, (2) execute a bit of code, (3) collect coverage, repeat.  A
typical coverage can be just a dozen of basic blocks (e.g.  an invalid
input).  In such context gcov becomes prohibitively expensive as
reset/collect coverage steps depend on total number of basic
blocks/edges in program (in case of kernel it is about 2M).  Cost of
kcov depends only on number of executed basic blocks/edges.  On top of
that, kernel requires per-thread coverage because there are always
background threads and unrelated processes that also produce coverage.
With inlined gcov instrumentation per-thread coverage is not possible.

kcov exposes kernel PCs and control flow to user-space which is
insecure.  But debugfs should not be mapped as user accessible.

Based on a patch by Quentin Casasnovas.

[akpm@linux-foundation.org: make task_struct.kcov_mode have type `enum kcov_mode']
[akpm@linux-foundation.org: unbreak allmodconfig]
[akpm@linux-foundation.org: follow x86 Makefile layout standards]
Signed-off-by: Dmitry Vyukov &lt;dvyukov@google.com&gt;
Reviewed-by: Kees Cook &lt;keescook@chromium.org&gt;
Cc: syzkaller &lt;syzkaller@googlegroups.com&gt;
Cc: Vegard Nossum &lt;vegard.nossum@oracle.com&gt;
Cc: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
Cc: Tavis Ormandy &lt;taviso@google.com&gt;
Cc: Will Deacon &lt;will.deacon@arm.com&gt;
Cc: Quentin Casasnovas &lt;quentin.casasnovas@oracle.com&gt;
Cc: Kostya Serebryany &lt;kcc@google.com&gt;
Cc: Eric Dumazet &lt;edumazet@google.com&gt;
Cc: Alexander Potapenko &lt;glider@google.com&gt;
Cc: Kees Cook &lt;keescook@google.com&gt;
Cc: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Cc: Sasha Levin &lt;sasha.levin@oracle.com&gt;
Cc: David Drysdale &lt;drysdale@google.com&gt;
Cc: Ard Biesheuvel &lt;ard.biesheuvel@linaro.org&gt;
Cc: Andrey Ryabinin &lt;ryabinin.a.a@gmail.com&gt;
Cc: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Cc: Jiri Slaby &lt;jslaby@suse.cz&gt;
Cc: Ingo Molnar &lt;mingo@elte.hu&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: "H. Peter Anvin" &lt;hpa@zytor.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
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