IF YOU WOULD LIKE TO GET AN ACCOUNT, please write an
email to Administrator. User accounts are meant only to access repo
and report issues and/or generate pull requests.
This is a purpose-specific Git hosting for
BaseALT
projects. Thank you for your understanding!
Только зарегистрированные пользователи имеют доступ к сервису!
Для получения аккаунта, обратитесь к администратору.
KCSAN is a dynamic race detector, which relies on compile-time
instrumentation, and uses a watchpoint-based sampling approach to detect
races.
The feature was under development for quite some time and has already found
legitimate bugs.
Unfortunately it comes with a limitation, which was only understood late in
the development cycle:
It requires an up to date CLANG-11 compiler
CLANG-11 is not yet released (scheduled for June), but it's the only
compiler today which handles the kernel requirements and especially the
annotations of functions to exclude them from KCSAN instrumentation
correctly.
These annotations really need to work so that low level entry code and
especially int3 text poke handling can be completely isolated.
A detailed discussion of the requirements and compiler issues can be found
here:
https://lore.kernel.org/lkml/CANpmjNMTsY_8241bS7=XAfqvZHFLrVEkv_uM4aDUWE_kh3Rvbw@mail.gmail.com/
We came to the conclusion that trying to work around compiler limitations
and bugs again would end up in a major trainwreck, so requiring a working
compiler seemed to be the best choice.
For Continous Integration purposes the compiler restriction is manageable
and that's where most xxSAN reports come from.
For a change this limitation might make GCC people actually look at their
bugs. Some issues with CSAN in GCC are 7 years old and one has been 'fixed'
3 years ago with a half baken solution which 'solved' the reported issue
but not the underlying problem.
The KCSAN developers also ponder to use a GCC plugin to become independent,
but that's not something which will show up in a few days.
Blocking KCSAN until wide spread compiler support is available is not a
really good alternative because the continuous growth of lockless
optimizations in the kernel demands proper tooling support.
-----BEGIN PGP SIGNATURE-----
iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl7im98THHRnbHhAbGlu
dXRyb25peC5kZQAKCRCmGPVMDXSYoQ3xD/9+q87OmwnyoRTs6O3GDDbWZYoJGolh
rctDOAYW8RSS73Fiw23z8hKlLl9tJCya6/X8Q9qoonB1YeIEPPRVj5HJWAMUNEIs
YgjlZJFmh+mnbP/KQFctm3AWpoX8kqt3ncqj6zG72oQ9qKui691BY/2NmGVSLxUV
DqtUYSKmi51XEQtZuXRuHEf3zBxoyeD43DaSCdJAXd6f5O2X7tmrWDuazHVeKzHV
lhijvkyBvGMWvPg0IBrXkkLmeOvS0++MTGm3o+L72XF6nWpzTkcV7N0E9GEDFg45
zwcidRVKD5d/1DoU5Tos96rCJpBEGh/wimlu0z14mcZpNiJgRQH5rzVEO9Y14UcP
KL9FgRrb5dFw7yfX2zRQ070OFJ4AEDBMK0o5Lbu/QO5KLkvFkqnuWlQfmmtZJWCW
DTRw/FgUgU7lvyPjRrao6HBvwy+yTb0u9K5seCOTRkuepR9nPJs0710pFiBsNCfV
RY3cyggNBipAzgBOgLxixnq9+rHt70ton6S8Gijxpvt0dGGfO8k0wuEhFtA4zKrQ
6HGK+pidxnoVdEgyQZhS+qzMMkyiUL0FXdaGJ2IX+/DC+Ij1UrUPjZBn7v25M0hQ
ESkvxWKCn7snH4/NJsNxqCV1zyEc3zAW/WvLJUc9I7H8zPwtVvKWPrKEMzrJJ5bA
aneySilbRxBFUg==
=iplm
-----END PGP SIGNATURE-----
Merge tag 'locking-kcsan-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull the Kernel Concurrency Sanitizer from Thomas Gleixner:
"The Kernel Concurrency Sanitizer (KCSAN) is a dynamic race detector,
which relies on compile-time instrumentation, and uses a
watchpoint-based sampling approach to detect races.
The feature was under development for quite some time and has already
found legitimate bugs.
Unfortunately it comes with a limitation, which was only understood
late in the development cycle:
It requires an up to date CLANG-11 compiler
CLANG-11 is not yet released (scheduled for June), but it's the only
compiler today which handles the kernel requirements and especially
the annotations of functions to exclude them from KCSAN
instrumentation correctly.
These annotations really need to work so that low level entry code and
especially int3 text poke handling can be completely isolated.
A detailed discussion of the requirements and compiler issues can be
found here:
https://lore.kernel.org/lkml/CANpmjNMTsY_8241bS7=XAfqvZHFLrVEkv_uM4aDUWE_kh3Rvbw@mail.gmail.com/
We came to the conclusion that trying to work around compiler
limitations and bugs again would end up in a major trainwreck, so
requiring a working compiler seemed to be the best choice.
For Continous Integration purposes the compiler restriction is
manageable and that's where most xxSAN reports come from.
For a change this limitation might make GCC people actually look at
their bugs. Some issues with CSAN in GCC are 7 years old and one has
been 'fixed' 3 years ago with a half baken solution which 'solved' the
reported issue but not the underlying problem.
The KCSAN developers also ponder to use a GCC plugin to become
independent, but that's not something which will show up in a few
days.
Blocking KCSAN until wide spread compiler support is available is not
a really good alternative because the continuous growth of lockless
optimizations in the kernel demands proper tooling support"
* tag 'locking-kcsan-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (76 commits)
compiler_types.h, kasan: Use __SANITIZE_ADDRESS__ instead of CONFIG_KASAN to decide inlining
compiler.h: Move function attributes to compiler_types.h
compiler.h: Avoid nested statement expression in data_race()
compiler.h: Remove data_race() and unnecessary checks from {READ,WRITE}_ONCE()
kcsan: Update Documentation to change supported compilers
kcsan: Remove 'noinline' from __no_kcsan_or_inline
kcsan: Pass option tsan-instrument-read-before-write to Clang
kcsan: Support distinguishing volatile accesses
kcsan: Restrict supported compilers
kcsan: Avoid inserting __tsan_func_entry/exit if possible
ubsan, kcsan: Don't combine sanitizer with kcov on clang
objtool, kcsan: Add kcsan_disable_current() and kcsan_enable_current_nowarn()
kcsan: Add __kcsan_{enable,disable}_current() variants
checkpatch: Warn about data_race() without comment
kcsan: Use GFP_ATOMIC under spin lock
Improve KCSAN documentation a bit
kcsan: Make reporting aware of KCSAN tests
kcsan: Fix function matching in report
kcsan: Change data_race() to no longer require marking racing accesses
kcsan: Move kcsan_{disable,enable}_current() to kcsan-checks.h
...
b791d1bdf9