tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/pmladek.2022.06.15a
head: 0ba7324b44282870af740a5a121add62c7f5f730
commit: db21b02f8044e812f8a5e3811f602409290e3ede [133/140] context_tracking: Convert state to atomic_t
config: x86_64-randconfig-r003-20220516 (https://download.01.org/0day-ci/archive/20220616/[email protected]/config)
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce (this is a W=1 build):
# https://github.com/ammarfaizi2/linux-block/commit/db21b02f8044e812f8a5e3811f602409290e3ede
git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/pmladek.2022.06.15a
git checkout db21b02f8044e812f8a5e3811f602409290e3ede
# save the config file
mkdir build_dir && cp config build_dir/.config
make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <[email protected]>
All warnings (new ones prefixed by >>):
>> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
>> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
--
0-DAY CI Kernel Test Service
https://01.org/lkp
On Thu, Jun 16, 2022 at 04:26:16AM +0800, kernel test robot wrote:
> tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/pmladek.2022.06.15a
> head: 0ba7324b44282870af740a5a121add62c7f5f730
> commit: db21b02f8044e812f8a5e3811f602409290e3ede [133/140] context_tracking: Convert state to atomic_t
> config: x86_64-randconfig-r003-20220516 (https://download.01.org/0day-ci/archive/20220616/[email protected]/config)
> compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
> reproduce (this is a W=1 build):
> # https://github.com/ammarfaizi2/linux-block/commit/db21b02f8044e812f8a5e3811f602409290e3ede
> git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
> git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/pmladek.2022.06.15a
> git checkout db21b02f8044e812f8a5e3811f602409290e3ede
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <[email protected]>
>
> All warnings (new ones prefixed by >>):
>
> >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
> >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
Marco, Dmitry, my guess is that this is due to the ct->active check in
both functions. Are we supposed to do something to make this sort of
thing safe for KASAN?
Thanx, Paul
On Wed, Jun 15, 2022 at 01:40:39PM -0700, Paul E. McKenney wrote:
> On Thu, Jun 16, 2022 at 04:26:16AM +0800, kernel test robot wrote:
> > tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/pmladek.2022.06.15a
> > head: 0ba7324b44282870af740a5a121add62c7f5f730
> > commit: db21b02f8044e812f8a5e3811f602409290e3ede [133/140] context_tracking: Convert state to atomic_t
> > config: x86_64-randconfig-r003-20220516 (https://download.01.org/0day-ci/archive/20220616/[email protected]/config)
> > compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
> > reproduce (this is a W=1 build):
> > # https://github.com/ammarfaizi2/linux-block/commit/db21b02f8044e812f8a5e3811f602409290e3ede
> > git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
> > git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/pmladek.2022.06.15a
> > git checkout db21b02f8044e812f8a5e3811f602409290e3ede
> > # save the config file
> > mkdir build_dir && cp config build_dir/.config
> > make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
> >
> > If you fix the issue, kindly add following tag where applicable
> > Reported-by: kernel test robot <[email protected]>
> >
> > All warnings (new ones prefixed by >>):
> >
> > >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
> > >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
>
> Marco, Dmitry, my guess is that this is due to the ct->active check in
> both functions. Are we supposed to do something to make this sort of
> thing safe for KASAN?
This time actually CCing Marco and Dmitry...
Thanx, Paul
On Wed, 15 Jun 2022 at 23:17, Paul E. McKenney <[email protected]> wrote:
>
> On Wed, Jun 15, 2022 at 01:40:39PM -0700, Paul E. McKenney wrote:
> > On Thu, Jun 16, 2022 at 04:26:16AM +0800, kernel test robot wrote:
> > > tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/pmladek.2022.06.15a
> > > head: 0ba7324b44282870af740a5a121add62c7f5f730
> > > commit: db21b02f8044e812f8a5e3811f602409290e3ede [133/140] context_tracking: Convert state to atomic_t
> > > config: x86_64-randconfig-r003-20220516 (https://download.01.org/0day-ci/archive/20220616/[email protected]/config)
> > > compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
> > > reproduce (this is a W=1 build):
> > > # https://github.com/ammarfaizi2/linux-block/commit/db21b02f8044e812f8a5e3811f602409290e3ede
> > > git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
> > > git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/pmladek.2022.06.15a
> > > git checkout db21b02f8044e812f8a5e3811f602409290e3ede
> > > # save the config file
> > > mkdir build_dir && cp config build_dir/.config
> > > make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
> > >
> > > If you fix the issue, kindly add following tag where applicable
> > > Reported-by: kernel test robot <[email protected]>
> > >
> > > All warnings (new ones prefixed by >>):
> > >
> > > >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
> > > >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
> >
> > Marco, Dmitry, my guess is that this is due to the ct->active check in
> > both functions. Are we supposed to do something to make this sort of
> > thing safe for KASAN?
>
> This time actually CCing Marco and Dmitry...
It's due to the atomic_read()s within the noinstr function. Within
noinstr you can use arch_atomic_read() to avoid the instrumentation.
Thanks,
-- Marco
On Thu, Jun 16, 2022 at 10:19:18AM +0200, Marco Elver wrote:
> On Wed, 15 Jun 2022 at 23:17, Paul E. McKenney <[email protected]> wrote:
> >
> > On Wed, Jun 15, 2022 at 01:40:39PM -0700, Paul E. McKenney wrote:
> > > On Thu, Jun 16, 2022 at 04:26:16AM +0800, kernel test robot wrote:
> > > > tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/pmladek.2022.06.15a
> > > > head: 0ba7324b44282870af740a5a121add62c7f5f730
> > > > commit: db21b02f8044e812f8a5e3811f602409290e3ede [133/140] context_tracking: Convert state to atomic_t
> > > > config: x86_64-randconfig-r003-20220516 (https://download.01.org/0day-ci/archive/20220616/[email protected]/config)
> > > > compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
> > > > reproduce (this is a W=1 build):
> > > > # https://github.com/ammarfaizi2/linux-block/commit/db21b02f8044e812f8a5e3811f602409290e3ede
> > > > git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
> > > > git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/pmladek.2022.06.15a
> > > > git checkout db21b02f8044e812f8a5e3811f602409290e3ede
> > > > # save the config file
> > > > mkdir build_dir && cp config build_dir/.config
> > > > make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
> > > >
> > > > If you fix the issue, kindly add following tag where applicable
> > > > Reported-by: kernel test robot <[email protected]>
> > > >
> > > > All warnings (new ones prefixed by >>):
> > > >
> > > > >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
> > > > >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
> > >
> > > Marco, Dmitry, my guess is that this is due to the ct->active check in
> > > both functions. Are we supposed to do something to make this sort of
> > > thing safe for KASAN?
> >
> > This time actually CCing Marco and Dmitry...
>
> It's due to the atomic_read()s within the noinstr function. Within
> noinstr you can use arch_atomic_read() to avoid the instrumentation.
Thank you, will fix!
Thanx, Paul
On Thu, Jun 16, 2022 at 06:40:21AM -0700, Paul E. McKenney wrote:
> On Thu, Jun 16, 2022 at 10:19:18AM +0200, Marco Elver wrote:
> > On Wed, 15 Jun 2022 at 23:17, Paul E. McKenney <[email protected]> wrote:
> > >
> > > On Wed, Jun 15, 2022 at 01:40:39PM -0700, Paul E. McKenney wrote:
> > > > On Thu, Jun 16, 2022 at 04:26:16AM +0800, kernel test robot wrote:
> > > > > tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/pmladek.2022.06.15a
> > > > > head: 0ba7324b44282870af740a5a121add62c7f5f730
> > > > > commit: db21b02f8044e812f8a5e3811f602409290e3ede [133/140] context_tracking: Convert state to atomic_t
> > > > > config: x86_64-randconfig-r003-20220516 (https://download.01.org/0day-ci/archive/20220616/[email protected]/config)
> > > > > compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
> > > > > reproduce (this is a W=1 build):
> > > > > # https://github.com/ammarfaizi2/linux-block/commit/db21b02f8044e812f8a5e3811f602409290e3ede
> > > > > git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
> > > > > git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/pmladek.2022.06.15a
> > > > > git checkout db21b02f8044e812f8a5e3811f602409290e3ede
> > > > > # save the config file
> > > > > mkdir build_dir && cp config build_dir/.config
> > > > > make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
> > > > >
> > > > > If you fix the issue, kindly add following tag where applicable
> > > > > Reported-by: kernel test robot <[email protected]>
> > > > >
> > > > > All warnings (new ones prefixed by >>):
> > > > >
> > > > > >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
> > > > > >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
> > > >
> > > > Marco, Dmitry, my guess is that this is due to the ct->active check in
> > > > both functions. Are we supposed to do something to make this sort of
> > > > thing safe for KASAN?
> > >
> > > This time actually CCing Marco and Dmitry...
> >
> > It's due to the atomic_read()s within the noinstr function. Within
> > noinstr you can use arch_atomic_read() to avoid the instrumentation.
>
> Thank you, will fix!
And please see below for an alleged fix.
Thanx, Paul
------------------------------------------------------------------------
commit 81e24ca26ee9933bcacf67a61e3f6ae41a025442
Author: Paul E. McKenney <[email protected]>
Date: Thu Jun 16 09:30:37 2022 -0700
context_tracking: Use arch_atomic_read() in __ct_state for KASAN
Context tracking's __ct_state() function can be invoked from noinstr state
where RCU is not watching. This means that its use of atomic_read()
causes KASAN to invoke the non-noinstr __kasan_check_read() function
from the noinstr function __ct_state(). This is problematic because
someone tracing the __kasan_check_read() function could get a nasty
surprise because of RCU not watching.
This commit therefore replaces the __ct_state() function's use of
atomic_read() with arch_atomic_read(), which KASAN does not attempt to
add instrumention to.
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Marco Elver <[email protected]>
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 0aecc07fb4f50..81c51e5f03143 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -49,7 +49,7 @@ DECLARE_PER_CPU(struct context_tracking, context_tracking);
static __always_inline int __ct_state(void)
{
- return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
+ return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
}
#endif
On Thu, Jun 16, 2022 at 07:32:14PM +0200, Marco Elver wrote:
> On Thu, 16 Jun 2022 at 18:44, Paul E. McKenney <[email protected]> wrote:
> [...]
> > > > > > > >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
> > > > > > > >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
> [...]
> > > > It's due to the atomic_read()s within the noinstr function. Within
> > > > noinstr you can use arch_atomic_read() to avoid the instrumentation.
> > >
> > > Thank you, will fix!
> >
> > And please see below for an alleged fix.
>
> Looks good, if this made the above warnings go away.
Here is hoping! I will see if I can reproduce locally. ;-)
> Btw, it's not just KASAN, but arch_atomic_read() also disables KCSAN
> checking. A similar warning would have been generated in a KCSAN
> config.
Good to know, thank you! Additional local-reproduce opportunities.
> Reviewed-by: Marco Elver <[email protected]>
Applied, thank you!
Thanx, Paul
> > ------------------------------------------------------------------------
> >
> > commit 81e24ca26ee9933bcacf67a61e3f6ae41a025442
> > Author: Paul E. McKenney <[email protected]>
> > Date: Thu Jun 16 09:30:37 2022 -0700
> >
> > context_tracking: Use arch_atomic_read() in __ct_state for KASAN
> >
> > Context tracking's __ct_state() function can be invoked from noinstr state
> > where RCU is not watching. This means that its use of atomic_read()
> > causes KASAN to invoke the non-noinstr __kasan_check_read() function
> > from the noinstr function __ct_state(). This is problematic because
> > someone tracing the __kasan_check_read() function could get a nasty
> > surprise because of RCU not watching.
> >
> > This commit therefore replaces the __ct_state() function's use of
> > atomic_read() with arch_atomic_read(), which KASAN does not attempt to
> > add instrumention to.
> >
> > Signed-off-by: Paul E. McKenney <[email protected]>
> > Cc: Frederic Weisbecker <[email protected]>
> > Cc: Marco Elver <[email protected]>
> >
> > diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
> > index 0aecc07fb4f50..81c51e5f03143 100644
> > --- a/include/linux/context_tracking_state.h
> > +++ b/include/linux/context_tracking_state.h
> > @@ -49,7 +49,7 @@ DECLARE_PER_CPU(struct context_tracking, context_tracking);
> >
> > static __always_inline int __ct_state(void)
> > {
> > - return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
> > + return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
> > }
> > #endif
> >
On Thu, 16 Jun 2022 at 18:44, Paul E. McKenney <[email protected]> wrote:
[...]
> > > > > > >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section
> > > > > > >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section
[...]
> > > It's due to the atomic_read()s within the noinstr function. Within
> > > noinstr you can use arch_atomic_read() to avoid the instrumentation.
> >
> > Thank you, will fix!
>
> And please see below for an alleged fix.
Looks good, if this made the above warnings go away.
Btw, it's not just KASAN, but arch_atomic_read() also disables KCSAN
checking. A similar warning would have been generated in a KCSAN
config.
Reviewed-by: Marco Elver <[email protected]>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 81e24ca26ee9933bcacf67a61e3f6ae41a025442
> Author: Paul E. McKenney <[email protected]>
> Date: Thu Jun 16 09:30:37 2022 -0700
>
> context_tracking: Use arch_atomic_read() in __ct_state for KASAN
>
> Context tracking's __ct_state() function can be invoked from noinstr state
> where RCU is not watching. This means that its use of atomic_read()
> causes KASAN to invoke the non-noinstr __kasan_check_read() function
> from the noinstr function __ct_state(). This is problematic because
> someone tracing the __kasan_check_read() function could get a nasty
> surprise because of RCU not watching.
>
> This commit therefore replaces the __ct_state() function's use of
> atomic_read() with arch_atomic_read(), which KASAN does not attempt to
> add instrumention to.
>
> Signed-off-by: Paul E. McKenney <[email protected]>
> Cc: Frederic Weisbecker <[email protected]>
> Cc: Marco Elver <[email protected]>
>
> diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
> index 0aecc07fb4f50..81c51e5f03143 100644
> --- a/include/linux/context_tracking_state.h
> +++ b/include/linux/context_tracking_state.h
> @@ -49,7 +49,7 @@ DECLARE_PER_CPU(struct context_tracking, context_tracking);
>
> static __always_inline int __ct_state(void)
> {
> - return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
> + return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
> }
> #endif
>