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Date: Fri, 24 Apr 2020 17:17:10 -0700 From: "Paul E. McKenney" <paulmck@...nel.org> To: Marco Elver <elver@...gle.com> Cc: Dmitry Vyukov <dvyukov@...gle.com>, Alexander Potapenko <glider@...gle.com>, Andrey Konovalov <andreyknvl@...gle.com>, Will Deacon <will@...nel.org>, kasan-dev <kasan-dev@...glegroups.com>, LKML <linux-kernel@...r.kernel.org>, Josh Poimboeuf <jpoimboe@...hat.com>, Peter Zijlstra <peterz@...radead.org> Subject: Re: [PATCH 1/2] kcsan: Add __kcsan_{enable,disable}_current() variants On Fri, Apr 24, 2020 at 05:57:04PM +0200, Marco Elver wrote: > On Fri, 24 Apr 2020 at 17:47, Marco Elver <elver@...gle.com> wrote: > > > > The __kcsan_{enable,disable}_current() variants only call into KCSAN if > > KCSAN is enabled for the current compilation unit. Note: This is > > typically not what we want, as we usually want to ensure that even calls > > into other functions still have KCSAN disabled. > > > > These variants may safely be used in header files that are shared > > between regular kernel code and code that does not link the KCSAN > > runtime. > > > > Signed-off-by: Marco Elver <elver@...gle.com> > > --- > > This is to help with the new READ_ONCE()/WRITE_ONCE(): > > https://lkml.kernel.org/r/20200424134238.GE21141@willie-the-truck > > > > These should be using __kcsan_disable_current() and > > __kcsan_enable_current(), instead of the non-'__' variants. > > --- > > Paul: These 2 patches may want to be in the set for 5.8, depending on > what Will wants to do. > > An alternative would be that Will takes my 2 patches and carries them, > avoiding some complex patch-dependency. That is assuming his set of > patches will go in -tip on top of KCSAN. For the moment I have pulled them into -rcu and am testing them, thank you! I will leave them in the v5.9 bucket for the moment, but please let me know how things proceed with Will. Thanx, Paul > Thanks, > -- Marco > > > include/linux/kcsan-checks.h | 17 ++++++++++++++--- > > kernel/kcsan/core.c | 7 +++++++ > > 2 files changed, 21 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h > > index ef95ddc49182..7b0b9c44f5f3 100644 > > --- a/include/linux/kcsan-checks.h > > +++ b/include/linux/kcsan-checks.h > > @@ -49,6 +49,7 @@ void kcsan_disable_current(void); > > * Supports nesting. > > */ > > void kcsan_enable_current(void); > > +void kcsan_enable_current_nowarn(void); /* Safe in uaccess regions. */ > > > > /** > > * kcsan_nestable_atomic_begin - begin nestable atomic region > > @@ -149,6 +150,7 @@ static inline void __kcsan_check_access(const volatile void *ptr, size_t size, > > > > static inline void kcsan_disable_current(void) { } > > static inline void kcsan_enable_current(void) { } > > +static inline void kcsan_enable_current_nowarn(void) { } > > static inline void kcsan_nestable_atomic_begin(void) { } > > static inline void kcsan_nestable_atomic_end(void) { } > > static inline void kcsan_flat_atomic_begin(void) { } > > @@ -165,15 +167,24 @@ static inline void kcsan_end_scoped_access(struct kcsan_scoped_access *sa) { } > > > > #endif /* CONFIG_KCSAN */ > > > > +#ifdef __SANITIZE_THREAD__ > > /* > > - * kcsan_*: Only calls into the runtime when the particular compilation unit has > > - * KCSAN instrumentation enabled. May be used in header files. > > + * Only calls into the runtime when the particular compilation unit has KCSAN > > + * instrumentation enabled. May be used in header files. > > */ > > -#ifdef __SANITIZE_THREAD__ > > #define kcsan_check_access __kcsan_check_access > > + > > +/* > > + * Only use these to disable KCSAN for accesses in the current compilation unit; > > + * calls into libraries may still perform KCSAN checks. > > + */ > > +#define __kcsan_disable_current kcsan_disable_current > > +#define __kcsan_enable_current kcsan_enable_current_nowarn > > #else > > static inline void kcsan_check_access(const volatile void *ptr, size_t size, > > int type) { } > > +static inline void __kcsan_enable_current(void) { } > > +static inline void __kcsan_disable_current(void) { } > > #endif > > > > /** > > diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c > > index 40919943617b..0a0f018cb154 100644 > > --- a/kernel/kcsan/core.c > > +++ b/kernel/kcsan/core.c > > @@ -625,6 +625,13 @@ void kcsan_enable_current(void) > > } > > EXPORT_SYMBOL(kcsan_enable_current); > > > > +void kcsan_enable_current_nowarn(void) > > +{ > > + if (get_ctx()->disable_count-- == 0) > > + kcsan_disable_current(); > > +} > > +EXPORT_SYMBOL(kcsan_enable_current_nowarn); > > + > > void kcsan_nestable_atomic_begin(void) > > { > > /* > > -- > > 2.26.2.303.gf8c07b1a785-goog > >
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