From: Mark Rutland <mark.rutland@arm.com> To: Thomas Gleixner <tglx@linutronix.de> Cc: Dmitry Vyukov <dvyukov@google.com>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Will Deacon <will.deacon@arm.com>, "H. Peter Anvin" <hpa@zytor.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, kasan-dev <kasan-dev@googlegroups.com>, "x86@kernel.org" <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Linus Torvalds <torvalds@linux-foundation.org> Subject: Re: [PATCH] locking/atomics: don't alias ____ptr Date: Wed, 28 Jun 2017 13:45:53 +0100 [thread overview] Message-ID: <20170628124552.GG5981@leverpostej> (raw) In-Reply-To: <alpine.DEB.2.20.1706281315170.1970@nanos> On Wed, Jun 28, 2017 at 01:21:43PM +0200, Thomas Gleixner wrote: > On Wed, 28 Jun 2017, Dmitry Vyukov wrote: > > On Wed, Jun 28, 2017 at 1:10 PM, Thomas Gleixner <tglx@linutronix.de> wrote: > > >> In my case I ended up with something like: > > >> > > >> __typeof__(foo) __ptr = __ptr; > > >> > > >> which compiler decided to turn into 0. > > >> > > >> Thank you, macros. > > >> > > >> We can add more underscores, but the problem can happen again. Should > > >> we prefix current function/macro name to all local vars?.. > > > > > > Actually we can void that ___ptr dance completely. > > > > > > Thanks, > > > > > > tglx > > > > > > 8<-------------------- > > > > > > --- a/include/asm-generic/atomic-instrumented.h > > > +++ b/include/asm-generic/atomic-instrumented.h > > > @@ -359,37 +359,32 @@ static __always_inline bool atomic64_add > > > > > > #define cmpxchg(ptr, old, new) \ > > > ({ \ > > > - __typeof__(ptr) ___ptr = (ptr); \ > > > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > > > + kasan_check_write((ptr), sizeof(*(ptr))); \ > > > arch_cmpxchg((ptr), (old), (new)); \ > > > }) > > > > > > #define sync_cmpxchg(ptr, old, new) \ > > > ({ \ > > > - __typeof__(ptr) ___ptr = (ptr); \ > > > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > > > - arch_sync_cmpxchg(___ptr, (old), (new)); \ > > > + kasan_check_write((ptr), sizeof(*(ptr))); \ > > > + arch_sync_cmpxchg((ptr), (old), (new)); \ > > > }) > > > > > > #define cmpxchg_local(ptr, old, new) \ > > > ({ \ > > > - __typeof__(ptr) ____ptr = (ptr); \ > > > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > > > - arch_cmpxchg_local(____ptr, (old), (new)); \ > > > + kasan_check_write((ptr), sizeof(*(ptr))); \ > > > + arch_cmpxchg_local((ptr), (old), (new)); \ > > > > > > /\/\/\/\/\/\/\/\/\/\/\/\ > > > > These are macros. > > If ptr is foo(), then we will call foo() twice. > > Sigh, is that actually used? For better or worse, we can't rule it out. We'd risk even more subtle bugs in future trying to rely on that not being the case. :/ > That's all insane. The whole crap gets worse because: > > cmpxchg() can be used on u8, u16, u32 .... Yup, that's the whole reason for the macro insanity in the fist place. Anoother option is something like: static inline unsigned long cmpxchg_size(unsigned long *ptr, unsigned long old, unsigned long new, int size) { kasan_check_write(ptr, size); switch (size) { case 1: return arch_cmpxchg((u8 *)ptr, (u8)old, (u8)new); case 2: return arch_cmpxchg((u16 *)ptr, (u16)old, (u16)new); case 4: return arch_cmpxchg((u32 *)ptr, (u32)old, (u32)new); case 8: return arch_cmpxchg((u64 *)ptr, (u64)old, (u64)new); } BUILD_BUG(); } #define cmpxchg(ptr, old, new) \ cmpxchg_size(ptr, old, new, sizeof(*ptr)) Thanks, Mark.
WARNING: multiple messages have this Message-ID (diff)
From: Mark Rutland <mark.rutland@arm.com> To: Thomas Gleixner <tglx@linutronix.de> Cc: Dmitry Vyukov <dvyukov@google.com>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Will Deacon <will.deacon@arm.com>, "H. Peter Anvin" <hpa@zytor.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, kasan-dev <kasan-dev@googlegroups.com>, "x86@kernel.org" <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Linus Torvalds <torvalds@linux-foundation.org> Subject: Re: [PATCH] locking/atomics: don't alias ____ptr Date: Wed, 28 Jun 2017 13:45:53 +0100 [thread overview] Message-ID: <20170628124552.GG5981@leverpostej> (raw) In-Reply-To: <alpine.DEB.2.20.1706281315170.1970@nanos> On Wed, Jun 28, 2017 at 01:21:43PM +0200, Thomas Gleixner wrote: > On Wed, 28 Jun 2017, Dmitry Vyukov wrote: > > On Wed, Jun 28, 2017 at 1:10 PM, Thomas Gleixner <tglx@linutronix.de> wrote: > > >> In my case I ended up with something like: > > >> > > >> __typeof__(foo) __ptr = __ptr; > > >> > > >> which compiler decided to turn into 0. > > >> > > >> Thank you, macros. > > >> > > >> We can add more underscores, but the problem can happen again. Should > > >> we prefix current function/macro name to all local vars?.. > > > > > > Actually we can void that ___ptr dance completely. > > > > > > Thanks, > > > > > > tglx > > > > > > 8<-------------------- > > > > > > --- a/include/asm-generic/atomic-instrumented.h > > > +++ b/include/asm-generic/atomic-instrumented.h > > > @@ -359,37 +359,32 @@ static __always_inline bool atomic64_add > > > > > > #define cmpxchg(ptr, old, new) \ > > > ({ \ > > > - __typeof__(ptr) ___ptr = (ptr); \ > > > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > > > + kasan_check_write((ptr), sizeof(*(ptr))); \ > > > arch_cmpxchg((ptr), (old), (new)); \ > > > }) > > > > > > #define sync_cmpxchg(ptr, old, new) \ > > > ({ \ > > > - __typeof__(ptr) ___ptr = (ptr); \ > > > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > > > - arch_sync_cmpxchg(___ptr, (old), (new)); \ > > > + kasan_check_write((ptr), sizeof(*(ptr))); \ > > > + arch_sync_cmpxchg((ptr), (old), (new)); \ > > > }) > > > > > > #define cmpxchg_local(ptr, old, new) \ > > > ({ \ > > > - __typeof__(ptr) ____ptr = (ptr); \ > > > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > > > - arch_cmpxchg_local(____ptr, (old), (new)); \ > > > + kasan_check_write((ptr), sizeof(*(ptr))); \ > > > + arch_cmpxchg_local((ptr), (old), (new)); \ > > > > > > /\/\/\/\/\/\/\/\/\/\/\/\ > > > > These are macros. > > If ptr is foo(), then we will call foo() twice. > > Sigh, is that actually used? For better or worse, we can't rule it out. We'd risk even more subtle bugs in future trying to rely on that not being the case. :/ > That's all insane. The whole crap gets worse because: > > cmpxchg() can be used on u8, u16, u32 .... Yup, that's the whole reason for the macro insanity in the fist place. Anoother option is something like: static inline unsigned long cmpxchg_size(unsigned long *ptr, unsigned long old, unsigned long new, int size) { kasan_check_write(ptr, size); switch (size) { case 1: return arch_cmpxchg((u8 *)ptr, (u8)old, (u8)new); case 2: return arch_cmpxchg((u16 *)ptr, (u16)old, (u16)new); case 4: return arch_cmpxchg((u32 *)ptr, (u32)old, (u32)new); case 8: return arch_cmpxchg((u64 *)ptr, (u64)old, (u64)new); } BUILD_BUG(); } #define cmpxchg(ptr, old, new) \ cmpxchg_size(ptr, old, new, sizeof(*ptr)) Thanks, Mark. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-06-28 12:46 UTC|newest] Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-06-22 14:14 [PATCH v5 0/4] x86, kasan: add KASAN checks to atomic operations Dmitry Vyukov [not found] ` <cover.1498140838.git.dvyukov@google.com> 2017-06-22 14:14 ` [PATCH v5 1/4] x86: switch atomic.h to use atomic-instrumented.h Dmitry Vyukov 2017-06-22 14:14 ` Dmitry Vyukov 2017-06-22 21:14 ` Andrew Morton 2017-06-22 21:14 ` Andrew Morton 2017-06-23 8:23 ` Dmitry Vyukov 2017-06-23 8:23 ` Dmitry Vyukov 2017-06-23 8:54 ` Ingo Molnar 2017-06-23 8:54 ` Ingo Molnar 2017-06-23 19:00 ` Andrew Morton 2017-06-23 19:00 ` Andrew Morton 2017-06-23 13:59 ` [tip:locking/core] locking/atomic/x86: Switch " tip-bot for Dmitry Vyukov 2017-06-22 14:14 ` [PATCH v5 2/4] kasan: allow kasan_check_read/write() to accept pointers to volatiles Dmitry Vyukov 2017-06-22 14:14 ` Dmitry Vyukov 2017-06-23 14:00 ` [tip:locking/core] kasan: Allow " tip-bot for Dmitry Vyukov 2017-07-26 12:10 ` tip-bot for Dmitry Vyukov 2017-06-22 14:14 ` [PATCH v5 3/4] asm-generic: add KASAN instrumentation to atomic operations Dmitry Vyukov 2017-06-22 14:14 ` Dmitry Vyukov 2017-06-23 14:01 ` [tip:locking/core] locking/atomics, asm-generic: Add " tip-bot for Dmitry Vyukov 2017-06-28 10:02 ` [PATCH] locking/atomics: don't alias ____ptr Sebastian Andrzej Siewior 2017-06-28 10:02 ` Sebastian Andrzej Siewior 2017-06-28 10:16 ` Dmitry Vyukov 2017-06-28 10:16 ` Dmitry Vyukov 2017-06-28 11:10 ` Thomas Gleixner 2017-06-28 11:10 ` Thomas Gleixner 2017-06-28 11:12 ` Dmitry Vyukov 2017-06-28 11:12 ` Dmitry Vyukov 2017-06-28 11:21 ` Thomas Gleixner 2017-06-28 11:21 ` Thomas Gleixner 2017-06-28 12:45 ` Mark Rutland [this message] 2017-06-28 12:45 ` Mark Rutland 2017-06-28 12:24 ` Thomas Gleixner 2017-06-28 12:24 ` Thomas Gleixner 2017-06-28 12:27 ` Dmitry Vyukov 2017-06-28 12:27 ` Dmitry Vyukov 2017-06-28 13:33 ` Thomas Gleixner 2017-06-28 13:33 ` Thomas Gleixner 2017-06-28 11:15 ` Andrey Ryabinin 2017-06-28 11:15 ` Andrey Ryabinin 2017-06-28 12:12 ` Sebastian Andrzej Siewior 2017-06-28 12:12 ` Sebastian Andrzej Siewior 2017-06-28 13:20 ` Thomas Gleixner 2017-06-28 13:20 ` Thomas Gleixner 2017-06-28 13:54 ` Thomas Gleixner 2017-06-28 13:54 ` Thomas Gleixner 2017-06-28 14:14 ` Mark Rutland 2017-06-28 14:14 ` Mark Rutland 2017-06-28 15:24 ` Thomas Gleixner 2017-06-28 15:24 ` Thomas Gleixner 2017-06-28 15:54 ` Mark Rutland 2017-06-28 15:54 ` Mark Rutland 2017-06-28 16:56 ` Ingo Molnar 2017-06-28 16:56 ` Ingo Molnar 2017-06-28 18:21 ` Thomas Gleixner 2017-06-28 18:21 ` Thomas Gleixner 2017-06-29 6:47 ` Thomas Gleixner 2017-06-29 6:47 ` Thomas Gleixner 2017-06-28 14:00 ` Andrey Ryabinin 2017-06-28 14:00 ` Andrey Ryabinin 2017-06-22 14:14 ` [PATCH v5 4/4] asm-generic, x86: add comments for atomic instrumentation Dmitry Vyukov 2017-06-22 14:14 ` Dmitry Vyukov 2017-06-23 14:01 ` [tip:locking/core] locking/atomic/x86, asm-generic: Add " tip-bot for Dmitry Vyukov
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