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[109.80.100.85]) by smtp.gmail.com with ESMTPSA id f133-v6sm8539333wme.42.2018.06.25.04.38.08 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 25 Jun 2018 04:38:09 -0700 (PDT) Date: Mon, 25 Jun 2018 13:38:03 +0200 From: Andrea Parri To: Mark Rutland Cc: linux-kernel@vger.kernel.org, will.deacon@arm.com, peterz@infradead.org, boqun.feng@gmail.com, Dmitry Vyukov Subject: Re: [PATCHv2 03/11] atomics: simplify cmpxchg() instrumentation Message-ID: <20180625113803.GA13628@andrea> References: <20180625105952.3756-1-mark.rutland@arm.com> <20180625105952.3756-4-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180625105952.3756-4-mark.rutland@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 25, 2018 at 11:59:44AM +0100, Mark Rutland wrote: > Currently we define some fairly verbose wrappers for the cmpxchg() > family so that we can pass a pointer and size into kasan_check_write(). > > The wrapper duplicate the size-switching logic necessary in arch code, > and only work for scalar types. On some architectures, (cmp)xchg are > used on non-scalar types, and thus the instrumented wrappers need to be > able to handle this. > > We could take the type-punning logic form {READ,WRITE}_ONCE(), but this > makes the wrappers even more verbose, and requires several local > variables in the macros. > > Instead, let's simplify the wrappers into simple macros which: > > * snapshot the pointer into a single local variable, called __ai_ptr to > avoid conflicts with variables in the scope of the caller. > > * call kasan_check_read() on __ai_ptr. Maybe I'm misreading the diff: aren't you calling kasan_check_write()? (not sure if it makes a difference in this case/for KTSan, but CMPXCHG does not necessarily perform a write...) Andrea > > * invoke the arch_ function, passing the original arguments, bar > __ai_ptr being substituted for ptr. > > There should be no functional change as a result of this patch. > > Signed-off-by: Mark Rutland > Cc: Boqun Feng > Cc: Dmitry Vyukov > Cc: Peter Zijlstra > Cc: Will Deacon > --- > include/asm-generic/atomic-instrumented.h | 100 +++++------------------------- > 1 file changed, 15 insertions(+), 85 deletions(-) > > diff --git a/include/asm-generic/atomic-instrumented.h b/include/asm-generic/atomic-instrumented.h > index 3c64e95d5ed0..c7c3e4cdd942 100644 > --- a/include/asm-generic/atomic-instrumented.h > +++ b/include/asm-generic/atomic-instrumented.h > @@ -408,109 +408,39 @@ static __always_inline bool atomic64_add_negative(s64 i, atomic64_t *v) > } > #endif > > -static __always_inline unsigned long > -cmpxchg_size(volatile void *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: > - BUILD_BUG_ON(sizeof(unsigned long) != 8); > - return arch_cmpxchg((u64 *)ptr, (u64)old, (u64)new); > - } > - BUILD_BUG(); > - return 0; > -} > - > #define cmpxchg(ptr, old, new) \ > ({ \ > - ((__typeof__(*(ptr)))cmpxchg_size((ptr), (unsigned long)(old), \ > - (unsigned long)(new), sizeof(*(ptr)))); \ > + typeof(ptr) __ai_ptr = (ptr); \ > + kasan_check_write(__ai_ptr, sizeof(*__ai_ptr)); \ > + arch_cmpxchg(__ai_ptr, (old), (new)); \ > }) > > -static __always_inline unsigned long > -sync_cmpxchg_size(volatile void *ptr, unsigned long old, unsigned long new, > - int size) > -{ > - kasan_check_write(ptr, size); > - switch (size) { > - case 1: > - return arch_sync_cmpxchg((u8 *)ptr, (u8)old, (u8)new); > - case 2: > - return arch_sync_cmpxchg((u16 *)ptr, (u16)old, (u16)new); > - case 4: > - return arch_sync_cmpxchg((u32 *)ptr, (u32)old, (u32)new); > - case 8: > - BUILD_BUG_ON(sizeof(unsigned long) != 8); > - return arch_sync_cmpxchg((u64 *)ptr, (u64)old, (u64)new); > - } > - BUILD_BUG(); > - return 0; > -} > - > #define sync_cmpxchg(ptr, old, new) \ > ({ \ > - ((__typeof__(*(ptr)))sync_cmpxchg_size((ptr), \ > - (unsigned long)(old), (unsigned long)(new), \ > - sizeof(*(ptr)))); \ > + typeof(ptr) __ai_ptr = (ptr); \ > + kasan_check_write(__ai_ptr, sizeof(*__ai_ptr)); \ > + arch_sync_cmpxchg(__ai_ptr, (old), (new)); \ > }) > > -static __always_inline unsigned long > -cmpxchg_local_size(volatile void *ptr, unsigned long old, unsigned long new, > - int size) > -{ > - kasan_check_write(ptr, size); > - switch (size) { > - case 1: > - return arch_cmpxchg_local((u8 *)ptr, (u8)old, (u8)new); > - case 2: > - return arch_cmpxchg_local((u16 *)ptr, (u16)old, (u16)new); > - case 4: > - return arch_cmpxchg_local((u32 *)ptr, (u32)old, (u32)new); > - case 8: > - BUILD_BUG_ON(sizeof(unsigned long) != 8); > - return arch_cmpxchg_local((u64 *)ptr, (u64)old, (u64)new); > - } > - BUILD_BUG(); > - return 0; > -} > - > #define cmpxchg_local(ptr, old, new) \ > ({ \ > - ((__typeof__(*(ptr)))cmpxchg_local_size((ptr), \ > - (unsigned long)(old), (unsigned long)(new), \ > - sizeof(*(ptr)))); \ > + typeof(ptr) __ai_ptr = (ptr); \ > + kasan_check_write(__ai_ptr, sizeof(*__ai_ptr)); \ > + arch_cmpxchg_local(__ai_ptr, (old), (new)); \ > }) > > -static __always_inline u64 > -cmpxchg64_size(volatile u64 *ptr, u64 old, u64 new) > -{ > - kasan_check_write(ptr, sizeof(*ptr)); > - return arch_cmpxchg64(ptr, old, new); > -} > - > #define cmpxchg64(ptr, old, new) \ > ({ \ > - ((__typeof__(*(ptr)))cmpxchg64_size((ptr), (u64)(old), \ > - (u64)(new))); \ > + typeof(ptr) __ai_ptr = (ptr); \ > + kasan_check_write(__ai_ptr, sizeof(*__ai_ptr)); \ > + arch_cmpxchg64(__ai_ptr, (old), (new)); \ > }) > > -static __always_inline u64 > -cmpxchg64_local_size(volatile u64 *ptr, u64 old, u64 new) > -{ > - kasan_check_write(ptr, sizeof(*ptr)); > - return arch_cmpxchg64_local(ptr, old, new); > -} > - > #define cmpxchg64_local(ptr, old, new) \ > ({ \ > - ((__typeof__(*(ptr)))cmpxchg64_local_size((ptr), (u64)(old), \ > - (u64)(new))); \ > + typeof(ptr) __ai_ptr = (ptr); \ > + kasan_check_write(__ai_ptr, sizeof(*__ai_ptr)); \ > + arch_cmpxchg64_local(__ai_ptr, (old), (new)); \ > }) > > /* > -- > 2.11.0 >