From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id CB2186B02C3 for ; Wed, 28 Jun 2017 11:55:40 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id t75so18957219pgb.0 for ; Wed, 28 Jun 2017 08:55:40 -0700 (PDT) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id 88si1835343pfi.181.2017.06.28.08.55.39 for ; Wed, 28 Jun 2017 08:55:39 -0700 (PDT) Date: Wed, 28 Jun 2017 16:54:45 +0100 From: Mark Rutland Subject: Re: [PATCH] locking/atomics: don't alias ____ptr Message-ID: <20170628155445.GD8252@leverpostej> References: <85d51d3551b676ba1fc40e8fbddd2eadd056d8dd.1498140838.git.dvyukov@google.com> <20170628100246.7nsvhblgi3xjbc4m@breakpoint.cc> <1c1cbbfb-8e34-dd33-0e73-bbb2a758e962@virtuozzo.com> <20170628121246.qnk2csgzbgpqrmw3@linutronix.de> <20170628141420.GK5981@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: Sebastian Andrzej Siewior , Andrey Ryabinin , Ingo Molnar , Dmitry Vyukov , Peter Zijlstra , Will Deacon , "H. Peter Anvin" , kasan-dev , "x86@kernel.org" , LKML , Andrew Morton , "linux-mm@kvack.org" , Linus Torvalds On Wed, Jun 28, 2017 at 05:24:24PM +0200, Thomas Gleixner wrote: > On Wed, 28 Jun 2017, Mark Rutland wrote: > > On Wed, Jun 28, 2017 at 03:54:42PM +0200, Thomas Gleixner wrote: > > > > static inline unsigned long cmpxchg_varsize(void *ptr, unsigned long old, > > > > unsigned long new, int size) > > > > { > > > > switch (size) { > > > > case 1: > > > > case 2: > > > > case 4: > > > > break; > > > > case 8: > > > > if (sizeof(unsigned long) == 8) > > > > break; > > > > default: > > > > BUILD_BUG_ON(1); > > > > } > > > > kasan_check(ptr, size); > > > > return arch_cmpxchg(ptr, old, new); > > > > } > > > > This'll need to re-cast things before the call to arch_cmpxchg(), and we > > can move the check above the switch, as in [2]. > > Sure, but I rather see that changed to: > > 1) Create arch_cmpxchg8/16/32/64() inlines first > > 2) Add that varsize wrapper: > > static inline unsigned long cmpxchg_varsize(void *ptr, unsigned long old, > unsigned long new, int size) > { > switch (size) { > case 1: > kasan_check_write(ptr, size); > return arch_cmpxchg8((u8 *)ptr, (u8) old, (u8)new); > case 2: > kasan_check_write(ptr, size); > return arch_cmpxchg16((u16 *)ptr, (u16) old, (u16)new); > case 4: > kasan_check_write(ptr, size); > return arch_cmpxchg32((u32 *)ptr, (u32) old, (u32)new); > case 8: > if (sizeof(unsigned long) == 8) { > kasan_check_write(ptr, size); > return arch_cmpxchg64((u64 *)ptr, (u64) old, (u64)new); > } > default: > BUILD_BUG(); > } > } > > #define cmpxchg(ptr, o, n) \ > ({ \ > ((__typeof__(*(ptr)))cmpxchg_varsize((ptr), (unsigned long)(o), \ > (unsigned long)(n), sizeof(*(ptr)))); \ > }) > > Which allows us to create: > > static inline u8 cmpxchg8(u8 *ptr, u8 old, u8 new) > { > kasan_check_write(ptr, sizeof(old)); > return arch_cmpxchg8(ptr, old, new); > } > > and friends as well and later migrate the existing users away from that > untyped macro mess. Sure, that makes sense to me. > > And instead of adding > > #include > > to the architecture code, we rather do > > # mv arch/xxx/include/asm/atomic.h mv arch/xxx/include/asm/arch_atomic.h > # echo '#include ' >arch/xxx/include/asm/atomic.h > > # mv include/asm-generic/atomic.h include/asm-generic/atomic_up.h > > and create a new include/asm-generic/atomic.h > > #ifndef __ASM_GENERIC_ATOMIC_H > #define __ASM_GENERIC_ATOMIC_H > > #ifdef CONFIG_ATOMIC_INSTRUMENTED_H > #include > #else > #include > #endif > > #endif Given we're gonig to clean things up, we may as well avoid the backwards include of , whcih was only there as a bodge: For the UP arches we do: # echo '#include ' >arch/xxx/include/asm/atomic.h # mv include/asm-generic/atomic.h include/asm-generic/atomic_up.h Then we add a : #ifndef __LINUX_ATOMIC_INSTRUMENTED_H #define __LINUX_ATOMIC INSTRUMENTED_H #include #if CONFIG_ATOMIC_INSTRUMENTED_H #endif #endif /* __LINUX_ATOMIC_ARCH_H */ ... and make incldue that rather than . That way the instrumentation's orthogonal to the UP-ness of the arch, and we can fold any other instrumentation in there, or later move it directly into 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: email@kvack.org