Messages in this thread | | | Date | Wed, 28 Jun 2017 16:54:45 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] locking/atomics: don't alias ____ptr |
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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 <asm/atomic-instrumented.h> > > to the architecture code, we rather do > > # mv arch/xxx/include/asm/atomic.h mv arch/xxx/include/asm/arch_atomic.h > # echo '#include <asm-generic/atomic.h>' >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 <asm-generic/atomic_instrumented.h> > #else > #include <asm-generic/atomic_up.h> > #endif > > #endif
Given we're gonig to clean things up, we may as well avoid the backwards include of <asm-generic/atomic_instrumented.h>, whcih was only there as a bodge:
For the UP arches we do: # echo '#include <asm-generic/atomic_up.h>' >arch/xxx/include/asm/atomic.h # mv include/asm-generic/atomic.h include/asm-generic/atomic_up.h
Then we add a <linux/atomic_instrumented.h>:
#ifndef __LINUX_ATOMIC_INSTRUMENTED_H #define __LINUX_ATOMIC INSTRUMENTED_H
#include <asm/atomic.h>
#if CONFIG_ATOMIC_INSTRUMENTED_H <instrumentation> #endif
#endif /* __LINUX_ATOMIC_ARCH_H */
... and make <linux/atomic.h> incldue that rather than <asm/atomic.h>.
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 <linux/atomic.h>
Thanks, Mark.
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