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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