On Fri, May 13, 2016 at 07:19:15PM +0200, Borislav Petkov wrote: > The only thing that needs to be corrected then is the misleading comment > above the 32-bit version "... Save the C-clobbered registers (%eax, %edx > and %ecx) .." - the 64-bit version comment is correct AFAICT. --- From: Borislav Petkov <bp@xxxxxxx> Date: Mon, 16 May 2016 11:29:22 +0200 Subject: [PATCH] locking/rwsem: Fix comment on register clobbering Document explicitly that %edx can get clobbered on the slow path, on 32-bit. Something I learned the hard way. :-\ Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> --- arch/x86/lib/rwsem.S | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S index a37462a23546..bb49caa4dd4c 100644 --- a/arch/x86/lib/rwsem.S +++ b/arch/x86/lib/rwsem.S @@ -29,8 +29,10 @@ * there is contention on the semaphore. * * %eax contains the semaphore pointer on entry. Save the C-clobbered - * registers (%eax, %edx and %ecx) except %eax whish is either a return - * value or just clobbered.. + * registers (%eax, %edx and %ecx) except %eax which is either a return + * value or just clobbered. Same is true for %edx so make sure gcc + * reloads it after the slow path, by making it hold a temporary, for + * example; see ____down_write(). */ #define save_common_regs \ -- 2.7.3 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) -- -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
