On Wed, Sep 06, 2017 at 04:33:02PM -0500, Josh Poimboeuf wrote: > On Wed, Sep 06, 2017 at 12:26:13AM -0500, Miguel Bernal Marin wrote: > > kernel/locking/rwsem.o: warning: objtool: downgrade_write()+0x22: call > > without frame pointer save/setup > > > > The warning means gcc 7.2.0 placed the __downgrade_write() inline asm (and > > its call instruction) before the frame pointer setup in downgrade_write(), > > which breaks frame pointer convention and can result in incorrect > > stack traces. > > > > Force a stack frame to be created before the call instruction by listing > > the stack pointer as an output operand in the inline asm statement. > > > > Signed-off-by: Miguel Bernal Marin <miguel.bernal.ma...@linux.intel.com> > > --- > > arch/x86/include/asm/rwsem.h | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h > > index d26b6916b935..a749dc6a3103 100644 > > --- a/arch/x86/include/asm/rwsem.h > > +++ b/arch/x86/include/asm/rwsem.h > > @@ -205,8 +205,10 @@ static inline void __up_write(struct rw_semaphore *sem) > > */ > > static inline void __downgrade_write(struct rw_semaphore *sem) > > { > > + register void *__sp asm(_ASM_SP); > > + > > asm volatile("# beginning __downgrade_write\n\t" > > - LOCK_PREFIX _ASM_ADD "%2,(%1)\n\t" > > + LOCK_PREFIX _ASM_ADD "%2,(%2)\n\t" > > The '%2' should be changed to '%3' > > LOCK_PREFIX _ASM_ADD "%3,(%2)\n\t" > > because both inputs' indices are shifted by the new output constraint. >
Thanks, I will send the V2. > > /* > > * transitions 0xZZZZ0001 -> 0xYYYY0001 (i386) > > * 0xZZZZZZZZ00000001 -> 0xYYYYYYYY00000001 (x86_64) > > @@ -215,7 +217,7 @@ static inline void __downgrade_write(struct > > rw_semaphore *sem) > > " call call_rwsem_downgrade_wake\n" > > "1:\n\t" > > "# ending __downgrade_write\n" > > - : "+m" (sem->count) > > + : "+m" (sem->count), "+r" (__sp) > > : "a" (sem), "er" (-RWSEM_WAITING_BIAS) > > : "memory", "cc"); > > -- > Josh -- Regards, Miguel Bernal Marin Open Source Technology Center https://clearlinux.org Intel Corporation