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Subject[PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for __up_read()
Date
kernel/locking/rwsem.o: warning: objtool: up_read()+0x11: call without frame pointer save/setup

The warning means gcc 7.2.0 placed the __up_read() inline asm (and its
call instruction) before the frame pointer setup in up_read(),
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.marin@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 a34e0d4b957d..762167afaec0 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -166,14 +166,16 @@ static inline bool __down_write_trylock(struct rw_semaphore *sem)
static inline void __up_read(struct rw_semaphore *sem)
{
long tmp;
+ register void *__sp asm(_ASM_SP);
+
asm volatile("# beginning __up_read\n\t"
- LOCK_PREFIX " xadd %1,(%2)\n\t"
+ LOCK_PREFIX " xadd %1,(%3)\n\t"
/* subtracts 1, returns the old value */
" jns 1f\n\t"
" call call_rwsem_wake\n" /* expects old value in %edx */
"1:\n"
"# ending __up_read\n"
- : "+m" (sem->count), "=d" (tmp)
+ : "+m" (sem->count), "=d" (tmp), "+r" (__sp)
: "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS)
: "memory", "cc");
}
--
2.14.1
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