diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2020-04-02 10:15:51 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-04-22 10:53:50 +0200 |
| commit | b746046238bb99b8f703c79f6d95357428fb6476 (patch) | |
| tree | 729da97c53ce749b6b2b27c2338404e05cfd8c04 /arch/x86/include/asm/processor.h | |
| parent | 65ea47dcf4f936987a5fbf839c97acea00f4f196 (diff) | |
objtool: Better handle IRET
Teach objtool a little more about IRET so that we can avoid using the
SAVE/RESTORE annotation. In particular, make the weird corner case in
insn->restore go away.
The purpose of that corner case is to deal with the fact that
UNWIND_HINT_RESTORE lands on the instruction after IRET, but that
instruction can end up being outside the basic block, consider:
if (cond)
sync_core()
foo();
Then the hint will land on foo(), and we'll encounter the restore
hint without ever having seen the save hint.
By teaching objtool about the arch specific exception frame size, and
assuming that any IRET in an STT_FUNC symbol is an exception frame
sized POP, we can remove the use of save/restore hints for this code.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200416115118.631224674@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/processor.h')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 3bcf27caf6c9..3eeaaeb75638 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -727,7 +727,6 @@ static inline void sync_core(void) unsigned int tmp; asm volatile ( - UNWIND_HINT_SAVE "mov %%ss, %0\n\t" "pushq %q0\n\t" "pushq %%rsp\n\t" @@ -737,7 +736,6 @@ static inline void sync_core(void) "pushq %q0\n\t" "pushq $1f\n\t" "iretq\n\t" - UNWIND_HINT_RESTORE "1:" : "=&r" (tmp), ASM_CALL_CONSTRAINT : : "cc", "memory"); #endif |