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 /tools/objtool/arch/x86 | |
| parent | objtool: Support multiple stack_op per instruction (diff) | |
| download | linux-b746046238bb99b8f703c79f6d95357428fb6476.tar.xz linux-b746046238bb99b8f703c79f6d95357428fb6476.zip | |
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 'tools/objtool/arch/x86')
| -rw-r--r-- | tools/objtool/arch/x86/decode.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 199b4084a13c..32736383ead1 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -446,9 +446,19 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, *type = INSN_RETURN; break; + case 0xcf: /* iret */ + *type = INSN_EXCEPTION_RETURN; + + /* add $40, %rsp */ + op->src.type = OP_SRC_ADD; + op->src.reg = CFI_SP; + op->src.offset = 5*8; + op->dest.type = OP_DEST_REG; + op->dest.reg = CFI_SP; + break; + case 0xca: /* retf */ case 0xcb: /* retf */ - case 0xcf: /* iret */ *type = INSN_CONTEXT_SWITCH; break; @@ -494,7 +504,7 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, *immediate = insn.immediate.nbytes ? insn.immediate.value : 0; - if (*type == INSN_STACK) + if (*type == INSN_STACK || *type == INSN_EXCEPTION_RETURN) list_add_tail(&op->list, ops_list); else free(op); |