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objtool: Move the IRET hack into the arch decoder

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Quoting Julien:

  "And the other suggestion is my other email was that you don't even
  need to add INSN_EXCEPTION_RETURN. You can keep IRET as
  INSN_CONTEXT_SWITCH by default and x86 decoder lookups the symbol
  conaining an iret. If it's a function symbol, it can just set the type
  to INSN_OTHER so that it caries on to the next instruction after
  having handled the stack_op."

Suggested-by: Julien Thierry <jthierry@redhat.com>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200428191659.913283807@infradead.org
This commit is contained in:
Miroslav Benes
2020-04-24 16:30:42 +02:00
committed by Peter Zijlstra
parent b09fb65e86
commit b490f45362
5 changed files with 21 additions and 25 deletions
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28
tools/objtool/arch/x86/decode.c
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@@ -94,6 +94,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,
modrm_reg = 0, sib = 0;
struct stack_op *op = NULL;
struct symbol *sym;
x86_64 = is_x86_64(elf);
if (x86_64 == -1)
@@ -469,17 +470,24 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
break;
case 0xcf: /* iret */
*type = INSN_EXCEPTION_RETURN;
ADD_OP(op) {
/* 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;
/*
* Handle sync_core(), which has an IRET to self.
* All other IRET are in STT_NONE entry code.
*/
sym = find_symbol_containing(sec, offset);
if (sym && sym->type == STT_FUNC) {
ADD_OP(op) {
/* 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;
}
break;
/* fallthrough */
case 0xca: /* retf */
case 0xcb: /* retf */