Commit b68b9907 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Thomas Gleixner

objtool: Support conditional retpolines

A Clang-built kernel is showing the following warning:

  arch/x86/kernel/platform-quirks.o: warning: objtool: x86_early_init_platform_quirks()+0x84: unreachable instruction

That corresponds to this code:

  7e:   0f 85 00 00 00 00       jne    84 <x86_early_init_platform_quirks+0x84>
                        80: R_X86_64_PC32       __x86_indirect_thunk_r11-0x4
  84:   c3                      retq

This is a conditional retpoline sibling call, which is now possible
thanks to retpolines.  Objtool hasn't seen that before.  It's
incorrectly interpreting the conditional jump as an unconditional
dynamic jump.
Reported-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/30d4c758b267ef487fb97e6ecb2f148ad007b554.1563413318.git.jpoimboe@redhat.com
parent 9fe7b764
...@@ -15,6 +15,7 @@ enum insn_type { ...@@ -15,6 +15,7 @@ enum insn_type {
INSN_JUMP_CONDITIONAL, INSN_JUMP_CONDITIONAL,
INSN_JUMP_UNCONDITIONAL, INSN_JUMP_UNCONDITIONAL,
INSN_JUMP_DYNAMIC, INSN_JUMP_DYNAMIC,
INSN_JUMP_DYNAMIC_CONDITIONAL,
INSN_CALL, INSN_CALL,
INSN_CALL_DYNAMIC, INSN_CALL_DYNAMIC,
INSN_RETURN, INSN_RETURN,
......
...@@ -575,7 +575,11 @@ static int add_jump_destinations(struct objtool_file *file) ...@@ -575,7 +575,11 @@ static int add_jump_destinations(struct objtool_file *file)
* Retpoline jumps are really dynamic jumps in * Retpoline jumps are really dynamic jumps in
* disguise, so convert them accordingly. * disguise, so convert them accordingly.
*/ */
insn->type = INSN_JUMP_DYNAMIC; if (insn->type == INSN_JUMP_UNCONDITIONAL)
insn->type = INSN_JUMP_DYNAMIC;
else
insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
insn->retpoline_safe = true; insn->retpoline_safe = true;
continue; continue;
} else { } else {
...@@ -2114,13 +2118,17 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, ...@@ -2114,13 +2118,17 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
break; break;
case INSN_JUMP_DYNAMIC: case INSN_JUMP_DYNAMIC:
case INSN_JUMP_DYNAMIC_CONDITIONAL:
if (func && is_sibling_call(insn)) { if (func && is_sibling_call(insn)) {
ret = validate_sibling_call(insn, &state); ret = validate_sibling_call(insn, &state);
if (ret) if (ret)
return ret; return ret;
} }
return 0; if (insn->type == INSN_JUMP_DYNAMIC)
return 0;
break;
case INSN_CONTEXT_SWITCH: case INSN_CONTEXT_SWITCH:
if (func && (!next_insn || !next_insn->hint)) { if (func && (!next_insn || !next_insn->hint)) {
......
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