diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2019-07-17 20:36:57 -0500 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-07-18 21:01:10 +0200 |
| commit | b68b9907069a8d3a65bc16a35360bf8f8603c8fa (patch) | |
| tree | ca8c51c1d05a67376139dd523809d6d84d8ccf57 | |
| parent | 9fe7b7642fe2c5158904d06fe31b740ca0695a01 (diff) | |
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: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/30d4c758b267ef487fb97e6ecb2f148ad007b554.1563413318.git.jpoimboe@redhat.com
| -rw-r--r-- | tools/objtool/arch.h | 1 | ||||
| -rw-r--r-- | tools/objtool/check.c | 12 |
2 files changed, 11 insertions, 2 deletions
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h index 50448c0c4bca..ced3765c4f44 100644 --- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -15,6 +15,7 @@ enum insn_type { INSN_JUMP_CONDITIONAL, INSN_JUMP_UNCONDITIONAL, INSN_JUMP_DYNAMIC, + INSN_JUMP_DYNAMIC_CONDITIONAL, INSN_CALL, INSN_CALL_DYNAMIC, INSN_RETURN, diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 04572a049cfc..5f26620f13f5 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -575,7 +575,11 @@ static int add_jump_destinations(struct objtool_file *file) * Retpoline jumps are really dynamic jumps in * 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; continue; } else { @@ -2114,13 +2118,17 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, break; case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: if (func && is_sibling_call(insn)) { ret = validate_sibling_call(insn, &state); if (ret) return ret; } - return 0; + if (insn->type == INSN_JUMP_DYNAMIC) + return 0; + + break; case INSN_CONTEXT_SWITCH: if (func && (!next_insn || !next_insn->hint)) { |