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authorJosh Poimboeuf <jpoimboe@redhat.com>2019-07-17 20:36:57 -0500
committerThomas Gleixner <tglx@linutronix.de>2019-07-18 21:01:10 +0200
commitb68b9907069a8d3a65bc16a35360bf8f8603c8fa (patch)
treeca8c51c1d05a67376139dd523809d6d84d8ccf57
parent9fe7b7642fe2c5158904d06fe31b740ca0695a01 (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.h1
-rw-r--r--tools/objtool/check.c12
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)) {