From 4855022a52262411ce38c93dec4cb1470705c0a0 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 7 Jul 2017 09:19:42 -0500 Subject: [PATCH] objtool: Fix sibling call detection logic With some configs, objtool reports the following warning: arch/x86/kernel/ftrace.o: warning: objtool: ftrace_modify_code_direct()+0x2d: sibling call from callable instruction with modified stack frame The instruction it's complaining about isn't actually a sibling call. It's just a normal jump to an address inside the function. Objtool thought it was a sibling call because the instruction's jump_dest wasn't initialized because the function was supposed to be ignored due to its use of sync_core(). Objtool ended up validating the function instead of ignoring it because it didn't properly recognize a sibling call to the function. So fix the sibling call logic. Also add a warning to catch ignored functions being validated so we'll get a more useful error message next time. Reported-by: Mike Galbraith Signed-off-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/96cc8ecbcdd8cb29ddd783817b4af918a6a171b0.1499437107.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- tools/objtool/check.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index fea222192c57..2c6d74880403 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1371,6 +1371,12 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, func = insn->func; + if (func && insn->ignore) { + WARN_FUNC("BUG: why am I validating an ignored function?", + sec, insn->offset); + return -1; + } + if (insn->visited) { if (!!insn_state_match(insn, &state)) return 1; @@ -1426,16 +1432,19 @@ static int validate_branch(struct objtool_file *file, struct instruction *first, case INSN_JUMP_CONDITIONAL: case INSN_JUMP_UNCONDITIONAL: - if (insn->jump_dest) { + if (insn->jump_dest && + (!func || !insn->jump_dest->func || + func == insn->jump_dest->func)) { ret = validate_branch(file, insn->jump_dest, state); if (ret) return 1; + } else if (func && has_modified_stack_frame(&state)) { WARN_FUNC("sibling call from callable instruction with modified stack frame", sec, insn->offset); return 1; - } /* else it's a sibling call */ + } if (insn->type == INSN_JUMP_UNCONDITIONAL) return 0;