| From e6f393bc939d566ce3def71232d8013de9aaadde Mon Sep 17 00:00:00 2001 |
| From: Josh Poimboeuf <jpoimboe@redhat.com> |
| Date: Mon, 13 May 2019 12:01:32 -0500 |
| Subject: objtool: Fix function fallthrough detection |
| |
| From: Josh Poimboeuf <jpoimboe@redhat.com> |
| |
| commit e6f393bc939d566ce3def71232d8013de9aaadde upstream. |
| |
| When a function falls through to the next function due to a compiler |
| bug, objtool prints some obscure warnings. For example: |
| |
| drivers/regulator/core.o: warning: objtool: regulator_count_voltages()+0x95: return with modified stack frame |
| drivers/regulator/core.o: warning: objtool: regulator_count_voltages()+0x0: stack state mismatch: cfa1=7+32 cfa2=7+8 |
| |
| Instead it should be printing: |
| |
| drivers/regulator/core.o: warning: objtool: regulator_supply_is_couple() falls through to next function regulator_count_voltages() |
| |
| This used to work, but was broken by the following commit: |
| |
| 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions") |
| |
| The padding nops at the end of a function aren't actually part of the |
| function, as defined by the symbol table. So the 'func' variable in |
| validate_branch() is getting cleared to NULL when a padding nop is |
| encountered, breaking the fallthrough detection. |
| |
| If the current instruction doesn't have a function associated with it, |
| just consider it to be part of the previously detected function by not |
| overwriting the previous value of 'func'. |
| |
| Reported-by: kbuild test robot <lkp@intel.com> |
| Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: <stable@vger.kernel.org> |
| Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions") |
| Link: http://lkml.kernel.org/r/546d143820cd08a46624ae8440d093dd6c902cae.1557766718.git.jpoimboe@redhat.com |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| tools/objtool/check.c | 3 ++- |
| 1 file changed, 2 insertions(+), 1 deletion(-) |
| |
| --- a/tools/objtool/check.c |
| +++ b/tools/objtool/check.c |
| @@ -1832,7 +1832,8 @@ static int validate_branch(struct objtoo |
| return 1; |
| } |
| |
| - func = insn->func ? insn->func->pfunc : NULL; |
| + if (insn->func) |
| + func = insn->func->pfunc; |
| |
| if (func && insn->ignore) { |
| WARN_FUNC("BUG: why am I validating an ignored function?", |
