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... 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 @@ -1779,7 +1779,8 @@ 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?",