From: Josh Poimboeuf <[email protected]>
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 <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: <[email protected]>
Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Link:
http://lkml.kernel.org/r/546d143820cd08a46624ae8440d093dd6c902cae.1557766718.git.jpoim...@redhat.com
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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?",
