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objtool: Detect missing __noreturn annotations

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Most "unreachable instruction" warnings these days seem to actually be
the result of a missing __noreturn annotation.  Add an explicit check
for that.

Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/6e2b93d8c65eaed6c4166a358269dc0ef01f890c.1681853186.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
This commit is contained in:
Josh Poimboeuf 2023-04-18 14:27:50 -07:00
parent ced23d2e37
commit fedb724c3d
2 changed files with 19 additions and 1 deletions
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6
tools/objtool/Documentation/objtool.txt
View file

@ -303,6 +303,12 @@ the objtool maintainers.
If it's not actually in a callable function (e.g. kernel entry code),
change ENDPROC to END.
3. file.o: warning: objtool: foo+0x48c: bar() is missing a __noreturn annotation
The call from foo() to bar() doesn't return, but bar() is missing the
__noreturn annotation. NOTE: In addition to adding the __noreturn
annotation, the function name also needs to be added to
'global_noreturns' in tools/objtool/check.c.
4. file.o: warning: objtool: func(): can't find starting instruction
or

14
tools/objtool/check.c
View file

@ -4507,7 +4507,8 @@ static int validate_sls(struct objtool_file *file)
static int validate_reachable_instructions(struct objtool_file *file)
{
struct instruction *insn;
struct instruction *insn, *prev_insn;
struct symbol *call_dest;
int warnings = 0;
if (file->ignore_unreachables)
@ -4517,6 +4518,17 @@ static int validate_reachable_instructions(struct objtool_file *file)
if (insn->visited || ignore_unreachable_insn(file, insn))
continue;
prev_insn = prev_insn_same_sec(file, insn);
if (prev_insn && prev_insn->dead_end) {
call_dest = insn_call_dest(prev_insn);
if (call_dest) {
WARN_INSN(insn, "%s() is missing a __noreturn annotation",
call_dest->name);
warnings++;
continue;
}
}
WARN_INSN(insn, "unreachable instruction");
warnings++;
}