linux-kernel - Re: objtool crashes on clang output (drivers/hwmon/pmbus/adm1275.o)

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Date:   Fri, 12 Jul 2019 22:40:59 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Jann Horn <jannh@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: objtool crashes on clang output (drivers/hwmon/pmbus/adm1275.o)

On Fri, Jul 12, 2019 at 6:59 PM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@...glegroups.com> wrote:
> > The issue still needs to get fixed in clang regardless.  There are other
> > noreturn functions in the kernel and this problem could easily pop back
> > up.
>
> Sure, thanks for the report.  Arnd, can you help us get a more minimal
> test case to understand the issue better?

I reduced it to this testcase:

int a, b;
void __reiserfs_panic(int, ...) __attribute__((noreturn));
void balance_internal() {
  if (a)
    __reiserfs_panic(0, "", __func__, "", 2, __func__, a);
  if (b)
    __reiserfs_panic(0, "", __func__, "", 5, __func__, a, 0);
}

https://godbolt.org/z/Byfvmx

$ clang-8 -mstack-alignment=8 -S ibalance.c -Wall -Os   -c
$ objtool orc generate ibalance.o
ibalance.o: warning: objtool: balance_internal()+0x61: stack state
mismatch: cfa1=7+8 cfa2=7+16

       Arnd