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SubjectRe: new objtool warnings again...
On Fri, Sep 23, 2016 at 01:33:45PM -0700, Linus Torvalds wrote:
> Josh,
>
> the current F24 toolchain causes
>
> kernel/signal.o: warning: objtool: .altinstr_replacement+0x54:
> call without frame pointer save/setup
>
> during a regular allmodconfig build.
>
> Doing an objdump says:
>
> ...
> 54: e8 00 00 00 00 callq 59 <.altinstr_replacement+0x59>
> 55: R_X86_64_PC32 copy_user_generic_string-0x4
> 59: e8 00 00 00 00 callq 5e <.altinstr_replacement+0x5e>
> 5a: R_X86_64_PC32
> copy_user_enhanced_fast_string-0x4
> ...
>
> so it seems to come from the alternative_call_2() in copy_user_generic().
>
> It's somewhere in copy_siginfo_to_user(), so I assume it's just the
>
> if (from->si_code < 0)
> return __copy_to_user(to, from, sizeof(siginfo_t))
> ? -EFAULT : 0;
>
> case. Looking at the code generation, it looks like the frame pointer
> generation in that function has been moved down past this code, so the
> objtool warning seems to be correct, but this indicates that gcc has
> decided that we don't need a frame for that alternative_call_2()
> thing.
>
> So this code is clearly missing the magic to tell gcc that the asm
> needs a frame pointer.
>
> What was that magic again? Mind sending a patch?

Is this with your latest pushed master branch? I have F24, but I don't
see the warning.

In any case, I'll come up with a patch for you to test.

--
Josh

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