Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps

Peter Zijlstra
2020-10-22T07:26:26Z

On Wed, Oct 21, 2020 at 04:27:47PM -0500, Josh Poimboeuf wrote:
> On Wed, Oct 21, 2020 at 11:32:13AM +0200, Peter Zijlstra wrote:
> > On Wed, Oct 21, 2020 at 10:56:06AM +0200, Peter Zijlstra wrote:
> >
> > > I do not see these in particular, although I do see a lot of:
> > >
> > > "sibling call from callable instruction with modified stack frame"
> >
> > defconfig-build/vmlinux.o: warning: objtool: msr_write()+0x10a: sibling call from callable instruction with modified stack frame
> > defconfig-build/vmlinux.o: warning: objtool: msr_write()+0x99: (branch)
> > defconfig-build/vmlinux.o: warning: objtool: msr_write()+0x3e: (branch)
> > defconfig-build/vmlinux.o: warning: objtool: msr_write()+0x0: <=== (sym)
> >
> > $ nm defconfig-build/vmlinux.o | grep msr_write
> > 0000000000043250 t msr_write
> > 00000000004289c0 T msr_write
> > 0000000000003056 t msr_write.cold
> >
> > Below 'fixes' it. So this is also caused by duplicate symbols.
>
> There's a new linker flag for renaming duplicates:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=26391
>
> But I guess that doesn't help us now.

Well, depends a bit if clang can do it; we only need this for LTO builds
for now.

> I don't have access to GCC 10 at the moment so I can't recreate it.
> Does this fix it?

Doesn't seem to do the trick :/ I'll try and have a poke later.