Re: [PATCH v4 00/21] KCFI support

[Peter Zijlstra]

On Thu, Sep 01, 2022 at 05:33:29PM -0700, Sami Tolvanen wrote:

> > I do see a few new objtool warnings as well:
> >
> > vmlinux.o: warning: objtool: apply_relocate_add+0x34: relocation to !ENDBR: memcpy+0x0
> > vmlinux.o: warning: objtool: ___ksymtab+__memcpy+0x0: data relocation to !ENDBR: memcpy+0x0
> > vmlinux.o: warning: objtool: ___ksymtab+memcpy+0x0: data relocation to !ENDBR: memcpy+0x0
> 
> That's interesting. I can only reproduce this warning with
> allmodconfig+LTO, even though the relocation exists in all builds (the
> code makes an indirect call to memcpy) and memcpy (aliased to
> __memcpy) doesn't start with endbr. I'll have to take a closer look at
> why this warning only appears with LTO.

>From just looking at the patches I'd say patch #19 breaks it. IIRC you
forgot to make the SYM_TYPED_FUNC things emit ENDBR.

Look at how x86/asm/linkage.h is overriding SYM_FUNC_START*().

You might have the same bug vs ARM64 BTI, they do the same thing.