Re: [PATCH v1 01/10] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

Michael Ellerman
2021-10-12T07:10:32Z

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> 'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h

Agree, but ...

> It was initially in module_64.c and commit 2d291e902791 ("Fix compile
> failure with non modular builds") moved it into asm/elf.h
>
> But it was by mistake added outside of __KERNEL__ section,
> therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
> arch/powerpc/include/asm") moved it to uapi/asm/elf.h

... it's been visible to userspace since the first commit moved it, ~13
years ago in 2008, v2.6.27.

> Move it back into asm/elf.h, this brings it back in line with
> IA64 and PARISC architectures.

Removing it from the uapi header risks breaking userspace, I doubt
anything uses it, but who knows.

Given how long it's been there I think it's a bit risky to remove it :/

> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index b8425e3cfd81..64b523848cd7 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -176,4 +176,11 @@ do { \
> /* Relocate the kernel image to @final_address */
> void relocate(unsigned long final_address);
>
> +/* There's actually a third entry here, but it's unused */
> +struct ppc64_opd_entry
> +{
> + unsigned long funcaddr;
> + unsigned long r2;
> +};
> +
> #endif /* _ASM_POWERPC_ELF_H */
> diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
> index 860c59291bfc..308857123a08 100644
> --- a/arch/powerpc/include/uapi/asm/elf.h
> +++ b/arch/powerpc/include/uapi/asm/elf.h
> @@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
> /* Keep this the last entry. */
> #define R_PPC64_NUM 253
>
> -/* There's actually a third entry here, but it's unused */
> -struct ppc64_opd_entry
> -{
> - unsigned long funcaddr;
> - unsigned long r2;
> -};

Rather than removing it we can make it uapi only with:

#ifndef __KERNEL__
/* There's actually a third entry here, but it's unused */
struct ppc64_opd_entry
{
unsigned long funcaddr;
unsigned long r2;
};
#endif

And then we can do whatever we want with the kernel internal version.

cheers