Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32

Catalin Marinas
2015-12-16T16:58:30Z

On Wed, Dec 16, 2015 at 04:54:34PM +0100, Arnd Bergmann wrote:
> On Wednesday 16 December 2015 00:42:35 Yury Norov wrote:
> >
> > #ifdef CONFIG_COMPAT
> > -#define COMPAT_ELF_HWCAP (compat_elf_hwcap)
> > -#define COMPAT_ELF_HWCAP2 (compat_elf_hwcap2)
> > extern unsigned int compat_elf_hwcap, compat_elf_hwcap2;
> > +#define COMPAT_ELF_HWCAP \
> > + (is_a32_compat_task() \
> > + ? compat_elf_hwcap \
> > + : elf_hwcap)
> > +
> > +#define COMPAT_ELF_HWCAP2 \
> > + (is_a32_compat_task() \
> > + ? compat_elf_hwcap2 \
> > + : 0)
> > +
> > #endif
>
> I'm trying to understand how this is used. Are you compiling
> fs/compat_binfmt_elf.c twice to handle both 32-bit ELF types?

It's the same compat_binfmt_elf.c which handles all 32-bit ELF types,
i.e. AArch32 and A64/ILP32. The above macros are not constants, so they
are evaluated every time a new ELF file is loaded. We do a similar trick
with COMPAT_SET_PERSONALITY in patch 11.

--
Catalin