Re: [PATCH v2] arm64: vdso: Fix ABI regression in compat vdso

Will Deacon
2019-07-11T09:45:15Z

On Wed, Jul 10, 2019 at 03:01:19PM +0100, Vincenzo Frascino wrote:
> Prior to the introduction of Unified vDSO support and compat layer for
> vDSO on arm64, AT_SYSINFO_EHDR was not defined for compat tasks.
> In the current implementation, AT_SYSINFO_EHDR is defined even if the
> compat vdso layer is not built and this causes a regression in the
> expected behavior of the ABI.
>
> Restore the ABI behavior making sure that AT_SYSINFO_EHDR for compat
> tasks is defined only when CONFIG_COMPAT_VDSO is enabled.
>
> Reported-by: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
> arch/arm64/include/asm/elf.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index 3c7037c6ba9b..b618017205a3 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -202,7 +202,7 @@ typedef compat_elf_greg_t compat_elf_gregset_t[COMPAT_ELF_NGREG];
> ({ \
> set_thread_flag(TIF_32BIT); \
> })
> -#ifdef CONFIG_GENERIC_COMPAT_VDSO
> +#ifdef CONFIG_COMPAT_VDSO
> #define COMPAT_ARCH_DLINFO \
> do { \
> /* \

Acked-by: Will Deacon <will@kernel.org>

I can take this at -rc1 via arm64 unless tglx plans to send it during the
rest of the merge window. Please let me know.

Will