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Date:   Thu, 11 Jul 2019 10:45:06 +0100
From:   Will Deacon <will@kernel.org>
To:     Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc:     linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
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        catalin.marinas@arm.com, daniel.lezcano@linaro.org,
        will.deacon@arm.com, linux@armlinux.org.uk, ralf@linux-mips.org,
        salyzyn@android.com, luto@kernel.org, paul.burton@mips.com,
        john.stultz@linaro.org, 0x7f454c46@gmail.com,
        linux@rasmusvillemoes.dk, tglx@linutronix.de, sthotton@marvell.com,
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Subject: Re: [PATCH v2] arm64: vdso: Fix ABI regression in compat vdso
Message-ID: <20190711094505.rwy6t6wu2cvmvwr6@willie-the-truck>
References: <20190621095252.32307-11-vincenzo.frascino@arm.com>
 <20190710140119.23417-1-vincenzo.frascino@arm.com>
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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