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

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Message-ID: <20190711113238.qefdp5zvrjhsmtfu@willie-the-truck>
Date:   Thu, 11 Jul 2019 12:32:39 +0100
From:   Will Deacon <will@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-kselftest@...r.kernel.org, shuah@...nel.org,
        andre.przywara@....com, arnd@...db.de, huw@...eweavers.com,
        catalin.marinas@....com, daniel.lezcano@...aro.org,
        will.deacon@....com, linux@...linux.org.uk, ralf@...ux-mips.org,
        salyzyn@...roid.com, luto@...nel.org, paul.burton@...s.com,
        john.stultz@...aro.org, 0x7f454c46@...il.com,
        linux@...musvillemoes.dk, sthotton@...vell.com, pcc@...gle.com
Subject: Re: [PATCH v2] arm64: vdso: Fix ABI regression in compat vdso

On Thu, Jul 11, 2019 at 12:34:27PM +0200, Thomas Gleixner wrote:
> On Thu, 11 Jul 2019, Will Deacon wrote:
> > 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@...aro.org>
> > > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....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@...nel.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.
> 
> I had no plan to pick it up, but if you want I can route it through timer
> urgents so it hits Linus tree before rc1.

I don't think it's urgent, so I'll just queue it along with any other fixes
that show up at -rc1.

Cheers,

Will