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

Will Deacon
2019-07-11T11:32:47Z

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@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.
>
> 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