From: Nick Desaulniers <ndesaulniers@google.com>
To: Will McVicker <willmcvicker@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Nathan Chancellor <natechancellor@gmail.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Andrei Vagin <avagin@gmail.com>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
kernel-team <kernel-team@android.com>
Subject: Re: [PATCH] arm64: Fix off-by-one vdso trampoline return value
Date: Wed, 11 Nov 2020 18:14:15 -0800 [thread overview]
Message-ID: <CAKwvOdnjMhjxawxNembM+XrMctitm13Cvh8gbMPEcXiPBhacPA@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdkDG2wt=ZT93GT7r60_qXn=tdW_zWiJ1Gr5JVdRvcU8uw@mail.gmail.com>
On Wed, Nov 11, 2020 at 5:00 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Wed, Nov 11, 2020 at 4:14 PM Will McVicker <willmcvicker@google.com> wrote:
> >
> > Depending on your host nm version, the generated header
> > `include/generated/vdso32-offsets.h` may have the bottom bit set for the
> > thumb vdso offset addresses (as observed when using llvm-nm). This
>
> Sorry, the commit message seems to imply a bug in llvm-nm, but I don't
> think that's the case. If it is, please, send us a bugreport.
>
> $ aarch64-linux-gnu-nm arch/arm64/kernel/vdso32/vdso.so.raw | grep thumb
> 00000968 T __kernel_rt_sigreturn_thumb
> 00000960 T __kernel_sigreturn_thumb
> 00000968 t VDSO_compat_rt_sigreturn_thumb
> 00000960 t VDSO_compat_sigreturn_thumb
> $ llvm-nm arch/arm64/kernel/vdso32/vdso.so.raw | grep thumb
> 00000968 t VDSO_compat_rt_sigreturn_thumb
> 00000960 t VDSO_compat_sigreturn_thumb
> 00000968 T __kernel_rt_sigreturn_thumb
> 00000960 T __kernel_sigreturn_thumb
> $ /usr/bin/nm arch/arm64/kernel/vdso32/vdso.so.raw | grep thumb
> 00000969 T __kernel_rt_sigreturn_thumb
> 00000961 T __kernel_sigreturn_thumb
> 00000969 t VDSO_compat_rt_sigreturn_thumb
> 00000961 t VDSO_compat_sigreturn_thumb
> $ /usr/bin/nm --version
> GNU nm (GNU Binutils for Debian) 2.35.1
>
> Would you mind amending the commit message to not imply that llvm-nm is broken?
Testing another set of configs:
$ aarch64-linux-android-nm arch/arm64/kernel/vdso32/vdso.so.dbg | grep thumb
00000950 T __kernel_rt_sigreturn_thumb
00000948 T __kernel_sigreturn_thumb
00000951 t VDSO_compat_rt_sigreturn_thumb
00000949 t VDSO_compat_sigreturn_thumb
$ /path/to/older/aarch64-linux-gnu-nm
arch/arm64/kernel/vdso32/vdso.so.dbg | grep thumb
00000950 T __kernel_rt_sigreturn_thumb
00000948 T __kernel_sigreturn_thumb
00000951 t VDSO_compat_rt_sigreturn_thumb
00000949 t VDSO_compat_sigreturn_thumb
$ /usr/bin/nm out/android-4.19-stable/common/arch/arm64/kernel/vdso32/vdso.so.dbg
| grep thumb
00000951 T __kernel_rt_sigreturn_thumb
00000949 T __kernel_sigreturn_thumb
00000951 t VDSO_compat_rt_sigreturn_thumb
00000949 t VDSO_compat_sigreturn_thumb
$ llvm-nm out/android-4.19-stable/common/arch/arm64/kernel/vdso32/vdso.so.dbg
| grep thumb
00000951 t VDSO_compat_rt_sigreturn_thumb
00000949 t VDSO_compat_sigreturn_thumb
00000950 T __kernel_rt_sigreturn_thumb
00000948 T __kernel_sigreturn_thumb
(That llvm-nm sorts the output makes this trickier to follow). But
shows that only host GNU `nm` differs.
>
> It might be of interest to find out why the host `nm` was invoked,
> rather than $(NM)/$(CROSS_COMPILE)nm.
Possibly commit 7b7891c7bdfd ("arm64: vdso32: Fix '--prefix=' value
for newer versions of clang") missing from your tree, but I fail to
see how that would mess up or invoke the incorrect $(NM).
>
> > results in an additional +1 for thumb vdso trampoline return values
> > since compat_setup_return() already includes `vdso_trampoline + thumb`.
> > As a result, I see a SIGBUS error when running the LTP test
> > syscalls.rt_sigaction01. To fix this, let's clear the bottom bit of the
> > vdso_offset in the VDSO_SYMBOL macro.
> >
> > Test: LTP test syscalls.rt_sigaction01
> > Fixes: f01703b3d2e6 ("arm64: compat: Get sigreturn trampolines from vDSO")
> > Signed-off-by: Will McVicker <willmcvicker@google.com>
> > ---
> > arch/arm64/include/asm/vdso.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/include/asm/vdso.h b/arch/arm64/include/asm/vdso.h
> > index f99dcb94b438..a7384379e8e1 100644
> > --- a/arch/arm64/include/asm/vdso.h
> > +++ b/arch/arm64/include/asm/vdso.h
> > @@ -23,7 +23,7 @@
> >
> > #define VDSO_SYMBOL(base, name) \
> > ({ \
> > - (void *)(vdso_offset_##name - VDSO_LBASE + (unsigned long)(base)); \
> > + (void *)((vdso_offset_##name & ~1UL) - VDSO_LBASE + (unsigned long)(base)); \
> > })
> >
> > #endif /* !__ASSEMBLY__ */
> > --
> > 2.29.2.299.gdc1121823c-goog
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2020-11-12 5:34 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-12 0:14 [PATCH] arm64: Fix off-by-one vdso trampoline return value Will McVicker
2020-11-12 1:00 ` Nick Desaulniers
2020-11-12 1:07 ` Nick Desaulniers
2020-11-12 2:14 ` Nick Desaulniers [this message]
2020-11-12 10:12 ` Will Deacon
2020-11-12 18:51 ` William Mcvicker
2020-11-16 22:55 ` William Mcvicker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAKwvOdnjMhjxawxNembM+XrMctitm13Cvh8gbMPEcXiPBhacPA@mail.gmail.com \
--to=ndesaulniers@google.com \
--cc=0x7f454c46@gmail.com \
--cc=avagin@gmail.com \
--cc=catalin.marinas@arm.com \
--cc=clang-built-linux@googlegroups.com \
--cc=kernel-team@android.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=natechancellor@gmail.com \
--cc=tglx@linutronix.de \
--cc=vincenzo.frascino@arm.com \
--cc=will@kernel.org \
--cc=willmcvicker@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).