From: Dave Martin <Dave.Martin@arm.com>
To: "Chang S. Bae" <chang.seok.bae@intel.com>
Cc: tglx@linutronix.de, mingo@kernel.org, bp@suse.de,
luto@kernel.org, x86@kernel.org, len.brown@intel.com,
dave.hansen@intel.com, hjl.tools@gmail.com, mpe@ellerman.id.au,
tony.luck@intel.com, ravi.v.shankar@intel.com,
libc-alpha@sourceware.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/4] x86: Improve Minimum Alternate Stack Size
Date: Mon, 5 Oct 2020 14:45:34 +0100 [thread overview]
Message-ID: <20201005134534.GT6642@arm.com> (raw)
In-Reply-To: <20200929205746.6763-1-chang.seok.bae@intel.com>
On Tue, Sep 29, 2020 at 01:57:42PM -0700, Chang S. Bae wrote:
> During signal entry, the kernel pushes data onto the normal userspace
> stack. On x86, the data pushed onto the user stack includes XSAVE state,
> which has grown over time as new features and larger registers have been
> added to the architecture.
>
> MINSIGSTKSZ is a constant provided in the kernel signal.h headers and
> typically distributed in lib-dev(el) packages, e.g. [1]. Its value is
> compiled into programs and is part of the user/kernel ABI. The MINSIGSTKSZ
> constant indicates to userspace how much data the kernel expects to push on
> the user stack, [2][3].
>
> However, this constant is much too small and does not reflect recent
> additions to the architecture. For instance, when AVX-512 states are in
> use, the signal frame size can be 3.5KB while MINSIGSTKSZ remains 2KB.
>
> The bug report [4] explains this as an ABI issue. The small MINSIGSTKSZ can
> cause user stack overflow when delivering a signal.
>
> In this series, we suggest a couple of things:
> 1. Provide a variable minimum stack size to userspace, as a similar
> approach to [5]
> 2. Avoid using a too-small alternate stack
I can't comment on the x86 specifics, but the approach followed in this
series does seem consistent with the way arm64 populates
AT_MINSIGSTKSZ.
I need to dig up my glibc hacks for providing a sysconf interface to
this...
Cheers
---Dave
>
> [1]: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/bits/sigstack.h;h=b9dca794da093dc4d41d39db9851d444e1b54d9b;hb=HEAD
> [2]: https://www.gnu.org/software/libc/manual/html_node/Signal-Stack.html
> [3]: https://man7.org/linux/man-pages/man2/sigaltstack.2.html
> [4]: https://bugzilla.kernel.org/show_bug.cgi?id=153531
> [5]: https://blog.linuxplumbersconf.org/2017/ocw/system/presentations/4671/original/plumbers-dm-2017.pdf
>
> Chang S. Bae (4):
> x86/signal: Introduce helpers to get the maximum signal frame size
> x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ
> x86/signal: Prevent an alternate stack overflow before a signal
> delivery
> selftest/x86/signal: Include test cases for validating sigaltstack
>
> arch/x86/ia32/ia32_signal.c | 11 +-
> arch/x86/include/asm/elf.h | 4 +
> arch/x86/include/asm/fpu/signal.h | 2 +
> arch/x86/include/asm/sigframe.h | 25 +++++
> arch/x86/include/uapi/asm/auxvec.h | 6 +-
> arch/x86/kernel/cpu/common.c | 3 +
> arch/x86/kernel/fpu/signal.c | 20 ++++
> arch/x86/kernel/signal.c | 66 +++++++++++-
> tools/testing/selftests/x86/Makefile | 2 +-
> tools/testing/selftests/x86/sigaltstack.c | 126 ++++++++++++++++++++++
> 10 files changed, 258 insertions(+), 7 deletions(-)
> create mode 100644 tools/testing/selftests/x86/sigaltstack.c
>
> --
> 2.17.1
>
next prev parent reply other threads:[~2020-10-05 13:45 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-29 20:57 Chang S. Bae
2020-09-29 20:57 ` [RFC PATCH 1/4] x86/signal: Introduce helpers to get the maximum signal frame size Chang S. Bae
2020-10-05 13:42 ` Dave Martin
2020-10-06 17:45 ` Bae, Chang Seok
2020-10-07 10:05 ` Dave Martin
2020-10-08 22:43 ` Bae, Chang Seok
2020-10-12 13:26 ` Dave Martin
2020-09-29 20:57 ` [RFC PATCH 2/4] x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ Chang S. Bae
2020-09-29 20:57 ` [RFC PATCH 3/4] x86/signal: Prevent an alternate stack overflow before a signal delivery Chang S. Bae
2020-09-29 20:57 ` [RFC PATCH 4/4] selftest/x86/signal: Include test cases for validating sigaltstack Chang S. Bae
2020-10-05 13:45 ` Dave Martin [this message]
2020-10-05 21:17 ` [RFC PATCH 0/4] x86: Improve Minimum Alternate Stack Size H.J. Lu
2020-10-06 9:25 ` Dave Martin
2020-10-06 12:12 ` H.J. Lu
2020-10-06 15:18 ` H.J. Lu
2020-10-06 15:43 ` Dave Martin
2020-10-06 16:52 ` H.J. Lu
2020-10-06 15:25 ` Dave Martin
2020-10-06 15:33 ` Dave Hansen
2020-10-06 17:00 ` Dave Martin
2020-10-06 18:21 ` Florian Weimer
2020-10-07 10:19 ` Dave Martin
2020-10-06 18:30 ` Dave Hansen
2020-10-07 10:20 ` Dave Martin
2020-10-06 15:34 ` H.J. Lu
2020-10-06 16:55 ` Dave Martin
2020-10-06 17:44 ` H.J. Lu
2020-10-07 10:47 ` Dave Martin
2020-10-07 13:30 ` H.J. Lu
2020-10-07 15:45 ` Dave Martin
2020-10-07 17:43 ` H.J. Lu
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