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Date: Thu, 23 Feb 2012 16:36:21 -0600
Message-ID: <CABqD9hbE_0mDADUAcU3JYeEroj-57Mz2etd2NaPV_Sb3JpJ21Q@mail.gmail.com>
Subject: Re: [PATCH v10 07/11] signal, x86: add SIGSYS info and make it synchronous.
From: Will Drewry <wad@chromium.org>
To: Markus Gutschke <markus@chromium.org>
Cc: Indan Zupancic <indan@nul.nu>, Roland McGrath <mcgrathr@google.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Kees Cook <keescook@chromium.org>,
        Andrew Lutomirski <luto@mit.edu>, linux-kernel@vger.kernel.org,
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        djm@mindrot.org, scarybeasts@gmail.com, pmoore@redhat.com,
        akpm@linux-foundation.org, corbet@lwn.net, eric.dumazet@gmail.com
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On Thu, Feb 23, 2012 at 4:33 PM, Markus Gutschke <markus@chromium.org> wrote:
> On Thu, Feb 23, 2012 at 14:15, Indan Zupancic <indan@nul.nu> wrote:
>> What about making SECCOMP_RET_TRAP dump core/send SIGSYS if there is
>> no tracer with PTRACE_O_SECCOMP set?
>
> Please don't make things dependent on having a tracer. There are
> applications that don't really need a tracer; in fact, these are
> typically the exact same applications that can benefit from receiving
> SIGSYS and then handling it internally.
>
> If a tracer was required to set this up, it would make it difficult to
> use gdb, strace, or any other common debugging tools.
>
>> Sending SIGSYS is useful, but it's quite a bit less useful if user
>> space can't handle it in a signal handler, so I don't think it's
>> worth it to make a unblockable version.
>
> Maybe, I am not parsing your e-mail correctly. But don't we already
> get the desired behavior, if SIGSYS is treated the same as any other
> synchronous signal? If it is unblocked and has a handler, the
> application can decide to handle it. If neither one of these
> conditions is true, it terminates the program. Ulimits and
> PR_SET_DUMPABLE determine whether a core file is generated.

Yeah - the current patchset does that just fine. The tweak I was
proposing was making ti possible to deliver an SIGSYS that always uses
SIG_DFL so that you don't have to play with signal call enforcement in
the filters.

This is a pretty minor tweak either way.
cheers!
will
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