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From: Markus Gutschke <markus@chromium.org>
Date: Thu, 23 Feb 2012 14:33:02 -0800
Message-ID: <CAE6n16kusCN9LxwqB1D2Dsm50mtc-6zkRje69D=QDdxxzWFTKw@mail.gmail.com>
Subject: Re: [PATCH v10 07/11] signal, x86: add SIGSYS info and make it synchronous.
To: Indan Zupancic <indan@nul.nu>
Cc: Will Drewry <wad@chromium.org>, 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,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        kernel-hardening@lists.openwall.com, netdev@vger.kernel.org,
        x86@kernel.org, arnd@arndb.de, davem@davemloft.net, mingo@redhat.com,
        oleg@redhat.com, peterz@infradead.org, rdunlap@xenotime.net,
        tglx@linutronix.de, eparis@redhat.com, serge.hallyn@canonical.com,
        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 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.


Markus
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