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Re: [PATCH -v2] Audit: push audit success and retcode into arch p

To: Eric Paris <eparis@redhat.com>
Subject: Re: [PATCH -v2] Audit: push audit success and retcode into arch ptrace.h
From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 8 Jun 2011 18:36:53 +0200
Cc: linux-kernel@vger.kernel.org, tony.luck@intel.com, fenghua.yu@intel.com, monstr@monstr.eu, ralf@linux-mips.org, benh@kernel.crashing.org, paulus@samba.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, linux390@de.ibm.com, lethal@linux-sh.org, davem@davemloft.net, jdike@addtoit.com, richard@nod.at, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, linux-ia64@vger.kernel.org, microblaze-uclinux@itee.uq.edu.au, linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net
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On 06/07, Eric Paris wrote:
>
> On Tue, 2011-06-07 at 19:19 +0200, Oleg Nesterov wrote:
> >
> > With or without this patch, can't we call audit_syscall_exit() twice
> > if there is something else in _TIF_WORK_SYSCALL_EXIT mask apart from
> > SYSCALL_AUDIT ? First time it is called from asm, then from
> > syscall_trace_leave(), no?
> >
> > For example. The task has TIF_SYSCALL_AUDIT and nothing else, it does
> > system_call->auditsys->system_call_fastpath. What if it gets, say,
> > TIF_SYSCALL_TRACE before ret_from_sys_call?
>
> No harm is done calling twice.  The first call will do the real work and
> cleanup.  It will set a flag in the audit data that the work has been
> done (in_syscall == 0) thus the second call will then not do any real
> work and won't have anything to clean up.

Hmm... and I assume context->previous != NULL is not possible on x86_64.
OK, thanks.

And I guess, all CONFIG_AUDITSYSCALL code in entry.S is only needed to
microoptimize the case when TIF_SYSCALL_AUDIT is the only reason for the
slow path. I wonder if it really makes the measureble difference...

Oleg.


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