linux-kernel - Re: [PATCH 0/7] Two-phase seccomp and x86 tracing changes

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Message-ID: <CAGXu5jJx8Wk-pZvhJY4xA=oywCZDLH3CLiLZ0wrBVqEqSaYT4A@mail.gmail.com>
Date:	Wed, 16 Jul 2014 13:41:52 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Will Drewry <wad@...omium.org>,
	James Morris <james.l.morris@...cle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-mips@...ux-mips.org,
	linux-arch <linux-arch@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Alexei Starovoitov <ast@...mgrid.com>
Subject: Re: [PATCH 0/7] Two-phase seccomp and x86 tracing changes

On Tue, Jul 15, 2014 at 12:32 PM, Andy Lutomirski <luto@...capital.net> wrote:
> This is both a cleanup and a speedup.  It reduces overhead due to
> installing a trivial seccomp filter by 87%.  The speedup comes from
> avoiding the full syscall tracing mechanism for filters that don't
> return SECCOMP_RET_TRACE.
>
> This series works by splitting the seccomp hooks into two phases.
> The first phase evaluates the filter; it can skip syscalls, allow
> them, kill the calling task, or pass a u32 to the second phase.  The
> second phase requires a full tracing context, and it sends ptrace
> events if necessary.
>
> Once this is done, I implemented a similar split for the x86 syscall
> entry work.  The C callback is invoked in two phases: the first has
> only a partial frame, and it can request phase 2 processing with a
> full frame.
>
> Finally, I switch the 64-bit system_call code to use the new split
> entry work.  This is a net deletion of assembly code: it replaces
> all of the audit entry muck.
>
> In the process, I fixed some bugs.
>
> If this is acceptable, someone can do the same tweak for the
> ia32entry and entry_32 code.
>
> This passes all seccomp tests that I know of, except for the ones
> that don't work on current kernels.

After fighting a bit with merging this with the tsync series, I can
confirm this all behaves nicely on x86_64 and ARM.

-Kees

-- 
Kees Cook
Chrome OS Security
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