linux-kernel - Re: [PATCH v5 0/5] x86: two-phase syscall tracing and seccomp fastpath

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Date:	Mon, 8 Sep 2014 12:29:45 -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>,
	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 Mailing List <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>,
	"H. Peter Anvin" <hpa@...or.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH v5 0/5] x86: two-phase syscall tracing and seccomp fastpath

On Fri, Sep 5, 2014 at 3:13 PM, Andy Lutomirski <luto@...capital.net> wrote:
> This applies to:
> git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git seccomp-fastpath
>
> Gitweb:
> https://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/log/?h=seccomp/fastpath
>
> 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 depends on 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.  The seccomp core part is in Kees' seccomp/fastpath
> tree.
>
> These patches implement 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.
>
> Changes from v4:
>  - Rebased (which seems to have been a no-op)
>  - Fixed embarrassing bug that broke allnoconfig
>    (patch 3 was missing an ifdef).
>
> Changes from v3:
>  - Dropped the core seccomp changes from the email -- Kees has applied them.
>  - Add patch 2 (the TIF_NOHZ change).
>  - Fix TIF_NOHZ in the two-phase entry code (thanks, Oleg).
>
> Changes from v2:
>  - Fixed 32-bit x86 build (and the tests pass).
>  - Put the doc patch where it belongs.
>
> Changes from v1:
>  - Rebased on top of Kees' shiny new seccomp tree (no effect on the x86
>    part).
>  - Improved patch 6 vs patch 7 split (thanks Alexei!)
>  - Fixed bogus -ENOSYS in patch 5 (thanks Kees!)
>  - Improved changelog message in patch 6.
>
> Changes from RFC version:
>  - The first three patches are more or less the same
>  - The rest is more or less a rewrite
>
> Andy Lutomirski (5):
>   x86,x32,audit: Fix x32's AUDIT_ARCH wrt audit
>   x86,entry: Only call user_exit if TIF_NOHZ
>   x86: Split syscall_trace_enter into two phases
>   x86_64,entry: Treat regs->ax the same in fastpath and slowpath
>     syscalls
>   x86_64,entry: Use split-phase syscall_trace_enter for 64-bit syscalls
>
>  arch/x86/include/asm/calling.h |   6 +-
>  arch/x86/include/asm/ptrace.h  |   5 ++
>  arch/x86/kernel/entry_64.S     |  51 +++++--------
>  arch/x86/kernel/ptrace.c       | 165 +++++++++++++++++++++++++++++++++--------
>  4 files changed, 164 insertions(+), 63 deletions(-)

Consider the series:

Acked-by: Kees Cook <keescook@...omium.org>

As far as doing pulls, Peter, can you take the seccomp change from my
tree as well? It makes sense to land all of this together.

Thanks!

-Kees

-- 
Kees Cook
Chrome OS Security
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