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

[Kees Cook]

On Tue, Jul 15, 2014 at 12:32 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> 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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