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

Andy Lutomirski luto at amacapital.net
Wed Jul 16 14:17:05 PDT 2014

On Wed, Jul 16, 2014 at 1:41 PM, Kees Cook <keescook at chromium.org> wrote:
> On Tue, Jul 15, 2014 at 12:32 PM, Andy Lutomirski <luto at amacapital.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
>> 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.

I'll hold off on v3 until your stuff lands.


> -Kees
> --
> Kees Cook
> Chrome OS Security

Andy Lutomirski
AMA Capital Management, LLC

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