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

[Andy Lutomirski <luto@amacapital.net>]

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(-)

-- 
1.9.3