UBUNTU: SAUCE: SECCOMP: x86: Enable HAVE_ARCH_SECCOMP_FILTER

UBUNTU: SAUCE: SECCOMP: x86: Enable HAVE_ARCH_SECCOMP_FILTER

Enable support for seccomp filter on x86:
- asm/tracehook.h exists
- syscall_get_arguments() works
- syscall_rollback() works
- ptrace_report_syscall() works
- secure_computing() return value is honored (see below)

This also adds support for honoring the return
value from secure_computing().

SECCOMP_RET_TRACE and SECCOMP_RET_TRAP may result in seccomp needing to
skip a system call without killing the process.  This is done by
returning a non-zero (-1) value from secure_computing.  This change
makes x86 respect that return value.

To ensure that minimal kernel code is exposed, a non-zero return value
results in an immediate return to user space (with an invalid syscall
number).

Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Kees Cook <kees@ubuntu.com>