tree e8d73a587966d9951599f29d857fe9a706f0ca72
parent 99abc08866edc4921d32c769d49eeb7afe489674
author Chris Dearman <chris.dearman@imgtec.com> 1460487742 -0700
committer Chris Dearman <chris.dearman@imgtec.com> 1460497572 +0000

FROMLIST: MIPS: scall: Handle seccomp filters which redirect syscalls

Commit d218af78492a ("MIPS: scall: Always run the seccomp syscall
filters") modified the syscall code to always call the seccomp filters,
but missed the case where a filter may redirect the syscall, as
revealed by the seccomp_bpf self test.

The syscall path now restores the syscall from the stack after the
filter rather than saving it locally. Syscall number checking and
syscall function table lookup is done after the filter may have run such
that redirected syscalls are also checked, and executed.

The regular path of syscall number checking and pointer lookup is also
made more consistent between ABIs with scall64-64.S being the reference.

With this patch in place, the seccomp_bpf self test now passes
TRACE_syscall.syscall_redirected and TRACE_syscall.syscall_dropped on
all MIPS ABIs.

(cherry picked from https://lkml.org/lkml/2016/3/29/178)
Fixes: d218af78492a ("MIPS: scall: Always run the seccomp syscall filters")
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Change-Id: I8376d9614d0632cd84ff1e9450e23f9aa33ecfe4