parisc: Fix and enable seccomp filter support

The seccomp filter support requires careful handling of task registers.  This
includes reloading of the return value (%r28) and proper syscall exit if
secure_computing() returned -1.

Additionally we need to sign-extend the syscall number from signed 32bit to
signed 64bit in do_syscall_trace_enter() since the ptrace interface only allows
storing 32bit values in compat mode.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # v4.5

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index fbafa0d0e2bf..c976ebfe2269 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -329,6 +329,7 @@ tracesys_next:
 
         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
         LDREG   TI_TASK(%r1), %r1
+        LDREG   TASK_PT_GR28(%r1), %r28         /* Restore return value */
         LDREG   TASK_PT_GR26(%r1), %r26         /* Restore the users args */
         LDREG   TASK_PT_GR25(%r1), %r25
         LDREG   TASK_PT_GR24(%r1), %r24
@@ -342,6 +343,7 @@ tracesys_next:
         stw     %r21, -56(%r30)                 /* 6th argument */
 #endif
 
+        cmpib,COND(=),n -1,%r20,tracesys_exit /* seccomp may have returned -1 */
         comiclr,>>=     __NR_Linux_syscalls, %r20, %r0
         b,n     .Ltracesys_nosys