MIPS: Sanitize restart logics

Put the original syscall number into ->regs[0] when we leave syscall
with error.  Use it in restart logics.  Everything else will have
it 0 since we pass through SAVE_SOME on all the ways in.  Note that
in places like bad_stack and inllegal_syscall we leave it 0 - it's not
restartable.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1698/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 4 insertions, 5 deletions

diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
index 17202bbe843f..73a061e85531 100644
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -63,9 +63,9 @@ stack_done:
         sw      t0, PT_R7(sp)           # set error flag
         beqz    t0, 1f
 
+        lw      t1, PT_R2(sp)           # syscall number
         negu    v0                      # error
-        sw      v0, PT_R0(sp)           # set flag for syscall
-                                        # restarting
+        sw      t1, PT_R0(sp)           # save it for syscall restarting
 1:      sw      v0, PT_R2(sp)           # result
 
 o32_syscall_exit:
@@ -104,9 +104,9 @@ syscall_trace_entry:
         sw      t0, PT_R7(sp)           # set error flag
         beqz    t0, 1f
 
+        lw      t1, PT_R2(sp)           # syscall number
         negu    v0                      # error
-        sw      v0, PT_R0(sp)           # set flag for syscall
-                                        # restarting
+        sw      t1, PT_R0(sp)           # save it for syscall restarting
 1:      sw      v0, PT_R2(sp)           # result
 
         j       syscall_exit
@@ -170,7 +170,6 @@ stackargs:
          */
 bad_stack:
         negu    v0                              # error
-        sw      v0, PT_R0(sp)
         sw      v0, PT_R2(sp)
         li      t0, 1                           # set error flag
         sw      t0, PT_R7(sp)