sh: Fix syscall tracing ordering.

The implementation of system call tracing in the kernel has a
couple of ordering problems:

 - the validity of the system call number is checked before
   calling out to system call tracing code, and should be
   done after

 - the system call number used when tracing is the one the
   system call was invoked with, while the system call tracing
   code can legitimatly change the call number (for example
   strace permutes fork into clone)

This patch fixes both of these problems, and also reoders the
code slightly to make the direct path through the code the
common case.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 22 insertions, 23 deletions

diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S
index 5bc7fa91d095..8f96d21fcb1c 100644
--- a/arch/sh/kernel/entry-common.S
+++ b/arch/sh/kernel/entry-common.S
@@ -256,8 +256,7 @@ syscall_trace_entry:
         mov.l   @(OFF_R6,r15), r6
         mov.l   @(OFF_R7,r15), r7   ! arg3
         mov.l   @(OFF_R3,r15), r3   ! syscall_nr
-        !                   Arrange for do_syscall_trace to be called
-        !                   again as the system call returns.
+        !
         mov.l   2f, r10                 ! Number of syscalls
         cmp/hs  r10, r3
         bf      syscall_call
@@ -273,6 +272,18 @@ __restore_all:
         .align  2
 1:      .long   restore_all
 
+        .align  2
+not_syscall_tra:        
+        bra     debug_trap
+         nop
+
+        .align  2
+syscall_badsys:                 ! Bad syscall number
+        mov     #-ENOSYS, r0
+        bra     resume_userspace
+         mov.l  r0, @(OFF_R0,r15)       ! Return value
+        
+
 /*
  * Syscall interface:
  *
@@ -316,39 +327,27 @@ ENTRY(system_call)
         ! Is the trap argument >= 0x20? (TRA will be >= 0x80)
         mov     #0x7f, r9
         cmp/hi  r9, r8
-        bt/s    0f
+        bt/s    not_syscall_tra
          mov    #OFF_TRA, r9
         add     r15, r9
-        !
         mov.l   r8, @r9                 ! set TRA value to tra
         sti
-        !                   Call the system call handler through the table.
-        !                   First check for bad syscall number
-        mov     r3, r9
-        mov.l   2f, r8                  ! Number of syscalls
-        cmp/hs  r8, r9
-        get_current_thread_info r8, r10
-        bf      good_system_call
-syscall_badsys:                 ! Bad syscall number
-        mov     #-ENOSYS, r0
-        bra     resume_userspace
-         mov.l  r0, @(OFF_R0,r15)       ! Return value
         !
-0:
-        bra     debug_trap
-         nop
-        !
-good_system_call:               ! Good syscall number
+        get_current_thread_info r8, r10
         mov.l   @(TI_FLAGS,r8), r8
         mov     #_TIF_SYSCALL_TRACE, r10
         tst     r10, r8
         bf      syscall_trace_entry
         !
+        mov.l   2f, r8                  ! Number of syscalls
+        cmp/hs  r8, r3
+        bt      syscall_badsys
+        !
 syscall_call:
-        shll2   r9              ! x4
+        shll2   r3              ! x4
         mov.l   3f, r8          ! Load the address of sys_call_table
-        add     r8, r9
-        mov.l   @r9, r8
+        add     r8, r3
+        mov.l   @r3, r8
         jsr     @r8             ! jump to specific syscall handler
          nop
         mov.l   @(OFF_R0,r15), r12              ! save r0