s390: system call path micro optimization

Add a pointer to the system call table to the thread_info structure.
The TIF_31BIT bit is set or cleared by SET_PERSONALITY exactly once
for the lifetime of a process. With the pointer to the correct system
call table in thread_info the system call code in entry64.S path can
drop the check for TIF_31BIT which saves a couple of instructions.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 2 insertions, 7 deletions

diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index 72f230baf5d1..4c17eece707e 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -216,6 +216,7 @@ sysc_vtime:
         mvc     __PT_INT_CODE(4,%r11),__LC_SVC_ILC
 sysc_do_svc:
         oi      __TI_flags+7(%r12),_TIF_SYSCALL
+        lg      %r10,__TI_sysc_table(%r12)      # address of system call table
         llgh    %r8,__PT_INT_CODE+2(%r11)
         slag    %r8,%r8,2                       # shift and test for svc 0
         jnz     sysc_nr_ok
@@ -226,13 +227,6 @@ sysc_do_svc:
         sth     %r1,__PT_INT_CODE+2(%r11)
         slag    %r8,%r1,2
 sysc_nr_ok:
-        larl    %r10,sys_call_table             # 64 bit system call table
-#ifdef CONFIG_COMPAT
-        tm      __TI_flags+5(%r12),(_TIF_31BIT>>16)
-        jno     sysc_noemu
-        larl    %r10,sys_call_table_emu         # 31 bit system call table
-sysc_noemu:
-#endif
         xc      __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
         stg     %r2,__PT_ORIG_GPR2(%r11)
         stg     %r7,STACK_FRAME_OVERHEAD(%r15)
@@ -1005,6 +999,7 @@ sys_call_table:
 #ifdef CONFIG_COMPAT
 
 #define SYSCALL(esa,esame,emu)  .long emu
+        .globl  sys_call_table_emu
 sys_call_table_emu:
 #include "syscalls.S"
 #undef SYSCALL