s390: lowcore stack pointer offsets

Store the stack pointers in the lowcore for the kernel stack, the async
stack and the panic stack with the offset required for the first user.
This avoids an unnecessary add instruction on the system call path.

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

1 files changed, 16 insertions, 20 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 94feff7d6132..17d5cc057893 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -45,6 +45,7 @@ _TIF_TRACE    = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
 
 STACK_SHIFT = PAGE_SHIFT + THREAD_ORDER
 STACK_SIZE  = 1 << STACK_SHIFT
+STACK_INIT  = STACK_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE
 
 #define BASED(name) name-system_call(%r13)
 
@@ -97,10 +98,10 @@ STACK_SIZE  = 1 << STACK_SHIFT
         sra     %r14,\shift
         jnz     1f
         CHECK_STACK 1<<\shift,\savearea
+        ahi     %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
         j       2f
 1:      l       %r15,\stack             # load target stack
-2:      ahi     %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
-        la      %r11,STACK_FRAME_OVERHEAD(%r15)
+2:      la      %r11,STACK_FRAME_OVERHEAD(%r15)
         .endm
 
         .macro  ADD64 high,low,timer
@@ -150,7 +151,7 @@ ENTRY(__switch_to)
         l       %r4,__THREAD_info(%r2)          # get thread_info of prev
         l       %r5,__THREAD_info(%r3)          # get thread_info of next
         lr      %r15,%r5
-        ahi     %r15,STACK_SIZE                 # end of kernel stack of next
+        ahi     %r15,STACK_INIT                 # end of kernel stack of next
         st      %r3,__LC_CURRENT                # store task struct of next
         st      %r5,__LC_THREAD_INFO            # store thread info of next
         st      %r15,__LC_KERNEL_STACK          # store end of kernel stack
@@ -178,7 +179,6 @@ sysc_stm:
         l       %r13,__LC_SVC_NEW_PSW+4
 sysc_per:
         l       %r15,__LC_KERNEL_STACK
-        ahi     %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
         la      %r11,STACK_FRAME_OVERHEAD(%r15) # pointer to pt_regs
 sysc_vtime:
         UPDATE_VTIME %r8,%r9,__LC_SYNC_ENTER_TIMER
@@ -359,11 +359,11 @@ ENTRY(pgm_check_handler)
         tm      __LC_PGM_ILC+3,0x80     # check for per exception
         jnz     pgm_svcper              # -> single stepped svc
 0:      CHECK_STACK STACK_SIZE,__LC_SAVE_AREA_SYNC
+        ahi     %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
         j       2f
 1:      UPDATE_VTIME %r14,%r15,__LC_SYNC_ENTER_TIMER
         l       %r15,__LC_KERNEL_STACK
-2:      ahi     %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
-        la      %r11,STACK_FRAME_OVERHEAD(%r15)
+2:      la      %r11,STACK_FRAME_OVERHEAD(%r15)
         stm     %r0,%r7,__PT_R0(%r11)
         mvc     __PT_R8(32,%r11),__LC_SAVE_AREA_SYNC
         stm     %r8,%r9,__PT_PSW(%r11)
@@ -485,7 +485,6 @@ io_work:
 #
 io_work_user:
         l       %r1,__LC_KERNEL_STACK
-        ahi     %r1,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
         mvc     STACK_FRAME_OVERHEAD(__PT_SIZE,%r1),0(%r11)
         xc      __SF_BACKCHAIN(4,%r1),__SF_BACKCHAIN(%r1)
         la      %r11,STACK_FRAME_OVERHEAD(%r1)
@@ -646,7 +645,6 @@ mcck_skip:
         tm      __PT_PSW+1(%r11),0x01   # returning to user ?
         jno     mcck_return
         l       %r1,__LC_KERNEL_STACK   # switch to kernel stack
-        ahi     %r1,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
         mvc     STACK_FRAME_OVERHEAD(__PT_SIZE,%r1),0(%r11)
         xc      __SF_BACKCHAIN(4,%r1),__SF_BACKCHAIN(%r1)
         la      %r11,STACK_FRAME_OVERHEAD(%r15)
@@ -674,6 +672,7 @@ mcck_panic:
         sra     %r14,PAGE_SHIFT
         jz      0f
         l       %r15,__LC_PANIC_STACK
+        j       mcck_skip
 0:      ahi     %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
         j       mcck_skip
 
@@ -714,12 +713,10 @@ ENTRY(restart_int_handler)
  */
 stack_overflow:
         l       %r15,__LC_PANIC_STACK   # change to panic stack
-        ahi     %r15,-__PT_SIZE         # create pt_regs
-        stm     %r0,%r7,__PT_R0(%r15)
-        stm     %r8,%r9,__PT_PSW(%r15)
+        la      %r11,STACK_FRAME_OVERHEAD(%r15)
+        stm     %r0,%r7,__PT_R0(%r11)
+        stm     %r8,%r9,__PT_PSW(%r11)
         mvc     __PT_R8(32,%r11),0(%r14)
-        lr      %r15,%r11
-        ahi     %r15,-STACK_FRAME_OVERHEAD
         l       %r1,BASED(1f)
         xc      __SF_BACKCHAIN(4,%r15),__SF_BACKCHAIN(%r15)
         lr      %r2,%r11                # pass pointer to pt_regs
@@ -799,15 +796,14 @@ cleanup_system_call:
         mvc     __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
         # set up saved register 11
         l       %r15,__LC_KERNEL_STACK
-        ahi     %r15,-__PT_SIZE
-        st      %r15,12(%r11)           # r11 pt_regs pointer
+        la      %r9,STACK_FRAME_OVERHEAD(%r15)
+        st      %r9,12(%r11)            # r11 pt_regs pointer
         # fill pt_regs
-        mvc     __PT_R8(32,%r15),__LC_SAVE_AREA_SYNC
-        stm     %r0,%r7,__PT_R0(%r15)
-        mvc     __PT_PSW(8,%r15),__LC_SVC_OLD_PSW
-        mvc     __PT_INT_CODE(4,%r15),__LC_SVC_ILC
+        mvc     __PT_R8(32,%r9),__LC_SAVE_AREA_SYNC
+        stm     %r0,%r7,__PT_R0(%r9)
+        mvc     __PT_PSW(8,%r9),__LC_SVC_OLD_PSW
+        mvc     __PT_INT_CODE(4,%r9),__LC_SVC_ILC
         # setup saved register 15
-        ahi     %r15,-STACK_FRAME_OVERHEAD
         st      %r15,28(%r11)           # r15 stack pointer
         # set new psw address and exit
         l       %r9,BASED(cleanup_table+4)      # sysc_do_svc + 0x80000000