[PATCH] fast vdso implementation for CLOCK_THREAD_CPUTIME_ID

The extract cpu time instruction (ectg) instruction allows the user
process to get the current thread cputime without calling into the
kernel. The code that uses the instruction needs to switch to the
access registers mode to get access to the per-cpu info page that
contains the two base values that are needed to calculate the current
cputime from the CPU timer with the ectg instruction.

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

1 files changed, 24 insertions, 21 deletions

diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index ae83c195171c..c6fbde13971a 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -177,8 +177,11 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
         .if !\sync
         ni      \psworg+1,0xfd          # clear wait state bit
         .endif
-        lmg     %r0,%r15,SP_R0(%r15)    # load gprs 0-15 of user
+        lg      %r14,__LC_VDSO_PER_CPU
+        lmg     %r0,%r13,SP_R0(%r15)    # load gprs 0-13 of user
         stpt    __LC_EXIT_TIMER
+        mvc     __VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER
+        lmg     %r14,%r15,SP_R14(%r15)  # load grps 14-15 of user
         lpswe   \psworg                 # back to caller
         .endm
 
@@ -980,23 +983,23 @@ cleanup_sysc_return:
 
 cleanup_sysc_leave:
         clc     8(8,%r12),BASED(cleanup_sysc_leave_insn)
-        je      2f
-        mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
+        je      3f
         clc     8(8,%r12),BASED(cleanup_sysc_leave_insn+8)
-        je      2f
-        mvc     __LC_RETURN_PSW(16),SP_PSW(%r15)
+        jhe     0f
+        mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
+0:      mvc     __LC_RETURN_PSW(16),SP_PSW(%r15)
         cghi    %r12,__LC_MCK_OLD_PSW
-        jne     0f
+        jne     1f
         mvc     __LC_SAVE_AREA+64(32),SP_R12(%r15)
-        j       1f
-0:      mvc     __LC_SAVE_AREA+32(32),SP_R12(%r15)
-1:      lmg     %r0,%r11,SP_R0(%r15)
+        j       2f
+1:      mvc     __LC_SAVE_AREA+32(32),SP_R12(%r15)
+2:      lmg     %r0,%r11,SP_R0(%r15)
         lg      %r15,SP_R15(%r15)
-2:      la      %r12,__LC_RETURN_PSW
+3:      la      %r12,__LC_RETURN_PSW
         br      %r14
 cleanup_sysc_leave_insn:
         .quad   sysc_done - 4
-        .quad   sysc_done - 8
+        .quad   sysc_done - 16
 
 cleanup_io_return:
         mvc     __LC_RETURN_PSW(8),0(%r12)
@@ -1006,23 +1009,23 @@ cleanup_io_return:
 
 cleanup_io_leave:
         clc     8(8,%r12),BASED(cleanup_io_leave_insn)
-        je      2f
-        mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
+        je      3f
         clc     8(8,%r12),BASED(cleanup_io_leave_insn+8)
-        je      2f
-        mvc     __LC_RETURN_PSW(16),SP_PSW(%r15)
+        jhe     0f
+        mvc     __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
+0:      mvc     __LC_RETURN_PSW(16),SP_PSW(%r15)
         cghi    %r12,__LC_MCK_OLD_PSW
-        jne     0f
+        jne     1f
         mvc     __LC_SAVE_AREA+64(32),SP_R12(%r15)
-        j       1f
-0:      mvc     __LC_SAVE_AREA+32(32),SP_R12(%r15)
-1:      lmg     %r0,%r11,SP_R0(%r15)
+        j       2f
+1:      mvc     __LC_SAVE_AREA+32(32),SP_R12(%r15)
+2:      lmg     %r0,%r11,SP_R0(%r15)
         lg      %r15,SP_R15(%r15)
-2:      la      %r12,__LC_RETURN_PSW
+3:      la      %r12,__LC_RETURN_PSW
         br      %r14
 cleanup_io_leave_insn:
         .quad   io_done - 4
-        .quad   io_done - 8
+        .quad   io_done - 16
 
 /*
  * Integer constants