[S390] introduce vdso on s390

Add a vdso to speed up gettimeofday and clock_getres/clock_gettime for
CLOCK_REALTIME/CLOCK_MONOTONIC.

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

1 files changed, 39 insertions, 0 deletions

diff --git a/arch/s390/kernel/vdso32/clock_getres.S b/arch/s390/kernel/vdso32/clock_getres.S
new file mode 100644
index 000000000000..9532c4e6a9d2
--- /dev/null
+++ b/arch/s390/kernel/vdso32/clock_getres.S
@@ -0,0 +1,39 @@
+/*
+ * Userland implementation of clock_getres() for 32 bits processes in a
+ * s390 kernel for use in the vDSO
+ *
+ *  Copyright IBM Corp. 2008
+ *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License (version 2 only)
+ * as published by the Free Software Foundation.
+ */
+#include <asm/vdso.h>
+#include <asm/asm-offsets.h>
+#include <asm/unistd.h>
+
+        .text
+        .align 4
+        .globl __kernel_clock_getres
+        .type  __kernel_clock_getres,@function
+__kernel_clock_getres:
+        .cfi_startproc
+        chi     %r2,CLOCK_REALTIME
+        je      0f
+        chi     %r2,CLOCK_MONOTONIC
+        jne     3f
+0:      ltr     %r3,%r3
+        jz      2f                              /* res == NULL */
+        basr    %r1,0
+1:      l       %r0,4f-1b(%r1)
+        xc      0(4,%r3),0(%r3)                 /* set tp->tv_sec to zero */
+        st      %r0,4(%r3)                      /* store tp->tv_usec */
+2:      lhi     %r2,0
+        br      %r14
+3:      lhi     %r1,__NR_clock_getres           /* fallback to svc */
+        svc     0
+        br      %r14
+4:      .long   CLOCK_REALTIME_RES
+        .cfi_endproc
+        .size   __kernel_clock_getres,.-__kernel_clock_getres