s390: convert to GENERIC_VDSO

Convert s390 to generic vDSO. There are a few special things on s390:

- vDSO can be called without a stack frame - glibc did this in the past.
  So we need to allocate a stackframe on our own.

- The former assembly code used stcke to get the TOD clock and applied
  time steering to it. We need to do the same in the new code. This is done
  in the architecture specific __arch_get_hw_counter function. The steering
  information is stored in an architecure specific area in the vDSO data.

- CPUCLOCK_VIRT is now handled with a syscall fallback, which might
  be slower/less accurate than the old implementation.

The getcpu() function stays as an assembly function because there is no
generic implementation and the code is just a few lines.

Performance number from my system do 100 mio gettimeofday() calls:

Plain syscall: 8.6s
Generic VDSO:  1.3s
old ASM VDSO:  1s

So it's a bit slower but still much faster than syscalls.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 3 insertions, 26 deletions

diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index c4baefaa6e34..f9da5b149141 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -20,6 +20,8 @@
 #include <linux/security.h>
 #include <linux/memblock.h>
 #include <linux/compat.h>
+#include <linux/binfmts.h>
+#include <vdso/datapage.h>
 #include <asm/asm-offsets.h>
 #include <asm/processor.h>
 #include <asm/mmu.h>
@@ -96,35 +98,12 @@ static union {
 	struct vdso_data	data;
 	u8			page[PAGE_SIZE];
 } vdso_data_store __page_aligned_data;
-struct vdso_data *vdso_data = &vdso_data_store.data;
-
-/*
- * Setup vdso data page.
- */
-static void __init vdso_init_data(struct vdso_data *vd)
-{
-	vd->ectg_available = test_facility(31);
-}
-
+struct vdso_data *vdso_data = (struct vdso_data *)&vdso_data_store.data;
 /*
  * Allocate/free per cpu vdso data.
  */
 #define SEGMENT_ORDER	2
 
-/*
- * The initial vdso_data structure for the boot CPU. Eventually
- * it is replaced with a properly allocated structure in vdso_init.
- * This is necessary because a valid S390_lowcore.vdso_per_cpu_data
- * pointer is required to be able to return from an interrupt or
- * program check. See the exit paths in entry.S.
- */
-struct vdso_data boot_vdso_data __initdata;
-
-void __init vdso_alloc_boot_cpu(struct lowcore *lowcore)
-{
-	lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data;
-}
-
 int vdso_alloc_per_cpu(struct lowcore *lowcore)
 {
 	unsigned long segment_table, page_table, page_frame;
@@ -246,8 +225,6 @@ static int __init vdso_init(void)
 {
 	int i;
 
-	vdso_init_data(vdso_data);
-
 	/* Calculate the size of the 64 bit vDSO */
 	vdso64_pages = ((&vdso64_end - &vdso64_start
 			 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;