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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2008-12-31 15:11:42 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2008-12-31 15:11:49 +0100
commitc742b31c03f37c5c499178f09f57381aa6c70131 (patch)
treedb0e95b8299d997fcb1264126bc8efe10d0ddd51 /arch/s390/kernel/vdso.c
parent9cfb9b3c3a7361c793c031e9c3583b177ac5debd (diff)
[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>
Diffstat (limited to 'arch/s390/kernel/vdso.c')
-rw-r--r--arch/s390/kernel/vdso.c123
1 files changed, 120 insertions, 3 deletions
diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
index 10a6ccef441..25a6a82f1c0 100644
--- a/arch/s390/kernel/vdso.c
+++ b/arch/s390/kernel/vdso.c
@@ -31,9 +31,6 @@
#include <asm/sections.h>
#include <asm/vdso.h>
-/* Max supported size for symbol names */
-#define MAX_SYMNAME 64
-
#if defined(CONFIG_32BIT) || defined(CONFIG_COMPAT)
extern char vdso32_start, vdso32_end;
static void *vdso32_kbase = &vdso32_start;
@@ -71,6 +68,119 @@ static union {
struct vdso_data *vdso_data = &vdso_data_store.data;
/*
+ * Setup vdso data page.
+ */
+static void vdso_init_data(struct vdso_data *vd)
+{
+ unsigned int facility_list;
+
+ facility_list = stfl();
+ vd->ectg_available = switch_amode && (facility_list & 1);
+}
+
+#ifdef CONFIG_64BIT
+/*
+ * Setup per cpu vdso data page.
+ */
+static void vdso_init_per_cpu_data(int cpu, struct vdso_per_cpu_data *vpcd)
+{
+}
+
+/*
+ * Allocate/free per cpu vdso data.
+ */
+#ifdef CONFIG_64BIT
+#define SEGMENT_ORDER 2
+#else
+#define SEGMENT_ORDER 1
+#endif
+
+int vdso_alloc_per_cpu(int cpu, struct _lowcore *lowcore)
+{
+ unsigned long segment_table, page_table, page_frame;
+ u32 *psal, *aste;
+ int i;
+
+ lowcore->vdso_per_cpu_data = __LC_PASTE;
+
+ if (!switch_amode || !vdso_enabled)
+ return 0;
+
+ segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
+ page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ page_frame = get_zeroed_page(GFP_KERNEL);
+ if (!segment_table || !page_table || !page_frame)
+ goto out;
+
+ clear_table((unsigned long *) segment_table, _SEGMENT_ENTRY_EMPTY,
+ PAGE_SIZE << SEGMENT_ORDER);
+ clear_table((unsigned long *) page_table, _PAGE_TYPE_EMPTY,
+ 256*sizeof(unsigned long));
+
+ *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
+ *(unsigned long *) page_table = _PAGE_RO + page_frame;
+
+ psal = (u32 *) (page_table + 256*sizeof(unsigned long));
+ aste = psal + 32;
+
+ for (i = 4; i < 32; i += 4)
+ psal[i] = 0x80000000;
+
+ lowcore->paste[4] = (u32)(addr_t) psal;
+ psal[0] = 0x20000000;
+ psal[2] = (u32)(addr_t) aste;
+ *(unsigned long *) (aste + 2) = segment_table +
+ _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
+ aste[4] = (u32)(addr_t) psal;
+ lowcore->vdso_per_cpu_data = page_frame;
+
+ vdso_init_per_cpu_data(cpu, (struct vdso_per_cpu_data *) page_frame);
+ return 0;
+
+out:
+ free_page(page_frame);
+ free_page(page_table);
+ free_pages(segment_table, SEGMENT_ORDER);
+ return -ENOMEM;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+void vdso_free_per_cpu(int cpu, struct _lowcore *lowcore)
+{
+ unsigned long segment_table, page_table, page_frame;
+ u32 *psal, *aste;
+
+ if (!switch_amode || !vdso_enabled)
+ return;
+
+ psal = (u32 *)(addr_t) lowcore->paste[4];
+ aste = (u32 *)(addr_t) psal[2];
+ segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK;
+ page_table = *(unsigned long *) segment_table;
+ page_frame = *(unsigned long *) page_table;
+
+ free_page(page_frame);
+ free_page(page_table);
+ free_pages(segment_table, SEGMENT_ORDER);
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+static void __vdso_init_cr5(void *dummy)
+{
+ unsigned long cr5;
+
+ cr5 = offsetof(struct _lowcore, paste);
+ __ctl_load(cr5, 5, 5);
+}
+
+static void vdso_init_cr5(void)
+{
+ if (switch_amode && vdso_enabled)
+ on_each_cpu(__vdso_init_cr5, NULL, 1);
+}
+#endif /* CONFIG_64BIT */
+
+/*
* This is called from binfmt_elf, we create the special vma for the
* vDSO and insert it into the mm struct tree
*/
@@ -172,6 +282,9 @@ static int __init vdso_init(void)
{
int i;
+ if (!vdso_enabled)
+ return 0;
+ vdso_init_data(vdso_data);
#if defined(CONFIG_32BIT) || defined(CONFIG_COMPAT)
/* Calculate the size of the 32 bit vDSO */
vdso32_pages = ((&vdso32_end - &vdso32_start
@@ -208,6 +321,10 @@ static int __init vdso_init(void)
}
vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
vdso64_pagelist[vdso64_pages] = NULL;
+#ifndef CONFIG_SMP
+ BUG_ON(vdso_alloc_per_cpu(0, S390_lowcore));
+#endif
+ vdso_init_cr5();
#endif /* CONFIG_64BIT */
get_page(virt_to_page(vdso_data));