[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, 234 insertions, 0 deletions

diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
new file mode 100644
index 000000000000..10a6ccef4412
--- /dev/null
+++ b/arch/s390/kernel/vdso.c
@@ -0,0 +1,234 @@
+/*
+ * vdso setup for s390
+ *
+ *  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 <linux/module.h>
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/stddef.h>
+#include <linux/unistd.h>
+#include <linux/slab.h>
+#include <linux/user.h>
+#include <linux/elf.h>
+#include <linux/security.h>
+#include <linux/bootmem.h>
+
+#include <asm/pgtable.h>
+#include <asm/system.h>
+#include <asm/processor.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+#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;
+static unsigned int vdso32_pages;
+static struct page **vdso32_pagelist;
+#endif
+
+#ifdef CONFIG_64BIT
+extern char vdso64_start, vdso64_end;
+static void *vdso64_kbase = &vdso64_start;
+static unsigned int vdso64_pages;
+static struct page **vdso64_pagelist;
+#endif /* CONFIG_64BIT */
+
+/*
+ * Should the kernel map a VDSO page into processes and pass its
+ * address down to glibc upon exec()?
+ */
+unsigned int __read_mostly vdso_enabled = 1;
+
+static int __init vdso_setup(char *s)
+{
+        vdso_enabled = simple_strtoul(s, NULL, 0);
+        return 1;
+}
+__setup("vdso=", vdso_setup);
+
+/*
+ * The vdso data page
+ */
+static union {
+        struct vdso_data        data;
+        u8                      page[PAGE_SIZE];
+} vdso_data_store __attribute__((__section__(".data.page_aligned")));
+struct vdso_data *vdso_data = &vdso_data_store.data;
+
+/*
+ * This is called from binfmt_elf, we create the special vma for the
+ * vDSO and insert it into the mm struct tree
+ */
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+        struct mm_struct *mm = current->mm;
+        struct page **vdso_pagelist;
+        unsigned long vdso_pages;
+        unsigned long vdso_base;
+        int rc;
+
+        if (!vdso_enabled)
+                return 0;
+        /*
+         * Only map the vdso for dynamically linked elf binaries.
+         */
+        if (!uses_interp)
+                return 0;
+
+        vdso_base = mm->mmap_base;
+#ifdef CONFIG_64BIT
+        vdso_pagelist = vdso64_pagelist;
+        vdso_pages = vdso64_pages;
+#ifdef CONFIG_COMPAT
+        if (test_thread_flag(TIF_31BIT)) {
+                vdso_pagelist = vdso32_pagelist;
+                vdso_pages = vdso32_pages;
+        }
+#endif
+#else
+        vdso_pagelist = vdso32_pagelist;
+        vdso_pages = vdso32_pages;
+#endif
+
+        /*
+         * vDSO has a problem and was disabled, just don't "enable" it for
+         * the process
+         */
+        if (vdso_pages == 0)
+                return 0;
+
+        current->mm->context.vdso_base = 0;
+
+        /*
+         * pick a base address for the vDSO in process space. We try to put
+         * it at vdso_base which is the "natural" base for it, but we might
+         * fail and end up putting it elsewhere.
+         */
+        down_write(&mm->mmap_sem);
+        vdso_base = get_unmapped_area(NULL, vdso_base,
+                                      vdso_pages << PAGE_SHIFT, 0, 0);
+        if (IS_ERR_VALUE(vdso_base)) {
+                rc = vdso_base;
+                goto out_up;
+        }
+
+        /*
+         * our vma flags don't have VM_WRITE so by default, the process
+         * isn't allowed to write those pages.
+         * gdb can break that with ptrace interface, and thus trigger COW
+         * on those pages but it's then your responsibility to never do that
+         * on the "data" page of the vDSO or you'll stop getting kernel
+         * updates and your nice userland gettimeofday will be totally dead.
+         * It's fine to use that for setting breakpoints in the vDSO code
+         * pages though
+         *
+         * Make sure the vDSO gets into every core dump.
+         * Dumping its contents makes post-mortem fully interpretable later
+         * without matching up the same kernel and hardware config to see
+         * what PC values meant.
+         */
+        rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
+                                     VM_READ|VM_EXEC|
+                                     VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
+                                     VM_ALWAYSDUMP,
+                                     vdso_pagelist);
+        if (rc)
+                goto out_up;
+
+        /* Put vDSO base into mm struct */
+        current->mm->context.vdso_base = vdso_base;
+
+        up_write(&mm->mmap_sem);
+        return 0;
+
+out_up:
+        up_write(&mm->mmap_sem);
+        return rc;
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+        if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base)
+                return "[vdso]";
+        return NULL;
+}
+
+static int __init vdso_init(void)
+{
+        int i;
+
+#if defined(CONFIG_32BIT) || defined(CONFIG_COMPAT)
+        /* Calculate the size of the 32 bit vDSO */
+        vdso32_pages = ((&vdso32_end - &vdso32_start
+                         + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
+
+        /* Make sure pages are in the correct state */
+        vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1),
+                                  GFP_KERNEL);
+        BUG_ON(vdso32_pagelist == NULL);
+        for (i = 0; i < vdso32_pages - 1; i++) {
+                struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
+                ClearPageReserved(pg);
+                get_page(pg);
+                vdso32_pagelist[i] = pg;
+        }
+        vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
+        vdso32_pagelist[vdso32_pages] = NULL;
+#endif
+
+#ifdef CONFIG_64BIT
+        /* Calculate the size of the 64 bit vDSO */
+        vdso64_pages = ((&vdso64_end - &vdso64_start
+                         + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
+
+        /* Make sure pages are in the correct state */
+        vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1),
+                                  GFP_KERNEL);
+        BUG_ON(vdso64_pagelist == NULL);
+        for (i = 0; i < vdso64_pages - 1; i++) {
+                struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
+                ClearPageReserved(pg);
+                get_page(pg);
+                vdso64_pagelist[i] = pg;
+        }
+        vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
+        vdso64_pagelist[vdso64_pages] = NULL;
+#endif /* CONFIG_64BIT */
+
+        get_page(virt_to_page(vdso_data));
+
+        smp_wmb();
+
+        return 0;
+}
+arch_initcall(vdso_init);
+
+int in_gate_area_no_task(unsigned long addr)
+{
+        return 0;
+}
+
+int in_gate_area(struct task_struct *task, unsigned long addr)
+{
+        return 0;
+}
+
+struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
+{
+        return NULL;
+}