1 files changed, 139 insertions, 0 deletions

diff --git a/arch/x86_64/vdso/vma.c b/arch/x86_64/vdso/vma.c
new file mode 100644
index 000000000000..d4cb83a6c066
--- /dev/null
+++ b/arch/x86_64/vdso/vma.c
@@ -0,0 +1,139 @@
+/*
+ * Set up the VMAs to tell the VM about the vDSO.
+ * Copyright 2007 Andi Kleen, SUSE Labs.
+ * Subject to the GPL, v.2
+ */
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/random.h>
+#include <asm/vsyscall.h>
+#include <asm/vgtod.h>
+#include <asm/proto.h>
+#include "voffset.h"
+
+int vdso_enabled = 1;
+
+#define VEXTERN(x) extern typeof(__ ## x) *vdso_ ## x;
+#include "vextern.h"
+#undef VEXTERN
+
+extern char vdso_kernel_start[], vdso_start[], vdso_end[];
+extern unsigned short vdso_sync_cpuid;
+
+struct page **vdso_pages;
+
+static inline void *var_ref(void *vbase, char *var, char *name)
+{
+        unsigned offset = var - &vdso_kernel_start[0] + VDSO_TEXT_OFFSET;
+        void *p = vbase + offset;
+        if (*(void **)p != (void *)VMAGIC) {
+                printk("VDSO: variable %s broken\n", name);
+                vdso_enabled = 0;
+        }
+        return p;
+}
+
+static int __init init_vdso_vars(void)
+{
+        int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
+        int i;
+        char *vbase;
+
+        vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL);
+        if (!vdso_pages)
+                goto oom;
+        for (i = 0; i < npages; i++) {
+                struct page *p;
+                p = alloc_page(GFP_KERNEL);
+                if (!p)
+                        goto oom;
+                vdso_pages[i] = p;
+                copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
+        }
+
+        vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL);
+        if (!vbase)
+                goto oom;
+
+        if (memcmp(vbase, "\177ELF", 4)) {
+                printk("VDSO: I'm broken; not ELF\n");
+                vdso_enabled = 0;
+        }
+
+#define V(x) *(typeof(x) *) var_ref(vbase, (char *)RELOC_HIDE(&x, 0), #x)
+#define VEXTERN(x) \
+        V(vdso_ ## x) = &__ ## x;
+#include "vextern.h"
+#undef VEXTERN
+        return 0;
+
+ oom:
+        printk("Cannot allocate vdso\n");
+        vdso_enabled = 0;
+        return -ENOMEM;
+}
+__initcall(init_vdso_vars);
+
+struct linux_binprm;
+
+/* Put the vdso above the (randomized) stack with another randomized offset.
+   This way there is no hole in the middle of address space.
+   To save memory make sure it is still in the same PTE as the stack top.
+   This doesn't give that many random bits */
+static unsigned long vdso_addr(unsigned long start, unsigned len)
+{
+        unsigned long addr, end;
+        unsigned offset;
+        end = (start + PMD_SIZE - 1) & PMD_MASK;
+        if (end >= TASK_SIZE64)
+                end = TASK_SIZE64;
+        end -= len;
+        /* This loses some more bits than a modulo, but is cheaper */
+        offset = get_random_int() & (PTRS_PER_PTE - 1);
+        addr = start + (offset << PAGE_SHIFT);
+        if (addr >= end)
+                addr = end;
+        return addr;
+}
+
+/* Setup a VMA at program startup for the vsyscall page.
+   Not called for compat tasks */
+int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
+{
+        struct mm_struct *mm = current->mm;
+        unsigned long addr;
+        int ret;
+        unsigned len = round_up(vdso_end - vdso_start, PAGE_SIZE);
+
+        if (!vdso_enabled)
+                return 0;
+
+        down_write(&mm->mmap_sem);
+        addr = vdso_addr(mm->start_stack, len);
+        addr = get_unmapped_area(NULL, addr, len, 0, 0);
+        if (IS_ERR_VALUE(addr)) {
+                ret = addr;
+                goto up_fail;
+        }
+
+        ret = install_special_mapping(mm, addr, len,
+                                      VM_READ|VM_EXEC|
+                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
+                                      VM_ALWAYSDUMP,
+                                      vdso_pages);
+        if (ret)
+                goto up_fail;
+
+        current->mm->context.vdso = (void *)addr;
+up_fail:
+        up_write(&mm->mmap_sem);
+        return ret;
+}
+
+static __init int vdso_setup(char *s)
+{
+        vdso_enabled = simple_strtoul(s, NULL, 0);
+        return 0;
+}
+__setup("vdso=", vdso_setup);