summaryrefslogtreecommitdiff
path: root/arch/x86/vdso/vma.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/vdso/vma.c')
-rw-r--r--arch/x86/vdso/vma.c140
1 files changed, 140 insertions, 0 deletions
diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
new file mode 100644
index 000000000000..ff9333e5fb08
--- /dev/null
+++ b/arch/x86/vdso/vma.c
@@ -0,0 +1,140 @@
+/*
+ * 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/err.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);