blob: 7abd2be0f9b95ff847770472b3ee015e92c47197 [file] [log] [blame]
Andi Kleen2aae9502007-07-21 17:10:01 +02001/*
2 * Set up the VMAs to tell the VM about the vDSO.
3 * Copyright 2007 Andi Kleen, SUSE Labs.
4 * Subject to the GPL, v.2
5 */
6#include <linux/mm.h>
Alexey Dobriyan4e950f62007-07-30 02:36:13 +04007#include <linux/err.h>
Andi Kleen2aae9502007-07-21 17:10:01 +02008#include <linux/sched.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +09009#include <linux/slab.h>
Andi Kleen2aae9502007-07-21 17:10:01 +020010#include <linux/init.h>
11#include <linux/random.h>
Jaswinder Singh Rajput3fa89ca2009-04-12 20:37:25 +053012#include <linux/elf.h>
Andi Kleen2aae9502007-07-21 17:10:01 +020013#include <asm/vsyscall.h>
14#include <asm/vgtod.h>
15#include <asm/proto.h>
Roland McGrath7f3646a2008-01-30 13:30:41 +010016#include <asm/vdso.h>
17
OGAWA Hirofumie6b0ede2008-05-12 15:43:38 +020018unsigned int __read_mostly vdso_enabled = 1;
Andi Kleen2aae9502007-07-21 17:10:01 +020019
Roland McGrath7f3646a2008-01-30 13:30:41 +010020extern char vdso_start[], vdso_end[];
Andi Kleen2aae9502007-07-21 17:10:01 +020021extern unsigned short vdso_sync_cpuid;
22
Jan Beulich369c9922008-07-18 13:37:53 +010023static struct page **vdso_pages;
24static unsigned vdso_size;
Andi Kleen2aae9502007-07-21 17:10:01 +020025
Andi Kleen2aae9502007-07-21 17:10:01 +020026static int __init init_vdso_vars(void)
27{
28 int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
29 int i;
Andi Kleen2aae9502007-07-21 17:10:01 +020030
Jan Beulich369c9922008-07-18 13:37:53 +010031 vdso_size = npages << PAGE_SHIFT;
Andi Kleen2aae9502007-07-21 17:10:01 +020032 vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL);
33 if (!vdso_pages)
34 goto oom;
35 for (i = 0; i < npages; i++) {
36 struct page *p;
37 p = alloc_page(GFP_KERNEL);
38 if (!p)
39 goto oom;
40 vdso_pages[i] = p;
41 copy_page(page_address(p), vdso_start + i*PAGE_SIZE);
42 }
43
Andi Kleen2aae9502007-07-21 17:10:01 +020044 return 0;
45
46 oom:
47 printk("Cannot allocate vdso\n");
48 vdso_enabled = 0;
49 return -ENOMEM;
50}
Jiri Slabyd7a03802010-06-16 22:30:42 +020051subsys_initcall(init_vdso_vars);
Andi Kleen2aae9502007-07-21 17:10:01 +020052
53struct linux_binprm;
54
55/* Put the vdso above the (randomized) stack with another randomized offset.
56 This way there is no hole in the middle of address space.
57 To save memory make sure it is still in the same PTE as the stack top.
58 This doesn't give that many random bits */
59static unsigned long vdso_addr(unsigned long start, unsigned len)
60{
61 unsigned long addr, end;
62 unsigned offset;
63 end = (start + PMD_SIZE - 1) & PMD_MASK;
Ingo Molnard9517342009-02-20 23:32:28 +010064 if (end >= TASK_SIZE_MAX)
65 end = TASK_SIZE_MAX;
Andi Kleen2aae9502007-07-21 17:10:01 +020066 end -= len;
67 /* This loses some more bits than a modulo, but is cheaper */
68 offset = get_random_int() & (PTRS_PER_PTE - 1);
69 addr = start + (offset << PAGE_SHIFT);
70 if (addr >= end)
71 addr = end;
72 return addr;
73}
74
75/* Setup a VMA at program startup for the vsyscall page.
76 Not called for compat tasks */
Martin Schwidefskyfc5243d2008-12-25 13:38:35 +010077int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
Andi Kleen2aae9502007-07-21 17:10:01 +020078{
79 struct mm_struct *mm = current->mm;
80 unsigned long addr;
81 int ret;
Andi Kleen2aae9502007-07-21 17:10:01 +020082
83 if (!vdso_enabled)
84 return 0;
85
86 down_write(&mm->mmap_sem);
Jan Beulich369c9922008-07-18 13:37:53 +010087 addr = vdso_addr(mm->start_stack, vdso_size);
88 addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0);
Andi Kleen2aae9502007-07-21 17:10:01 +020089 if (IS_ERR_VALUE(addr)) {
90 ret = addr;
91 goto up_fail;
92 }
93
Peter Zijlstraf7b6eb32009-06-05 14:04:51 +020094 current->mm->context.vdso = (void *)addr;
95
Jan Beulich369c9922008-07-18 13:37:53 +010096 ret = install_special_mapping(mm, addr, vdso_size,
Andi Kleen2aae9502007-07-21 17:10:01 +020097 VM_READ|VM_EXEC|
98 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
99 VM_ALWAYSDUMP,
100 vdso_pages);
Peter Zijlstraf7b6eb32009-06-05 14:04:51 +0200101 if (ret) {
102 current->mm->context.vdso = NULL;
Andi Kleen2aae9502007-07-21 17:10:01 +0200103 goto up_fail;
Peter Zijlstraf7b6eb32009-06-05 14:04:51 +0200104 }
Andi Kleen2aae9502007-07-21 17:10:01 +0200105
Andi Kleen2aae9502007-07-21 17:10:01 +0200106up_fail:
107 up_write(&mm->mmap_sem);
108 return ret;
109}
110
111static __init int vdso_setup(char *s)
112{
113 vdso_enabled = simple_strtoul(s, NULL, 0);
114 return 0;
115}
116__setup("vdso=", vdso_setup);