Commit | Line | Data |
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2aae950b AK |
1 | /* |
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> | |
4e950f6f | 7 | #include <linux/err.h> |
2aae950b AK |
8 | #include <linux/sched.h> |
9 | #include <linux/init.h> | |
10 | #include <linux/random.h> | |
3fa89ca7 | 11 | #include <linux/elf.h> |
2aae950b AK |
12 | #include <asm/vsyscall.h> |
13 | #include <asm/vgtod.h> | |
14 | #include <asm/proto.h> | |
7f3646aa | 15 | #include <asm/vdso.h> |
2aae950b | 16 | |
7f3646aa | 17 | #include "vextern.h" /* Just for VMAGIC. */ |
2aae950b AK |
18 | #undef VEXTERN |
19 | ||
e6b0edef | 20 | unsigned int __read_mostly vdso_enabled = 1; |
7f3646aa RM |
21 | |
22 | extern char vdso_start[], vdso_end[]; | |
2aae950b AK |
23 | extern unsigned short vdso_sync_cpuid; |
24 | ||
369c9920 JB |
25 | static struct page **vdso_pages; |
26 | static unsigned vdso_size; | |
2aae950b | 27 | |
7f3646aa | 28 | static inline void *var_ref(void *p, char *name) |
2aae950b | 29 | { |
2aae950b AK |
30 | if (*(void **)p != (void *)VMAGIC) { |
31 | printk("VDSO: variable %s broken\n", name); | |
32 | vdso_enabled = 0; | |
33 | } | |
34 | return p; | |
35 | } | |
36 | ||
37 | static int __init init_vdso_vars(void) | |
38 | { | |
39 | int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE; | |
40 | int i; | |
41 | char *vbase; | |
42 | ||
369c9920 | 43 | vdso_size = npages << PAGE_SHIFT; |
2aae950b AK |
44 | vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL); |
45 | if (!vdso_pages) | |
46 | goto oom; | |
47 | for (i = 0; i < npages; i++) { | |
48 | struct page *p; | |
49 | p = alloc_page(GFP_KERNEL); | |
50 | if (!p) | |
51 | goto oom; | |
52 | vdso_pages[i] = p; | |
53 | copy_page(page_address(p), vdso_start + i*PAGE_SIZE); | |
54 | } | |
55 | ||
56 | vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL); | |
57 | if (!vbase) | |
58 | goto oom; | |
59 | ||
60 | if (memcmp(vbase, "\177ELF", 4)) { | |
61 | printk("VDSO: I'm broken; not ELF\n"); | |
62 | vdso_enabled = 0; | |
63 | } | |
64 | ||
2aae950b | 65 | #define VEXTERN(x) \ |
7f3646aa | 66 | *(typeof(__ ## x) **) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x; |
2aae950b AK |
67 | #include "vextern.h" |
68 | #undef VEXTERN | |
69 | return 0; | |
70 | ||
71 | oom: | |
72 | printk("Cannot allocate vdso\n"); | |
73 | vdso_enabled = 0; | |
74 | return -ENOMEM; | |
75 | } | |
76 | __initcall(init_vdso_vars); | |
77 | ||
78 | struct linux_binprm; | |
79 | ||
80 | /* Put the vdso above the (randomized) stack with another randomized offset. | |
81 | This way there is no hole in the middle of address space. | |
82 | To save memory make sure it is still in the same PTE as the stack top. | |
83 | This doesn't give that many random bits */ | |
84 | static unsigned long vdso_addr(unsigned long start, unsigned len) | |
85 | { | |
86 | unsigned long addr, end; | |
87 | unsigned offset; | |
88 | end = (start + PMD_SIZE - 1) & PMD_MASK; | |
d9517346 IM |
89 | if (end >= TASK_SIZE_MAX) |
90 | end = TASK_SIZE_MAX; | |
2aae950b AK |
91 | end -= len; |
92 | /* This loses some more bits than a modulo, but is cheaper */ | |
93 | offset = get_random_int() & (PTRS_PER_PTE - 1); | |
94 | addr = start + (offset << PAGE_SHIFT); | |
95 | if (addr >= end) | |
96 | addr = end; | |
97 | return addr; | |
98 | } | |
99 | ||
100 | /* Setup a VMA at program startup for the vsyscall page. | |
101 | Not called for compat tasks */ | |
fc5243d9 | 102 | int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) |
2aae950b AK |
103 | { |
104 | struct mm_struct *mm = current->mm; | |
105 | unsigned long addr; | |
106 | int ret; | |
2aae950b AK |
107 | |
108 | if (!vdso_enabled) | |
109 | return 0; | |
110 | ||
111 | down_write(&mm->mmap_sem); | |
369c9920 JB |
112 | addr = vdso_addr(mm->start_stack, vdso_size); |
113 | addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0); | |
2aae950b AK |
114 | if (IS_ERR_VALUE(addr)) { |
115 | ret = addr; | |
116 | goto up_fail; | |
117 | } | |
118 | ||
f7b6eb3f PZ |
119 | current->mm->context.vdso = (void *)addr; |
120 | ||
369c9920 | 121 | ret = install_special_mapping(mm, addr, vdso_size, |
2aae950b AK |
122 | VM_READ|VM_EXEC| |
123 | VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| | |
124 | VM_ALWAYSDUMP, | |
125 | vdso_pages); | |
f7b6eb3f PZ |
126 | if (ret) { |
127 | current->mm->context.vdso = NULL; | |
2aae950b | 128 | goto up_fail; |
f7b6eb3f | 129 | } |
2aae950b | 130 | |
2aae950b AK |
131 | up_fail: |
132 | up_write(&mm->mmap_sem); | |
133 | return ret; | |
134 | } | |
135 | ||
136 | static __init int vdso_setup(char *s) | |
137 | { | |
138 | vdso_enabled = simple_strtoul(s, NULL, 0); | |
139 | return 0; | |
140 | } | |
141 | __setup("vdso=", vdso_setup); |