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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> | |
11 | #include <asm/vsyscall.h> | |
12 | #include <asm/vgtod.h> | |
13 | #include <asm/proto.h> | |
7f3646aa | 14 | #include <asm/vdso.h> |
2aae950b | 15 | |
7f3646aa | 16 | #include "vextern.h" /* Just for VMAGIC. */ |
2aae950b AK |
17 | #undef VEXTERN |
18 | ||
e6b0edef | 19 | unsigned int __read_mostly vdso_enabled = 1; |
7f3646aa RM |
20 | |
21 | extern char vdso_start[], vdso_end[]; | |
2aae950b AK |
22 | extern unsigned short vdso_sync_cpuid; |
23 | ||
369c9920 JB |
24 | static struct page **vdso_pages; |
25 | static unsigned vdso_size; | |
2aae950b | 26 | |
7f3646aa | 27 | static inline void *var_ref(void *p, char *name) |
2aae950b | 28 | { |
2aae950b AK |
29 | if (*(void **)p != (void *)VMAGIC) { |
30 | printk("VDSO: variable %s broken\n", name); | |
31 | vdso_enabled = 0; | |
32 | } | |
33 | return p; | |
34 | } | |
35 | ||
36 | static int __init init_vdso_vars(void) | |
37 | { | |
38 | int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE; | |
39 | int i; | |
40 | char *vbase; | |
41 | ||
369c9920 | 42 | vdso_size = npages << PAGE_SHIFT; |
2aae950b AK |
43 | vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL); |
44 | if (!vdso_pages) | |
45 | goto oom; | |
46 | for (i = 0; i < npages; i++) { | |
47 | struct page *p; | |
48 | p = alloc_page(GFP_KERNEL); | |
49 | if (!p) | |
50 | goto oom; | |
51 | vdso_pages[i] = p; | |
52 | copy_page(page_address(p), vdso_start + i*PAGE_SIZE); | |
53 | } | |
54 | ||
55 | vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL); | |
56 | if (!vbase) | |
57 | goto oom; | |
58 | ||
59 | if (memcmp(vbase, "\177ELF", 4)) { | |
60 | printk("VDSO: I'm broken; not ELF\n"); | |
61 | vdso_enabled = 0; | |
62 | } | |
63 | ||
2aae950b | 64 | #define VEXTERN(x) \ |
7f3646aa | 65 | *(typeof(__ ## x) **) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x; |
2aae950b AK |
66 | #include "vextern.h" |
67 | #undef VEXTERN | |
68 | return 0; | |
69 | ||
70 | oom: | |
71 | printk("Cannot allocate vdso\n"); | |
72 | vdso_enabled = 0; | |
73 | return -ENOMEM; | |
74 | } | |
75 | __initcall(init_vdso_vars); | |
76 | ||
77 | struct linux_binprm; | |
78 | ||
79 | /* Put the vdso above the (randomized) stack with another randomized offset. | |
80 | This way there is no hole in the middle of address space. | |
81 | To save memory make sure it is still in the same PTE as the stack top. | |
82 | This doesn't give that many random bits */ | |
83 | static unsigned long vdso_addr(unsigned long start, unsigned len) | |
84 | { | |
85 | unsigned long addr, end; | |
86 | unsigned offset; | |
87 | end = (start + PMD_SIZE - 1) & PMD_MASK; | |
88 | if (end >= TASK_SIZE64) | |
89 | end = TASK_SIZE64; | |
90 | end -= len; | |
91 | /* This loses some more bits than a modulo, but is cheaper */ | |
92 | offset = get_random_int() & (PTRS_PER_PTE - 1); | |
93 | addr = start + (offset << PAGE_SHIFT); | |
94 | if (addr >= end) | |
95 | addr = end; | |
96 | return addr; | |
97 | } | |
98 | ||
99 | /* Setup a VMA at program startup for the vsyscall page. | |
100 | Not called for compat tasks */ | |
101 | int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack) | |
102 | { | |
103 | struct mm_struct *mm = current->mm; | |
104 | unsigned long addr; | |
105 | int ret; | |
2aae950b AK |
106 | |
107 | if (!vdso_enabled) | |
108 | return 0; | |
109 | ||
110 | down_write(&mm->mmap_sem); | |
369c9920 JB |
111 | addr = vdso_addr(mm->start_stack, vdso_size); |
112 | addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0); | |
2aae950b AK |
113 | if (IS_ERR_VALUE(addr)) { |
114 | ret = addr; | |
115 | goto up_fail; | |
116 | } | |
117 | ||
369c9920 | 118 | ret = install_special_mapping(mm, addr, vdso_size, |
2aae950b AK |
119 | VM_READ|VM_EXEC| |
120 | VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| | |
121 | VM_ALWAYSDUMP, | |
122 | vdso_pages); | |
123 | if (ret) | |
124 | goto up_fail; | |
125 | ||
126 | current->mm->context.vdso = (void *)addr; | |
127 | up_fail: | |
128 | up_write(&mm->mmap_sem); | |
129 | return ret; | |
130 | } | |
131 | ||
132 | static __init int vdso_setup(char *s) | |
133 | { | |
134 | vdso_enabled = simple_strtoul(s, NULL, 0); | |
135 | return 0; | |
136 | } | |
137 | __setup("vdso=", vdso_setup); |