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