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 | 8 | #include <linux/sched.h> |
5a0e3ad6 | 9 | #include <linux/slab.h> |
2aae950b AK |
10 | #include <linux/init.h> |
11 | #include <linux/random.h> | |
3fa89ca7 | 12 | #include <linux/elf.h> |
2aae950b AK |
13 | #include <asm/vsyscall.h> |
14 | #include <asm/vgtod.h> | |
15 | #include <asm/proto.h> | |
7f3646aa | 16 | #include <asm/vdso.h> |
2aae950b | 17 | |
7f3646aa | 18 | #include "vextern.h" /* Just for VMAGIC. */ |
2aae950b AK |
19 | #undef VEXTERN |
20 | ||
e6b0edef | 21 | unsigned int __read_mostly vdso_enabled = 1; |
7f3646aa RM |
22 | |
23 | extern char vdso_start[], vdso_end[]; | |
2aae950b AK |
24 | extern unsigned short vdso_sync_cpuid; |
25 | ||
369c9920 JB |
26 | static struct page **vdso_pages; |
27 | static unsigned vdso_size; | |
2aae950b | 28 | |
7f3646aa | 29 | static inline void *var_ref(void *p, char *name) |
2aae950b | 30 | { |
2aae950b AK |
31 | if (*(void **)p != (void *)VMAGIC) { |
32 | printk("VDSO: variable %s broken\n", name); | |
33 | vdso_enabled = 0; | |
34 | } | |
35 | return p; | |
36 | } | |
37 | ||
38 | static int __init init_vdso_vars(void) | |
39 | { | |
40 | int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE; | |
41 | int i; | |
42 | char *vbase; | |
43 | ||
369c9920 | 44 | vdso_size = npages << PAGE_SHIFT; |
2aae950b AK |
45 | vdso_pages = kmalloc(sizeof(struct page *) * npages, GFP_KERNEL); |
46 | if (!vdso_pages) | |
47 | goto oom; | |
48 | for (i = 0; i < npages; i++) { | |
49 | struct page *p; | |
50 | p = alloc_page(GFP_KERNEL); | |
51 | if (!p) | |
52 | goto oom; | |
53 | vdso_pages[i] = p; | |
54 | copy_page(page_address(p), vdso_start + i*PAGE_SIZE); | |
55 | } | |
56 | ||
57 | vbase = vmap(vdso_pages, npages, 0, PAGE_KERNEL); | |
58 | if (!vbase) | |
59 | goto oom; | |
60 | ||
61 | if (memcmp(vbase, "\177ELF", 4)) { | |
62 | printk("VDSO: I'm broken; not ELF\n"); | |
63 | vdso_enabled = 0; | |
64 | } | |
65 | ||
2aae950b | 66 | #define VEXTERN(x) \ |
7f3646aa | 67 | *(typeof(__ ## x) **) var_ref(VDSO64_SYMBOL(vbase, x), #x) = &__ ## x; |
2aae950b AK |
68 | #include "vextern.h" |
69 | #undef VEXTERN | |
70 | return 0; | |
71 | ||
72 | oom: | |
73 | printk("Cannot allocate vdso\n"); | |
74 | vdso_enabled = 0; | |
75 | return -ENOMEM; | |
76 | } | |
77 | __initcall(init_vdso_vars); | |
78 | ||
79 | struct linux_binprm; | |
80 | ||
81 | /* Put the vdso above the (randomized) stack with another randomized offset. | |
82 | This way there is no hole in the middle of address space. | |
83 | To save memory make sure it is still in the same PTE as the stack top. | |
84 | This doesn't give that many random bits */ | |
85 | static unsigned long vdso_addr(unsigned long start, unsigned len) | |
86 | { | |
87 | unsigned long addr, end; | |
88 | unsigned offset; | |
89 | end = (start + PMD_SIZE - 1) & PMD_MASK; | |
d9517346 IM |
90 | if (end >= TASK_SIZE_MAX) |
91 | end = TASK_SIZE_MAX; | |
2aae950b AK |
92 | end -= len; |
93 | /* This loses some more bits than a modulo, but is cheaper */ | |
94 | offset = get_random_int() & (PTRS_PER_PTE - 1); | |
95 | addr = start + (offset << PAGE_SHIFT); | |
96 | if (addr >= end) | |
97 | addr = end; | |
98 | return addr; | |
99 | } | |
100 | ||
101 | /* Setup a VMA at program startup for the vsyscall page. | |
102 | Not called for compat tasks */ | |
fc5243d9 | 103 | int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) |
2aae950b AK |
104 | { |
105 | struct mm_struct *mm = current->mm; | |
106 | unsigned long addr; | |
107 | int ret; | |
2aae950b AK |
108 | |
109 | if (!vdso_enabled) | |
110 | return 0; | |
111 | ||
112 | down_write(&mm->mmap_sem); | |
369c9920 JB |
113 | addr = vdso_addr(mm->start_stack, vdso_size); |
114 | addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0); | |
2aae950b AK |
115 | if (IS_ERR_VALUE(addr)) { |
116 | ret = addr; | |
117 | goto up_fail; | |
118 | } | |
119 | ||
f7b6eb3f PZ |
120 | current->mm->context.vdso = (void *)addr; |
121 | ||
369c9920 | 122 | ret = install_special_mapping(mm, addr, vdso_size, |
2aae950b AK |
123 | VM_READ|VM_EXEC| |
124 | VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| | |
125 | VM_ALWAYSDUMP, | |
126 | vdso_pages); | |
f7b6eb3f PZ |
127 | if (ret) { |
128 | current->mm->context.vdso = NULL; | |
2aae950b | 129 | goto up_fail; |
f7b6eb3f | 130 | } |
2aae950b | 131 | |
2aae950b AK |
132 | up_fail: |
133 | up_write(&mm->mmap_sem); | |
134 | return ret; | |
135 | } | |
136 | ||
137 | static __init int vdso_setup(char *s) | |
138 | { | |
139 | vdso_enabled = simple_strtoul(s, NULL, 0); | |
140 | return 0; | |
141 | } | |
142 | __setup("vdso=", vdso_setup); |