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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 | 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> |
aafade24 | 17 | #include <asm/page.h> |
2aae950b | 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 | ||
aafade24 | 24 | extern struct page *vdso_pages[]; |
369c9920 | 25 | static unsigned vdso_size; |
2aae950b | 26 | |
1b3f2a72 AL |
27 | static void __init patch_vdso(void *vdso, size_t len) |
28 | { | |
29 | Elf64_Ehdr *hdr = vdso; | |
30 | Elf64_Shdr *sechdrs, *alt_sec = 0; | |
31 | char *secstrings; | |
32 | void *alt_data; | |
33 | int i; | |
34 | ||
35 | BUG_ON(len < sizeof(Elf64_Ehdr)); | |
36 | BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0); | |
37 | ||
38 | sechdrs = (void *)hdr + hdr->e_shoff; | |
39 | secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; | |
40 | ||
41 | for (i = 1; i < hdr->e_shnum; i++) { | |
42 | Elf64_Shdr *shdr = &sechdrs[i]; | |
43 | if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) { | |
44 | alt_sec = shdr; | |
45 | goto found; | |
46 | } | |
47 | } | |
48 | ||
49 | /* If we get here, it's probably a bug. */ | |
50 | pr_warning("patch_vdso: .altinstructions not found\n"); | |
51 | return; /* nothing to patch */ | |
52 | ||
53 | found: | |
54 | alt_data = (void *)hdr + alt_sec->sh_offset; | |
55 | apply_alternatives(alt_data, alt_data + alt_sec->sh_size); | |
56 | } | |
57 | ||
aafade24 | 58 | static int __init init_vdso(void) |
2aae950b AK |
59 | { |
60 | int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE; | |
61 | int i; | |
2aae950b | 62 | |
1b3f2a72 AL |
63 | patch_vdso(vdso_start, vdso_end - vdso_start); |
64 | ||
369c9920 | 65 | vdso_size = npages << PAGE_SHIFT; |
aafade24 AL |
66 | for (i = 0; i < npages; i++) |
67 | vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE); | |
2aae950b | 68 | |
2aae950b | 69 | return 0; |
2aae950b | 70 | } |
aafade24 | 71 | subsys_initcall(init_vdso); |
2aae950b AK |
72 | |
73 | struct linux_binprm; | |
74 | ||
75 | /* Put the vdso above the (randomized) stack with another randomized offset. | |
76 | This way there is no hole in the middle of address space. | |
77 | To save memory make sure it is still in the same PTE as the stack top. | |
78 | This doesn't give that many random bits */ | |
79 | static unsigned long vdso_addr(unsigned long start, unsigned len) | |
80 | { | |
81 | unsigned long addr, end; | |
82 | unsigned offset; | |
83 | end = (start + PMD_SIZE - 1) & PMD_MASK; | |
d9517346 IM |
84 | if (end >= TASK_SIZE_MAX) |
85 | end = TASK_SIZE_MAX; | |
2aae950b AK |
86 | end -= len; |
87 | /* This loses some more bits than a modulo, but is cheaper */ | |
88 | offset = get_random_int() & (PTRS_PER_PTE - 1); | |
89 | addr = start + (offset << PAGE_SHIFT); | |
90 | if (addr >= end) | |
91 | addr = end; | |
dfb09f9b BP |
92 | |
93 | /* | |
94 | * page-align it here so that get_unmapped_area doesn't | |
95 | * align it wrongfully again to the next page. addr can come in 4K | |
96 | * unaligned here as a result of stack start randomization. | |
97 | */ | |
98 | addr = PAGE_ALIGN(addr); | |
99 | addr = align_addr(addr, NULL, ALIGN_VDSO); | |
100 | ||
2aae950b AK |
101 | return addr; |
102 | } | |
103 | ||
104 | /* Setup a VMA at program startup for the vsyscall page. | |
105 | Not called for compat tasks */ | |
fc5243d9 | 106 | int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) |
2aae950b AK |
107 | { |
108 | struct mm_struct *mm = current->mm; | |
109 | unsigned long addr; | |
110 | int ret; | |
2aae950b AK |
111 | |
112 | if (!vdso_enabled) | |
113 | return 0; | |
114 | ||
115 | down_write(&mm->mmap_sem); | |
369c9920 JB |
116 | addr = vdso_addr(mm->start_stack, vdso_size); |
117 | addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0); | |
2aae950b AK |
118 | if (IS_ERR_VALUE(addr)) { |
119 | ret = addr; | |
120 | goto up_fail; | |
121 | } | |
122 | ||
f7b6eb3f PZ |
123 | current->mm->context.vdso = (void *)addr; |
124 | ||
369c9920 | 125 | ret = install_special_mapping(mm, addr, vdso_size, |
2aae950b | 126 | VM_READ|VM_EXEC| |
909af768 | 127 | VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, |
2aae950b | 128 | vdso_pages); |
f7b6eb3f PZ |
129 | if (ret) { |
130 | current->mm->context.vdso = NULL; | |
2aae950b | 131 | goto up_fail; |
f7b6eb3f | 132 | } |
2aae950b | 133 | |
2aae950b AK |
134 | up_fail: |
135 | up_write(&mm->mmap_sem); | |
136 | return ret; | |
137 | } | |
138 | ||
139 | static __init int vdso_setup(char *s) | |
140 | { | |
141 | vdso_enabled = simple_strtoul(s, NULL, 0); | |
142 | return 0; | |
143 | } | |
144 | __setup("vdso=", vdso_setup); |