1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
/*
* Set up the VMAs to tell the VM about the vDSO.
* Copyright 2007 Andi Kleen, SUSE Labs.
* Subject to the GPL, v.2
*/
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/elf.h>
#include <asm/vsyscall.h>
#include <asm/vgtod.h>
#include <asm/proto.h>
#include <asm/vdso.h>
#include <asm/page.h>
#if defined(CONFIG_X86_64)
unsigned int __read_mostly vdso_enabled = 1;
DECLARE_VDSO_IMAGE(vdso);
extern unsigned short vdso_sync_cpuid;
static unsigned vdso_size;
#ifdef CONFIG_X86_X32_ABI
DECLARE_VDSO_IMAGE(vdsox32);
static unsigned vdsox32_size;
#endif
#endif
#if defined(CONFIG_X86_32) || defined(CONFIG_X86_X32_ABI) || \
defined(CONFIG_COMPAT)
void __init patch_vdso32(void *vdso, size_t len)
{
Elf32_Ehdr *hdr = vdso;
Elf32_Shdr *sechdrs, *alt_sec = 0;
char *secstrings;
void *alt_data;
int i;
BUG_ON(len < sizeof(Elf32_Ehdr));
BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0);
sechdrs = (void *)hdr + hdr->e_shoff;
secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
for (i = 1; i < hdr->e_shnum; i++) {
Elf32_Shdr *shdr = &sechdrs[i];
if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) {
alt_sec = shdr;
goto found;
}
}
/* If we get here, it's probably a bug. */
pr_warning("patch_vdso32: .altinstructions not found\n");
return; /* nothing to patch */
found:
alt_data = (void *)hdr + alt_sec->sh_offset;
apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
}
#endif
#if defined(CONFIG_X86_64)
static void __init patch_vdso64(void *vdso, size_t len)
{
Elf64_Ehdr *hdr = vdso;
Elf64_Shdr *sechdrs, *alt_sec = 0;
char *secstrings;
void *alt_data;
int i;
BUG_ON(len < sizeof(Elf64_Ehdr));
BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0);
sechdrs = (void *)hdr + hdr->e_shoff;
secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
for (i = 1; i < hdr->e_shnum; i++) {
Elf64_Shdr *shdr = &sechdrs[i];
if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) {
alt_sec = shdr;
goto found;
}
}
/* If we get here, it's probably a bug. */
pr_warning("patch_vdso64: .altinstructions not found\n");
return; /* nothing to patch */
found:
alt_data = (void *)hdr + alt_sec->sh_offset;
apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
}
static int __init init_vdso(void)
{
int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
int i;
patch_vdso64(vdso_start, vdso_end - vdso_start);
vdso_size = npages << PAGE_SHIFT;
for (i = 0; i < npages; i++)
vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE);
#ifdef CONFIG_X86_X32_ABI
patch_vdso32(vdsox32_start, vdsox32_end - vdsox32_start);
npages = (vdsox32_end - vdsox32_start + PAGE_SIZE - 1) / PAGE_SIZE;
vdsox32_size = npages << PAGE_SHIFT;
for (i = 0; i < npages; i++)
vdsox32_pages[i] = virt_to_page(vdsox32_start + i*PAGE_SIZE);
#endif
return 0;
}
subsys_initcall(init_vdso);
struct linux_binprm;
/* Put the vdso above the (randomized) stack with another randomized offset.
This way there is no hole in the middle of address space.
To save memory make sure it is still in the same PTE as the stack top.
This doesn't give that many random bits */
static unsigned long vdso_addr(unsigned long start, unsigned len)
{
unsigned long addr, end;
unsigned offset;
end = (start + PMD_SIZE - 1) & PMD_MASK;
if (end >= TASK_SIZE_MAX)
end = TASK_SIZE_MAX;
end -= len;
/* This loses some more bits than a modulo, but is cheaper */
offset = get_random_int() & (PTRS_PER_PTE - 1);
addr = start + (offset << PAGE_SHIFT);
if (addr >= end)
addr = end;
/*
* page-align it here so that get_unmapped_area doesn't
* align it wrongfully again to the next page. addr can come in 4K
* unaligned here as a result of stack start randomization.
*/
addr = PAGE_ALIGN(addr);
addr = align_vdso_addr(addr);
return addr;
}
/* Setup a VMA at program startup for the vsyscall page.
Not called for compat tasks */
static int setup_additional_pages(struct linux_binprm *bprm,
int uses_interp,
struct page **pages,
unsigned size)
{
struct mm_struct *mm = current->mm;
unsigned long addr;
int ret;
if (!vdso_enabled)
return 0;
down_write(&mm->mmap_sem);
addr = vdso_addr(mm->start_stack, size);
addr = get_unmapped_area(NULL, addr, size, 0, 0);
if (IS_ERR_VALUE(addr)) {
ret = addr;
goto up_fail;
}
current->mm->context.vdso = (void *)addr;
ret = install_special_mapping(mm, addr, size,
VM_READ|VM_EXEC|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
pages);
if (ret) {
current->mm->context.vdso = NULL;
goto up_fail;
}
up_fail:
up_write(&mm->mmap_sem);
return ret;
}
int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
return setup_additional_pages(bprm, uses_interp, vdso_pages,
vdso_size);
}
#ifdef CONFIG_X86_X32_ABI
int x32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
return setup_additional_pages(bprm, uses_interp, vdsox32_pages,
vdsox32_size);
}
#endif
static __init int vdso_setup(char *s)
{
vdso_enabled = simple_strtoul(s, NULL, 0);
return 0;
}
__setup("vdso=", vdso_setup);
#endif
|
