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4a556f4f CM |
1 | /* |
2 | * Copyright 2012 Tilera Corporation. All Rights Reserved. | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation, version 2. | |
7 | * | |
8 | * This program is distributed in the hope that it will be useful, but | |
9 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
10 | * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or | |
11 | * NON INFRINGEMENT. See the GNU General Public License for | |
12 | * more details. | |
13 | */ | |
14 | ||
15 | #include <linux/binfmts.h> | |
16 | #include <linux/compat.h> | |
17 | #include <linux/elf.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/pagemap.h> | |
20 | ||
21 | #include <asm/vdso.h> | |
22 | #include <asm/mman.h> | |
23 | #include <asm/sections.h> | |
24 | ||
25 | #include <arch/sim.h> | |
26 | ||
27 | /* The alignment of the vDSO. */ | |
28 | #define VDSO_ALIGNMENT PAGE_SIZE | |
29 | ||
30 | ||
31 | static unsigned int vdso_pages; | |
32 | static struct page **vdso_pagelist; | |
33 | ||
34 | #ifdef CONFIG_COMPAT | |
35 | static unsigned int vdso32_pages; | |
36 | static struct page **vdso32_pagelist; | |
37 | #endif | |
38 | static int vdso_ready; | |
39 | ||
40 | /* | |
41 | * The vdso data page. | |
42 | */ | |
43 | static union { | |
44 | struct vdso_data data; | |
45 | u8 page[PAGE_SIZE]; | |
46 | } vdso_data_store __page_aligned_data; | |
47 | ||
48 | struct vdso_data *vdso_data = &vdso_data_store.data; | |
49 | ||
50 | static unsigned int __read_mostly vdso_enabled = 1; | |
51 | ||
52 | static struct page **vdso_setup(void *vdso_kbase, unsigned int pages) | |
53 | { | |
54 | int i; | |
55 | struct page **pagelist; | |
56 | ||
57 | pagelist = kzalloc(sizeof(struct page *) * (pages + 1), GFP_KERNEL); | |
58 | BUG_ON(pagelist == NULL); | |
59 | for (i = 0; i < pages - 1; i++) { | |
60 | struct page *pg = virt_to_page(vdso_kbase + i*PAGE_SIZE); | |
61 | ClearPageReserved(pg); | |
62 | pagelist[i] = pg; | |
63 | } | |
64 | pagelist[pages - 1] = virt_to_page(vdso_data); | |
65 | pagelist[pages] = NULL; | |
66 | ||
67 | return pagelist; | |
68 | } | |
69 | ||
70 | static int __init vdso_init(void) | |
71 | { | |
72 | int data_pages = sizeof(vdso_data_store) >> PAGE_SHIFT; | |
73 | ||
74 | /* | |
75 | * We can disable vDSO support generally, but we need to retain | |
76 | * one page to support the two-bundle (16-byte) rt_sigreturn path. | |
77 | */ | |
78 | if (!vdso_enabled) { | |
79 | size_t offset = (unsigned long)&__vdso_rt_sigreturn; | |
80 | static struct page *sigret_page; | |
81 | sigret_page = alloc_page(GFP_KERNEL | __GFP_ZERO); | |
82 | BUG_ON(sigret_page == NULL); | |
83 | vdso_pagelist = &sigret_page; | |
84 | vdso_pages = 1; | |
85 | BUG_ON(offset >= PAGE_SIZE); | |
86 | memcpy(page_address(sigret_page) + offset, | |
87 | vdso_start + offset, 16); | |
88 | #ifdef CONFIG_COMPAT | |
89 | vdso32_pages = vdso_pages; | |
90 | vdso32_pagelist = vdso_pagelist; | |
91 | #endif | |
92 | vdso_ready = 1; | |
93 | return 0; | |
94 | } | |
95 | ||
96 | vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; | |
97 | vdso_pages += data_pages; | |
98 | vdso_pagelist = vdso_setup(vdso_start, vdso_pages); | |
99 | ||
100 | #ifdef CONFIG_COMPAT | |
101 | vdso32_pages = (vdso32_end - vdso32_start) >> PAGE_SHIFT; | |
102 | vdso32_pages += data_pages; | |
103 | vdso32_pagelist = vdso_setup(vdso32_start, vdso32_pages); | |
104 | #endif | |
105 | ||
106 | smp_wmb(); | |
107 | vdso_ready = 1; | |
108 | ||
109 | return 0; | |
110 | } | |
111 | arch_initcall(vdso_init); | |
112 | ||
113 | const char *arch_vma_name(struct vm_area_struct *vma) | |
114 | { | |
115 | if (vma->vm_mm && vma->vm_start == VDSO_BASE) | |
116 | return "[vdso]"; | |
117 | #ifndef __tilegx__ | |
118 | if (vma->vm_start == MEM_USER_INTRPT) | |
119 | return "[intrpt]"; | |
120 | #endif | |
121 | return NULL; | |
122 | } | |
123 | ||
4a556f4f CM |
124 | int setup_vdso_pages(void) |
125 | { | |
126 | struct page **pagelist; | |
127 | unsigned long pages; | |
128 | struct mm_struct *mm = current->mm; | |
129 | unsigned long vdso_base = 0; | |
130 | int retval = 0; | |
131 | ||
132 | if (!vdso_ready) | |
133 | return 0; | |
134 | ||
135 | mm->context.vdso_base = 0; | |
136 | ||
137 | pagelist = vdso_pagelist; | |
138 | pages = vdso_pages; | |
139 | #ifdef CONFIG_COMPAT | |
140 | if (is_compat_task()) { | |
141 | pagelist = vdso32_pagelist; | |
142 | pages = vdso32_pages; | |
143 | } | |
144 | #endif | |
145 | ||
146 | /* | |
147 | * vDSO has a problem and was disabled, just don't "enable" it for the | |
148 | * process. | |
149 | */ | |
150 | if (pages == 0) | |
151 | return 0; | |
152 | ||
153 | vdso_base = get_unmapped_area(NULL, vdso_base, | |
154 | (pages << PAGE_SHIFT) + | |
155 | ((VDSO_ALIGNMENT - 1) & PAGE_MASK), | |
156 | 0, 0); | |
157 | if (IS_ERR_VALUE(vdso_base)) { | |
158 | retval = vdso_base; | |
159 | return retval; | |
160 | } | |
161 | ||
162 | /* Add required alignment. */ | |
163 | vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT); | |
164 | ||
165 | /* | |
166 | * Put vDSO base into mm struct. We need to do this before calling | |
167 | * install_special_mapping or the perf counter mmap tracking code | |
168 | * will fail to recognise it as a vDSO (since arch_vma_name fails). | |
169 | */ | |
170 | mm->context.vdso_base = vdso_base; | |
171 | ||
172 | /* | |
173 | * our vma flags don't have VM_WRITE so by default, the process isn't | |
174 | * allowed to write those pages. | |
175 | * gdb can break that with ptrace interface, and thus trigger COW on | |
176 | * those pages but it's then your responsibility to never do that on | |
177 | * the "data" page of the vDSO or you'll stop getting kernel updates | |
178 | * and your nice userland gettimeofday will be totally dead. | |
179 | * It's fine to use that for setting breakpoints in the vDSO code | |
180 | * pages though | |
181 | */ | |
182 | retval = install_special_mapping(mm, vdso_base, | |
183 | pages << PAGE_SHIFT, | |
184 | VM_READ|VM_EXEC | | |
185 | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, | |
186 | pagelist); | |
187 | if (retval) | |
188 | mm->context.vdso_base = 0; | |
189 | ||
190 | return retval; | |
191 | } | |
192 | ||
193 | static __init int vdso_func(char *s) | |
194 | { | |
195 | return kstrtouint(s, 0, &vdso_enabled); | |
196 | } | |
197 | __setup("vdso=", vdso_func); |