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
vdso_setup(void * vdso_kbase,unsigned int pages)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
vdso_init(void)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
arch_vma_name(struct vm_area_struct * vma)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
setup_vdso_pages(void)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
vdso_func(char * s)193 static __init int vdso_func(char *s)
194 {
195 return kstrtouint(s, 0, &vdso_enabled);
196 }
197 __setup("vdso=", vdso_func);
198