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
8 #include <linux/sched.h>
9 #include <linux/slab.h>
10 #include <linux/init.h>
11 #include <linux/random.h>
12 #include <linux/elf.h>
13 #include <asm/vsyscall.h>
14 #include <asm/vgtod.h>
15 #include <asm/proto.h>
19 #if defined(CONFIG_X86_64)
20 unsigned int __read_mostly vdso_enabled = 1;
22 DECLARE_VDSO_IMAGE(vdso);
23 extern unsigned short vdso_sync_cpuid;
24 static unsigned vdso_size;
26 #ifdef CONFIG_X86_X32_ABI
27 DECLARE_VDSO_IMAGE(vdsox32);
28 static unsigned vdsox32_size;
32 #if defined(CONFIG_X86_32) || defined(CONFIG_X86_X32_ABI) || \
33 defined(CONFIG_COMPAT)
34 void __init patch_vdso32(void *vdso, size_t len)
36 Elf32_Ehdr *hdr = vdso;
37 Elf32_Shdr *sechdrs, *alt_sec = 0;
42 BUG_ON(len < sizeof(Elf32_Ehdr));
43 BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0);
45 sechdrs = (void *)hdr + hdr->e_shoff;
46 secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
48 for (i = 1; i < hdr->e_shnum; i++) {
49 Elf32_Shdr *shdr = &sechdrs[i];
50 if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) {
56 /* If we get here, it's probably a bug. */
57 pr_warning("patch_vdso32: .altinstructions not found\n");
58 return; /* nothing to patch */
61 alt_data = (void *)hdr + alt_sec->sh_offset;
62 apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
66 #if defined(CONFIG_X86_64)
67 static void __init patch_vdso64(void *vdso, size_t len)
69 Elf64_Ehdr *hdr = vdso;
70 Elf64_Shdr *sechdrs, *alt_sec = 0;
75 BUG_ON(len < sizeof(Elf64_Ehdr));
76 BUG_ON(memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0);
78 sechdrs = (void *)hdr + hdr->e_shoff;
79 secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
81 for (i = 1; i < hdr->e_shnum; i++) {
82 Elf64_Shdr *shdr = &sechdrs[i];
83 if (!strcmp(secstrings + shdr->sh_name, ".altinstructions")) {
89 /* If we get here, it's probably a bug. */
90 pr_warning("patch_vdso64: .altinstructions not found\n");
91 return; /* nothing to patch */
94 alt_data = (void *)hdr + alt_sec->sh_offset;
95 apply_alternatives(alt_data, alt_data + alt_sec->sh_size);
98 static int __init init_vdso(void)
100 int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE;
103 patch_vdso64(vdso_start, vdso_end - vdso_start);
105 vdso_size = npages << PAGE_SHIFT;
106 for (i = 0; i < npages; i++)
107 vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE);
109 #ifdef CONFIG_X86_X32_ABI
110 patch_vdso32(vdsox32_start, vdsox32_end - vdsox32_start);
111 npages = (vdsox32_end - vdsox32_start + PAGE_SIZE - 1) / PAGE_SIZE;
112 vdsox32_size = npages << PAGE_SHIFT;
113 for (i = 0; i < npages; i++)
114 vdsox32_pages[i] = virt_to_page(vdsox32_start + i*PAGE_SIZE);
119 subsys_initcall(init_vdso);
123 /* Put the vdso above the (randomized) stack with another randomized offset.
124 This way there is no hole in the middle of address space.
125 To save memory make sure it is still in the same PTE as the stack top.
126 This doesn't give that many random bits */
127 static unsigned long vdso_addr(unsigned long start, unsigned len)
129 unsigned long addr, end;
131 end = (start + PMD_SIZE - 1) & PMD_MASK;
132 if (end >= TASK_SIZE_MAX)
135 /* This loses some more bits than a modulo, but is cheaper */
136 offset = get_random_int() & (PTRS_PER_PTE - 1);
137 addr = start + (offset << PAGE_SHIFT);
142 * page-align it here so that get_unmapped_area doesn't
143 * align it wrongfully again to the next page. addr can come in 4K
144 * unaligned here as a result of stack start randomization.
146 addr = PAGE_ALIGN(addr);
147 addr = align_vdso_addr(addr);
152 /* Setup a VMA at program startup for the vsyscall page.
153 Not called for compat tasks */
154 static int setup_additional_pages(struct linux_binprm *bprm,
159 struct mm_struct *mm = current->mm;
166 down_write(&mm->mmap_sem);
167 addr = vdso_addr(mm->start_stack, size);
168 addr = get_unmapped_area(NULL, addr, size, 0, 0);
169 if (IS_ERR_VALUE(addr)) {
174 current->mm->context.vdso = (void *)addr;
176 ret = install_special_mapping(mm, addr, size,
178 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
181 current->mm->context.vdso = NULL;
186 up_write(&mm->mmap_sem);
190 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
192 return setup_additional_pages(bprm, uses_interp, vdso_pages,
196 #ifdef CONFIG_X86_X32_ABI
197 int x32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
199 return setup_additional_pages(bprm, uses_interp, vdsox32_pages,
204 static __init int vdso_setup(char *s)
206 vdso_enabled = simple_strtoul(s, NULL, 0);
209 __setup("vdso=", vdso_setup);