Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 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> |
Alexey Dobriyan | 4e950f6 | 2007-07-30 02:36:13 +0400 | [diff] [blame] | 7 | #include <linux/err.h> |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 8 | #include <linux/sched.h> |
Tejun Heo | 5a0e3ad | 2010-03-24 17:04:11 +0900 | [diff] [blame] | 9 | #include <linux/slab.h> |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 10 | #include <linux/init.h> |
| 11 | #include <linux/random.h> |
Jaswinder Singh Rajput | 3fa89ca | 2009-04-12 20:37:25 +0530 | [diff] [blame] | 12 | #include <linux/elf.h> |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 13 | #include <asm/vsyscall.h> |
| 14 | #include <asm/vgtod.h> |
| 15 | #include <asm/proto.h> |
Roland McGrath | 7f3646a | 2008-01-30 13:30:41 +0100 | [diff] [blame] | 16 | #include <asm/vdso.h> |
Andy Lutomirski | aafade2 | 2011-07-21 15:47:10 -0400 | [diff] [blame] | 17 | #include <asm/page.h> |
Roland McGrath | 7f3646a | 2008-01-30 13:30:41 +0100 | [diff] [blame] | 18 | |
OGAWA Hirofumi | e6b0ede | 2008-05-12 15:43:38 +0200 | [diff] [blame] | 19 | unsigned int __read_mostly vdso_enabled = 1; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 20 | |
Roland McGrath | 7f3646a | 2008-01-30 13:30:41 +0100 | [diff] [blame] | 21 | extern char vdso_start[], vdso_end[]; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 22 | extern unsigned short vdso_sync_cpuid; |
| 23 | |
Andy Lutomirski | aafade2 | 2011-07-21 15:47:10 -0400 | [diff] [blame] | 24 | extern struct page *vdso_pages[]; |
Jan Beulich | 369c992 | 2008-07-18 13:37:53 +0100 | [diff] [blame] | 25 | static unsigned vdso_size; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 26 | |
Andy Lutomirski | 1b3f2a7 | 2011-07-13 09:24:11 -0400 | [diff] [blame] | 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 | |
Andy Lutomirski | aafade2 | 2011-07-21 15:47:10 -0400 | [diff] [blame] | 58 | static int __init init_vdso(void) |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 59 | { |
| 60 | int npages = (vdso_end - vdso_start + PAGE_SIZE - 1) / PAGE_SIZE; |
| 61 | int i; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 62 | |
Andy Lutomirski | 1b3f2a7 | 2011-07-13 09:24:11 -0400 | [diff] [blame] | 63 | patch_vdso(vdso_start, vdso_end - vdso_start); |
| 64 | |
Jan Beulich | 369c992 | 2008-07-18 13:37:53 +0100 | [diff] [blame] | 65 | vdso_size = npages << PAGE_SHIFT; |
Andy Lutomirski | aafade2 | 2011-07-21 15:47:10 -0400 | [diff] [blame] | 66 | for (i = 0; i < npages; i++) |
| 67 | vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE); |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 68 | |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 69 | return 0; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 70 | } |
Andy Lutomirski | aafade2 | 2011-07-21 15:47:10 -0400 | [diff] [blame] | 71 | subsys_initcall(init_vdso); |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 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; |
Ingo Molnar | d951734 | 2009-02-20 23:32:28 +0100 | [diff] [blame] | 84 | if (end >= TASK_SIZE_MAX) |
| 85 | end = TASK_SIZE_MAX; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 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; |
Borislav Petkov | dfb09f9 | 2011-08-05 15:15:08 +0200 | [diff] [blame] | 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 | |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 101 | return addr; |
| 102 | } |
| 103 | |
| 104 | /* Setup a VMA at program startup for the vsyscall page. |
| 105 | Not called for compat tasks */ |
Martin Schwidefsky | fc5243d | 2008-12-25 13:38:35 +0100 | [diff] [blame] | 106 | int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 107 | { |
| 108 | struct mm_struct *mm = current->mm; |
| 109 | unsigned long addr; |
| 110 | int ret; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 111 | |
| 112 | if (!vdso_enabled) |
| 113 | return 0; |
| 114 | |
| 115 | down_write(&mm->mmap_sem); |
Jan Beulich | 369c992 | 2008-07-18 13:37:53 +0100 | [diff] [blame] | 116 | addr = vdso_addr(mm->start_stack, vdso_size); |
| 117 | addr = get_unmapped_area(NULL, addr, vdso_size, 0, 0); |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 118 | if (IS_ERR_VALUE(addr)) { |
| 119 | ret = addr; |
| 120 | goto up_fail; |
| 121 | } |
| 122 | |
Peter Zijlstra | f7b6eb3 | 2009-06-05 14:04:51 +0200 | [diff] [blame] | 123 | current->mm->context.vdso = (void *)addr; |
| 124 | |
Jan Beulich | 369c992 | 2008-07-18 13:37:53 +0100 | [diff] [blame] | 125 | ret = install_special_mapping(mm, addr, vdso_size, |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 126 | VM_READ|VM_EXEC| |
| 127 | VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| |
| 128 | VM_ALWAYSDUMP, |
| 129 | vdso_pages); |
Peter Zijlstra | f7b6eb3 | 2009-06-05 14:04:51 +0200 | [diff] [blame] | 130 | if (ret) { |
| 131 | current->mm->context.vdso = NULL; |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 132 | goto up_fail; |
Peter Zijlstra | f7b6eb3 | 2009-06-05 14:04:51 +0200 | [diff] [blame] | 133 | } |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 134 | |
Andi Kleen | 2aae950 | 2007-07-21 17:10:01 +0200 | [diff] [blame] | 135 | up_fail: |
| 136 | up_write(&mm->mmap_sem); |
| 137 | return ret; |
| 138 | } |
| 139 | |
| 140 | static __init int vdso_setup(char *s) |
| 141 | { |
| 142 | vdso_enabled = simple_strtoul(s, NULL, 0); |
| 143 | return 0; |
| 144 | } |
| 145 | __setup("vdso=", vdso_setup); |