1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Copyright (c) 2022 Helge Deller <deller@gmx.de> |
4 | * |
5 | * based on arch/s390/kernel/vdso.c which is |
6 | * Copyright IBM Corp. 2008 |
7 | * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com) |
8 | */ |
9 | |
10 | #include <linux/kernel.h> |
11 | #include <linux/mm.h> |
12 | #include <linux/slab.h> |
13 | #include <linux/elf.h> |
14 | #include <linux/timekeeper_internal.h> |
15 | #include <linux/compat.h> |
16 | #include <linux/nsproxy.h> |
17 | #include <linux/time_namespace.h> |
18 | #include <linux/random.h> |
19 | |
20 | #include <asm/pgtable.h> |
21 | #include <asm/page.h> |
22 | #include <asm/sections.h> |
23 | #include <asm/vdso.h> |
24 | #include <asm/cacheflush.h> |
25 | |
26 | extern char vdso32_start, vdso32_end; |
27 | extern char vdso64_start, vdso64_end; |
28 | |
29 | static int vdso_mremap(const struct vm_special_mapping *sm, |
30 | struct vm_area_struct *vma) |
31 | { |
32 | current->mm->context.vdso_base = vma->vm_start; |
33 | return 0; |
34 | } |
35 | |
36 | #ifdef CONFIG_64BIT |
37 | static struct vm_special_mapping vdso64_mapping = { |
38 | .name = "[vdso]" , |
39 | .mremap = vdso_mremap, |
40 | }; |
41 | #endif |
42 | |
43 | static struct vm_special_mapping vdso32_mapping = { |
44 | .name = "[vdso]" , |
45 | .mremap = vdso_mremap, |
46 | }; |
47 | |
48 | /* |
49 | * This is called from binfmt_elf, we create the special vma for the |
50 | * vDSO and insert it into the mm struct tree |
51 | */ |
52 | int arch_setup_additional_pages(struct linux_binprm *bprm, |
53 | int executable_stack) |
54 | { |
55 | |
56 | unsigned long vdso_text_start, vdso_text_len, map_base; |
57 | struct vm_special_mapping *vdso_mapping; |
58 | struct mm_struct *mm = current->mm; |
59 | struct vm_area_struct *vma; |
60 | int rc; |
61 | |
62 | if (mmap_write_lock_killable(mm)) |
63 | return -EINTR; |
64 | |
65 | #ifdef CONFIG_64BIT |
66 | if (!is_compat_task()) { |
67 | vdso_text_len = &vdso64_end - &vdso64_start; |
68 | vdso_mapping = &vdso64_mapping; |
69 | } else |
70 | #endif |
71 | { |
72 | vdso_text_len = &vdso32_end - &vdso32_start; |
73 | vdso_mapping = &vdso32_mapping; |
74 | } |
75 | |
76 | map_base = mm->mmap_base; |
77 | if (current->flags & PF_RANDOMIZE) |
78 | map_base -= get_random_u32_below(ceil: 0x20) * PAGE_SIZE; |
79 | |
80 | vdso_text_start = get_unmapped_area(NULL, map_base, vdso_text_len, 0, 0); |
81 | |
82 | /* VM_MAYWRITE for COW so gdb can set breakpoints */ |
83 | vma = _install_special_mapping(mm, addr: vdso_text_start, len: vdso_text_len, |
84 | VM_READ|VM_EXEC| |
85 | VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, |
86 | spec: vdso_mapping); |
87 | if (IS_ERR(ptr: vma)) { |
88 | do_munmap(mm, vdso_text_start, PAGE_SIZE, NULL); |
89 | rc = PTR_ERR(ptr: vma); |
90 | } else { |
91 | current->mm->context.vdso_base = vdso_text_start; |
92 | rc = 0; |
93 | } |
94 | |
95 | mmap_write_unlock(mm); |
96 | return rc; |
97 | } |
98 | |
99 | static struct page ** __init vdso_setup_pages(void *start, void *end) |
100 | { |
101 | int pages = (end - start) >> PAGE_SHIFT; |
102 | struct page **pagelist; |
103 | int i; |
104 | |
105 | pagelist = kcalloc(n: pages + 1, size: sizeof(struct page *), GFP_KERNEL); |
106 | if (!pagelist) |
107 | panic(fmt: "%s: Cannot allocate page list for VDSO" , __func__); |
108 | for (i = 0; i < pages; i++) |
109 | pagelist[i] = virt_to_page(start + i * PAGE_SIZE); |
110 | return pagelist; |
111 | } |
112 | |
113 | static int __init vdso_init(void) |
114 | { |
115 | #ifdef CONFIG_64BIT |
116 | vdso64_mapping.pages = vdso_setup_pages(start: &vdso64_start, end: &vdso64_end); |
117 | #endif |
118 | if (IS_ENABLED(CONFIG_COMPAT) || !IS_ENABLED(CONFIG_64BIT)) |
119 | vdso32_mapping.pages = vdso_setup_pages(start: &vdso32_start, end: &vdso32_end); |
120 | return 0; |
121 | } |
122 | arch_initcall(vdso_init); |
123 | |