1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * arch/sh/kernel/vsyscall/vsyscall.c |
4 | * |
5 | * Copyright (C) 2006 Paul Mundt |
6 | * |
7 | * vDSO randomization |
8 | * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar |
9 | */ |
10 | #include <linux/mm.h> |
11 | #include <linux/kernel.h> |
12 | #include <linux/init.h> |
13 | #include <linux/gfp.h> |
14 | #include <linux/module.h> |
15 | #include <linux/elf.h> |
16 | #include <linux/sched.h> |
17 | #include <linux/err.h> |
18 | |
19 | /* |
20 | * Should the kernel map a VDSO page into processes and pass its |
21 | * address down to glibc upon exec()? |
22 | */ |
23 | unsigned int __read_mostly vdso_enabled = 1; |
24 | EXPORT_SYMBOL_GPL(vdso_enabled); |
25 | |
26 | static int __init vdso_setup(char *s) |
27 | { |
28 | vdso_enabled = simple_strtoul(s, NULL, 0); |
29 | return 1; |
30 | } |
31 | __setup("vdso=" , vdso_setup); |
32 | |
33 | /* |
34 | * These symbols are defined by vsyscall.o to mark the bounds |
35 | * of the ELF DSO images included therein. |
36 | */ |
37 | extern const char vsyscall_trapa_start, vsyscall_trapa_end; |
38 | static struct page *syscall_pages[1]; |
39 | |
40 | int __init vsyscall_init(void) |
41 | { |
42 | void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC); |
43 | syscall_pages[0] = virt_to_page(syscall_page); |
44 | |
45 | /* |
46 | * XXX: Map this page to a fixmap entry if we get around |
47 | * to adding the page to ELF core dumps |
48 | */ |
49 | |
50 | memcpy(syscall_page, |
51 | &vsyscall_trapa_start, |
52 | &vsyscall_trapa_end - &vsyscall_trapa_start); |
53 | |
54 | return 0; |
55 | } |
56 | |
57 | /* Setup a VMA at program startup for the vsyscall page */ |
58 | int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) |
59 | { |
60 | struct mm_struct *mm = current->mm; |
61 | unsigned long addr; |
62 | int ret; |
63 | |
64 | if (mmap_write_lock_killable(mm)) |
65 | return -EINTR; |
66 | |
67 | addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); |
68 | if (IS_ERR_VALUE(addr)) { |
69 | ret = addr; |
70 | goto up_fail; |
71 | } |
72 | |
73 | ret = install_special_mapping(mm, addr, PAGE_SIZE, |
74 | VM_READ | VM_EXEC | |
75 | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, |
76 | pages: syscall_pages); |
77 | if (unlikely(ret)) |
78 | goto up_fail; |
79 | |
80 | current->mm->context.vdso = (void *)addr; |
81 | |
82 | up_fail: |
83 | mmap_write_unlock(mm); |
84 | return ret; |
85 | } |
86 | |
87 | const char *arch_vma_name(struct vm_area_struct *vma) |
88 | { |
89 | if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) |
90 | return "[vdso]" ; |
91 | |
92 | return NULL; |
93 | } |
94 | |