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
vdso_setup(char * s)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
vsyscall_init(void)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 */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)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 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
arch_vma_name(struct vm_area_struct * vma)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