1 /*
2 * arch/sh/kernel/vsyscall/vsyscall.c
3 *
4 * Copyright (C) 2006 Paul Mundt
5 *
6 * vDSO randomization
7 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
8 *
9 * This file is subject to the terms and conditions of the GNU General Public
10 * License. See the file "COPYING" in the main directory of this archive
11 * for more details.
12 */
13 #include <linux/mm.h>
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/gfp.h>
17 #include <linux/module.h>
18 #include <linux/elf.h>
19 #include <linux/sched.h>
20 #include <linux/err.h>
21
22 /*
23 * Should the kernel map a VDSO page into processes and pass its
24 * address down to glibc upon exec()?
25 */
26 unsigned int __read_mostly vdso_enabled = 1;
27 EXPORT_SYMBOL_GPL(vdso_enabled);
28
vdso_setup(char * s)29 static int __init vdso_setup(char *s)
30 {
31 vdso_enabled = simple_strtoul(s, NULL, 0);
32 return 1;
33 }
34 __setup("vdso=", vdso_setup);
35
36 /*
37 * These symbols are defined by vsyscall.o to mark the bounds
38 * of the ELF DSO images included therein.
39 */
40 extern const char vsyscall_trapa_start, vsyscall_trapa_end;
41 static struct page *syscall_pages[1];
42
vsyscall_init(void)43 int __init vsyscall_init(void)
44 {
45 void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
46 syscall_pages[0] = virt_to_page(syscall_page);
47
48 /*
49 * XXX: Map this page to a fixmap entry if we get around
50 * to adding the page to ELF core dumps
51 */
52
53 memcpy(syscall_page,
54 &vsyscall_trapa_start,
55 &vsyscall_trapa_end - &vsyscall_trapa_start);
56
57 return 0;
58 }
59
60 /* Setup a VMA at program startup for the vsyscall page */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)61 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
62 {
63 struct mm_struct *mm = current->mm;
64 unsigned long addr;
65 int ret;
66
67 if (down_write_killable(&mm->mmap_sem))
68 return -EINTR;
69
70 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
71 if (IS_ERR_VALUE(addr)) {
72 ret = addr;
73 goto up_fail;
74 }
75
76 ret = install_special_mapping(mm, addr, PAGE_SIZE,
77 VM_READ | VM_EXEC |
78 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
79 syscall_pages);
80 if (unlikely(ret))
81 goto up_fail;
82
83 current->mm->context.vdso = (void *)addr;
84
85 up_fail:
86 up_write(&mm->mmap_sem);
87 return ret;
88 }
89
arch_vma_name(struct vm_area_struct * vma)90 const char *arch_vma_name(struct vm_area_struct *vma)
91 {
92 if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
93 return "[vdso]";
94
95 return NULL;
96 }
97
