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 */
26unsigned int __read_mostly vdso_enabled = 1;
27EXPORT_SYMBOL_GPL(vdso_enabled);
28
29static 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 */
40extern const char vsyscall_trapa_start, vsyscall_trapa_end;
41static struct page *syscall_pages[1];
42
43int __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 */
61int 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	down_write(&mm->mmap_sem);
68	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
69	if (IS_ERR_VALUE(addr)) {
70		ret = addr;
71		goto up_fail;
72	}
73
74	ret = install_special_mapping(mm, addr, PAGE_SIZE,
75				      VM_READ | VM_EXEC |
76				      VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
77				      syscall_pages);
78	if (unlikely(ret))
79		goto up_fail;
80
81	current->mm->context.vdso = (void *)addr;
82
83up_fail:
84	up_write(&mm->mmap_sem);
85	return ret;
86}
87
88const char *arch_vma_name(struct vm_area_struct *vma)
89{
90	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
91		return "[vdso]";
92
93	return NULL;
94}
95