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/slab.h>
15 #include <linux/kernel.h>
16 #include <linux/init.h>
17 #include <linux/gfp.h>
18 #include <linux/module.h>
19 #include <linux/elf.h>
20 #include <linux/sched.h>
21 #include <linux/err.h>
22
23 /*
24 * Should the kernel map a VDSO page into processes and pass its
25 * address down to glibc upon exec()?
26 */
27 unsigned int __read_mostly vdso_enabled = 1;
28 EXPORT_SYMBOL_GPL(vdso_enabled);
29
vdso_setup(char * s)30 static int __init vdso_setup(char *s)
31 {
32 vdso_enabled = simple_strtoul(s, NULL, 0);
33 return 1;
34 }
35 __setup("vdso=", vdso_setup);
36
37 /*
38 * These symbols are defined by vsyscall.o to mark the bounds
39 * of the ELF DSO images included therein.
40 */
41 extern const char vsyscall_trapa_start, vsyscall_trapa_end;
42 static struct page *syscall_pages[1];
43
vsyscall_init(void)44 int __init vsyscall_init(void)
45 {
46 void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
47 syscall_pages[0] = virt_to_page(syscall_page);
48
49 /*
50 * XXX: Map this page to a fixmap entry if we get around
51 * to adding the page to ELF core dumps
52 */
53
54 memcpy(syscall_page,
55 &vsyscall_trapa_start,
56 &vsyscall_trapa_end - &vsyscall_trapa_start);
57
58 return 0;
59 }
60
61 /* Setup a VMA at program startup for the vsyscall page */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)62 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
63 {
64 struct mm_struct *mm = current->mm;
65 unsigned long addr;
66 int ret;
67
68 down_write(&mm->mmap_sem);
69 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
70 if (IS_ERR_VALUE(addr)) {
71 ret = addr;
72 goto up_fail;
73 }
74
75 ret = install_special_mapping(mm, addr, PAGE_SIZE,
76 VM_READ | VM_EXEC |
77 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC |
78 VM_ALWAYSDUMP,
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
get_gate_vma(struct task_struct * task)98 struct vm_area_struct *get_gate_vma(struct task_struct *task)
99 {
100 return NULL;
101 }
102
in_gate_area(struct task_struct * task,unsigned long address)103 int in_gate_area(struct task_struct *task, unsigned long address)
104 {
105 return 0;
106 }
107
in_gate_area_no_task(unsigned long address)108 int in_gate_area_no_task(unsigned long address)
109 {
110 return 0;
111 }
112