1 /*
2  * Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8 
9 #include <linux/slab.h>
10 #include <linux/sched.h>
11 #include <linux/mm.h>
12 #include <asm/page.h>
13 #include <linux/init.h>
14 
15 unsigned int __read_mostly vdso_enabled = 1;
16 unsigned long um_vdso_addr;
17 
18 extern unsigned long task_size;
19 extern char vdso_start[], vdso_end[];
20 
21 static struct page **vdsop;
22 
init_vdso(void)23 static int __init init_vdso(void)
24 {
25 	struct page *um_vdso;
26 
27 	BUG_ON(vdso_end - vdso_start > PAGE_SIZE);
28 
29 	um_vdso_addr = task_size - PAGE_SIZE;
30 
31 	vdsop = kmalloc(sizeof(struct page *), GFP_KERNEL);
32 	if (!vdsop)
33 		goto oom;
34 
35 	um_vdso = alloc_page(GFP_KERNEL);
36 	if (!um_vdso) {
37 		kfree(vdsop);
38 
39 		goto oom;
40 	}
41 
42 	copy_page(page_address(um_vdso), vdso_start);
43 	*vdsop = um_vdso;
44 
45 	return 0;
46 
47 oom:
48 	printk(KERN_ERR "Cannot allocate vdso\n");
49 	vdso_enabled = 0;
50 
51 	return -ENOMEM;
52 }
53 subsys_initcall(init_vdso);
54 
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)55 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
56 {
57 	int err;
58 	struct mm_struct *mm = current->mm;
59 
60 	if (!vdso_enabled)
61 		return 0;
62 
63 	down_write(&mm->mmap_sem);
64 
65 	err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE,
66 		VM_READ|VM_EXEC|
67 		VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
68 		vdsop);
69 
70 	up_write(&mm->mmap_sem);
71 
72 	return err;
73 }
74