1/*
2 * vDSO implementation for Hexagon
3 *
4 * Copyright (c) 2011, The Linux Foundation. All rights reserved.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 and
8 * only version 2 as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 * 02110-1301, USA.
19 */
20
21#include <linux/err.h>
22#include <linux/mm.h>
23#include <linux/vmalloc.h>
24#include <linux/binfmts.h>
25
26#include <asm/vdso.h>
27
28static struct page *vdso_page;
29
30/* Create a vDSO page holding the signal trampoline.
31 * We want this for a non-executable stack.
32 */
33static int __init vdso_init(void)
34{
35	struct hexagon_vdso *vdso;
36
37	vdso_page = alloc_page(GFP_KERNEL);
38	if (!vdso_page)
39		panic("Cannot allocate vdso");
40
41	vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
42	if (!vdso)
43		panic("Cannot map vdso");
44	clear_page(vdso);
45
46	/* Install the signal trampoline; currently looks like this:
47	 *	r6 = #__NR_rt_sigreturn;
48	 *	trap0(#1);
49	 */
50	vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0];
51	vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1];
52
53	vunmap(vdso);
54
55	return 0;
56}
57arch_initcall(vdso_init);
58
59/*
60 * Called from binfmt_elf.  Create a VMA for the vDSO page.
61 */
62int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
63{
64	int ret;
65	unsigned long vdso_base;
66	struct mm_struct *mm = current->mm;
67
68	down_write(&mm->mmap_sem);
69
70	/* Try to get it loaded right near ld.so/glibc. */
71	vdso_base = STACK_TOP;
72
73	vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0);
74	if (IS_ERR_VALUE(vdso_base)) {
75		ret = vdso_base;
76		goto up_fail;
77	}
78
79	/* MAYWRITE to allow gdb to COW and set breakpoints. */
80	ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
81				      VM_READ|VM_EXEC|
82				      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
83				      &vdso_page);
84
85	if (ret)
86		goto up_fail;
87
88	mm->context.vdso = (void *)vdso_base;
89
90up_fail:
91	up_write(&mm->mmap_sem);
92	return ret;
93}
94
95const char *arch_vma_name(struct vm_area_struct *vma)
96{
97	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
98		return "[vdso]";
99	return NULL;
100}
101