1/*
  2 * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
  3 *                    <benh@kernel.crashing.org>
  4 * Copyright (C) 2012 ARM Limited
  5 * Copyright (C) 2015 Regents of the University of California
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License version 2 as
  9 * published by the Free Software Foundation.
 10 *
 11 * This program is distributed in the hope that it will be useful,
 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 14 * GNU General Public License for more details.
 15 *
 16 * You should have received a copy of the GNU General Public License
 17 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 18 */
 19
 20#include <linux/mm.h>
 21#include <linux/slab.h>
 22#include <linux/binfmts.h>
 23#include <linux/err.h>
 24
 25#include <asm/vdso.h>
 26
 27extern char vdso_start[], vdso_end[];
 28
 29static unsigned int vdso_pages;
 30static struct page **vdso_pagelist;
 31
 32/*
 33 * The vDSO data page.
 34 */
 35static union {
 36	struct vdso_data	data;
 37	u8			page[PAGE_SIZE];
 38} vdso_data_store __page_aligned_data;
 39struct vdso_data *vdso_data = &vdso_data_store.data;
 40
 41static int __init vdso_init(void)
 42{
 43	unsigned int i;
 44
 45	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
 46	vdso_pagelist =
 47		kcalloc(vdso_pages + 1, sizeof(struct page *), GFP_KERNEL);
 48	if (unlikely(vdso_pagelist == NULL)) {
 49		pr_err("vdso: pagelist allocation failed\n");
 50		return -ENOMEM;
 51	}
 52
 53	for (i = 0; i < vdso_pages; i++) {
 54		struct page *pg;
 55
 56		pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
 57		ClearPageReserved(pg);
 58		vdso_pagelist[i] = pg;
 59	}
 60	vdso_pagelist[i] = virt_to_page(vdso_data);
 61
 62	return 0;
 63}
 64arch_initcall(vdso_init);
 65
 66int arch_setup_additional_pages(struct linux_binprm *bprm,
 67	int uses_interp)
 68{
 69	struct mm_struct *mm = current->mm;
 70	unsigned long vdso_base, vdso_len;
 71	int ret;
 72
 73	vdso_len = (vdso_pages + 1) << PAGE_SHIFT;
 74
 75	down_write(&mm->mmap_sem);
 76	vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
 77	if (IS_ERR_VALUE(vdso_base)) {
 78		ret = vdso_base;
 79		goto end;
 80	}
 81
 82	/*
 83	 * Put vDSO base into mm struct. We need to do this before calling
 84	 * install_special_mapping or the perf counter mmap tracking code
 85	 * will fail to recognise it as a vDSO (since arch_vma_name fails).
 86	 */
 87	mm->context.vdso = (void *)vdso_base;
 88
 89	ret = install_special_mapping(mm, vdso_base, vdso_len,
 90		(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
 91		vdso_pagelist);
 92
 93	if (unlikely(ret))
 94		mm->context.vdso = NULL;
 95
 96end:
 97	up_write(&mm->mmap_sem);
 98	return ret;
 99}
100
101const char *arch_vma_name(struct vm_area_struct *vma)
102{
103	if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
104		return "[vdso]";
105	return NULL;
106}
107
108/*
109 * Function stubs to prevent linker errors when AT_SYSINFO_EHDR is defined
110 */
111
112int in_gate_area_no_mm(unsigned long addr)
113{
114	return 0;
115}
116
117int in_gate_area(struct mm_struct *mm, unsigned long addr)
118{
119	return 0;
120}
121
122struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
123{
124	return NULL;
125}