vdso.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
  4 *                    <benh@kernel.crashing.org>
  5 * Copyright (C) 2012 ARM Limited
  6 * Copyright (C) 2015 Regents of the University of California
  7 */
  8
  9#include <linux/elf.h>
 10#include <linux/mm.h>
 11#include <linux/slab.h>
 12#include <linux/binfmts.h>
 13#include <linux/err.h>
 14#include <asm/page.h>
 15#include <asm/vdso.h>
 16#include <linux/vdso_datastore.h>
 17#include <vdso/datapage.h>
 18#include <vdso/vsyscall.h>
 19
 20#define VVAR_SIZE  (VDSO_NR_PAGES << PAGE_SHIFT)
 21
 22struct __vdso_info {
 23	const char *name;
 24	const char *vdso_code_start;
 25	const char *vdso_code_end;
 26	unsigned long vdso_pages;
 27	/* Code Mapping */
 28	struct vm_special_mapping *cm;
 29};
 30
 31static struct __vdso_info vdso_info;
 32#ifdef CONFIG_COMPAT
 33static struct __vdso_info compat_vdso_info;
 34#endif
 35
 36static int vdso_mremap(const struct vm_special_mapping *sm,
 37		       struct vm_area_struct *new_vma)
 38{
 39	current->mm->context.vdso = (void *)new_vma->vm_start;
 40
 41	return 0;
 42}
 43
 44static void __init __vdso_init(struct __vdso_info *vdso_info)
 45{
 46	unsigned int i;
 47	struct page **vdso_pagelist;
 48	unsigned long pfn;
 49
 50	if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4))
 51		panic("vDSO is not a valid ELF object!\n");
 52
 53	vdso_info->vdso_pages = (
 54		vdso_info->vdso_code_end -
 55		vdso_info->vdso_code_start) >>
 56		PAGE_SHIFT;
 57
 58	vdso_pagelist = kcalloc(vdso_info->vdso_pages,
 59				sizeof(struct page *),
 60				GFP_KERNEL);
 61	if (vdso_pagelist == NULL)
 62		panic("vDSO kcalloc failed!\n");
 63
 64	/* Grab the vDSO code pages. */
 65	pfn = sym_to_pfn(vdso_info->vdso_code_start);
 66
 67	for (i = 0; i < vdso_info->vdso_pages; i++)
 68		vdso_pagelist[i] = pfn_to_page(pfn + i);
 69
 70	vdso_info->cm->pages = vdso_pagelist;
 71}
 72
 73static struct vm_special_mapping rv_vdso_map __ro_after_init = {
 74	.name   = "[vdso]",
 75	.mremap = vdso_mremap,
 76};
 77
 78static struct __vdso_info vdso_info __ro_after_init = {
 79	.name = "vdso",
 80	.vdso_code_start = vdso_start,
 81	.vdso_code_end = vdso_end,
 82	.cm = &rv_vdso_map,
 83};
 84
 85#ifdef CONFIG_COMPAT
 86static struct vm_special_mapping rv_compat_vdso_map __ro_after_init = {
 87	.name   = "[vdso]",
 88	.mremap = vdso_mremap,
 89};
 90
 91static struct __vdso_info compat_vdso_info __ro_after_init = {
 92	.name = "compat_vdso",
 93	.vdso_code_start = compat_vdso_start,
 94	.vdso_code_end = compat_vdso_end,
 95	.cm = &rv_compat_vdso_map,
 96};
 97#endif
 98
 99static int __init vdso_init(void)
100{
101	__vdso_init(&vdso_info);
102#ifdef CONFIG_COMPAT
103	__vdso_init(&compat_vdso_info);
104#endif
105
106	return 0;
107}
108arch_initcall(vdso_init);
109
110static int __setup_additional_pages(struct mm_struct *mm,
111				    struct linux_binprm *bprm,
112				    int uses_interp,
113				    struct __vdso_info *vdso_info)
114{
115	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
116	void *ret;
117
118	BUILD_BUG_ON(VDSO_NR_PAGES != __VDSO_PAGES);
119
120	vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT;
121	/* Be sure to map the data page */
122	vdso_mapping_len = vdso_text_len + VVAR_SIZE;
123
124	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
125	if (IS_ERR_VALUE(vdso_base)) {
126		ret = ERR_PTR(vdso_base);
127		goto up_fail;
128	}
129
130	ret = vdso_install_vvar_mapping(mm, vdso_base);
131	if (IS_ERR(ret))
132		goto up_fail;
133
134	vdso_base += VVAR_SIZE;
135	mm->context.vdso = (void *)vdso_base;
136
137	ret =
138	   _install_special_mapping(mm, vdso_base, vdso_text_len,
139		(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC | VM_SEALED_SYSMAP),
140		vdso_info->cm);
141
142	if (IS_ERR(ret))
143		goto up_fail;
144
145	return 0;
146
147up_fail:
148	mm->context.vdso = NULL;
149	return PTR_ERR(ret);
150}
151
152#ifdef CONFIG_COMPAT
153int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
154				       int uses_interp)
155{
156	struct mm_struct *mm = current->mm;
157	int ret;
158
159	if (mmap_write_lock_killable(mm))
160		return -EINTR;
161
162	ret = __setup_additional_pages(mm, bprm, uses_interp,
163							&compat_vdso_info);
164	mmap_write_unlock(mm);
165
166	return ret;
167}
168#endif
169
170int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
171{
172	struct mm_struct *mm = current->mm;
173	int ret;
174
175	if (mmap_write_lock_killable(mm))
176		return -EINTR;
177
178	ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info);
179	mmap_write_unlock(mm);
180
181	return ret;
182}