1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  Copyright (c) 2022 Helge Deller <deller@gmx.de>
4 *
5 *  based on arch/s390/kernel/vdso.c which is
6 *  Copyright IBM Corp. 2008
7 *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
8 */
9
10#include <linux/kernel.h>
11#include <linux/mm.h>
12#include <linux/slab.h>
13#include <linux/elf.h>
14#include <linux/timekeeper_internal.h>
15#include <linux/compat.h>
16#include <linux/nsproxy.h>
17#include <linux/time_namespace.h>
18#include <linux/random.h>
19
20#include <asm/pgtable.h>
21#include <asm/page.h>
22#include <asm/sections.h>
23#include <asm/vdso.h>
24#include <asm/cacheflush.h>
25
26extern char vdso32_start, vdso32_end;
27extern char vdso64_start, vdso64_end;
28
29static int vdso_mremap(const struct vm_special_mapping *sm,
30		       struct vm_area_struct *vma)
31{
32	current->mm->context.vdso_base = vma->vm_start;
33	return 0;
34}
35
36#ifdef CONFIG_64BIT
37static struct vm_special_mapping vdso64_mapping = {
38	.name = "[vdso]",
39	.mremap = vdso_mremap,
40};
41#endif
42
43static struct vm_special_mapping vdso32_mapping = {
44	.name = "[vdso]",
45	.mremap = vdso_mremap,
46};
47
48/*
49 * This is called from binfmt_elf, we create the special vma for the
50 * vDSO and insert it into the mm struct tree
51 */
52int arch_setup_additional_pages(struct linux_binprm *bprm,
53				int executable_stack)
54{
55
56	unsigned long vdso_text_start, vdso_text_len, map_base;
57	struct vm_special_mapping *vdso_mapping;
58	struct mm_struct *mm = current->mm;
59	struct vm_area_struct *vma;
60	int rc;
61
62	if (mmap_write_lock_killable(mm))
63		return -EINTR;
64
65#ifdef CONFIG_64BIT
66	if (!is_compat_task()) {
67		vdso_text_len = &vdso64_end - &vdso64_start;
68		vdso_mapping = &vdso64_mapping;
69	} else
70#endif
71	{
72		vdso_text_len = &vdso32_end - &vdso32_start;
73		vdso_mapping = &vdso32_mapping;
74	}
75
76	map_base = mm->mmap_base;
77	if (current->flags & PF_RANDOMIZE)
78		map_base -= get_random_u32_below(0x20) * PAGE_SIZE;
79
80	vdso_text_start = get_unmapped_area(NULL, map_base, vdso_text_len, 0, 0);
81
82	/* VM_MAYWRITE for COW so gdb can set breakpoints */
83	vma = _install_special_mapping(mm, vdso_text_start, vdso_text_len,
84				       VM_READ|VM_EXEC|
85				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
86				       vdso_mapping);
87	if (IS_ERR(vma)) {
88		do_munmap(mm, vdso_text_start, PAGE_SIZE, NULL);
89		rc = PTR_ERR(vma);
90	} else {
91		current->mm->context.vdso_base = vdso_text_start;
92		rc = 0;
93	}
94
95	mmap_write_unlock(mm);
96	return rc;
97}
98
99static struct page ** __init vdso_setup_pages(void *start, void *end)
100{
101	int pages = (end - start) >> PAGE_SHIFT;
102	struct page **pagelist;
103	int i;
104
105	pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
106	if (!pagelist)
107		panic("%s: Cannot allocate page list for VDSO", __func__);
108	for (i = 0; i < pages; i++)
109		pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
110	return pagelist;
111}
112
113static int __init vdso_init(void)
114{
115#ifdef CONFIG_64BIT
116	vdso64_mapping.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);
117#endif
118	if (IS_ENABLED(CONFIG_COMPAT) || !IS_ENABLED(CONFIG_64BIT))
119		vdso32_mapping.pages = vdso_setup_pages(&vdso32_start, &vdso32_end);
120	return 0;
121}
122arch_initcall(vdso_init);
123