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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 
17 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
18 #include <vdso/datapage.h>
19 #else
20 struct vdso_data {
21 };
22 #endif
23 
24 extern char vdso_start[], vdso_end[];
25 
26 enum vvar_pages {
27 	VVAR_DATA_PAGE_OFFSET,
28 	VVAR_NR_PAGES,
29 };
30 
31 #define VVAR_SIZE  (VVAR_NR_PAGES << PAGE_SHIFT)
32 
33 static unsigned int vdso_pages __ro_after_init;
34 static struct page **vdso_pagelist __ro_after_init;
35 
36 /*
37  * The vDSO data page.
38  */
39 static union {
40 	struct vdso_data	data;
41 	u8			page[PAGE_SIZE];
42 } vdso_data_store __page_aligned_data;
43 struct vdso_data *vdso_data = &vdso_data_store.data;
44 
vdso_init(void)45 static int __init vdso_init(void)
46 {
47 	unsigned int i;
48 
49 	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
50 	vdso_pagelist =
51 		kcalloc(vdso_pages + VVAR_NR_PAGES, sizeof(struct page *), GFP_KERNEL);
52 	if (unlikely(vdso_pagelist == NULL)) {
53 		pr_err("vdso: pagelist allocation failed\n");
54 		return -ENOMEM;
55 	}
56 
57 	for (i = 0; i < vdso_pages; i++) {
58 		struct page *pg;
59 
60 		pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
61 		vdso_pagelist[i] = pg;
62 	}
63 	vdso_pagelist[i] = virt_to_page(vdso_data);
64 
65 	return 0;
66 }
67 arch_initcall(vdso_init);
68 
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)69 int arch_setup_additional_pages(struct linux_binprm *bprm,
70 	int uses_interp)
71 {
72 	struct mm_struct *mm = current->mm;
73 	unsigned long vdso_base, vdso_len;
74 	int ret;
75 
76 	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
77 
78 	vdso_len = (vdso_pages + VVAR_NR_PAGES) << PAGE_SHIFT;
79 
80 	if (mmap_write_lock_killable(mm))
81 		return -EINTR;
82 
83 	vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
84 	if (IS_ERR_VALUE(vdso_base)) {
85 		ret = vdso_base;
86 		goto end;
87 	}
88 
89 	mm->context.vdso = NULL;
90 	ret = install_special_mapping(mm, vdso_base, VVAR_SIZE,
91 		(VM_READ | VM_MAYREAD), &vdso_pagelist[vdso_pages]);
92 	if (unlikely(ret))
93 		goto end;
94 
95 	ret =
96 	   install_special_mapping(mm, vdso_base + VVAR_SIZE,
97 		vdso_pages << PAGE_SHIFT,
98 		(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
99 		vdso_pagelist);
100 
101 	if (unlikely(ret))
102 		goto end;
103 
104 	/*
105 	 * Put vDSO base into mm struct. We need to do this before calling
106 	 * install_special_mapping or the perf counter mmap tracking code
107 	 * will fail to recognise it as a vDSO (since arch_vma_name fails).
108 	 */
109 	mm->context.vdso = (void *)vdso_base + VVAR_SIZE;
110 
111 end:
112 	mmap_write_unlock(mm);
113 	return ret;
114 }
115 
arch_vma_name(struct vm_area_struct * vma)116 const char *arch_vma_name(struct vm_area_struct *vma)
117 {
118 	if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
119 		return "[vdso]";
120 	if (vma->vm_mm && (vma->vm_start ==
121 			   (long)vma->vm_mm->context.vdso - VVAR_SIZE))
122 		return "[vdso_data]";
123 	return NULL;
124 }
125