vdso.c

 1// SPDX-License-Identifier: GPL-2.0
 2// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
 3
 4#include <linux/binfmts.h>
 5#include <linux/elf.h>
 6#include <linux/err.h>
 7#include <linux/mm.h>
 8#include <linux/slab.h>
 9
10#include <asm/page.h>
11
12extern char vdso_start[], vdso_end[];
13
14static unsigned int vdso_pages;
15static struct page **vdso_pagelist;
16
17static int __init vdso_init(void)
18{
19	unsigned int i;
20
21	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
22	vdso_pagelist =
23		kcalloc(vdso_pages, sizeof(struct page *), GFP_KERNEL);
24	if (unlikely(vdso_pagelist == NULL)) {
25		pr_err("vdso: pagelist allocation failed\n");
26		return -ENOMEM;
27	}
28
29	for (i = 0; i < vdso_pages; i++) {
30		struct page *pg;
31
32		pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
33		vdso_pagelist[i] = pg;
34	}
35
36	return 0;
37}
38arch_initcall(vdso_init);
39
40int arch_setup_additional_pages(struct linux_binprm *bprm,
41	int uses_interp)
42{
43	struct vm_area_struct *vma;
44	struct mm_struct *mm = current->mm;
45	unsigned long vdso_base, vdso_len;
46	int ret;
47	static struct vm_special_mapping vdso_mapping = {
48		.name = "[vdso]",
49	};
50
51	vdso_len = vdso_pages << PAGE_SHIFT;
52
53	mmap_write_lock(mm);
54	vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
55	if (IS_ERR_VALUE(vdso_base)) {
56		ret = vdso_base;
57		goto end;
58	}
59
60	/*
61	 * Put vDSO base into mm struct. We need to do this before calling
62	 * install_special_mapping or the perf counter mmap tracking code
63	 * will fail to recognise it as a vDSO (since arch_vma_name fails).
64	 */
65	mm->context.vdso = (void *)vdso_base;
66
67	vdso_mapping.pages = vdso_pagelist;
68	vma =
69	   _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
70		(VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
71		&vdso_mapping);
72
73	if (IS_ERR(vma)) {
74		ret = PTR_ERR(vma);
75		mm->context.vdso = NULL;
76		goto end;
77	}
78
79	vdso_base += (vdso_pages << PAGE_SHIFT);
80	ret = 0;
81end:
82	mmap_write_unlock(mm);
83	return ret;
84}