1// SPDX-License-Identifier: GPL-2.0
2#include <linux/slab.h>
3#include <linux/proc_fs.h>
4#include <asm/setup.h>
5#include <asm/types.h>
6#include <asm/page.h>
7
8struct buffer {
9	size_t size;
10	char data[] __counted_by(size);
11};
12
13static ssize_t atags_read(struct file *file, char __user *buf,
14			  size_t count, loff_t *ppos)
15{
16	struct buffer *b = pde_data(file_inode(file));
17	return simple_read_from_buffer(buf, count, ppos, b->data, b->size);
18}
19
20static const struct proc_ops atags_proc_ops = {
21	.proc_read	= atags_read,
22	.proc_lseek	= default_llseek,
23};
24
25#define BOOT_PARAMS_SIZE 1536
26static char __initdata atags_copy[BOOT_PARAMS_SIZE];
27
28void __init save_atags(const struct tag *tags)
29{
30	memcpy(atags_copy, tags, sizeof(atags_copy));
31}
32
33static int __init init_atags_procfs(void)
34{
35	/*
36	 * This cannot go into save_atags() because kmalloc and proc don't work
37	 * yet when it is called.
38	 */
39	struct proc_dir_entry *tags_entry;
40	struct tag *tag = (struct tag *)atags_copy;
41	struct buffer *b;
42	size_t size;
43
44	if (tag->hdr.tag != ATAG_CORE) {
45		pr_info("No ATAGs?\n");
46		return -EINVAL;
47	}
48
49	for (; tag->hdr.size; tag = tag_next(tag))
50		;
51
52	/* include the terminating ATAG_NONE */
53	size = (char *)tag - atags_copy + sizeof(struct tag_header);
54
55	WARN_ON(tag->hdr.tag != ATAG_NONE);
56
57	b = kmalloc(struct_size(b, data, size), GFP_KERNEL);
58	if (!b)
59		goto nomem;
60
61	b->size = size;
62	memcpy(b->data, atags_copy, size);
63
64	tags_entry = proc_create_data("atags", 0400, NULL, &atags_proc_ops, b);
65	if (!tags_entry)
66		goto nomem;
67
68	return 0;
69
70nomem:
71	kfree(b);
72	pr_err("Exporting ATAGs: not enough memory\n");
73
74	return -ENOMEM;
75}
76arch_initcall(init_atags_procfs);
77