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(inode: file_inode(f: file));
17 return simple_read_from_buffer(to: buf, count, ppos, from: b->data, available: 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(objp: b);
72 pr_err("Exporting ATAGs: not enough memory\n");
73
74 return -ENOMEM;
75}
76arch_initcall(init_atags_procfs);
77

source code of linux/arch/arm/kernel/atags_proc.c