xref: /openbmc/linux/arch/arm/kernel/atags_proc.c (revision 359745d7)
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 
8 struct buffer {
9 	size_t size;
10 	char data[];
11 };
12 
atags_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)13 static 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 
20 static 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
26 static char __initdata atags_copy[BOOT_PARAMS_SIZE];
27 
save_atags(const struct tag * tags)28 void __init save_atags(const struct tag *tags)
29 {
30 	memcpy(atags_copy, tags, sizeof(atags_copy));
31 }
32 
init_atags_procfs(void)33 static 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(sizeof(*b) + 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 
70 nomem:
71 	kfree(b);
72 	pr_err("Exporting ATAGs: not enough memory\n");
73 
74 	return -ENOMEM;
75 }
76 arch_initcall(init_atags_procfs);
77