xref: /openbmc/linux/kernel/kheaders.c (revision e5bd61e8)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Provide kernel headers useful to build tracing programs
4  * such as for running eBPF tracing tools.
5  *
6  * (Borrowed code from kernel/configs.c)
7  */
8 
9 #include <linux/kernel.h>
10 #include <linux/module.h>
11 #include <linux/kobject.h>
12 #include <linux/init.h>
13 
14 /*
15  * Define kernel_headers_data and kernel_headers_data_end, within which the
16  * compressed kernel headers are stored. The file is first compressed with xz.
17  */
18 
19 asm (
20 "	.pushsection .rodata, \"a\"		\n"
21 "	.global kernel_headers_data		\n"
22 "kernel_headers_data:				\n"
23 "	.incbin \"kernel/kheaders_data.tar.xz\"	\n"
24 "	.global kernel_headers_data_end		\n"
25 "kernel_headers_data_end:			\n"
26 "	.popsection				\n"
27 );
28 
29 extern char kernel_headers_data;
30 extern char kernel_headers_data_end;
31 
32 static ssize_t
33 ikheaders_read(struct file *file,  struct kobject *kobj,
34 	       struct bin_attribute *bin_attr,
35 	       char *buf, loff_t off, size_t len)
36 {
37 	memcpy(buf, &kernel_headers_data + off, len);
38 	return len;
39 }
40 
41 static struct bin_attribute kheaders_attr __ro_after_init = {
42 	.attr = {
43 		.name = "kheaders.tar.xz",
44 		.mode = 0444,
45 	},
46 	.read = &ikheaders_read,
47 };
48 
49 static int __init ikheaders_init(void)
50 {
51 	kheaders_attr.size = (&kernel_headers_data_end -
52 			      &kernel_headers_data);
53 	return sysfs_create_bin_file(kernel_kobj, &kheaders_attr);
54 }
55 
56 static void __exit ikheaders_cleanup(void)
57 {
58 	sysfs_remove_bin_file(kernel_kobj, &kheaders_attr);
59 }
60 
61 module_init(ikheaders_init);
62 module_exit(ikheaders_cleanup);
63 
64 MODULE_LICENSE("GPL v2");
65 MODULE_AUTHOR("Joel Fernandes");
66 MODULE_DESCRIPTION("Echo the kernel header artifacts used to build the kernel");
67