kernel/kheaders.c

   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/proc_fs.h>
  12 #include <linux/init.h>
  13 #include <linux/uaccess.h>
  14
  15 /*
  16  * Define kernel_headers_data and kernel_headers_data_end, within which the
  17  * compressed kernel headers are stored. The file is first compressed with xz.
  18  */
  19
  20 asm (
  21 "       .pushsection .rodata, \"a\"             \n"
  22 "       .global kernel_headers_data             \n"
  23 "kernel_headers_data:                           \n"
  24 "       .incbin \"kernel/kheaders_data.tar.xz\" \n"
  25 "       .global kernel_headers_data_end         \n"
  26 "kernel_headers_data_end:                       \n"
  27 "       .popsection                             \n"
  28 );
  29
  30 extern char kernel_headers_data;
  31 extern char kernel_headers_data_end;
  32
  33 static ssize_t
  34 ikheaders_read_current(struct file *file, char __user *buf,
  35                       size_t len, loff_t *offset)
  36 {
  37         return simple_read_from_buffer(buf, len, offset,
  38                                        &kernel_headers_data,
  39                                        &kernel_headers_data_end -
  40                                        &kernel_headers_data);
  41 }
  42
  43 static const struct file_operations ikheaders_file_ops = {
  44         .read = ikheaders_read_current,
  45         .llseek = default_llseek,
  46 };
  47
  48 static int __init ikheaders_init(void)
  49 {
  50         struct proc_dir_entry *entry;
  51
  52         /* create the current headers file */
  53         entry = proc_create("kheaders.tar.xz", S_IRUGO, NULL,
  54                             &ikheaders_file_ops);
  55         if (!entry)
  56                 return -ENOMEM;
  57
  58         proc_set_size(entry,
  59                       &kernel_headers_data_end -
  60                       &kernel_headers_data);
  61         return 0;
  62 }
  63
  64 static void __exit ikheaders_cleanup(void)
  65 {
  66         remove_proc_entry("kheaders.tar.xz", NULL);
  67 }
  68
  69 module_init(ikheaders_init);
  70 module_exit(ikheaders_cleanup);
  71
  72 MODULE_LICENSE("GPL v2");
  73 MODULE_AUTHOR("Joel Fernandes");
  74 MODULE_DESCRIPTION("Echo the kernel header artifacts used to build the kernel");