kernel/bpf/preload/bpf_preload_kern.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   3 #include <linux/init.h>
   4 #include <linux/module.h>
   5 #include "bpf_preload.h"
   6 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
   7 #include "iterators/iterators.lskel-little-endian.h"
   8 #else
   9 #include "iterators/iterators.lskel-big-endian.h"
  10 #endif
  11
  12 static struct bpf_link *maps_link, *progs_link;
  13 static struct iterators_bpf *skel;
  14
  15 static void free_links_and_skel(void)
  16 {
  17         if (!IS_ERR_OR_NULL(maps_link))
  18                 bpf_link_put(maps_link);
  19         if (!IS_ERR_OR_NULL(progs_link))
  20                 bpf_link_put(progs_link);
  21         iterators_bpf__destroy(skel);
  22 }
  23
  24 static int preload(struct bpf_preload_info *obj)
  25 {
  26         strscpy(obj[0].link_name, "maps.debug", sizeof(obj[0].link_name));
  27         obj[0].link = maps_link;
  28         strscpy(obj[1].link_name, "progs.debug", sizeof(obj[1].link_name));
  29         obj[1].link = progs_link;
  30         return 0;
  31 }
  32
  33 static struct bpf_preload_ops ops = {
  34         .preload = preload,
  35         .owner = THIS_MODULE,
  36 };
  37
  38 static int load_skel(void)
  39 {
  40         int err;
  41
  42         skel = iterators_bpf__open();
  43         if (!skel)
  44                 return -ENOMEM;
  45         err = iterators_bpf__load(skel);
  46         if (err)
  47                 goto out;
  48         err = iterators_bpf__attach(skel);
  49         if (err)
  50                 goto out;
  51         maps_link = bpf_link_get_from_fd(skel->links.dump_bpf_map_fd);
  52         if (IS_ERR(maps_link)) {
  53                 err = PTR_ERR(maps_link);
  54                 goto out;
  55         }
  56         progs_link = bpf_link_get_from_fd(skel->links.dump_bpf_prog_fd);
  57         if (IS_ERR(progs_link)) {
  58                 err = PTR_ERR(progs_link);
  59                 goto out;
  60         }
  61         /* Avoid taking over stdin/stdout/stderr of init process. Zeroing out
  62          * makes skel_closenz() a no-op later in iterators_bpf__destroy().
  63          */
  64         close_fd(skel->links.dump_bpf_map_fd);
  65         skel->links.dump_bpf_map_fd = 0;
  66         close_fd(skel->links.dump_bpf_prog_fd);
  67         skel->links.dump_bpf_prog_fd = 0;
  68         return 0;
  69 out:
  70         free_links_and_skel();
  71         return err;
  72 }
  73
  74 static int __init load(void)
  75 {
  76         int err;
  77
  78         err = load_skel();
  79         if (err)
  80                 return err;
  81         bpf_preload_ops = &ops;
  82         return err;
  83 }
  84
  85 static void __exit fini(void)
  86 {
  87         bpf_preload_ops = NULL;
  88         free_links_and_skel();
  89 }
  90 late_initcall(load);
  91 module_exit(fini);
  92 MODULE_LICENSE("GPL");