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