LXR linux/tools/testing/selftests/bpf/progs/dev

   1/* Copyright (c) 2017 Facebook
   2 *
   3 * This program is free software; you can redistribute it and/or
   4 * modify it under the terms of version 2 of the GNU General Public
   5 * License as published by the Free Software Foundation.
   6 */
   7
   8#include <linux/bpf.h>
   9#include <linux/version.h>
  10#include <bpf/bpf_helpers.h>
  11
  12SEC("cgroup/dev")
  13int bpf_prog1(struct bpf_cgroup_dev_ctx *ctx)
  14{
  15        short type = ctx->access_type & 0xFFFF;
  16#ifdef DEBUG
  17        short access = ctx->access_type >> 16;
  18        char fmt[] = "  %d:%d    \n";
  19
  20        switch (type) {
  21        case BPF_DEVCG_DEV_BLOCK:
  22                fmt[0] = 'b';
  23                break;
  24        case BPF_DEVCG_DEV_CHAR:
  25                fmt[0] = 'c';
  26                break;
  27        default:
  28                fmt[0] = '?';
  29                break;
  30        }
  31
  32        if (access & BPF_DEVCG_ACC_READ)
  33                fmt[8] = 'r';
  34
  35        if (access & BPF_DEVCG_ACC_WRITE)
  36                fmt[9] = 'w';
  37
  38        if (access & BPF_DEVCG_ACC_MKNOD)
  39                fmt[10] = 'm';
  40
  41        bpf_trace_printk(fmt, sizeof(fmt), ctx->major, ctx->minor);
  42#endif
  43
  44        /* Allow access to /dev/zero and /dev/random.
  45         * Forbid everything else.
  46         */
  47        if (ctx->major != 1 || type != BPF_DEVCG_DEV_CHAR)
  48                return 0;
  49
  50        switch (ctx->minor) {
  51        case 5: /* 1:5 /dev/zero */
  52        case 9: /* 1:9 /dev/urandom */
  53                return 1;
  54        }
  55
  56        return 0;
  57}
  58
  59char _license[] SEC("license") = "GPL";
  60__u32 _version SEC("version") = LINUX_VERSION_CODE;
  61