tools/testing/selftests/bpf/prog_tests/recursive_attach.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2023 Red Hat, Inc. */
   3 #include <test_progs.h>
   4 #include "fentry_recursive.skel.h"
   5 #include "fentry_recursive_target.skel.h"
   6 #include <bpf/btf.h>
   7 #include "bpf/libbpf_internal.h"
   8
   9 /* Test recursive attachment of tracing progs with more than one nesting level
  10  * is not possible. Create a chain of attachment, verify that the last prog
  11  * will fail. Depending on the arguments, following cases are tested:
  12  *
  13  * - Recursive loading of tracing progs, without attaching (attach = false,
  14  *   detach = false). The chain looks like this:
  15  *       load target
  16  *       load fentry1 -> target
  17  *       load fentry2 -> fentry1 (fail)
  18  *
  19  * - Recursive attach of tracing progs (attach = true, detach = false). The
  20  *   chain looks like this:
  21  *       load target
  22  *       load fentry1 -> target
  23  *       attach fentry1 -> target
  24  *       load fentry2 -> fentry1 (fail)
  25  *
  26  * - Recursive attach and detach of tracing progs (attach = true, detach =
  27  *   true). This validates that attach_tracing_prog flag will be set throughout
  28  *   the whole lifecycle of an fentry prog, independently from whether it's
  29  *   detached. The chain looks like this:
  30  *       load target
  31  *       load fentry1 -> target
  32  *       attach fentry1 -> target
  33  *       detach fentry1
  34  *       load fentry2 -> fentry1 (fail)
  35  */
  36 static void test_recursive_fentry_chain(bool attach, bool detach)
  37 {
  38         struct fentry_recursive_target *target_skel = NULL;
  39         struct fentry_recursive *tracing_chain[2] = {};
  40         struct bpf_program *prog;
  41         int prev_fd, err;
  42
  43         target_skel = fentry_recursive_target__open_and_load();
  44         if (!ASSERT_OK_PTR(target_skel, "fentry_recursive_target__open_and_load"))
  45                 return;
  46
  47         /* Create an attachment chain with two fentry progs */
  48         for (int i = 0; i < 2; i++) {
  49                 tracing_chain[i] = fentry_recursive__open();
  50                 if (!ASSERT_OK_PTR(tracing_chain[i], "fentry_recursive__open"))
  51                         goto close_prog;
  52
  53                 /* The first prog in the chain is going to be attached to the target
  54                  * fentry program, the second one to the previous in the chain.
  55                  */
  56                 prog = tracing_chain[i]->progs.recursive_attach;
  57                 if (i == 0) {
  58                         prev_fd = bpf_program__fd(target_skel->progs.test1);
  59                         err = bpf_program__set_attach_target(prog, prev_fd, "test1");
  60                 } else {
  61                         prev_fd = bpf_program__fd(tracing_chain[i-1]->progs.recursive_attach);
  62                         err = bpf_program__set_attach_target(prog, prev_fd, "recursive_attach");
  63                 }
  64
  65                 if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
  66                         goto close_prog;
  67
  68                 err = fentry_recursive__load(tracing_chain[i]);
  69                 /* The first attach should succeed, the second fail */
  70                 if (i == 0) {
  71                         if (!ASSERT_OK(err, "fentry_recursive__load"))
  72                                 goto close_prog;
  73
  74                         if (attach) {
  75                                 err = fentry_recursive__attach(tracing_chain[i]);
  76                                 if (!ASSERT_OK(err, "fentry_recursive__attach"))
  77                                         goto close_prog;
  78                         }
  79
  80                         if (detach) {
  81                                 /* Flag attach_tracing_prog should still be set, preventing
  82                                  * attachment of the following prog.
  83                                  */
  84                                 fentry_recursive__detach(tracing_chain[i]);
  85                         }
  86                 } else {
  87                         if (!ASSERT_ERR(err, "fentry_recursive__load"))
  88                                 goto close_prog;
  89                 }
  90         }
  91
  92 close_prog:
  93         fentry_recursive_target__destroy(target_skel);
  94         for (int i = 0; i < 2; i++) {
  95                 fentry_recursive__destroy(tracing_chain[i]);
  96         }
  97 }
  98
  99 void test_recursive_fentry(void)
 100 {
 101         if (test__start_subtest("attach"))
 102                 test_recursive_fentry_chain(true, false);
 103         if (test__start_subtest("load"))
 104                 test_recursive_fentry_chain(false, false);
 105         if (test__start_subtest("detach"))
 106                 test_recursive_fentry_chain(true, true);
 107 }
 108
 109 /* Test that a tracing prog reattachment (when we land in
 110  * "prog->aux->dst_trampoline and tgt_prog is NULL" branch in
 111  * bpf_tracing_prog_attach) does not lead to a crash due to missing attach_btf
 112  */
 113 void test_fentry_attach_btf_presence(void)
 114 {
 115         struct fentry_recursive_target *target_skel = NULL;
 116         struct fentry_recursive *tracing_skel = NULL;
 117         struct bpf_program *prog;
 118         int err, link_fd, tgt_prog_fd;
 119
 120         target_skel = fentry_recursive_target__open_and_load();
 121         if (!ASSERT_OK_PTR(target_skel, "fentry_recursive_target__open_and_load"))
 122                 goto close_prog;
 123
 124         tracing_skel = fentry_recursive__open();
 125         if (!ASSERT_OK_PTR(tracing_skel, "fentry_recursive__open"))
 126                 goto close_prog;
 127
 128         prog = tracing_skel->progs.recursive_attach;
 129         tgt_prog_fd = bpf_program__fd(target_skel->progs.fentry_target);
 130         err = bpf_program__set_attach_target(prog, tgt_prog_fd, "fentry_target");
 131         if (!ASSERT_OK(err, "bpf_program__set_attach_target"))
 132                 goto close_prog;
 133
 134         err = fentry_recursive__load(tracing_skel);
 135         if (!ASSERT_OK(err, "fentry_recursive__load"))
 136                 goto close_prog;
 137
 138         tgt_prog_fd = bpf_program__fd(tracing_skel->progs.recursive_attach);
 139         link_fd = bpf_link_create(tgt_prog_fd, 0, BPF_TRACE_FENTRY, NULL);
 140         if (!ASSERT_GE(link_fd, 0, "link_fd"))
 141                 goto close_prog;
 142
 143         fentry_recursive__detach(tracing_skel);
 144
 145         err = fentry_recursive__attach(tracing_skel);
 146         ASSERT_ERR(err, "fentry_recursive__attach");
 147
 148 close_prog:
 149         fentry_recursive_target__destroy(target_skel);
 150         fentry_recursive__destroy(tracing_skel);
 151 }