1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2022 Red Hat */
3 #include <test_progs.h>
4 #include <bpf/btf.h>
5 #include "bpf/libbpf_internal.h"
6 #include "cgroup_helpers.h"
7
8 static const char *module_name = "bpf_testmod";
9 static const char *symbol_name = "bpf_fentry_shadow_test";
10
11 static int get_bpf_testmod_btf_fd(void)
12 {
13 struct bpf_btf_info info;
14 char name[64];
15 __u32 id = 0, len;
16 int err, fd;
17
18 while (true) {
19 err = bpf_btf_get_next_id(id, &id);
20 if (err) {
21 log_err("failed to iterate BTF objects");
22 return err;
23 }
24
25 fd = bpf_btf_get_fd_by_id(id);
26 if (fd < 0) {
27 if (errno == ENOENT)
28 continue; /* expected race: BTF was unloaded */
29 err = -errno;
30 log_err("failed to get FD for BTF object #%d", id);
31 return err;
32 }
33
34 len = sizeof(info);
35 memset(&info, 0, sizeof(info));
36 info.name = ptr_to_u64(name);
37 info.name_len = sizeof(name);
38
39 err = bpf_obj_get_info_by_fd(fd, &info, &len);
40 if (err) {
41 err = -errno;
42 log_err("failed to get info for BTF object #%d", id);
43 close(fd);
44 return err;
45 }
46
47 if (strcmp(name, module_name) == 0)
48 return fd;
49
50 close(fd);
51 }
52 return -ENOENT;
53 }
54
55 void test_module_fentry_shadow(void)
56 {
57 struct btf *vmlinux_btf = NULL, *mod_btf = NULL;
58 int err, i;
59 int btf_fd[2] = {};
60 int prog_fd[2] = {};
61 int link_fd[2] = {};
62 __s32 btf_id[2] = {};
63
64 if (!env.has_testmod) {
65 test__skip();
66 return;
67 }
68
69 LIBBPF_OPTS(bpf_prog_load_opts, load_opts,
70 .expected_attach_type = BPF_TRACE_FENTRY,
71 );
72
73 const struct bpf_insn trace_program[] = {
74 BPF_MOV64_IMM(BPF_REG_0, 0),
75 BPF_EXIT_INSN(),
76 };
77
78 vmlinux_btf = btf__load_vmlinux_btf();
79 if (!ASSERT_OK_PTR(vmlinux_btf, "load_vmlinux_btf"))
80 return;
81
82 btf_fd[1] = get_bpf_testmod_btf_fd();
83 if (!ASSERT_GE(btf_fd[1], 0, "get_bpf_testmod_btf_fd"))
84 goto out;
85
86 mod_btf = btf_get_from_fd(btf_fd[1], vmlinux_btf);
87 if (!ASSERT_OK_PTR(mod_btf, "btf_get_from_fd"))
88 goto out;
89
90 btf_id[0] = btf__find_by_name_kind(vmlinux_btf, symbol_name, BTF_KIND_FUNC);
91 if (!ASSERT_GT(btf_id[0], 0, "btf_find_by_name"))
92 goto out;
93
94 btf_id[1] = btf__find_by_name_kind(mod_btf, symbol_name, BTF_KIND_FUNC);
95 if (!ASSERT_GT(btf_id[1], 0, "btf_find_by_name"))
96 goto out;
97
98 for (i = 0; i < 2; i++) {
99 load_opts.attach_btf_id = btf_id[i];
100 load_opts.attach_btf_obj_fd = btf_fd[i];
101 prog_fd[i] = bpf_prog_load(BPF_PROG_TYPE_TRACING, NULL, "GPL",
102 trace_program,
103 sizeof(trace_program) / sizeof(struct bpf_insn),
104 &load_opts);
105 if (!ASSERT_GE(prog_fd[i], 0, "bpf_prog_load"))
106 goto out;
107
108 /* If the verifier incorrectly resolves addresses of the
109 * shadowed functions and uses the same address for both the
110 * vmlinux and the bpf_testmod functions, this will fail on
111 * attempting to create two trampolines for the same address,
112 * which is forbidden.
113 */
114 link_fd[i] = bpf_link_create(prog_fd[i], 0, BPF_TRACE_FENTRY, NULL);
115 if (!ASSERT_GE(link_fd[i], 0, "bpf_link_create"))
116 goto out;
117 }
118
119 err = bpf_prog_test_run_opts(prog_fd[0], NULL);
120 ASSERT_OK(err, "running test");
121
122 out:
123 btf__free(vmlinux_btf);
124 btf__free(mod_btf);
125 for (i = 0; i < 2; i++) {
126 if (btf_fd[i])
127 close(btf_fd[i]);
128 if (prog_fd[i] > 0)
129 close(prog_fd[i]);
130 if (link_fd[i] > 0)
131 close(link_fd[i]);
132 }
133 }
134
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