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
8static const char *module_name = "bpf_testmod";
9static const char *symbol_name = "bpf_fentry_shadow_test";
10
11static 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
55void 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
122out:
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