tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2#include <test_progs.h>
3
4static __u64 read_perf_max_sample_freq(void)
5{
6 __u64 sample_freq = 5000; /* fallback to 5000 on error */
7 FILE *f;
8
9 f = fopen("/proc/sys/kernel/perf_event_max_sample_rate", "r");
10 if (f == NULL)
11 return sample_freq;
12 fscanf(f, "%llu", &sample_freq);
13 fclose(f);
14 return sample_freq;
15}
16
17void test_stacktrace_build_id_nmi(void)
18{
19 int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
20 const char *prog_name = "tracepoint/random/urandom_read";
21 const char *file = "./test_stacktrace_build_id.o";
22 int err, pmu_fd, prog_fd;
23 struct perf_event_attr attr = {
24 .freq = 1,
25 .type = PERF_TYPE_HARDWARE,
26 .config = PERF_COUNT_HW_CPU_CYCLES,
27 };
28 __u32 key, previous_key, val, duration = 0;
29 struct bpf_program *prog;
30 struct bpf_object *obj;
31 struct bpf_link *link;
32 char buf[256];
33 int i, j;
34 struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
35 int build_id_matches = 0;
36 int retry = 1;
37
38 attr.sample_freq = read_perf_max_sample_freq();
39
40retry:
41 err = bpf_prog_load(file, BPF_PROG_TYPE_PERF_EVENT, &obj, &prog_fd);
42 if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
43 return;
44
45 prog = bpf_object__find_program_by_title(obj, prog_name);
46 if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
47 goto close_prog;
48
49 pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
50 0 /* cpu 0 */, -1 /* group id */,
51 0 /* flags */);
52 if (CHECK(pmu_fd < 0, "perf_event_open",
53 "err %d errno %d. Does the test host support PERF_COUNT_HW_CPU_CYCLES?\n",
54 pmu_fd, errno))
55 goto close_prog;
56
57 link = bpf_program__attach_perf_event(prog, pmu_fd);
58 if (CHECK(IS_ERR(link), "attach_perf_event",
59 "err %ld\n", PTR_ERR(link))) {
60 close(pmu_fd);
61 goto close_prog;
62 }
63
64 /* find map fds */
65 control_map_fd = bpf_find_map(__func__, obj, "control_map");
66 if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
67 "err %d errno %d\n", err, errno))
68 goto disable_pmu;
69
70 stackid_hmap_fd = bpf_find_map(__func__, obj, "stackid_hmap");
71 if (CHECK(stackid_hmap_fd < 0, "bpf_find_map stackid_hmap",
72 "err %d errno %d\n", err, errno))
73 goto disable_pmu;
74
75 stackmap_fd = bpf_find_map(__func__, obj, "stackmap");
76 if (CHECK(stackmap_fd < 0, "bpf_find_map stackmap", "err %d errno %d\n",
77 err, errno))
78 goto disable_pmu;
79
80 stack_amap_fd = bpf_find_map(__func__, obj, "stack_amap");
81 if (CHECK(stack_amap_fd < 0, "bpf_find_map stack_amap",
82 "err %d errno %d\n", err, errno))
83 goto disable_pmu;
84
85 assert(system("dd if=/dev/urandom of=/dev/zero count=4 2> /dev/null")
86 == 0);
87 assert(system("taskset 0x1 ./urandom_read 100000") == 0);
88 /* disable stack trace collection */
89 key = 0;
90 val = 1;
91 bpf_map_update_elem(control_map_fd, &key, &val, 0);
92
93 /* for every element in stackid_hmap, we can find a corresponding one
94 * in stackmap, and vise versa.
95 */
96 err = compare_map_keys(stackid_hmap_fd, stackmap_fd);
97 if (CHECK(err, "compare_map_keys stackid_hmap vs. stackmap",
98 "err %d errno %d\n", err, errno))
99 goto disable_pmu;
100
101 err = compare_map_keys(stackmap_fd, stackid_hmap_fd);
102 if (CHECK(err, "compare_map_keys stackmap vs. stackid_hmap",
103 "err %d errno %d\n", err, errno))
104 goto disable_pmu;
105
106 err = extract_build_id(buf, 256);
107
108 if (CHECK(err, "get build_id with readelf",
109 "err %d errno %d\n", err, errno))
110 goto disable_pmu;
111
112 err = bpf_map_get_next_key(stackmap_fd, NULL, &key);
113 if (CHECK(err, "get_next_key from stackmap",
114 "err %d, errno %d\n", err, errno))
115 goto disable_pmu;
116
117 do {
118 char build_id[64];
119
120 err = bpf_map_lookup_elem(stackmap_fd, &key, id_offs);
121 if (CHECK(err, "lookup_elem from stackmap",
122 "err %d, errno %d\n", err, errno))
123 goto disable_pmu;
124 for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
125 if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
126 id_offs[i].offset != 0) {
127 for (j = 0; j < 20; ++j)
128 sprintf(build_id + 2 * j, "%02x",
129 id_offs[i].build_id[j] & 0xff);
130 if (strstr(buf, build_id) != NULL)
131 build_id_matches = 1;
132 }
133 previous_key = key;
134 } while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);
135
136 /* stack_map_get_build_id_offset() is racy and sometimes can return
137 * BPF_STACK_BUILD_ID_IP instead of BPF_STACK_BUILD_ID_VALID;
138 * try it one more time.
139 */
140 if (build_id_matches < 1 && retry--) {
141 bpf_link__destroy(link);
142 bpf_object__close(obj);
143 printf("%s:WARN:Didn't find expected build ID from the map, retrying\n",
144 __func__);
145 goto retry;
146 }
147
148 if (CHECK(build_id_matches < 1, "build id match",
149 "Didn't find expected build ID from the map\n"))
150 goto disable_pmu;
151
152 /*
153 * We intentionally skip compare_stack_ips(). This is because we
154 * only support one in_nmi() ips-to-build_id translation per cpu
155 * at any time, thus stack_amap here will always fallback to
156 * BPF_STACK_BUILD_ID_IP;
157 */
158
159disable_pmu:
160 bpf_link__destroy(link);
161close_prog:
162 bpf_object__close(obj);
163}