This test uses bpf_get_branch_snapshot from a fexit program. The test uses
a target kernel function (bpf_fexit_loop_test1) and compares the record
against kallsyms. If there isn't enough record matching kallsyms, the
test fails.
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
net/bpf/test_run.c | 15 ++-
.../bpf/prog_tests/get_branch_snapshot.c | 106 ++++++++++++++++++
.../selftests/bpf/progs/get_branch_snapshot.c | 41 +++++++
tools/testing/selftests/bpf/trace_helpers.c | 30 +++++
tools/testing/selftests/bpf/trace_helpers.h | 5 +
5 files changed, 196 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
create mode 100644 tools/testing/selftests/bpf/progs/get_branch_snapshot.c
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 2eb0e55ef54d2..6cc179a532c9c 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -231,6 +231,18 @@ struct sock * noinline bpf_kfunc_call_test3(struct sock *sk)
return sk;
}
+noinline int bpf_fexit_loop_test1(int n)
+{
+ int i, sum = 0;
+
+ /* the primary goal of this test is to test LBR. Create a lot of
+ * branches in the function, so we can catch it easily.
+ */
+ for (i = 0; i < n; i++)
+ sum += i;
+ return sum;
+}
+
__diag_pop();
ALLOW_ERROR_INJECTION(bpf_modify_return_test, ERRNO);
@@ -293,7 +305,8 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog,
bpf_fentry_test5(11, (void *)12, 13, 14, 15) != 65 ||
bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111 ||
bpf_fentry_test7((struct bpf_fentry_test_t *)0) != 0 ||
- bpf_fentry_test8(&arg) != 0)
+ bpf_fentry_test8(&arg) != 0 ||
+ bpf_fexit_loop_test1(101) != 5050)
goto out;
break;
case BPF_MODIFY_RETURN:
diff --git a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
new file mode 100644
index 0000000000000..9bb16826418fb
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <test_progs.h>
+#include "get_branch_snapshot.skel.h"
+
+static int *pfd_array;
+static int cpu_cnt;
+
+static int create_perf_events(void)
+{
+ struct perf_event_attr attr = {0};
+ int cpu;
+
+ /* create perf event */
+ attr.size = sizeof(attr);
+ attr.type = PERF_TYPE_RAW;
+ attr.config = 0x1b00;
+ attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
+ attr.branch_sample_type = PERF_SAMPLE_BRANCH_KERNEL |
+ PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY;
+
+ cpu_cnt = libbpf_num_possible_cpus();
+ pfd_array = malloc(sizeof(int) * cpu_cnt);
+ if (!pfd_array) {
+ cpu_cnt = 0;
+ return 1;
+ }
+
+ for (cpu = 0; cpu < libbpf_num_possible_cpus(); cpu++) {
+ pfd_array[cpu] = syscall(__NR_perf_event_open, &attr,
+ -1, cpu, -1, PERF_FLAG_FD_CLOEXEC);
+ if (pfd_array[cpu] < 0)
+ break;
+ }
+
+ return cpu == 0;
+}
+
+static void close_perf_events(void)
+{
+ int cpu = 0;
+ int fd;
+
+ while (cpu++ < cpu_cnt) {
+ fd = pfd_array[cpu];
+ if (fd < 0)
+ break;
+ close(fd);
+ }
+ free(pfd_array);
+}
+
+void test_get_branch_snapshot(void)
+{
+ struct get_branch_snapshot *skel;
+ int err, prog_fd;
+ __u32 retval;
+
+ if (create_perf_events()) {
+ test__skip(); /* system doesn't support LBR */
+ goto cleanup;
+ }
+
+ skel = get_branch_snapshot__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "get_branch_snapshot__open_and_load"))
+ goto cleanup;
+
+ err = kallsyms_find("bpf_fexit_loop_test1", &skel->bss->address_low);
+ if (!ASSERT_OK(err, "kallsyms_find"))
+ goto cleanup;
+
+ err = kallsyms_find_next("bpf_fexit_loop_test1", &skel->bss->address_high);
+ if (!ASSERT_OK(err, "kallsyms_find_next"))
+ goto cleanup;
+
+ err = get_branch_snapshot__attach(skel);
+ if (!ASSERT_OK(err, "get_branch_snapshot__attach"))
+ goto cleanup;
+
+ prog_fd = bpf_program__fd(skel->progs.test1);
+ err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
+ NULL, 0, &retval, NULL);
+
+ if (!ASSERT_OK(err, "bpf_prog_test_run"))
+ goto cleanup;
+
+ if (skel->bss->total_entries < 16) {
+ /* too few entries for the hit/waste test */
+ test__skip();
+ goto cleanup;
+ }
+
+ ASSERT_GT(skel->bss->test1_hits, 5, "find_test1_in_lbr");
+
+ /* Given we stop LBR in software, we will waste a few entries.
+ * But we should try to waste as few as possibleentries. We are at
+ * about 7 on x86_64 systems.
+ * Add a check for < 10 so that we get heads-up when something
+ * changes and wastes too many entries.
+ */
+ ASSERT_LT(skel->bss->wasted_entries, 10, "check_wasted_entries");
+
+cleanup:
+ get_branch_snapshot__destroy(skel);
+ close_perf_events();
+}
diff --git a/tools/testing/selftests/bpf/progs/get_branch_snapshot.c b/tools/testing/selftests/bpf/progs/get_branch_snapshot.c
new file mode 100644
index 0000000000000..9c944e7480b95
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/get_branch_snapshot.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+__u64 test1_hits = 0;
+__u64 address_low = 0;
+__u64 address_high = 0;
+int wasted_entries = 0;
+long total_entries = 0;
+
+#define MAX_LBR_ENTRIES 32
+
+struct perf_branch_entry entries[MAX_LBR_ENTRIES] = {};
+
+
+static inline bool in_range(__u64 val)
+{
+ return (val >= address_low) && (val < address_high);
+}
+
+SEC("fexit/bpf_fexit_loop_test1")
+int BPF_PROG(test1, int n, int ret)
+{
+ long i;
+
+ total_entries = bpf_get_branch_snapshot(entries, sizeof(entries));
+
+ for (i = 0; i < MAX_LBR_ENTRIES; i++) {
+ if (i >= total_entries)
+ break;
+ if (in_range(entries[i].from) && in_range(entries[i].to))
+ test1_hits++;
+ else if (!test1_hits)
+ wasted_entries++;
+ }
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
index e7a19b04d4eaf..2926a3b626821 100644
--- a/tools/testing/selftests/bpf/trace_helpers.c
+++ b/tools/testing/selftests/bpf/trace_helpers.c
@@ -117,6 +117,36 @@ int kallsyms_find(const char *sym, unsigned long long *addr)
return err;
}
+/* find the address of the next symbol, this can be used to determine the
+ * end of a function
+ */
+int kallsyms_find_next(const char *sym, unsigned long long *addr)
+{
+ char type, name[500];
+ unsigned long long value;
+ bool found = false;
+ int err = 0;
+ FILE *f;
+
+ f = fopen("/proc/kallsyms", "r");
+ if (!f)
+ return -EINVAL;
+
+ while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) {
+ if (found) {
+ *addr = value;
+ goto out;
+ }
+ if (strcmp(name, sym) == 0)
+ found = true;
+ }
+ err = -ENOENT;
+
+out:
+ fclose(f);
+ return err;
+}
+
void read_trace_pipe(void)
{
int trace_fd;
diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h
index d907b445524d5..bc8ed86105d94 100644
--- a/tools/testing/selftests/bpf/trace_helpers.h
+++ b/tools/testing/selftests/bpf/trace_helpers.h
@@ -16,6 +16,11 @@ long ksym_get_addr(const char *name);
/* open kallsyms and find addresses on the fly, faster than load + search. */
int kallsyms_find(const char *sym, unsigned long long *addr);
+/* find the address of the next symbol, this can be used to determine the
+ * end of a function
+ */
+int kallsyms_find_next(const char *sym, unsigned long long *addr);
+
void read_trace_pipe(void);
ssize_t get_uprobe_offset(const void *addr, ssize_t base);
--
2.30.2
