On Tue, Aug 31, 2021 at 7:01 PM Song Liu <songliubraving@xxxxxx> wrote:
>
> This test uses bpf_get_branch_snapshot from a fexit program. The test uses
> a target function (bpf_testmod_loop_test) and compares the record against
> kallsyms. If there isn't enough record matching kallsyms, the test fails.
>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
LGTM, few minor nits below
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> .../selftests/bpf/bpf_testmod/bpf_testmod.c | 14 ++-
> .../bpf/prog_tests/get_branch_snapshot.c | 101 ++++++++++++++++++
> .../selftests/bpf/progs/get_branch_snapshot.c | 44 ++++++++
> tools/testing/selftests/bpf/trace_helpers.c | 37 +++++++
> tools/testing/selftests/bpf/trace_helpers.h | 5 +
> 5 files changed, 200 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
>
[...]
> +
> +void test_get_branch_snapshot(void)
> +{
> + struct get_branch_snapshot *skel = NULL;
> + int err;
> +
> + 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_testmod_loop_test", &skel->bss->address_low);
> + if (!ASSERT_OK(err, "kallsyms_find"))
> + goto cleanup;
> +
> + err = kallsyms_find_next("bpf_testmod_loop_test", &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;
> +
> + /* trigger the program */
> + system("cat /sys/kernel/bpf_testmod > /dev/null 2>& 1");
ugh :( see prog_tests/module_attach.c, we can extract and reuse
trigger_module_test_read() and trigger_module_test_write()
> +
> + if (skel->bss->total_entries < 16) {
> + /* too few entries for the hit/waste test */
> + test__skip();
> + goto cleanup;
> + }
> +
[...]
> +SEC("fexit/bpf_testmod_loop_test")
> +int BPF_PROG(test1, int n, int ret)
> +{
> + long i;
> +
> + total_entries = bpf_get_branch_snapshot(entries, sizeof(entries), 0);
> + total_entries /= sizeof(struct perf_branch_entry);
> +
> + bpf_printk("total_entries %lu\n", total_entries);
> +
> + for (i = 0; i < PERF_MAX_BRANCH_SNAPSHOT; 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++;
> + bpf_printk("i %d from %llx to %llx", i, entries[i].from,
> + entries[i].to);
debug leftovers? this will be polluting trace_pipe unnecessarily; same
for above total_entries bpf_printk()
> + }
> + return 0;
> +}
> diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c
> index e7a19b04d4eaf..5100a169b72b1 100644
> --- a/tools/testing/selftests/bpf/trace_helpers.c
> +++ b/tools/testing/selftests/bpf/trace_helpers.c
> @@ -1,4 +1,5 @@
> // SPDX-License-Identifier: GPL-2.0
> +#include <ctype.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> @@ -117,6 +118,42 @@ int kallsyms_find(const char *sym, unsigned long long *addr)
> return err;
> }
>
[...]
