[PATCH v2 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack()

From: Song Liu
Date: Thu Jun 25 2020 - 20:14:02 EST


The new test is similar to other bpf_iter tests.

Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
.../selftests/bpf/prog_tests/bpf_iter.c | 17 ++++++
.../selftests/bpf/progs/bpf_iter_task_stack.c | 60 +++++++++++++++++++
2 files changed, 77 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index 87c29dde1cf96..baa83328f810d 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -5,6 +5,7 @@
#include "bpf_iter_netlink.skel.h"
#include "bpf_iter_bpf_map.skel.h"
#include "bpf_iter_task.skel.h"
+#include "bpf_iter_task_stack.skel.h"
#include "bpf_iter_task_file.skel.h"
#include "bpf_iter_test_kern1.skel.h"
#include "bpf_iter_test_kern2.skel.h"
@@ -106,6 +107,20 @@ static void test_task(void)
bpf_iter_task__destroy(skel);
}

+static void test_task_stack(void)
+{
+ struct bpf_iter_task_stack *skel;
+
+ skel = bpf_iter_task_stack__open_and_load();
+ if (CHECK(!skel, "bpf_iter_task_stack__open_and_load",
+ "skeleton open_and_load failed\n"))
+ return;
+
+ do_dummy_read(skel->progs.dump_task_stack);
+
+ bpf_iter_task_stack__destroy(skel);
+}
+
static void test_task_file(void)
{
struct bpf_iter_task_file *skel;
@@ -392,6 +407,8 @@ void test_bpf_iter(void)
test_bpf_map();
if (test__start_subtest("task"))
test_task();
+ if (test__start_subtest("task_stack"))
+ test_task_stack();
if (test__start_subtest("task_file"))
test_task_file();
if (test__start_subtest("anon"))
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c
new file mode 100644
index 0000000000000..83aca5b1a7965
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+/* "undefine" structs in vmlinux.h, because we "override" them below */
+#define bpf_iter_meta bpf_iter_meta___not_used
+#define bpf_iter__task bpf_iter__task___not_used
+#include "vmlinux.h"
+#undef bpf_iter_meta
+#undef bpf_iter__task
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+/* bpf_get_task_stack needs a stackmap to work */
+struct {
+ __uint(type, BPF_MAP_TYPE_STACK_TRACE);
+ __uint(max_entries, 16384);
+ __uint(key_size, sizeof(__u32));
+ __uint(value_size, sizeof(__u64) * 20);
+} stackmap SEC(".maps");
+
+struct bpf_iter_meta {
+ struct seq_file *seq;
+ __u64 session_id;
+ __u64 seq_num;
+} __attribute__((preserve_access_index));
+
+struct bpf_iter__task {
+ struct bpf_iter_meta *meta;
+ struct task_struct *task;
+} __attribute__((preserve_access_index));
+
+#define MAX_STACK_TRACE_DEPTH 64
+unsigned long entries[MAX_STACK_TRACE_DEPTH];
+
+SEC("iter/task")
+int dump_task_stack(struct bpf_iter__task *ctx)
+{
+ struct seq_file *seq = ctx->meta->seq;
+ struct task_struct *task = ctx->task;
+ int i, retlen;
+
+ if (task == (void *)0)
+ return 0;
+
+ retlen = bpf_get_task_stack(task, entries,
+ MAX_STACK_TRACE_DEPTH * sizeof(unsigned long), 0);
+ if (retlen < 0)
+ return 0;
+
+ BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid,
+ retlen / sizeof(unsigned long));
+ for (i = 0; i < MAX_STACK_TRACE_DEPTH / sizeof(unsigned long); i++) {
+ if (retlen > i * sizeof(unsigned long))
+ BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]);
+ }
+ BPF_SEQ_PRINTF(seq, "\n");
+
+ return 0;
+}
--
2.24.1