[PATCH v3 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack()

[Song Liu]

The new test is similar to other bpf_iter tests.

Signed-off-by: Song Liu <songliubrav...@fb.com>
---
 .../selftests/bpf/prog_tests/bpf_iter.c       | 17 ++++++
 .../selftests/bpf/progs/bpf_iter_task_stack.c | 53 +++++++++++++++++++
 2 files changed, 70 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 1e2e0fced6e81..fed42755416db 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_tcp4.skel.h"
 #include "bpf_iter_tcp6.skel.h"
@@ -110,6 +111,20 @@ 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;
@@ -452,6 +467,8 @@ 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("tcp4"))
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..39b21df17c3ee
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c
@@ -0,0 +1,53 @@
+// 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";
+
+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];
+#define SIZE_OF_ULONG (sizeof(unsigned long))
+
+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;
+       long i, retlen;
+
+       if (task == (void *)0)
+               return 0;
+
+       retlen = bpf_get_task_stack(task, entries,
+                                   MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0);
+       if (retlen < 0)
+               return 0;
+
+       BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid,
+                      retlen / SIZE_OF_ULONG);
+       for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) {
+               if (retlen > i * SIZE_OF_ULONG)
+                       BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]);
+       }
+       BPF_SEQ_PRINTF(seq, "\n");
+
+       return 0;
+}
-- 
2.24.1