[PATCH bpf-next v1 18/19] tools/bpf: selftests: add iter progs for bpf_map/task/task_file

Yonghong Song
2020-04-27T20:13:11Z

The implementation is arbitrary, just to show how the bpf programs
can be written for bpf_map/task/task_file. They can be costomized
for specific needs.

For example, for bpf_map, the iterator prints out:
$ cat /sys/fs/bpf/my_bpf_map
id refcnt usercnt locked_vm
3 2 0 20
6 2 0 20
9 2 0 20
12 2 0 20
13 2 0 20
16 2 0 20
19 2 0 20
=== END ===

For task, the iterator prints out:
$ cat /sys/fs/bpf/my_task
tgid gid
1 1
2 2
....
1944 1944
1948 1948
1949 1949
1953 1953
=== END ===

For task/file, the iterator prints out:
$ cat /sys/fs/bpf/my_task_file
tgid gid fd file
1 1 0 ffffffff95c97600
1 1 1 ffffffff95c97600
1 1 2 ffffffff95c97600
....
1895 1895 255 ffffffff95c8fe00
1932 1932 0 ffffffff95c8fe00
1932 1932 1 ffffffff95c8fe00
1932 1932 2 ffffffff95c8fe00
1932 1932 3 ffffffff95c185c0

This is able to print out all open files (fd and file->f_op), so user can compare
f_op against a particular kernel file operations to find what it is.
For example, from /proc/kallsyms, we can find
ffffffff95c185c0 r eventfd_fops
so we will know tgid 1932 fd 3 is an eventfd file descriptor.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
.../selftests/bpf/progs/bpf_iter_bpf_map.c | 32 +++++++++++++++++++
.../selftests/bpf/progs/bpf_iter_task.c | 29 +++++++++++++++++
.../selftests/bpf/progs/bpf_iter_task_file.c | 28 ++++++++++++++++
3 files changed, 89 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_bpf_map.c
create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task.c
create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_file.c

diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_map.c b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_map.c
new file mode 100644
index 000000000000..d4973ba4f337
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_map.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_endian.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("iter/bpf_map")
+int dump_bpf_map(struct bpf_iter__bpf_map *ctx)
+{
+ static const char banner[] = " id refcnt usercnt locked_vm\n";
+ static const char footer[] = " === END ===\n";
+ static const char fmt[] = "%8u %8ld %8ld %10lu\n";
+ struct seq_file *seq = ctx->meta->seq;
+ __u64 seq_num = ctx->meta->seq_num;
+ struct bpf_map *map = ctx->map;
+
+ if (map == (void *)0) {
+ BPF_SEQ_PRINTF0(seq, footer);
+ return 0;
+ }
+
+ if (seq_num == 0)
+ BPF_SEQ_PRINTF0(seq, banner);
+
+ BPF_SEQ_PRINTF(seq, fmt, map->id, map->refcnt.counter,
+ map->usercnt.counter,
+ map->memory.user->locked_vm.counter);
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task.c b/tools/testing/selftests/bpf/progs/bpf_iter_task.c
new file mode 100644
index 000000000000..78583dda3739
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_task.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_endian.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("iter/task")
+int dump_tasks(struct bpf_iter__task *ctx)
+{
+ static char const banner[] = " tgid gid\n";
+ static char const footer[] = "=== END ===\n";
+ static char const fmt[] = "%8d %8d\n";
+ struct seq_file *seq = ctx->meta->seq;
+ struct task_struct *task = ctx->task;
+
+ if (task == (void *)0) {
+ BPF_SEQ_PRINTF0(seq, footer);
+ return 0;
+ }
+
+ if (ctx->meta->seq_num == 0)
+ BPF_SEQ_PRINTF0(seq, banner);
+
+ BPF_SEQ_PRINTF(seq, fmt, task->tgid, task->pid);
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_file.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_file.c
new file mode 100644
index 000000000000..7ade0303a1a5
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_file.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_endian.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("iter/task_file")
+int dump_tasks(struct bpf_iter__task_file *ctx)
+{
+ static char const banner[] = " tgid gid fd file\n";
+ static char const fmt[] = "%8d %8d %8d %lx\n";
+ struct seq_file *seq = ctx->meta->seq;
+ struct task_struct *task = ctx->task;
+ __u32 fd = ctx->fd;
+ struct file *file = ctx->file;
+
+ if (task == (void *)0 || file == (void *)0)
+ return 0;
+
+ if (ctx->meta->seq_num == 0)
+ BPF_SEQ_PRINTF0(seq, banner);
+
+ BPF_SEQ_PRINTF(seq, fmt, task->tgid, task->pid, fd, (long)file->f_op);
+ return 0;
+}
--
2.24.1