[RFC PATCH bpf-next 15/16] tools/bpf: selftests: add dumper progs for bpf_map/task/task_file

Yonghong Song
2020-04-08T23:25:55Z

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 dumper prints out:
$ cat /sys/kernel/bpfdump/bpf_map/my1
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

For task, the dumper prints out:
$ cat /sys/kernel/bpfdump/task/my1
tgid gid
1 1
2 2
....
1944 1944
1948 1948
1949 1949
1953 1953

For task/file, the dumper prints out:
$ cat /sys/kernel/bpfdump/task/file/my1
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/bpfdump_bpf_map.c | 24 +++++++++++++++++++
.../selftests/bpf/progs/bpfdump_task.c | 21 ++++++++++++++++
.../selftests/bpf/progs/bpfdump_task_file.c | 24 +++++++++++++++++++
3 files changed, 69 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/bpfdump_bpf_map.c
create mode 100644 tools/testing/selftests/bpf/progs/bpfdump_task.c
create mode 100644 tools/testing/selftests/bpf/progs/bpfdump_task_file.c

diff --git a/tools/testing/selftests/bpf/progs/bpfdump_bpf_map.c b/tools/testing/selftests/bpf/progs/bpfdump_bpf_map.c
new file mode 100644
index 000000000000..c85f5a330010
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpfdump_bpf_map.c
@@ -0,0 +1,24 @@
+// 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("dump//sys/kernel/bpfdump/bpf_map")
+int BPF_PROG(dump_bpf_map, struct bpf_map *map, struct seq_file *seq, u64 seq_num)
+{
+ static const char banner[] = " id refcnt usercnt locked_vm\n";
+ static const char fmt1[] = "%8u %8ld ";
+ static const char fmt2[] = "%8ld %10lu\n";
+
+ if (seq_num == 0)
+ bpf_seq_printf(seq, banner, sizeof(banner));
+
+ bpf_seq_printf(seq, fmt1, sizeof(fmt1), map->id, map->refcnt.counter);
+ bpf_seq_printf(seq, fmt2, sizeof(fmt2), map->usercnt.counter,
+ map->memory.user->locked_vm.counter);
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/bpfdump_task.c b/tools/testing/selftests/bpf/progs/bpfdump_task.c
new file mode 100644
index 000000000000..4d90ba97fbda
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpfdump_task.c
@@ -0,0 +1,21 @@
+// 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("dump//sys/kernel/bpfdump/task")
+int BPF_PROG(dump_tasks, struct task_struct *task, struct seq_file *seq, u64 seq_num)
+{
+ static char const banner[] = " tgid gid\n";
+ static char const fmt[] = "%8d %8d\n";
+
+ if (seq_num == 0)
+ bpf_seq_printf(seq, banner, sizeof(banner));
+
+ bpf_seq_printf(seq, fmt, sizeof(fmt), task->tgid, task->pid);
+ return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/bpfdump_task_file.c b/tools/testing/selftests/bpf/progs/bpfdump_task_file.c
new file mode 100644
index 000000000000..5cf02c050e1f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpfdump_task_file.c
@@ -0,0 +1,24 @@
+// 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("dump//sys/kernel/bpfdump/task/file")
+int BPF_PROG(dump_tasks, struct task_struct *task, __u32 fd, struct file *file,
+ struct seq_file *seq, u64 seq_num)
+{
+ static char const banner[] = " tgid gid fd file\n";
+ static char const fmt1[] = "%8d %8d";
+ static char const fmt2[] = " %8d %lx\n";
+
+ if (seq_num == 0)
+ bpf_seq_printf(seq, banner, sizeof(banner));
+
+ bpf_seq_printf(seq, fmt1, sizeof(fmt1), task->tgid, task->pid);
+ bpf_seq_printf(seq, fmt2, sizeof(fmt2), fd, (long)file->f_op);
+ return 0;
+}
--
2.24.1