Commit acf61631 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

tools/bpf: selftests: Add iter progs for bpf_map/task/task_file 



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: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175922.2477576-1-yhs@fb.com
parent 7c128a6b

tools/testing/selftests/bpf/progs/bpf_iter_bpf_map.c

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2020 Facebook */

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



char _license[] SEC("license") = "GPL";



SEC("iter/bpf_map")

int dump_bpf_map(struct bpf_iter__bpf_map *ctx)

{

	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_PRINTF(seq, "      %%%%%% END %%%%%%\n");

		return 0;

	}



	if (seq_num == 0)

		BPF_SEQ_PRINTF(seq, "      id   refcnt  usercnt  locked_vm\n");



	BPF_SEQ_PRINTF(seq, "%8u %8ld %8ld %10lu\n", map->id, map->refcnt.counter,

		       map->usercnt.counter,

		       map->memory.user->locked_vm.counter);

	return 0;

}

tools/testing/selftests/bpf/progs/bpf_iter_task.c

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2020 Facebook */

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



char _license[] SEC("license") = "GPL";



SEC("iter/task")

int dump_task(struct bpf_iter__task *ctx)

{

	struct seq_file *seq = ctx->meta->seq;

	struct task_struct *task = ctx->task;



	if (task == (void *)0) {

		BPF_SEQ_PRINTF(seq, "    === END ===\n");

		return 0;

	}



	if (ctx->meta->seq_num == 0)

		BPF_SEQ_PRINTF(seq, "    tgid      gid\n");



	BPF_SEQ_PRINTF(seq, "%8d %8d\n", task->tgid, task->pid);

	return 0;

}

tools/testing/selftests/bpf/progs/bpf_iter_task_file.c

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// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2020 Facebook */

#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



char _license[] SEC("license") = "GPL";



SEC("iter/task_file")

int dump_task_file(struct bpf_iter__task_file *ctx)

{

	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_PRINTF(seq, "    tgid      gid       fd      file\n");



	BPF_SEQ_PRINTF(seq, "%8d %8d %8d %lx\n", task->tgid, task->pid, fd,

		       (long)file->f_op);

	return 0;

}

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