From: Yonghong Song <yhs@fb.com>
To: Song Liu <songliubraving@fb.com>, <bpf@vger.kernel.org>,
<netdev@vger.kernel.org>
Cc: <ast@kernel.org>, <daniel@iogearbox.net>, <kernel-team@fb.com>,
<john.fastabend@gmail.com>, <kpsingh@chromium.org>
Subject: Re: [PATCH bpf-next 3/3] selftests/bpf: add bpf_iter test with bpf_get_task_stack_trace()
Date: Tue, 23 Jun 2020 11:57:32 -0700 [thread overview]
Message-ID: <445e1e04-882f-7ff7-9bd4-ebcf679cebbb@fb.com> (raw)
In-Reply-To: <20200623070802.2310018-4-songliubraving@fb.com>
On 6/23/20 12:08 AM, Song Liu wrote:
> The new test is similar to other bpf_iter tests.
>
> Signed-off-by: Song Liu <songliubraving@fb.com>
> ---
> .../selftests/bpf/prog_tests/bpf_iter.c | 17 +++++++
> .../selftests/bpf/progs/bpf_iter_task_stack.c | 50 +++++++++++++++++++
> 2 files changed, 67 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..4fc939e0fca77
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c
> @@ -0,0 +1,50 @@
> +// 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];
> +
> +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;
> + unsigned int i, num_entries;
> +
> + if (task == (void *)0)
> + return 0;
> +
> + num_entries = bpf_get_task_stack_trace(task, entries, MAX_STACK_TRACE_DEPTH);
> +
> + BPF_SEQ_PRINTF(seq, "pid: %8u\n", task->pid);
> +
> + for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) {
> + if (num_entries > i)
> + BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]);
We may have an issue on 32bit issue.
On 32bit system, the following is called in the kernel
+ return stack_trace_save_tsk(task, (unsigned long *)entries, size, 0);
it will pack addresses at 4 byte increment.
But in BPF program, the reading is in 8 byte increment.
If "entries" are handled in user space, user space can just using "long
*" pointer and will be able to correctly retrieve the stack addresses.
Maybe add some comments to clarify this prog only works for 64bit system.
> + }
> +
> + BPF_SEQ_PRINTF(seq, "\n");
> +
> + return 0;
> +}
>
next prev parent reply other threads:[~2020-06-23 18:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 7:07 [PATCH bpf-next 0/3] bpf: introduce bpf_get_task_stack_trace() Song Liu
2020-06-23 7:08 ` [PATCH bpf-next 1/3] bpf: introduce helper bpf_get_task_stack_trace() Song Liu
2020-06-23 15:19 ` Alexei Starovoitov
2020-06-23 16:59 ` Song Liu
2020-06-23 17:40 ` Song Liu
2020-06-23 18:41 ` Andrii Nakryiko
2020-06-23 15:22 ` Daniel Borkmann
2020-06-23 17:19 ` Song Liu
2020-06-23 18:45 ` Andrii Nakryiko
2020-06-23 22:53 ` Song Liu
2020-06-23 7:08 ` [PATCH bpf-next 2/3] bpf: allow %pB in bpf_seq_printf() Song Liu
2020-06-23 15:29 ` Daniel Borkmann
2020-06-23 17:19 ` Song Liu
2020-06-23 7:08 ` [PATCH bpf-next 3/3] selftests/bpf: add bpf_iter test with bpf_get_task_stack_trace() Song Liu
2020-06-23 18:57 ` Yonghong Song [this message]
2020-06-23 22:07 ` Song Liu
2020-06-23 22:27 ` Yonghong Song
2020-06-24 20:37 ` Song Liu
2020-06-25 5:29 ` Yonghong Song
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