From: Yonghong Song <yhs@fb.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andriin@fb.com>,
"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
<netdev@vger.kernel.org>, <bpf@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>, Daniel Xu <dxu@dxuuu.xyz>,
Viktor Malik <vmalik@redhat.com>
Subject: Re: [PATCH 13/19] bpf: Add support to link multi func tracing program
Date: Mon, 7 Jun 2021 12:39:55 -0700 [thread overview]
Message-ID: <22358f97-f188-c592-2577-a3c79c5c668d@fb.com> (raw)
In-Reply-To: <YL5ksRAvQEW+0csh@krava>
On 6/7/21 11:25 AM, Jiri Olsa wrote:
> On Sun, Jun 06, 2021 at 10:36:57PM -0700, Yonghong Song wrote:
>>
>>
>> On 6/5/21 4:10 AM, Jiri Olsa wrote:
>>> Adding support to attach multiple functions to tracing program
>>> by using the link_create/link_update interface.
>>>
>>> Adding multi_btf_ids/multi_btf_ids_cnt pair to link_create struct
>>> API, that define array of functions btf ids that will be attached
>>> to prog_fd.
>>>
>>> The prog_fd needs to be multi prog tracing program (BPF_F_MULTI_FUNC).
>>>
>>> The new link_create interface creates new BPF_LINK_TYPE_TRACING_MULTI
>>> link type, which creates separate bpf_trampoline and registers it
>>> as direct function for all specified btf ids.
>>>
>>> The new bpf_trampoline is out of scope (bpf_trampoline_lookup) of
>>> standard trampolines, so all registered functions need to be free
>>> of direct functions, otherwise the link fails.
>>
>> I am not sure how severe such a limitation could be in practice.
>> It is possible in production some non-multi fentry/fexit program
>> may run continuously. Does kprobe program impact this as well?
>
> I did not find a way how to combine current trampolines with the
> new ones for multiple programs.. what you described is a limitation
> of the current approach
>
> I'm not sure about kprobes and trampolines, but the limitation
> should be same as we do have for current trampolines.. I'll check
>
>>
>>>
>>> The new bpf_trampoline will store and pass to bpf program the highest
>>> number of arguments from all given functions.
>>>
>>> New programs (fentry or fexit) can be added to the existing trampoline
>>> through the link_update interface via new_prog_fd descriptor.
>>
>> Looks we do not support replacing old programs. Do we support
>> removing old programs?
>
> we don't.. it's not what bpftrace would do, it just adds programs
> to trace and close all when it's done.. I think interface for removal
> could be added if you think it's needed
This can be a followup patch. Indeed removing selective old programs
probably not a common use case.
>
>>
>>>
>>> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
>>> ---
>>> include/linux/bpf.h | 3 +
>>> include/uapi/linux/bpf.h | 5 +
>>> kernel/bpf/syscall.c | 185 ++++++++++++++++++++++++++++++++-
>>> kernel/bpf/trampoline.c | 53 +++++++---
>>> tools/include/uapi/linux/bpf.h | 5 +
>>> 5 files changed, 237 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>>> index 23221e0e8d3c..99a81c6c22e6 100644
>>> --- a/include/linux/bpf.h
>>> +++ b/include/linux/bpf.h
>>> @@ -661,6 +661,7 @@ struct bpf_trampoline {
>>> struct bpf_tramp_image *cur_image;
>>> u64 selector;
>>> struct module *mod;
>>> + bool multi;
>>> };
>>> struct bpf_attach_target_info {
>>> @@ -746,6 +747,8 @@ void bpf_ksym_add(struct bpf_ksym *ksym);
>>> void bpf_ksym_del(struct bpf_ksym *ksym);
>>> int bpf_jit_charge_modmem(u32 pages);
>>> void bpf_jit_uncharge_modmem(u32 pages);
>>> +struct bpf_trampoline *bpf_trampoline_multi_alloc(void);
>>> +void bpf_trampoline_multi_free(struct bpf_trampoline *tr);
>>> #else
>>> static inline int bpf_trampoline_link_prog(struct bpf_prog *prog,
>>> struct bpf_trampoline *tr)
[...]
>>> @@ -363,9 +366,15 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
>>> goto out;
>>> }
>>> + if (tr->multi)
>>> + flags |= BPF_TRAMP_F_IP_ARG;
>>> +
>>> if (tprogs[BPF_TRAMP_FEXIT].nr_progs ||
>>> - tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs)
>>> + tprogs[BPF_TRAMP_MODIFY_RETURN].nr_progs) {
>>> flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
>>> + if (tr->multi)
>>> + flags |= BPF_TRAMP_F_ORIG_STACK | BPF_TRAMP_F_IP_ARG;
>>
>> BPF_TRAMP_F_IP_ARG is not needed. It has been added before.
>
> it's erased in 2 lines above.. which reminds me that I forgot to check
> if that's a bug or intended ;-)
Oh, yes, I miss that too :-) I guess it would be good if you can
re-organize the code to avoid resetting of flags.
>
> jirka
>
next prev parent reply other threads:[~2021-06-07 19:40 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-05 11:10 [RFCv3 00/19] x86/ftrace/bpf: Add batch support for direct/tracing attach Jiri Olsa
2021-06-05 11:10 ` [PATCH 01/19] x86/ftrace: Remove extra orig rax move Jiri Olsa
2021-06-05 11:10 ` [PATCH 02/19] x86/ftrace: Remove fault protection code in prepare_ftrace_return Jiri Olsa
2021-06-05 11:10 ` [PATCH 03/19] x86/ftrace: Make function graph use ftrace directly Jiri Olsa
2021-06-08 18:35 ` Andrii Nakryiko
2021-06-08 18:51 ` Jiri Olsa
2021-06-08 19:11 ` Steven Rostedt
2021-06-05 11:10 ` [PATCH 04/19] tracing: Add trampoline/graph selftest Jiri Olsa
2021-06-05 11:10 ` [PATCH 05/19] ftrace: Add ftrace_add_rec_direct function Jiri Olsa
2021-06-05 11:10 ` [PATCH 06/19] ftrace: Add multi direct register/unregister interface Jiri Olsa
2021-06-05 11:10 ` [PATCH 07/19] ftrace: Add multi direct modify interface Jiri Olsa
2021-06-05 11:10 ` [PATCH 08/19] ftrace/samples: Add multi direct interface test module Jiri Olsa
2021-06-05 11:10 ` [PATCH 09/19] bpf, x64: Allow to use caller address from stack Jiri Olsa
2021-06-07 3:07 ` Yonghong Song
2021-06-07 18:13 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 10/19] bpf: Allow to store caller's ip as argument Jiri Olsa
2021-06-07 3:21 ` Yonghong Song
2021-06-07 18:15 ` Jiri Olsa
2021-06-08 18:49 ` Andrii Nakryiko
2021-06-08 20:58 ` Jiri Olsa
2021-06-08 21:02 ` Andrii Nakryiko
2021-06-08 21:11 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 11/19] bpf: Add support to load multi func tracing program Jiri Olsa
2021-06-07 3:56 ` Yonghong Song
2021-06-07 18:18 ` Jiri Olsa
2021-06-07 19:35 ` Yonghong Song
2021-06-05 11:10 ` [PATCH 12/19] bpf: Add bpf_trampoline_alloc function Jiri Olsa
2021-06-05 11:10 ` [PATCH 13/19] bpf: Add support to link multi func tracing program Jiri Olsa
2021-06-07 5:36 ` Yonghong Song
2021-06-07 18:25 ` Jiri Olsa
2021-06-07 19:39 ` Yonghong Song [this message]
2021-06-08 15:42 ` Alexei Starovoitov
2021-06-08 18:17 ` Jiri Olsa
2021-06-08 18:49 ` Alexei Starovoitov
2021-06-08 21:07 ` Jiri Olsa
2021-06-08 23:05 ` Alexei Starovoitov
2021-06-09 5:08 ` Andrii Nakryiko
2021-06-09 13:42 ` Jiri Olsa
2021-06-09 13:33 ` Jiri Olsa
2021-06-09 5:18 ` Andrii Nakryiko
2021-06-09 13:53 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 14/19] libbpf: Add btf__find_by_pattern_kind function Jiri Olsa
2021-06-09 5:29 ` Andrii Nakryiko
2021-06-09 13:59 ` Jiri Olsa
2021-06-09 14:19 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 15/19] libbpf: Add support to link multi func tracing program Jiri Olsa
2021-06-07 5:49 ` Yonghong Song
2021-06-07 18:28 ` Jiri Olsa
2021-06-07 19:42 ` Yonghong Song
2021-06-07 20:11 ` Jiri Olsa
2021-06-09 5:34 ` Andrii Nakryiko
2021-06-09 14:17 ` Jiri Olsa
2021-06-10 17:05 ` Andrii Nakryiko
2021-06-10 20:35 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 16/19] selftests/bpf: Add fentry multi func test Jiri Olsa
2021-06-07 6:06 ` Yonghong Song
2021-06-07 18:42 ` Jiri Olsa
2021-06-09 5:40 ` Andrii Nakryiko
2021-06-09 14:29 ` Jiri Olsa
2021-06-10 17:00 ` Andrii Nakryiko
2021-06-10 20:28 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 17/19] selftests/bpf: Add fexit " Jiri Olsa
2021-06-05 11:10 ` [PATCH 18/19] selftests/bpf: Add fentry/fexit " Jiri Olsa
2021-06-09 5:41 ` Andrii Nakryiko
2021-06-09 14:29 ` Jiri Olsa
2021-06-05 11:10 ` [PATCH 19/19] selftests/bpf: Temporary fix for fentry_fexit_multi_test Jiri Olsa
2021-06-17 20:29 ` [RFCv3 00/19] x86/ftrace/bpf: Add batch support for direct/tracing attach Andrii Nakryiko
2021-06-19 8:33 ` Jiri Olsa
2021-06-19 16:19 ` Yonghong Song
2021-06-19 17:09 ` Jiri Olsa
2021-06-20 16:56 ` Yonghong Song
2021-06-20 17:47 ` Alexei Starovoitov
2021-06-21 6:46 ` Andrii Nakryiko
2021-06-21 6:50 ` Andrii Nakryiko
2021-07-06 20:26 ` Andrii Nakryiko
2021-07-07 15:19 ` Jiri Olsa
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