From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3156EC4332F for ; Tue, 1 Nov 2022 18:47:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230127AbiKASrP (ORCPT ); Tue, 1 Nov 2022 14:47:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57362 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229462AbiKASrM (ORCPT ); Tue, 1 Nov 2022 14:47:12 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E00371C91B; Tue, 1 Nov 2022 11:47:10 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 155D1CE1DBE; Tue, 1 Nov 2022 18:47:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 246AAC433D6; Tue, 1 Nov 2022 18:47:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667328427; bh=QLdC5NhmlPCsZ0fQmjLQ1e7hJz99WGjywddDhFXtMLw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=fN/bZfOXY8KV51v5e96jmg59JEkoMANra1x65SSyTmWwyGs6gZJh1P92p+oWqulwP gXlJ1rwaerpAu7IZ1yhZWhpJuhNlvLgX5BonQpF2lFVh2E3oUwEa/qnYZW5h+2Oc2q I9pXK97sKXNNxIu1Q2INqW3r1kUKlv1VPHyOAEQ/ZkRJdCAcQs+of61HrPpWUzONSs QQPUO2W6YAYOPg1icW0qQmzDoytmrgBcAesiEo1Pwd3QMLG2tkTKuUL6aaB3LSF0ij s2x5ZGvjBJ8d3G6hm5ol2KqI/b1ptmr9VgDFBsNJAsjG6JL2h8btWw1vZBg81Waks7 icf4yaqPFIPxQ== Received: by mail-ed1-f43.google.com with SMTP id z18so18069029edb.9; Tue, 01 Nov 2022 11:47:07 -0700 (PDT) X-Gm-Message-State: ACrzQf3gZJHObIJmBbfKvKzh1JjKljwN1owQzQyae7d4RnLaAsErPGm4 b2TvdcLwchrUNbeB+KPZDQZr8GivwEJ63F70OQg= X-Google-Smtp-Source: AMsMyM7NG+V8QRtMbNL/bl9B7tt5Ew1cnsBIqP2w5Q3U6mKYB6o20GQfUPZVH4oFcKHsN5dOIuUhYpiqRFHpKG2zU0M= X-Received: by 2002:aa7:d710:0:b0:463:bd7b:2b44 with SMTP id t16-20020aa7d710000000b00463bd7b2b44mr3721414edq.385.1667328425396; Tue, 01 Nov 2022 11:47:05 -0700 (PDT) MIME-Version: 1.0 References: <20221101052340.1210239-1-namhyung@kernel.org> <20221101052340.1210239-3-namhyung@kernel.org> In-Reply-To: From: Song Liu Date: Tue, 1 Nov 2022 11:46:52 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH bpf-next 2/3] bpf: Add bpf_perf_event_read_sample() helper To: Alexei Starovoitov Cc: Jiri Olsa , Namhyung Kim , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Song Liu , Peter Zijlstra , Martin KaFai Lau , Yonghong Song , John Fastabend , KP Singh , Hao Luo , Stanislav Fomichev , LKML , bpf , Steven Rostedt , Ingo Molnar , Arnaldo Carvalho de Melo Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 1, 2022 at 11:26 AM Alexei Starovoitov wrote: > > On Tue, Nov 1, 2022 at 3:03 AM Jiri Olsa wrote: > > > > On Mon, Oct 31, 2022 at 10:23:39PM -0700, Namhyung Kim wrote: > > > The bpf_perf_event_read_sample() helper is to get the specified sample > > > data (by using PERF_SAMPLE_* flag in the argument) from BPF to make a > > > decision for filtering on samples. Currently PERF_SAMPLE_IP and > > > PERF_SAMPLE_DATA flags are supported only. > > > > > > Signed-off-by: Namhyung Kim > > > --- > > > include/uapi/linux/bpf.h | 23 ++++++++++++++++ > > > kernel/trace/bpf_trace.c | 49 ++++++++++++++++++++++++++++++++++ > > > tools/include/uapi/linux/bpf.h | 23 ++++++++++++++++ > > > 3 files changed, 95 insertions(+) > > > > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > > > index 94659f6b3395..cba501de9373 100644 > > > --- a/include/uapi/linux/bpf.h > > > +++ b/include/uapi/linux/bpf.h > > > @@ -5481,6 +5481,28 @@ union bpf_attr { > > > * 0 on success. > > > * > > > * **-ENOENT** if the bpf_local_storage cannot be found. > > > + * > > > + * long bpf_perf_event_read_sample(struct bpf_perf_event_data *ctx, void *buf, u32 size, u64 sample_flags) > > > + * Description > > > + * For an eBPF program attached to a perf event, retrieve the > > > + * sample data associated to *ctx* and store it in the buffer > > > + * pointed by *buf* up to size *size* bytes. > > > + * > > > + * The *sample_flags* should contain a single value in the > > > + * **enum perf_event_sample_format**. > > > + * Return > > > + * On success, number of bytes written to *buf*. On error, a > > > + * negative value. > > > + * > > > + * The *buf* can be set to **NULL** to return the number of bytes > > > + * required to store the requested sample data. > > > + * > > > + * **-EINVAL** if *sample_flags* is not a PERF_SAMPLE_* flag. > > > + * > > > + * **-ENOENT** if the associated perf event doesn't have the data. > > > + * > > > + * **-ENOSYS** if system doesn't support the sample data to be > > > + * retrieved. > > > */ > > > #define ___BPF_FUNC_MAPPER(FN, ctx...) \ > > > FN(unspec, 0, ##ctx) \ > > > @@ -5695,6 +5717,7 @@ union bpf_attr { > > > FN(user_ringbuf_drain, 209, ##ctx) \ > > > FN(cgrp_storage_get, 210, ##ctx) \ > > > FN(cgrp_storage_delete, 211, ##ctx) \ > > > + FN(perf_event_read_sample, 212, ##ctx) \ > > > /* */ > > > > > > /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't > > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > > index ce0228c72a93..befd937afa3c 100644 > > > --- a/kernel/trace/bpf_trace.c > > > +++ b/kernel/trace/bpf_trace.c > > > @@ -28,6 +28,7 @@ > > > > > > #include > > > #include > > > +#include > > > > > > #include > > > > > > @@ -1743,6 +1744,52 @@ static const struct bpf_func_proto bpf_read_branch_records_proto = { > > > .arg4_type = ARG_ANYTHING, > > > }; > > > > > > +BPF_CALL_4(bpf_perf_event_read_sample, struct bpf_perf_event_data_kern *, ctx, > > > + void *, buf, u32, size, u64, flags) > > > +{ > > > > I wonder we could add perf_btf (like we have tp_btf) program type that > > could access ctx->data directly without helpers > > > > > + struct perf_sample_data *sd = ctx->data; > > > + void *data; > > > + u32 to_copy = sizeof(u64); > > > + > > > + /* only allow a single sample flag */ > > > + if (!is_power_of_2(flags)) > > > + return -EINVAL; > > > + > > > + /* support reading only already populated info */ > > > + if (flags & ~sd->sample_flags) > > > + return -ENOENT; > > > + > > > + switch (flags) { > > > + case PERF_SAMPLE_IP: > > > + data = &sd->ip; > > > + break; > > > + case PERF_SAMPLE_ADDR: > > > + data = &sd->addr; > > > + break; > > > > AFAICS from pe_prog_convert_ctx_access you should be able to read addr > > directly from context right? same as sample_period.. so I think if this > > will be generic way to read sample data, should we add sample_period > > as well? > > +1 > Let's avoid new stable helpers for this. > Pls use CORE and read perf_sample_data directly. We have legacy ways to access sample_period and addr with struct bpf_perf_event_data and struct bpf_perf_event_data_kern. I think mixing that with CORE makes it confusing for the user. And a helper or a kfunc would make it easier to follow. perf_btf might also be a good approach for this. Thanks, Song