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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A332C3F68F for ; Wed, 22 Jan 2020 20:23:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F1FD2465A for ; Wed, 22 Jan 2020 20:23:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=dxuuu.xyz header.i=@dxuuu.xyz header.b="JTKFSBjZ"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="Ojk+cIoL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729076AbgAVUXZ (ORCPT ); Wed, 22 Jan 2020 15:23:25 -0500 Received: from new2-smtp.messagingengine.com ([66.111.4.224]:43767 "EHLO new2-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725827AbgAVUXZ (ORCPT ); Wed, 22 Jan 2020 15:23:25 -0500 Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailnew.nyi.internal (Postfix) with ESMTP id 247234B78; Wed, 22 Jan 2020 15:23:24 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute4.internal (MEProxy); Wed, 22 Jan 2020 15:23:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=dxuuu.xyz; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; s=fm2; bh=8Xg2pG8bpEa91 uOgyrlRmXd7HBJkZ4W+CJgY/E8Av+s=; b=JTKFSBjZXfSFsYHt0RLx++rzBSOBa e5qAkczXA2TjexLX9r8D2q5o4Lt9i9BEENgjGjLBU9uIOQoHIoSY3qtLlrw/tyOa ezdwYV6yLbR+4+q+/JjhOCUfNbp0GGtU0Gin31bwrk6Tz4pZPTBz+AEyNnFNK9YD sbShPPUXG3uEgozYXS/QVg/yyr2hKO4OhYSD0LC92EmRTKr4py1wjMLr+o8EWAlj p2xvHmTcqkr7szQ20Ktp7mywYjTpTGcq8mit7wsdM6sefCNqmoxbYge2oHRDnfbd J4M5htmqTaaV8rkaTAv1I7YJxBbPdvUplQ8gb+N18ZkPElyfbe+aFQGIA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:date:from :in-reply-to:message-id:mime-version:references:subject:to :x-me-proxy:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s= fm1; bh=8Xg2pG8bpEa91uOgyrlRmXd7HBJkZ4W+CJgY/E8Av+s=; b=Ojk+cIoL mQrM8XO1l2OHwWjdnbet1YqfUuK800SAjWk7Lay3tbzDRKHMMRukA0hg0dRZXgRf 03Vhdw9rpBtE+8wO/+U3cciHsfPPaGGgVGMiiO6v5fYHqFYVChT+JJkHmOSSn2RV +gDEIQ9WbTVvkVO0xOVAOuGEVF4FEkqauER1qdyVfPpeibq07K4ho1xpgqQGrKhN 6RZIWv5+GsQ6Io421xKR1dwWQcsXwm+jaomR6j1+XgpUdRIK0C4hE3WDnDZtV3Hv Vt9t6d6AzJoZnzJQKAumbl7bvkRKzMYcqK3TX4C/0EC6/+4g1uGAOsipSg/GKxAd hRtGbxHVzarUUg== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedugedrvddtgddufeduucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucgfrhhlucfvnfffucdljedtmdenucfjughrpefhvf fufffkofgjfhgggfestdekredtredttdenucfhrhhomhepffgrnhhivghlucgiuhcuoegu gihusegugihuuhhurdighiiiqeenucfkphepudelledrvddtuddrieegrddvnecuvehluh hsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepugiguhesugiguhhu uhdrgiihii X-ME-Proxy: Received: from dlxu-fedora-R90QNFJV.thefacebook.com (unknown [199.201.64.2]) by mail.messagingengine.com (Postfix) with ESMTPA id DC9E5328005C; Wed, 22 Jan 2020 15:23:21 -0500 (EST) From: Daniel Xu To: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, songliubraving@fb.com, yhs@fb.com, andriin@fb.com Cc: Daniel Xu , linux-kernel@vger.kernel.org, kernel-team@fb.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org Subject: [PATCH v2 bpf-next 1/3] bpf: Add bpf_perf_prog_read_branches() helper Date: Wed, 22 Jan 2020 12:22:18 -0800 Message-Id: <20200122202220.21335-2-dxu@dxuuu.xyz> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200122202220.21335-1-dxu@dxuuu.xyz> References: <20200122202220.21335-1-dxu@dxuuu.xyz> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Branch records are a CPU feature that can be configured to record certain branches that are taken during code execution. This data is particularly interesting for profile guided optimizations. perf has had branch record support for a while but the data collection can be a bit coarse grained. We (Facebook) have seen in experiments that associating metadata with branch records can improve results (after postprocessing). We generally use bpf_probe_read_*() to get metadata out of userspace. That's why bpf support for branch records is useful. Aside from this particular use case, having branch data available to bpf progs can be useful to get stack traces out of userspace applications that omit frame pointers. Signed-off-by: Daniel Xu --- include/uapi/linux/bpf.h | 13 ++++++++++++- kernel/trace/bpf_trace.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 43 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 033d90a2282d..7350c5be6158 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2885,6 +2885,16 @@ union bpf_attr { * **-EPERM** if no permission to send the *sig*. * * **-EAGAIN** if bpf program can try again. + * + * int bpf_perf_prog_read_branches(struct bpf_perf_event_data *ctx, void *buf, u32 buf_size) + * Description + * For en eBPF program attached to a perf event, retrieve the + * branch records (struct perf_branch_entry) associated to *ctx* + * and store it in the buffer pointed by *buf* up to size + * *buf_size* bytes. + * Return + * On success, number of bytes written to *buf*. On error, a + * negative value. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3004,7 +3014,8 @@ union bpf_attr { FN(probe_read_user_str), \ FN(probe_read_kernel_str), \ FN(tcp_send_ack), \ - FN(send_signal_thread), + FN(send_signal_thread), \ + FN(perf_prog_read_branches), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 19e793aa441a..24c51272a1f7 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1028,6 +1028,35 @@ static const struct bpf_func_proto bpf_perf_prog_read_value_proto = { .arg3_type = ARG_CONST_SIZE, }; +BPF_CALL_3(bpf_perf_prog_read_branches, struct bpf_perf_event_data_kern *, ctx, + void *, buf, u32, size) +{ + struct perf_branch_stack *br_stack = ctx->data->br_stack; + u32 to_copy = 0, to_clear = size; + int err = -EINVAL; + + if (unlikely(!br_stack)) + goto clear; + + to_copy = min_t(u32, br_stack->nr * sizeof(struct perf_branch_entry), size); + to_clear -= to_copy; + + memcpy(buf, br_stack->entries, to_copy); + err = to_copy; +clear: + memset(buf + to_copy, 0, to_clear); + return err; +} + +static const struct bpf_func_proto bpf_perf_prog_read_branches_proto = { + .func = bpf_perf_prog_read_branches, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_PTR_TO_UNINIT_MEM, + .arg3_type = ARG_CONST_SIZE, +}; + static const struct bpf_func_proto * pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { @@ -1040,6 +1069,8 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_stack_proto_tp; case BPF_FUNC_perf_prog_read_value: return &bpf_perf_prog_read_value_proto; + case BPF_FUNC_perf_prog_read_branches: + return &bpf_perf_prog_read_branches_proto; default: return tracing_func_proto(func_id, prog); } -- 2.21.1