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=-9.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 D5211C43387 for ; Fri, 18 Jan 2019 15:09:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9213420883 for ; Fri, 18 Jan 2019 15:09:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547824186; bh=/MmtBO+7gMhtAOtPUjX2vsTL4/QJAU/4pvc2R8ZDAb4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=mPi1Qy8XRQ6G0DPxGCnhKQMtuRNy0BjctcT46jOruyqo6NrUbkoADwgCIcjkp2A6O LsiQKfAkEICyAAMcen1/2qK0THdOLsWn140YT4QPUj1wC0lu+Z7ALHmCzuk/s6y2iH kdD0dtDbJMe8yeClGigb6VPfwkX3oweFUPEhGFkg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727915AbfARPJo (ORCPT ); Fri, 18 Jan 2019 10:09:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:44010 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727415AbfARPJo (ORCPT ); Fri, 18 Jan 2019 10:09:44 -0500 Received: from quaco.ghostprotocols.net (unknown [189.40.100.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 843E62086D; Fri, 18 Jan 2019 15:09:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547824183; bh=/MmtBO+7gMhtAOtPUjX2vsTL4/QJAU/4pvc2R8ZDAb4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m6DcAvtWEovcEIFuwXJNQfCx9aWmVNnr2wHdhQG1H9i43pRgUb+DOBuWuRfqqQvpc 5Fak2ve0S0Fzxet0eDF8S22aGCziwweoJ6USEjwVFvkW4b6V9bPM4tHzcvS87UWwjp Zg/ngiSlakHDes5PmrT3Zk7PuVZ5M/lKwqxNTtlA= Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 073D341AB5; Fri, 18 Jan 2019 12:09:38 -0300 (-03) Date: Fri, 18 Jan 2019 12:09:38 -0300 From: Arnaldo Carvalho de Melo To: Peter Zijlstra Cc: Ingo Molnar , Alexei Starovoitov , Daniel Borkmann , Jamal Hadi Salim , Clark Williams , Linux Kernel Mailing List , Linux Networking Development Mailing List Subject: Re: [PATCH/RFC] Make perf_event_open() propagate errors for use in bpf_perf_event_open() Message-ID: <20190118150938.GN5823@kernel.org> References: <20190111155538.GX22483@kernel.org> <20190118145237.GD27931@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190118145237.GD27931@hirez.programming.kicks-ass.net> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, Jan 18, 2019 at 03:52:37PM +0100, Peter Zijlstra escreveu: > On Fri, Jan 11, 2019 at 12:55:38PM -0300, Arnaldo Carvalho de Melo wrote: > > Hi Peter, > > > > bpf_perf_event_open() already returns a value, but if > > perf_event_output's output_begin (mostly perf_output_begin) fails, > > the only way to know about that is looking before/after the rb->lost, > > right? > > > > For ring buffer users that is ok, we'll get a PERF_RECORD_LOST, > > etc, but for BPF programs it would be convenient to get that -ENOSPC and > > do some fallback, whatever makes sense, like in my augmented_syscalls > > stuff for 'perf trace', i.e. don't augment it (i.e. push stuff at the > > end of the normal payload), just don't filter the > > raw_syscalls:sys_enter, 'perf trace' will get the enter syscall enter > > event without the pointer dereference at the end, etc, warn the user but > > don't lose a syscall in the strace-like output. > > > > What do you think? Am I missing something? Probably ;-) > > Seems ok to do this. Can I take that as an Acked-by? This is the patch with a cset comment, if you're ok, I'll put it together with Song's PERF_RECORD_{KSYMBOL,BPF_EVENT} into my perf/core branch and send to Ingo, please advise, - Arnaldo commit 1b3b3dee572d0b77a316ab6715091201be6832de Author: Arnaldo Carvalho de Melo Date: Fri Jan 11 13:20:20 2019 -0300 perf: Make perf_event_output() propagate the output() return For the original mode of operation it isn't needed, since we report back errors via PERF_RECORD_LOST records in the ring buffer, but for use in bpf_perf_event_output() it is convenient to return the errors, basically -ENOSPC. Currently bpf_perf_event_output() returns an error indication, the last thing it does, which is to push it to the ring buffer is that can fail and if so, this failure won't be reported back to its users, fix it. Reported-by: Jamal Hadi Salim Tested-by: Jamal Hadi Salim Cc: Adrian Hunter Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Link: https://lkml.kernel.org/r/20190111155538.GX22483@kernel.org Signed-off-by: Arnaldo Carvalho de Melo diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 1d5c551a5add..9ed2af2abd6d 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -978,9 +978,9 @@ extern void perf_event_output_forward(struct perf_event *event, extern void perf_event_output_backward(struct perf_event *event, struct perf_sample_data *data, struct pt_regs *regs); -extern void perf_event_output(struct perf_event *event, - struct perf_sample_data *data, - struct pt_regs *regs); +extern int perf_event_output(struct perf_event *event, + struct perf_sample_data *data, + struct pt_regs *regs); static inline bool is_default_overflow_handler(struct perf_event *event) diff --git a/kernel/events/core.c b/kernel/events/core.c index 3cd13a30f732..dcbb2b508034 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6489,7 +6489,7 @@ void perf_prepare_sample(struct perf_event_header *header, data->phys_addr = perf_virt_to_phys(data->addr); } -static __always_inline void +static __always_inline int __perf_event_output(struct perf_event *event, struct perf_sample_data *data, struct pt_regs *regs, @@ -6499,13 +6499,15 @@ __perf_event_output(struct perf_event *event, { struct perf_output_handle handle; struct perf_event_header header; + int err; /* protect the callchain buffers */ rcu_read_lock(); perf_prepare_sample(&header, data, event, regs); - if (output_begin(&handle, event, header.size)) + err = output_begin(&handle, event, header.size); + if (err) goto exit; perf_output_sample(&handle, &header, data, event); @@ -6514,6 +6516,7 @@ __perf_event_output(struct perf_event *event, exit: rcu_read_unlock(); + return err; } void @@ -6532,12 +6535,12 @@ perf_event_output_backward(struct perf_event *event, __perf_event_output(event, data, regs, perf_output_begin_backward); } -void +int perf_event_output(struct perf_event *event, struct perf_sample_data *data, struct pt_regs *regs) { - __perf_event_output(event, data, regs, perf_output_begin); + return __perf_event_output(event, data, regs, perf_output_begin); } /* diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 8b068adb9da1..088c2032ceaf 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -431,8 +431,7 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map, if (unlikely(event->oncpu != cpu)) return -EOPNOTSUPP; - perf_event_output(event, sd, regs); - return 0; + return perf_event_output(event, sd, regs); } BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map, diff --git a/tools/perf/examples/bpf/augmented_raw_syscalls.c b/tools/perf/examples/bpf/augmented_raw_syscalls.c index 53c233370fae..9e9d4c66e53c 100644 --- a/tools/perf/examples/bpf/augmented_raw_syscalls.c +++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c @@ -141,8 +141,8 @@ int sys_enter(struct syscall_enter_args *args) len = sizeof(augmented_args.args); } - perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len); - return 0; + /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ + return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, &augmented_args, len); } SEC("raw_syscalls:sys_exit") diff --git a/tools/perf/examples/bpf/augmented_syscalls.c b/tools/perf/examples/bpf/augmented_syscalls.c index 2ae44813ef2d..b7dba114e36c 100644 --- a/tools/perf/examples/bpf/augmented_syscalls.c +++ b/tools/perf/examples/bpf/augmented_syscalls.c @@ -55,9 +55,9 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args) \ len -= sizeof(augmented_args.filename.value) - augmented_args.filename.size; \ len &= sizeof(augmented_args.filename.value) - 1; \ } \ - perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ - &augmented_args, len); \ - return 0; \ + /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ \ + return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ + &augmented_args, len); \ } \ int syscall_exit(syscall)(struct syscall_exit_args *args) \ { \ @@ -125,10 +125,10 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args) \ /* addrlen = augmented_args.args.addrlen; */ \ /* */ \ probe_read(&augmented_args.addr, addrlen, args->addr_ptr); \ - perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ - &augmented_args, \ - sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen); \ - return 0; \ + /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ \ + return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ + &augmented_args, \ + sizeof(augmented_args) - sizeof(augmented_args.addr) + addrlen);\ } \ int syscall_exit(syscall)(struct syscall_exit_args *args) \ { \ diff --git a/tools/perf/examples/bpf/etcsnoop.c b/tools/perf/examples/bpf/etcsnoop.c index b59e8812ee8c..550e69c2e8d1 100644 --- a/tools/perf/examples/bpf/etcsnoop.c +++ b/tools/perf/examples/bpf/etcsnoop.c @@ -49,11 +49,11 @@ int syscall_enter(syscall)(struct syscall_enter_##syscall##_args *args) \ args->filename_ptr); \ if (__builtin_memcmp(augmented_args.filename.value, etc, 4) != 0) \ return 0; \ - perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ - &augmented_args, \ - (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \ - augmented_args.filename.size)); \ - return 0; \ + /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ \ + return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, \ + &augmented_args, \ + (sizeof(augmented_args) - sizeof(augmented_args.filename.value) + \ + augmented_args.filename.size)); \ } struct syscall_enter_openat_args {