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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 0AC79C433E0 for ; Tue, 9 Jun 2020 15:27:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE18D207C3 for ; Tue, 9 Jun 2020 15:27:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591716444; bh=+G6K2bBk9m7F6q10jOAFNy2mtaj6j/CL2mVQ8BMDbMU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=yLcKATb5T/2XWwX2ZgnJwC+sa5mua86uiDYo85nItTS720ZqXc5DGeq4MdKJTAOKM xihTyPIsOBUL0zGN4A9ErF4WqWsgXA1AYm2sP1U6dLo11VnhLHkhTGRRWt+UsaWPgR kjr8IRHGLVmA7GWhiaq0XkWJGuqmTvErIv2wvVeA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730800AbgFIP1U (ORCPT ); Tue, 9 Jun 2020 11:27:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:54624 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728609AbgFIP1R (ORCPT ); Tue, 9 Jun 2020 11:27:17 -0400 Received: from quaco.ghostprotocols.net (unknown [179.97.37.151]) (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 370412072F; Tue, 9 Jun 2020 15:27:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591716436; bh=+G6K2bBk9m7F6q10jOAFNy2mtaj6j/CL2mVQ8BMDbMU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=X4ksryTqYamNQ2lrRDMtUA7tUZ9RD4TCRYardbbTPbb8w9eVNJW7yxmbVq7I01zld Gz8n7FtUfdufEaHH7kt7Lvys1aLPFHv6Kgb2y43QBDM6B6ml+ZWHsT50mlLzUG1xl9 9+4O7DwehXT1rjvzMusRo8vdqk+E5cbLZOdcmki8= Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 51C9440AFD; Tue, 9 Jun 2020 12:27:14 -0300 (-03) Date: Tue, 9 Jun 2020 12:27:14 -0300 From: Arnaldo Carvalho de Melo To: Sumanth Korikkar Cc: linux-perf-users@vger.kernel.org, bpf@vger.kernel.org, Jiri Olsa , tmricht@linux.ibm.com, heiko.carstens@de.ibm.com, mhiramat@kernel.org, iii@linux.ibm.com, Steven Rostedt , Namhyung Kim , Wang Nan , Linux Kernel Mailing List Subject: Re: [PATCH v2 2/2] perf: Fix bpf prologue generation Message-ID: <20200609152714.GE24868@kernel.org> References: <20200609081019.60234-1-sumanthk@linux.ibm.com> <20200609081019.60234-3-sumanthk@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200609081019.60234-3-sumanthk@linux.ibm.com> X-Url: http://acmel.wordpress.com Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Em Tue, Jun 09, 2020 at 10:10:19AM +0200, Sumanth Korikkar escreveu: > Issue: > bpf_probe_read is no longer available for architecture which has > overlapping address space. Hence bpf prologue generation fails > > Fix: > Use bpf_probe_read_kernel for kernel member access. For user > attribute access in kprobes, use bpf_probe_read_user. > > Other: > @user attribute was introduced in commit 1e032f7cfa14 ("perf-probe: > Add user memory access attribute support") > > Test: > 1. ulimit -l 128 ; ./perf record -e tests/bpf_sched_setscheduler.c > 2. cat tests/bpf_sched_setscheduler.c > > static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) = > (void *) 6; > static int (*bpf_probe_read_user)(void *dst, __u32 size, > const void *unsafe_ptr) = (void *) 112; > static int (*bpf_probe_read_kernel)(void *dst, __u32 size, > const void *unsafe_ptr) = (void *) 113; > > SEC("func=do_sched_setscheduler pid policy param->sched_priority@user") > int bpf_func__setscheduler(void *ctx, int err, pid_t pid, int policy, > int param) > { > char fmt[] = "prio: %ld"; > bpf_trace_printk(fmt, sizeof(fmt), param); > return 1; > } > > char _license[] SEC("license") = "GPL"; > int _version SEC("version") = LINUX_VERSION_CODE; > > 3. ./perf script > sched 305669 [000] 1614458.838675: perf_bpf_probe:func: (2904e508) > pid=261614 policy=2 sched_priority=1 > > 4. cat /sys/kernel/debug/tracing/trace > <...>-309956 [006] .... 1616098.093957: 0: prio: 1 Thanks for providing a detailed set of steps to test your patch, that is great! I added this, an alterenative way to test it, combining all the aspects in one 'perf trace' call: Committer testing: I had to add some missing headers in the bpf_sched_setscheduler.c test proggie, then instead of using record+script I used 'perf trace' to drive everything in one go: # cat bpf_sched_setscheduler.c #include #include static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) = (void *) 6; static int (*bpf_probe_read_user)(void *dst, __u32 size, const void *unsafe_ptr) = (void *) 112; static int (*bpf_probe_read_kernel)(void *dst, __u32 size, const void *unsafe_ptr) = (void *) 113; SEC("func=do_sched_setscheduler pid policy param->sched_priority@user") int bpf_func__setscheduler(void *ctx, int err, pid_t pid, int policy, int param) { char fmt[] = "prio: %ld"; bpf_trace_printk(fmt, sizeof(fmt), param); return 1; } char _license[] SEC("license") = "GPL"; int _version SEC("version") = LINUX_VERSION_CODE; # # # perf trace -e bpf_sched_setscheduler.c chrt -f 42 sleep 1 0.000 chrt/80125 perf_bpf_probe:func(__probe_ip: -1676607808, policy: 1, sched_priority: 42) # And even with backtraces :-) # perf trace -e bpf_sched_setscheduler.c/max-stack=8/ chrt -f 42 sleep 1 0.000 chrt/79805 perf_bpf_probe:func(__probe_ip: -1676607808, policy: 1, sched_priority: 42) do_sched_setscheduler ([kernel.kallsyms]) __x64_sys_sched_setscheduler ([kernel.kallsyms]) do_syscall_64 ([kernel.kallsyms]) entry_SYSCALL_64 ([kernel.kallsyms]) __GI___sched_setscheduler (/usr/lib64/libc-2.30.so) # - Arnaldo