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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 9144FC433DF for ; Mon, 8 Jun 2020 16:43:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E5F6206A4 for ; Mon, 8 Jun 2020 16:43:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591634613; bh=poD2j79xftnkyVeVqoS2PoHl9GnQGkmyzAxMsg36dZc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=vh+HMsT6KIN+BF6MF1qtCVpmeLZd6xPfW3RFduP/ERFxmeh/sKJF13CSK2T8KIDs/ i/2l78mkdx94ZvrXs2vIWKae16fneZJcVE/ezweQpLRLUZkqhI6ns/Hz56sVLxeZ3C iPXoFU+iy81VdAlFBVO2lwo0kOou+Wkwo5sneMnQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730583AbgFHQnc (ORCPT ); Mon, 8 Jun 2020 12:43:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:47522 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730443AbgFHQnb (ORCPT ); Mon, 8 Jun 2020 12:43:31 -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 5C719206A4; Mon, 8 Jun 2020 16:43:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591634609; bh=poD2j79xftnkyVeVqoS2PoHl9GnQGkmyzAxMsg36dZc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RYbrOqLb/OiVLfd+eqEBq2dpFNz9zufzclJoTzUwBuF+KtJ/aHIWVtkCt9rzLFqK6 rzfGZbkoKpBcMLo53KgKfHWkSvH+pdJDxjJ1T0bxjAuEw9Pz3mR3JBi7rPXAUzaSGb FqpkMqdRXxKCnVGk2fm0tAoY7yK5UhxhVniAfrEw= Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 7B29540AFD; Mon, 8 Jun 2020 13:43:27 -0300 (-03) Date: Mon, 8 Jun 2020 13:43:27 -0300 From: Arnaldo Carvalho de Melo To: Sumanth Korikkar Cc: linux-perf-users@vger.kernel.org, bpf@vger.kernel.org, jolsa@redhat.com, tmricht@linux.ibm.com, heiko.carstens@de.ibm.com, mhiramat@kernel.org, iii@linux.ibm.com Subject: Re: [PATCH] perf: Fix bpf prologue generation, user attribute access in kprobes Message-ID: <20200608164327.GD3073@kernel.org> References: <20200604091028.101569-1-sumanthk@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200604091028.101569-1-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 Thu, Jun 04, 2020 at 11:10:28AM +0200, Sumanth Korikkar escreveu: > Issues: > 1. bpf_probe_read is no longer available for architecture which has > overlapping address space. Hence bpf prologue generation fails > 2. perf probe -a 'do_sched_setscheduler pid policy > param->sched_priority@user' did not work before. This looks super nice, thanks for working on this! But please split this into multiple patches, one for the 'perf probe' part, add the Acked-by provided by Masami to that one, and the other for the part fixing the lack of bpf_probe_read(), ok? Thanks! - Arnaldo > Fixes: > 1. Use bpf_probe_read_kernel for kernel member access. For user > attribute access in kprobes, bpf_probe_read_user is utilized > 2. Make (perf probe -a 'do_sched_setscheduler pid policy > param->sched_priority@user') output equivalent to ftrace > ('p:probe/do_sched_setscheduler _text+517384 pid=%r2:s32 > policy=%r3:s32 sched_priority=+u0 (%r4):s32' > kprobe_events) > > Other: > 1. Right now, __match_glob() does not handle [u]. For now, use > *u]. > 2. @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 > > 5. bpf_probe_read_user is used when @user attribute is used. Otherwise, > defaults to bpf_probe_read_kernel > > 6. ./perf test bpf (null_lseek - kernel member access) > 42: BPF filter : > 42.1: Basic BPF filtering : Ok > 42.2: BPF pinning : Ok > 42.3: BPF prologue generation : Ok > 42.4: BPF relocation checker : FAILED! > > Signed-off-by: Sumanth Korikkar > Reviewed-by: Thomas Richter > --- > tools/perf/util/bpf-prologue.c | 14 ++++++++++---- > tools/perf/util/probe-event.c | 7 +++++-- > tools/perf/util/probe-file.c | 2 +- > 3 files changed, 16 insertions(+), 7 deletions(-) > > diff --git a/tools/perf/util/bpf-prologue.c b/tools/perf/util/bpf-prologue.c > index b020a8678eb9..9887ae09242d 100644 > --- a/tools/perf/util/bpf-prologue.c > +++ b/tools/perf/util/bpf-prologue.c > @@ -142,7 +142,8 @@ static int > gen_read_mem(struct bpf_insn_pos *pos, > int src_base_addr_reg, > int dst_addr_reg, > - long offset) > + long offset, > + int probeid) > { > /* mov arg3, src_base_addr_reg */ > if (src_base_addr_reg != BPF_REG_ARG3) > @@ -159,7 +160,7 @@ gen_read_mem(struct bpf_insn_pos *pos, > ins(BPF_MOV64_REG(BPF_REG_ARG1, dst_addr_reg), pos); > > /* Call probe_read */ > - ins(BPF_EMIT_CALL(BPF_FUNC_probe_read), pos); > + ins(BPF_EMIT_CALL(probeid), pos); > /* > * Error processing: if read fail, goto error code, > * will be relocated. Target should be the start of > @@ -241,7 +242,7 @@ static int > gen_prologue_slowpath(struct bpf_insn_pos *pos, > struct probe_trace_arg *args, int nargs) > { > - int err, i; > + int err, i, probeid; > > for (i = 0; i < nargs; i++) { > struct probe_trace_arg *arg = &args[i]; > @@ -276,11 +277,16 @@ gen_prologue_slowpath(struct bpf_insn_pos *pos, > stack_offset), pos); > > ref = arg->ref; > + probeid = BPF_FUNC_probe_read_kernel; > while (ref) { > pr_debug("prologue: arg %d: offset %ld\n", > i, ref->offset); > + > + if (ref->user_access) > + probeid = BPF_FUNC_probe_read_user; > + > err = gen_read_mem(pos, BPF_REG_3, BPF_REG_7, > - ref->offset); > + ref->offset, probeid); > if (err) { > pr_err("prologue: failed to generate probe_read function call\n"); > goto errout; > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index eea132f512b0..7cdb66ef3baa 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -1565,7 +1565,7 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg) > } > > tmp = strchr(str, '@'); > - if (tmp && tmp != str && strcmp(tmp + 1, "user")) { /* user attr */ > + if (tmp && tmp != str && !strcmp(tmp + 1, "user")) { /* user attr */ > if (!user_access_is_supported()) { > semantic_error("ftrace does not support user access\n"); > return -EINVAL; > @@ -1986,7 +1986,10 @@ static int __synthesize_probe_trace_arg_ref(struct probe_trace_arg_ref *ref, > if (depth < 0) > return depth; > } > - err = strbuf_addf(buf, "%+ld(", ref->offset); > + if (ref->user_access) > + err = strbuf_addf(buf, "%s%ld(", "+u", ref->offset); > + else > + err = strbuf_addf(buf, "%+ld(", ref->offset); > return (err < 0) ? err : depth; > } > > diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c > index 8c852948513e..064b63a6a3f3 100644 > --- a/tools/perf/util/probe-file.c > +++ b/tools/perf/util/probe-file.c > @@ -1044,7 +1044,7 @@ static struct { > DEFINE_TYPE(FTRACE_README_PROBE_TYPE_X, "*type: * x8/16/32/64,*"), > DEFINE_TYPE(FTRACE_README_KRETPROBE_OFFSET, "*place (kretprobe): *"), > DEFINE_TYPE(FTRACE_README_UPROBE_REF_CTR, "*ref_ctr_offset*"), > - DEFINE_TYPE(FTRACE_README_USER_ACCESS, "*[u]*"), > + DEFINE_TYPE(FTRACE_README_USER_ACCESS, "*u]*"), > DEFINE_TYPE(FTRACE_README_MULTIPROBE_EVENT, "*Create/append/*"), > DEFINE_TYPE(FTRACE_README_IMMEDIATE_VALUE, "*\\imm-value,*"), > }; > -- > 2.25.4 > -- - Arnaldo