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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 1DF8FC433DB for ; Wed, 17 Feb 2021 12:42:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB9D264E45 for ; Wed, 17 Feb 2021 12:42:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232716AbhBQMl7 (ORCPT ); Wed, 17 Feb 2021 07:41:59 -0500 Received: from mail.kernel.org ([198.145.29.99]:54094 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232663AbhBQMlu (ORCPT ); Wed, 17 Feb 2021 07:41:50 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 855CC64E42; Wed, 17 Feb 2021 12:41:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613565669; bh=pk2DzGEAD1eovee2oFpVglKFrPVDtINUHjBP2+2ZhdM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=FebzngLcpSFbOy68kRsF9MmFmSVvoTs+3+fXZ6absW5W/FOdEB0/im9NWtv4an18+ smkVseWnfKx4/oKylooBezQUCBJtPTpG7NSsacvZM7K0dTVfcZjNEsFKbe7mcT5IZs LLrLgllBjGT44MkYKDmD/+r9TgnOpim9jrAwRa3JLIeXfPZEMkIbA81i5kneOsx0I8 fBz5ragq5N0r123fUYd+/8P7iG7Y3wKNTDZDzFhVO9OlLyAy0qw+Z2XHdVfSF7j+jL Tzngai51diiN+1yVUgvLTb7Y9dUJXlD5LSjPdi/lRnXHnzcQJjP52T6jlc29RERWsN CQ2+RBfKKLllg== Date: Wed, 17 Feb 2021 21:40:58 +0900 From: Masami Hiramatsu To: Jianlin Lv Cc: peterz@infradead.org, mingo@redhat.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, nathan@kernel.org, ndesaulniers@google.com, fche@redhat.com, irogers@google.com, sumanthk@linux.ibm.com, iecedge@gmail.com, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: Re: [PATCH v3] perf probe: fix kretprobe issue caused by GCC bug Message-Id: <20210217214058.0307cf0ac87f4feb58ab5e4d@kernel.org> In-Reply-To: <20210216103026.323157-1-Jianlin.Lv@arm.com> References: <20210216103026.323157-1-Jianlin.Lv@arm.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 16 Feb 2021 18:30:26 +0800 Jianlin Lv wrote: > Perf failed to add kretprobe event with debuginfo of vmlinux which is > compiled by gcc with -fpatchable-function-entry option enabled. > The same issue with kernel module. > > Issue: > > # perf probe -v 'kernel_clone%return $retval' > ...... > Writing event: r:probe/kernel_clone__return _text+599624 $retval > Failed to write event: Invalid argument > Error: Failed to add events. Reason: Invalid argument (Code: -22) > > # cat /sys/kernel/debug/tracing/error_log > [156.75] trace_kprobe: error: Retprobe address must be an function entry > Command: r:probe/kernel_clone__return _text+599624 $retval > ^ > > # llvm-dwarfdump vmlinux |grep -A 10 -w 0x00df2c2b > 0x00df2c2b: DW_TAG_subprogram > DW_AT_external (true) > DW_AT_name ("kernel_clone") > DW_AT_decl_file ("/home/code/linux-next/kernel/fork.c") > DW_AT_decl_line (2423) > DW_AT_decl_column (0x07) > DW_AT_prototyped (true) > DW_AT_type (0x00dcd492 "pid_t") > DW_AT_low_pc (0xffff800010092648) > DW_AT_high_pc (0xffff800010092b9c) > DW_AT_frame_base (DW_OP_call_frame_cfa) > > # cat /proc/kallsyms |grep kernel_clone > ffff800010092640 T kernel_clone > # readelf -s vmlinux |grep -i kernel_clone > 183173: ffff800010092640 1372 FUNC GLOBAL DEFAULT 2 kernel_clone > > # objdump -d vmlinux |grep -A 10 -w \: > ffff800010092640 : > ffff800010092640: d503201f nop > ffff800010092644: d503201f nop > ffff800010092648: d503233f paciasp > ffff80001009264c: a9b87bfd stp x29, x30, [sp, #-128]! > ffff800010092650: 910003fd mov x29, sp > ffff800010092654: a90153f3 stp x19, x20, [sp, #16] > > The entry address of kernel_clone converted by debuginfo is _text+599624 > (0x92648), which is consistent with the value of DW_AT_low_pc attribute. > But the symbolic address of kernel_clone from /proc/kallsyms is > ffff800010092640. > > This issue is found on arm64, -fpatchable-function-entry=2 is enabled when > CONFIG_DYNAMIC_FTRACE_WITH_REGS=y; > Just as objdump displayed the assembler contents of kernel_clone, > GCC generate 2 NOPs at the beginning of each function. > > kprobe_on_func_entry detects that (_text+599624) is not the entry address > of the function, which leads to the failure of adding kretprobe event. > > kprobe_on_func_entry > ->_kprobe_addr > ->kallsyms_lookup_size_offset > ->arch_kprobe_on_func_entry // FALSE > > The cause of the issue is that the first instruction in the compile unit > indicated by DW_AT_low_pc does not include NOPs. > This issue exists in all gcc versions that support > -fpatchable-function-entry option. > > I have reported it to the GCC community: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98776 > > Currently arm64 and PA-RISC may enable fpatchable-function-entry option. > The kernel compiled with clang does not have this issue. > > FIX: > > This GCC issue only cause the registration failure of the kretprobe event > which doesn't need debuginfo. So, stop using debuginfo for retprobe. > map will be used to query the probe function address. > > Signed-off-by: Jianlin Lv Looks good to me. Acked-by: Masami Hiramatsu Thank you! > --- > v2: stop using debuginfo for retprobe, and update changelog. > v3: Update changelog, fixed misuse of --- marker. > --- > tools/perf/util/probe-event.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index 8eae2afff71a..a59d3268adb0 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -894,6 +894,16 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev, > struct debuginfo *dinfo; > int ntevs, ret = 0; > > + /* Workaround for gcc #98776 issue. > + * Perf failed to add kretprobe event with debuginfo of vmlinux which is > + * compiled by gcc with -fpatchable-function-entry option enabled. The > + * same issue with kernel module. The retprobe doesn`t need debuginfo. > + * This workaround solution use map to query the probe function address > + * for retprobe event. > + */ > + if (pev->point.retprobe) > + return 0; > + > dinfo = open_debuginfo(pev->target, pev->nsi, !need_dwarf); > if (!dinfo) { > if (need_dwarf) > -- > 2.25.1 > -- Masami Hiramatsu