From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 73F1A13AC0 for ; Wed, 20 Mar 2024 03:44:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710906267; cv=none; b=psUupubdlmDWQIamDw+BGRzpbcXy88aZ6Xx00InThJQASyRmi9vW5wUOTCmKuwEYPLQQa/qnWEQenX06//yZMnY1ct6OwOdpqBYpR476UiCYv2SuPOlX475LFrds8gDCIEBVKKssUKnMzOF/z31NDhllfE76vu+HJl1woXsqMuE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710906267; c=relaxed/simple; bh=333B+8NYzcR8ybiLlWgtlZDcGDpqQjlE1EWL2/4e6Y8=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=uQ0AJC95ozKMCuPCWKSyNGSPfmb084h8DHGTB+brD/7tqM92LPXvpYBXcsOfCkGBnX6LA3x3XulY4yK0XhXOnw2P18H+234XkrKfya28yJtlWHudr3VYPz+8vl5sZMcNpvZsrIQIz1RI3J6DM8Nd8QLDivMtBFKU2V1Whacp7Gk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Yd6sGDLc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Yd6sGDLc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98743C433C7; Wed, 20 Mar 2024 03:44:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1710906267; bh=333B+8NYzcR8ybiLlWgtlZDcGDpqQjlE1EWL2/4e6Y8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Yd6sGDLcreFeoREUD3oWJARew7ibyz8gYRd+Yiv0kRgQaNfV5AiZ9+NcyIgLaAF+j jeFtvIpVBv7BR3Jq7LavDoFBAg6r/nVUM6e5Fsr6ossU+zFScsULr2RTjwEJc6Z1tf 4oxmlNH9Ybt28woDm2ncQHB9RX02G1V3qzCbEjGHeQyiU5LU6q7z+PqWLtzZ9UxrQn NhA/tjR49vKDMz+egDN7HoChzBpTKKNOvhhDwVVPU0QA1T1bmrlxX1aYdEoKV1Kg1C VBUVjTp0PhluWebG0c2SmDjwc34qonKWQIL2esWPNwSZxDCjQVDiv0p7fDBl7lvtNf pPWUvKJBH2Igg== Date: Wed, 20 Mar 2024 12:44:23 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: Dan Carpenter , mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [bug report] tracing/probes: Support $argN in return probe (kprobe and fprobe) Message-Id: <20240320124423.54cdb56dc8a07378fd09de38@kernel.org> In-Reply-To: <20240319101000.4dbe0cc5@gandalf.local.home> References: <20240319101000.4dbe0cc5@gandalf.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 19 Mar 2024 10:10:00 -0400 Steven Rostedt wrote: > On Tue, 19 Mar 2024 10:19:09 +0300 > Dan Carpenter wrote: > > > Hello Masami Hiramatsu (Google), > > > > Commit 25f00e40ce79 ("tracing/probes: Support $argN in return probe > > (kprobe and fprobe)") from Mar 4, 2024 (linux-next), leads to the > > following Smatch static checker warning: > > > > kernel/trace/trace_probe.c:856 store_trace_entry_data() > > error: uninitialized symbol 'val'. > > > > kernel/trace/trace_probe.c > > 846 return; > > 847 > > 848 for (i = 0; i < earg->size; i++) { > > 849 struct fetch_insn *code = &earg->code[i]; > > 850 > > 851 switch (code->op) { > > 852 case FETCH_OP_ARG: > > 853 val = regs_get_kernel_argument(regs, code->param); > > 854 break; > > 855 case FETCH_OP_ST_EDATA: > > --> 856 *(unsigned long *)((unsigned long)edata + code->offset) = val; > > > > Probably the earg->code[i] always has FETCH_OP_ARG before > > FETCH_OP_ST_EDATA but Smatch isn't smart enough to figure that out... > > Looks that way: > > case FETCH_OP_END: > earg->code[i].op = FETCH_OP_ARG; > earg->code[i].param = argnum; > earg->code[i + 1].op = FETCH_OP_ST_EDATA; > earg->code[i + 1].offset = offset; > return offset; > > But probably should still initialize val to zero or have a WARN_ON() if > that doesn't happen. OK, let's val = 0 in the store_trace_entry_data(), but WARN_ON() in this loop is a bit strange. I think we should have a verifiler. Thank you, > > -- Steve > > > > > > 857 break; > > 858 case FETCH_OP_END: > > 859 goto end; > > 860 default: > > 861 break; > > 862 } > > 863 } > > 864 end: > > 865 return; > > 866 } > > > > regards, > > dan carpenter > -- Masami Hiramatsu (Google)