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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64903C636CC for ; Mon, 13 Feb 2023 15:24:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229688AbjBMPYY (ORCPT ); Mon, 13 Feb 2023 10:24:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38126 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229588AbjBMPYX (ORCPT ); Mon, 13 Feb 2023 10:24:23 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7CD1558E; Mon, 13 Feb 2023 07:24:22 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 726D96117A; Mon, 13 Feb 2023 15:24:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E4B2C433D2; Mon, 13 Feb 2023 15:24:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1676301861; bh=U7/h4PcTTuCP83D457yoOt5YF99KmnT1gMD+1Gv9zu8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=WSeKozxjmCZSrIOiZjQSNIY7gNPXnrv+gAWu8A67aNA1zez2cpOQx6cIg0D3AIlSH nQlvKfiVfnSsYaHZdVUd0fSiWCXsr51Al0KcqqkrXlow9DNJ5PhrFdrV/zI/SLrJHw hXYAlsBbwEP+PdRZUM15/MWobMl6JVjUpCCNXtiQTuyNt+ogVYw2xdiLhf0wB04ZO5 tHLBpw8/dFOAbWoOzm4M+2oLZIZuMc/mBun77faH6TOrRY8K5rqJxzfgSe6VSvj+NX c6Njr5wlmD9YUebD4aq/Q3KywBT3VsDysa3EFDudMsHufUvCqsEWR9wN8gpd4y0yfI rnD1ub70DGIhg== Date: Tue, 14 Feb 2023 00:24:18 +0900 From: Masami Hiramatsu (Google) To: Tom Zanussi Cc: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, akpm@linux-foundation.org, zwisler@google.com, chinglinyu@google.com Subject: Re: [PATCH 1/4] tracing/histogram: Don't use strlen to find length of stacktrace variables Message-Id: <20230214002418.0103b9e765d3e5c374d2aa7d@kernel.org> In-Reply-To: <1ed6906cd9d6477ef2bd8e63c61de20a9ffe64d7.1676063532.git.zanussi@kernel.org> References: <1ed6906cd9d6477ef2bd8e63c61de20a9ffe64d7.1676063532.git.zanussi@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; 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-trace-kernel@vger.kernel.org On Fri, 10 Feb 2023 15:33:03 -0600 Tom Zanussi wrote: > Because stacktraces are saved in dynamic strings, > trace_event_raw_event_synth() uses strlen to determine the length of > the stack. Stacktraces may contain 0-bytes, though, in the saved > addresses, so the length found and passed to reserve() will be too > small. Good catch! > > Fix this by using the first unsigned long in the stack variables to > store the actual number of elements in the stack and have > trace_event_raw_event_synth() use that to determine the length of the > stack. > > Signed-off-by: Tom Zanussi > --- > kernel/trace/trace_events_hist.c | 12 ++++++++---- > kernel/trace/trace_events_synth.c | 7 ++++++- > 2 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > index 888b7a394ce5..76bd105988c6 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -3135,13 +3135,15 @@ static inline void __update_field_vars(struct tracing_map_elt *elt, > size = min(val->size, STR_VAR_LEN_MAX); > strscpy(str, val_str, size); > } else { > + char *stack_start = str + sizeof(unsigned long); > int e; > > - e = stack_trace_save((void *)str, > + e = stack_trace_save((void *)stack_start, > HIST_STACKTRACE_DEPTH, > HIST_STACKTRACE_SKIP); BTW, the size of "str" is enough to store HIST_STACKTRACE_DEPTH? In string case, size = min(val->size, STR_VAR_LEN_MAX); will limit the max size. Thank you, > if (e < HIST_STACKTRACE_DEPTH - 1) > - ((unsigned long *)str)[e] = 0; > + ((unsigned long *)stack_start)[e] = 0; > + *((unsigned long *)str) = e; > } > var_val = (u64)(uintptr_t)str; > } > @@ -5133,13 +5135,15 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data, > size = min(hist_field->size, STR_VAR_LEN_MAX); > strscpy(str, val_str, size); > } else { > + char *stack_start = str + sizeof(unsigned long); > int e; > > - e = stack_trace_save((void *)str, > + e = stack_trace_save((void *)stack_start, > HIST_STACKTRACE_DEPTH, > HIST_STACKTRACE_SKIP); > if (e < HIST_STACKTRACE_DEPTH - 1) > - ((unsigned long *)str)[e] = 0; > + ((unsigned long *)stack_start)[e] = 0; > + *((unsigned long *)str) = e; > } > hist_val = (u64)(uintptr_t)str; > } > diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c > index d458d7a0dfd7..6209b23c863f 100644 > --- a/kernel/trace/trace_events_synth.c > +++ b/kernel/trace/trace_events_synth.c > @@ -538,7 +538,12 @@ static notrace void trace_event_raw_event_synth(void *__data, > val_idx = var_ref_idx[field_pos]; > str_val = (char *)(long)var_ref_vals[val_idx]; > > - len = kern_fetch_store_strlen((unsigned long)str_val); > + if (event->dynamic_fields[i]->is_stack) { > + len = *((unsigned long *)str_val); > + len *= sizeof(unsigned long); > + } else { > + len = kern_fetch_store_strlen((unsigned long)str_val); > + } > > fields_size += len; > } > -- > 2.34.1 > -- Masami Hiramatsu (Google)