From patchwork Wed Jul 10 15:25:49 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 11038697 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8A3CD6C5 for ; Wed, 10 Jul 2019 15:25:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7E0BC287D4 for ; Wed, 10 Jul 2019 15:25:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 727F3289F1; Wed, 10 Jul 2019 15:25:56 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 0E0A2289C6 for ; Wed, 10 Jul 2019 15:25:56 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 1FDDB6E101; Wed, 10 Jul 2019 15:25:53 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by gabe.freedesktop.org (Postfix) with ESMTPS id 97A166E0E4; Wed, 10 Jul 2019 15:25:51 +0000 (UTC) Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 E2B9F20645; Wed, 10 Jul 2019 15:25:50 +0000 (UTC) Date: Wed, 10 Jul 2019 11:25:49 -0400 From: Steven Rostedt To: Ville =?utf-8?b?U3lyasOkbMOk?= , Maarten Lankhorst Subject: Need to remove char pointers from trace events Message-ID: <20190710112549.0366bb03@gandalf.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Airlie , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, LKML Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP I was doing a bit of an audit on trace events and found this: # cat /debug/tracing/events/i915/intel_disable_plane/format name: intel_disable_plane ID: 1358 format: field:unsigned short common_type; offset:0; size:2; signed:0; field:unsigned char common_flags; offset:2; size:1; signed:0; field:unsigned char common_preempt_count; offset:3; size:1; signed:0; field:int common_pid; offset:4; size:4; signed:1; field:enum pipe pipe; offset:8; size:4; signed:1; field:const char * name; offset:16; size:8; signed:0; field:u32 frame; offset:24; size:4; signed:0; field:u32 scanline; offset:28; size:4; signed:0; print fmt: "pipe %c, plane %s, frame=%u, scanline=%u", ((REC->pipe) + 'A'), REC->name, REC->frame, REC->scanline Same goes for intel_update_plane. The problem here is: field:const char * name; offset:16; size:8; signed:0; print fmt: "pipe %c, plane %s, frame=%u, scanline=%u", ((REC->pipe) + 'A'), REC->name, REC->frame, REC->scanline Where the TRACE_EVENT() macro has: TP_fast_assign( __entry->pipe = crtc->pipe; __entry->name = plane->name; __entry->frame = crtc->base.dev->driver->get_vblank_counter(crtc->base.dev, crtc->pipe); __entry->scanline = intel_get_crtc_scanline(crtc); ), TP_printk("pipe %c, plane %s, frame=%u, scanline=%u", pipe_name(__entry->pipe), __entry->name, __entry->frame, __entry->scanline) The issue here is that you record a pointer address to "plane->name" and then sometime in the distant future access that same address. There's usually no guarantee that the contents at that address will exist when the buffer is read. The proper way to record strings, is to record the string into the ring buffer itself, and not rely on it existing hours or days later. I recommend the following patch: -- Steve diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h index 12893304c8f8..d41d914a16ca 100644 --- a/drivers/gpu/drm/i915/i915_trace.h +++ b/drivers/gpu/drm/i915/i915_trace.h @@ -298,16 +298,16 @@ TRACE_EVENT(intel_update_plane, TP_STRUCT__entry( __field(enum pipe, pipe) - __field(const char *, name) __field(u32, frame) __field(u32, scanline) __array(int, src, 4) __array(int, dst, 4) + __string(name, plane->name) ), TP_fast_assign( + __assign_str(name, plane->name); __entry->pipe = crtc->pipe; - __entry->name = plane->name; __entry->frame = crtc->base.dev->driver->get_vblank_counter(crtc->base.dev, crtc->pipe); __entry->scanline = intel_get_crtc_scanline(crtc); @@ -316,7 +316,7 @@ TRACE_EVENT(intel_update_plane, ), TP_printk("pipe %c, plane %s, frame=%u, scanline=%u, " DRM_RECT_FP_FMT " -> " DRM_RECT_FMT, - pipe_name(__entry->pipe), __entry->name, + pipe_name(__entry->pipe), __get_str(name), __entry->frame, __entry->scanline, DRM_RECT_FP_ARG((const struct drm_rect *)__entry->src), DRM_RECT_ARG((const struct drm_rect *)__entry->dst)) @@ -328,21 +328,21 @@ TRACE_EVENT(intel_disable_plane, TP_STRUCT__entry( __field(enum pipe, pipe) - __field(const char *, name) __field(u32, frame) __field(u32, scanline) + __string(name, plane->name) ), TP_fast_assign( + __assign_str(name, plane->name); __entry->pipe = crtc->pipe; - __entry->name = plane->name; __entry->frame = crtc->base.dev->driver->get_vblank_counter(crtc->base.dev, crtc->pipe); __entry->scanline = intel_get_crtc_scanline(crtc); ), TP_printk("pipe %c, plane %s, frame=%u, scanline=%u", - pipe_name(__entry->pipe), __entry->name, + pipe_name(__entry->pipe), __get_str(name), __entry->frame, __entry->scanline) );