Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755023AbbDONXL (ORCPT ); Wed, 15 Apr 2015 09:23:11 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:35214 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751675AbbDONXD (ORCPT ); Wed, 15 Apr 2015 09:23:03 -0400 Message-ID: <552E661D.5060502@oracle.com> Date: Wed, 15 Apr 2015 09:22:37 -0400 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Steven Rostedt , linux-kernel@vger.kernel.org CC: Ingo Molnar , Andrew Morton , Arnaldo Carvalho de Melo , Namhyung Kim , Masami Hiramatsu , Mathieu Desnoyers , Guilherme Cox , Tony Luck , Xie XiuQi Subject: Re: [PATCH 07/18 v3] tracing: Add TRACE_DEFINE_ENUM() macro to map enums to their values References: <20150403013802.220157513@goodmis.org> <20150403014123.997385206@goodmis.org> In-Reply-To: <20150403014123.997385206@goodmis.org> Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5101 Lines: 104 On 04/02/2015 09:38 PM, Steven Rostedt wrote: > From: "Steven Rostedt (Red Hat)" > > Several tracepoints use the helper functions __print_symbolic() or > __print_flags() and pass in enums that do the mapping between the > binary data stored and the value to print. This works well for reading > the ASCII trace files, but when the data is read via userspace tools > such as perf and trace-cmd, the conversion of the binary value to a > human string format is lost if an enum is used, as userspace does not > have access to what the ENUM is. > > For example, the tracepoint trace_tlb_flush() has: > > __print_symbolic(REC->reason, > { TLB_FLUSH_ON_TASK_SWITCH, "flush on task switch" }, > { TLB_REMOTE_SHOOTDOWN, "remote shootdown" }, > { TLB_LOCAL_SHOOTDOWN, "local shootdown" }, > { TLB_LOCAL_MM_SHOOTDOWN, "local mm shootdown" }) > > Which maps the enum values to the strings they represent. But perf and > trace-cmd do no know what value TLB_LOCAL_MM_SHOOTDOWN is, and would > not be able to map it. > > With TRACE_DEFINE_ENUM(), developers can place these in the event header > files and ftrace will convert the enums to their values: > > By adding: > > TRACE_DEFINE_ENUM(TLB_FLUSH_ON_TASK_SWITCH); > TRACE_DEFINE_ENUM(TLB_REMOTE_SHOOTDOWN); > TRACE_DEFINE_ENUM(TLB_LOCAL_SHOOTDOWN); > TRACE_DEFINE_ENUM(TLB_LOCAL_MM_SHOOTDOWN); > > $ cat /sys/kernel/debug/tracing/events/tlb/tlb_flush/format > [...] > __print_symbolic(REC->reason, > { 0, "flush on task switch" }, > { 1, "remote shootdown" }, > { 2, "local shootdown" }, > { 3, "local mm shootdown" }) > > The above is what userspace expects to see, and tools do not need to > be modified to parse them. > > Cc: Guilherme Cox > Cc: Tony Luck > Cc: Xie XiuQi > Signed-off-by: Steven Rostedt > --- Hey Steven, I'm seeing the following when booting: [ 10.678876] BUG: KASan: out of bounds access in trace_event_enum_update+0xb1d/0xb70 at addr ffffffffa6c4dc68 [ 10.680222] Read of size 1 by task swapper/0/1 [ 10.680222] Address belongs to variable print_fmt_9p_client_req+0x848/0x880 [ 10.680222] CPU: 19 PID: 1 Comm: swapper/0 Not tainted 4.0.0-next-20150415-sasha-00064-g7858a62 #2147 [ 10.680222] ffffffffa6c4dc68 00000000915e69dc ffff88004e8efb18 ffffffffa1b4f7a6 [ 10.680222] 0000000000000000 ffff88004e8efba8 ffff88004e8efb98 ffffffff976544b1 [ 10.680222] ffff88004e8efbd8 ffffffff990134a4 0000000000000282 ffffffffa444e381 [ 10.680222] Call Trace: [ 10.680222] dump_stack (lib/dump_stack.c:52) [ 10.680222] kasan_report_error (mm/kasan/report.c:132 mm/kasan/report.c:193) [ 10.680222] ? snprintf (lib/vsprintf.c:2069) [ 10.680222] ? vsprintf (lib/vsprintf.c:2069) [ 10.680222] ? trace_event_enum_update (kernel/trace/trace_events.c:1807) [ 10.680222] __asan_report_load1_noabort (mm/kasan/report.c:230 mm/kasan/report.c:248) [ 10.680222] ? trace_event_enum_update (kernel/trace/trace_events.c:1807) [ 10.680222] trace_event_enum_update (kernel/trace/trace_events.c:1807) [ 10.680222] tracer_init_tracefs (kernel/trace/trace.c:4122 kernel/trace/trace.c:6750 kernel/trace/trace.c:6848) [ 10.680222] ? clear_boot_tracer (kernel/trace/trace.c:6825) [ 10.680222] ? clear_boot_tracer (kernel/trace/trace.c:6825) [ 10.680222] do_one_initcall (init/main.c:788) [ 10.680222] ? try_to_run_init_process (init/main.c:777) [ 10.680222] ? parse_args (kernel/params.c:131 kernel/params.c:216) [ 10.680222] ? trace_hardirqs_on (kernel/locking/lockdep.c:2630) [ 10.680222] kernel_init_freeable (init/main.c:853 init/main.c:861 init/main.c:880 init/main.c:1001) [ 10.680222] ? local_clock (kernel/sched/clock.c:392) [ 10.680222] ? start_kernel (init/main.c:973) [ 10.680222] ? finish_task_switch (kernel/sched/core.c:2249) [ 10.680222] ? finish_task_switch (include/linux/tick.h:186 kernel/sched/core.c:2263) [ 10.680222] ? finish_task_switch (kernel/sched/sched.h:1077 kernel/sched/core.c:2245) [ 10.680222] ? rest_init (init/main.c:928) [ 10.680222] kernel_init (init/main.c:933) [ 10.680222] ? rest_init (init/main.c:928) [ 10.680222] ret_from_fork (arch/x86/kernel/entry_64.S:631) [ 10.680222] ? rest_init (init/main.c:928) [ 10.680222] Memory state around the buggy address: [ 10.680222] ffffffffa6c4db00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 10.680222] ffffffffa6c4db80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 10.680222] >ffffffffa6c4dc00: 00 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa [ 10.680222] ^ [ 10.680222] ffffffffa6c4dc80: fa fa fa fa 00 00 00 00 fa fa fa fa 00 00 00 00 [ 10.680222] ffffffffa6c4dd00: fa fa fa fa 00 00 00 00 fa fa fa fa 00 00 00 00 Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/