From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753471AbcBZNCH (ORCPT ); Fri, 26 Feb 2016 08:02:07 -0500 Received: from mail-pf0-f196.google.com ([209.85.192.196]:33652 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751376AbcBZNCF (ORCPT ); Fri, 26 Feb 2016 08:02:05 -0500 From: Taeung Song Subject: Re: [PATCH v2 1/3] tracing/syscalls: Rename variable 'nr' to 'syscall_nr' To: Arnaldo Carvalho de Melo References: <1456421937-16840-1-git-send-email-treeze.taeung@gmail.com> <20160225175710.GP8720@kernel.org> <56CF4877.8000107@gmail.com> <20160225184234.GQ8720@kernel.org> <56D0440E.1000605@gmail.com> Cc: Steven Rostedt , Ingo Molnar , Jiri Olsa , Namhyung Kim , linux-kernel@vger.kernel.org, Thomas Gleixner , Lai Jiangshan Message-ID: <56D04CC7.4010605@gmail.com> Date: Fri, 26 Feb 2016 22:01:59 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <56D0440E.1000605@gmail.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/26/2016 09:24 PM, Taeung Song wrote: > Hi, Arnaldo > > On 02/26/2016 03:42 AM, Arnaldo Carvalho de Melo wrote: >> Em Fri, Feb 26, 2016 at 03:31:19AM +0900, Taeung Song escreveu: >>> Hi, Arnaldo >>> >>> On 02/26/2016 02:57 AM, Arnaldo Carvalho de Melo wrote: >>>> Em Fri, Feb 26, 2016 at 02:38:57AM +0900, Taeung Song escreveu: >>>>> There is a problem about duplicated variable name i.e. >>>>> # cat >>>>> /sys/kernel/debug/tracing/events/syscalls/sys_enter_io_getevents/format >>>>> >>>>> name: sys_enter_io_getevents >>>>> ID: 739 >>>>> 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:int nr; offset:8; size:4; >>>>> signed:1; >>>>> field:aio_context_t ctx_id; offset:16; size:8; >>>>> signed:0; >>>>> field:long min_nr; offset:24; size:8; >>>>> signed:0; >>>>> field:long nr; offset:32; size:8; >>>>> signed:0; >>>>> field:struct io_event * events; offset:40; size:8; >>>>> signed:0; >>>>> field:struct timespec * timeout; offset:48; size:8; >>>>> signed:0; >>>>> >>>>> print fmt: "ctx_id: 0x%08lx, min_nr: 0x%08lx, nr: >>>>> 0x%08lx, >>>>> events: 0x%08lx, timeout: 0x%08lx", >>>>> ((unsigned long)(REC->ctx_id)), >>>>> ((unsigned long)(REC->min_nr)), ((unsigned >>>>> long)(REC->nr)), >>>>> ((unsigned long)(REC->events)), ((unsigned >>>>> long)(REC->timeout)) >>>>> >>>>> As above 'int nr;' and 'long nr;' variables have >>>>> duplicated name so problems are occurred in perf-script i.e. >>>>> >>>>> # perf record -e syscalls:* >>>>> # perf script -g python >>>>> # perf script -s perf-script.py >>>>> File "perf-script.py", line 8694 >>>>> def syscalls__sys_enter_io_getevents(event_name, context, >>>>> common_cpu, >>>>> SyntaxError: duplicate argument 'nr' in function definition >>>>> Error running python script perf-script.py >>>> >>>> Please test this with 'perf trace', which this patch breaks, this patch >>>> should make it understand this 3rd variation of the non common list of >>>> fields in syscall tracepoints: >>> >>> OK, I will test it. >>> But IMHO, I think the bottom change has a problem. >>> Because sys_enter_io_getevent() has a argument 'long nr'. >> >> It doesn't matter >> >>> So this if statement must not have strcmp(sc->args->name, "nr") == 0. >> >> This is checking for the first variable, if that has that name, it >> should be discarded, as in the past it wasn't there, so for the tool to >> work on kernels with "nr" as the first (for the syscall number) variable >> and for kernels without it, we must check and discard. >> >> Now we must check and discard the first "nr" (for kernels with this >> meaning the syscall number) and also if it is called "syscall_nr"). >> The other fields are taken as the syscall arguments, in the order that >> they come, that is what what we will match with what is in the >> raw_syscalls:sys_enter args array: >> >> [root@jouet ~]# cat >> /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/format >> name: sys_enter >> ID: 17 >> 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:long id; offset:8; size:8; signed:1; >> field:unsigned long args[6]; offset:16; size:48; signed:0; >> >> print fmt: "NR %ld (%lx, %lx, %lx, %lx, %lx, %lx)", REC->id, >> REC->args[0], REC->args[1], REC->args[2], REC->args[3], REC->args[4], >> REC->args[5] >> [root@jouet ~]# >> >>> + if (sc->args && strcmp(sc->args->name, "syscall_nr") == 0) { >>> >>> I think the above instance seem better than the bottom. >>> >>> + if (sc->args && (strcmp(sc->args->name, "syscall_nr") || >>> strcmp(sc->args->name, "nr")) == 0) { >> >> Right in this 'if' body we do: >> >> sc->args = sc->args->next; >> sc->nr_args--; >> >> something like that. >> >> - Arnaldo >> >>> But I'll test again with perf-trace. >> >> Right, look at the output of 'perf trace' before and after, so that you >> can check if, say, we're using that syscall_nr value as the fd for the >> 'write' syscall ('fd' comes right after 'nr'/'syscall_nr'). >> > > Sorry, I'm late. > > I tested perf-trace with the bottom change. > (does not rename it to '__syscall_nr' on kernel) > > + if (sc->args && (strcmp(sc->args->name, "__syscall_nr") || > strcmp(sc->args->name, "nr")) == 0) { > sc->args = sc->args->next; > --sc->nr_args; > } > > But there are some problems as below. > > 0.322 ( 0.012 ms): a.out/27045 write(nr: 3, fd: 4196046, buf: 0x4, > count: 2140 ) = 4 > > So, I modified the above change. (I'll send it as new patch) > And then I tested again as below > > 0.345 ( 0.016 ms): a.out/27695 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 > > And I tested perf-trace with renamed '__syscall_nr' on modified kernel. > Everything is ok for aught I know. > > 0.345 ( 0.016 ms): a.out/27695 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 > > I'm writing another patchset. I'll send it soon. > [Result of perf-trace test about exception handling for 'nr' or '__syscall_nr'] diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 20916dd..a252f3a 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -1724,8 +1724,12 @@ static int trace__read_syscall_info(struct trace *trace, int id) sc->args = sc->tp_format->format.fields; sc->nr_args = sc->tp_format->format.nr_fields; - /* drop nr field - not relevant here; does not exist on older kernels */ - if (sc->args && strcmp(sc->args->name, "nr") == 0) { + /* + * We need to check and discard the first variable '__syscall_nr' + * or 'nr' that mean the syscall number. It is needless here. + * So drop '__syscall_nr' or 'nr' field but does not exist on older kernels. + */ + if (sc->args && (!strcmp(sc->args->name, "__syscall_nr") || !strcmp(sc->args->name, "nr"))) { sc->args = sc->args->next; --sc->nr_args; } Case 1) => "original environment" kernel : has 'nr' (4.2.0-30-generic) builtin-trace.c : not modified # perf trace ./a.out ...(omitted)... 0.369 ( 0.099 ms): a.out/3790 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 ...(omitted)... Case 2) kernel : has 'nr' (4.2.0-30-generic) builtin-trace.c : modified # perf trace ./a.out 0.269 ( 0.012 ms): a.out/4488 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 Case 3) => "has some problems" kernel : has '__syscall_nr' (4.5.0-rc4+) builtin-trace.c : not modified # perf trace ./a.out 0.288 ( 0.009 ms): a.out/4452 write(__syscall_nr: 3, fd: 4196046, buf: 0x4, count: 2140 ) = 4 Case 4) => "final environment" kernel : has '__syscall_nr' (4.5.0-rc4+) builtin-trace.c : modified (for '__syscall_nr') # perf trace ./a.out 0.334 ( 0.012 ms): a.out/5517 write(fd: 3, buf: 0x4006ce, count: 4 ) = 4 I'll send modified patchset soon. Thanks, Taeung