Em Fri, Feb 26, 2016 at 09:24:46PM +0900, Taeung Song escreveu:
> 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)
"With this change:"
>
> + 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.
Right, there is a silly error, we have to test both strcmp(), checking
if one of them is equal to zero, i.e. if there was a match.
- Arnaldo
> 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.
>
> Thanks,
> Taeung
