netdev - Re: [PATCH v2 3/4] perf augmented_raw_syscalls: Support arm64 raw syscalls

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Date:   Sat, 15 Jun 2019 13:52:49 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 3/4] perf augmented_raw_syscalls: Support arm64 raw
 syscalls

On Thu, Jun 13, 2019 at 03:15:14PM -0300, Arnaldo Carvalho de Melo wrote:

[...]

> > > > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> > > > index 1a2a605cf068..eb70a4b71755 100644
> > > > --- a/tools/perf/builtin-trace.c
> > > > +++ b/tools/perf/builtin-trace.c
> > > > @@ -1529,6 +1529,7 @@ static int trace__read_syscall_info(struct trace *trace, int id)
> > > >  static int trace__validate_ev_qualifier(struct trace *trace)
> > > >  {
> > > >  	int err = 0, i;
> > > > +	bool printed_invalid_prefix = false;
> > > >  	size_t nr_allocated;
> > > >  	struct str_node *pos;
> > > >  
> > > > @@ -1555,14 +1556,15 @@ static int trace__validate_ev_qualifier(struct trace *trace)
> > > >  			if (id >= 0)
> > > >  				goto matches;
> > > >  
> > > > -			if (err == 0) {
> > > > -				fputs("Error:\tInvalid syscall ", trace->output);
> > > > -				err = -EINVAL;
> > > > +			if (!printed_invalid_prefix) {
> > > > +				pr_debug("Skipping unknown syscalls: ");
> > > > +				printed_invalid_prefix = true;
> > > >  			} else {
> > > > -				fputs(", ", trace->output);
> > > > +				pr_debug(", ");
> > > >  			}
> > > >  
> > > > -			fputs(sc, trace->output);
> > > > +			pr_debug("%s", sc);
> > > > +			continue;
> > > 
> > > Here adds 'continue' so that we want to let ev_qualifier_ids.entries
> > > to only store valid system call ids.  But this is not sufficient,
> > > because we have initialized ev_qualifier_ids.nr at the beginning of
> > > the function:
> > > 
> > >   trace->ev_qualifier_ids.nr = strlist__nr_entries(trace->ev_qualifier);
> > > This sentence will set ids number to the string table's length; but
> > > actually some strings are not really supported; this leads to some
> > > items in trace->ev_qualifier_ids.entries[] will be not initialized
> > > properly.
> > > 
> > > If we want to get neat entries and entry number, I suggest at the
> > > beginning of the function we use variable 'nr_allocated' to store
> > > string table length and use it to allocate entries:
> > > 
> > >   nr_allocated = strlist__nr_entries(trace->ev_qualifier);
> > >   trace->ev_qualifier_ids.entries = malloc(nr_allocated *
> > >                                            sizeof(trace->ev_qualifier_ids.entries[0]));
> > > 
> > > If we find any matched string, then increment the nr field under
> > > 'matches' tag:
> > > 
> > > matches:
> > >                 trace->ev_qualifier_ids.nr++;
> > >                 trace->ev_qualifier_ids.entries[i++] = id;
> > > 
> > > This can ensure the entries[0..nr-1] has valid id and we can use
> > > ev_qualifier_ids.nr to maintain the valid system call numbers.
> > 
> > yeah, you're right, I'll address these issues in a followup patch,
> > tomorrow.
> 
> This is equivalent and I think the smallest patch, I'll add one on top
> doing what you suggested about nr_allocated getting the
> strlist__nr_entries() and also will rename i to nr_used to contrast with
> nr_allocated, and then at the end set ev_qualifier_ids.nr to nr_used.

Thanks for this patch, I tested below changes and 'perf trace' works
well.  You could add my test tag:

Tested-by: Leo Yan <leo.yan@...aro.org>

> - Arnaldo
> 
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index eb70a4b71755..bd1f00e7a2eb 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -1528,9 +1528,9 @@ static int trace__read_syscall_info(struct trace *trace, int id)
>  
>  static int trace__validate_ev_qualifier(struct trace *trace)
>  {
> -	int err = 0, i;
> +	int err = 0;
>  	bool printed_invalid_prefix = false;
> -	size_t nr_allocated;
> +	size_t nr_allocated, i;
>  	struct str_node *pos;
>  
>  	trace->ev_qualifier_ids.nr = strlist__nr_entries(trace->ev_qualifier);
> @@ -1575,7 +1575,7 @@ static int trace__validate_ev_qualifier(struct trace *trace)
>  			id = syscalltbl__strglobmatch_next(trace->sctbl, sc, &match_next);
>  			if (id < 0)
>  				break;
> -			if (nr_allocated == trace->ev_qualifier_ids.nr) {
> +			if (nr_allocated == i) {
>  				void *entries;
>  
>  				nr_allocated += 8;
> @@ -1588,11 +1588,11 @@ static int trace__validate_ev_qualifier(struct trace *trace)
>  				}
>  				trace->ev_qualifier_ids.entries = entries;
>  			}
> -			trace->ev_qualifier_ids.nr++;
>  			trace->ev_qualifier_ids.entries[i++] = id;
>  		}
>  	}
>  
> +	trace->ev_qualifier_ids.nr = i;
>  out:
>  	if (printed_invalid_prefix)
>  		pr_debug("\n");