Re: [PATCH 16/53] perf tools: Fix mmap2 event allocation in synthesize code

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Mon, Jan 11, 2016 at 01:48:07PM +0000, Wang Nan escreveu:
> perf_event__synthesize_mmap_events() issues mmap2 events, but the
> memory of that event is allocated using:
> 
>  mmap_event = malloc(sizeof(mmap_event->mmap) + machine->id_hdr_size);
> 
> If path of mmap source file is long (near PATH_MAX), random crash
> would happen. Should use sizeof(mmap_event->mmap2).
> 
> Fix two memory allocations and rename all mmap_event to mmap2_event
> to make it clear.

Try not doing two things in the same patch, i.e. do one minimal patch
with just the fix, i.e. this part:

-     mmap_event = malloc(sizeof(mmap_event->mmap) + > machine->id_hdr_size);
+     mmap_event = malloc(sizeof(mmap_event->mmap2) + > machine->id_hdr_size);

This way we see the fix straight away, no extra renaming noise.

And the other with the rename, but I wouldn't bother doing that,
'mmap_event' is descriptive enough, and we may end up having a mmap3
event, when we would go on touching all those places again...

We're moving around union perf_event pointers, what we could do would be
to, at perf_event allocation time, set the mmap_event->header.type to
PERF_RECORD_MMAP2 and when going to use the mmap_event->mmap2 fields,
check that what was passed is indeed the type (and size) expected.

- Arnaldo
 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: He Kuang <hekuang@huawei.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
> ---
>  tools/perf/util/event.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index cd61bb1..cde8228 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -413,7 +413,7 @@ int perf_event__synthesize_modules(struct perf_tool *tool,
>  }
>  
>  static int __event__synthesize_thread(union perf_event *comm_event,
> -				      union perf_event *mmap_event,
> +				      union perf_event *mmap2_event,
>  				      union perf_event *fork_event,
>  				      pid_t pid, int full,
>  					  perf_event__handler_t process,
> @@ -436,7 +436,7 @@ static int __event__synthesize_thread(union perf_event *comm_event,
>  		if (tgid == -1)
>  			return -1;
>  
> -		return perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid,
> +		return perf_event__synthesize_mmap_events(tool, mmap2_event, pid, tgid,
>  							  process, machine, mmap_data,
>  							  proc_map_timeout);
>  	}
> @@ -478,7 +478,7 @@ static int __event__synthesize_thread(union perf_event *comm_event,
>  		rc = 0;
>  		if (_pid == pid) {
>  			/* process the parent's maps too */
> -			rc = perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid,
> +			rc = perf_event__synthesize_mmap_events(tool, mmap2_event, pid, tgid,
>  						process, machine, mmap_data, proc_map_timeout);
>  			if (rc)
>  				break;
> @@ -496,15 +496,15 @@ int perf_event__synthesize_thread_map(struct perf_tool *tool,
>  				      bool mmap_data,
>  				      unsigned int proc_map_timeout)
>  {
> -	union perf_event *comm_event, *mmap_event, *fork_event;
> +	union perf_event *comm_event, *mmap2_event, *fork_event;
>  	int err = -1, thread, j;
>  
>  	comm_event = malloc(sizeof(comm_event->comm) + machine->id_hdr_size);
>  	if (comm_event == NULL)
>  		goto out;
>  
> -	mmap_event = malloc(sizeof(mmap_event->mmap) + machine->id_hdr_size);
> -	if (mmap_event == NULL)
> +	mmap2_event = malloc(sizeof(mmap2_event->mmap2) + machine->id_hdr_size);
> +	if (mmap2_event == NULL)
>  		goto out_free_comm;
>  
>  	fork_event = malloc(sizeof(fork_event->fork) + machine->id_hdr_size);
> @@ -513,7 +513,7 @@ int perf_event__synthesize_thread_map(struct perf_tool *tool,
>  
>  	err = 0;
>  	for (thread = 0; thread < threads->nr; ++thread) {
> -		if (__event__synthesize_thread(comm_event, mmap_event,
> +		if (__event__synthesize_thread(comm_event, mmap2_event,
>  					       fork_event,
>  					       thread_map__pid(threads, thread), 0,
>  					       process, tool, machine,
> @@ -539,7 +539,7 @@ int perf_event__synthesize_thread_map(struct perf_tool *tool,
>  
>  			/* if not, generate events for it */
>  			if (need_leader &&
> -			    __event__synthesize_thread(comm_event, mmap_event,
> +			    __event__synthesize_thread(comm_event, mmap2_event,
>  						       fork_event,
>  						       comm_event->comm.pid, 0,
>  						       process, tool, machine,
> @@ -551,7 +551,7 @@ int perf_event__synthesize_thread_map(struct perf_tool *tool,
>  	}
>  	free(fork_event);
>  out_free_mmap:
> -	free(mmap_event);
> +	free(mmap2_event);
>  out_free_comm:
>  	free(comm_event);
>  out:
> @@ -567,7 +567,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
>  	DIR *proc;
>  	char proc_path[PATH_MAX];
>  	struct dirent dirent, *next;
> -	union perf_event *comm_event, *mmap_event, *fork_event;
> +	union perf_event *comm_event, *mmap2_event, *fork_event;
>  	int err = -1;
>  
>  	if (machine__is_default_guest(machine))
> @@ -577,8 +577,8 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
>  	if (comm_event == NULL)
>  		goto out;
>  
> -	mmap_event = malloc(sizeof(mmap_event->mmap) + machine->id_hdr_size);
> -	if (mmap_event == NULL)
> +	mmap2_event = malloc(sizeof(mmap2_event->mmap2) + machine->id_hdr_size);
> +	if (mmap2_event == NULL)
>  		goto out_free_comm;
>  
>  	fork_event = malloc(sizeof(fork_event->fork) + machine->id_hdr_size);
> @@ -601,7 +601,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
>   		 * We may race with exiting thread, so don't stop just because
>   		 * one thread couldn't be synthesized.
>   		 */
> -		__event__synthesize_thread(comm_event, mmap_event, fork_event, pid,
> +		__event__synthesize_thread(comm_event, mmap2_event, fork_event, pid,
>  					   1, process, tool, machine, mmap_data,
>  					   proc_map_timeout);
>  	}
> @@ -611,7 +611,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
>  out_free_fork:
>  	free(fork_event);
>  out_free_mmap:
> -	free(mmap_event);
> +	free(mmap2_event);
>  out_free_comm:
>  	free(comm_event);
>  out:
> -- 
> 1.8.3.4