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perf tools: Use scandir() to iterate threads when synthesizing PERF_RECORD_ events

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Like in __event__synthesize_thread(), I think it's better to use
scandir() instead of the readdir() loop.  In case some malicious task
continues to create new threads, the readdir() loop will run over and
over to collect tids.  The scandir() also has the problem but the window
is much smaller since it doesn't do much work during the iteration.

Also add filter_task() function as we only care the tasks.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20210202090118.2008551-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2021-02-02 18:01:18 +09:00 committed by Arnaldo Carvalho de Melo
parent c1b907953b
commit 473f742e18
1 changed files with 17 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
tools/perf/util/synthetic-events.c
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@ -704,6 +704,11 @@ int perf_event__synthesize_modules(struct perf_tool *tool, perf_event__handler_t
return rc;
}
static int filter_task(const struct dirent *dirent)
{
return isdigit(dirent->d_name[0]);
}
static int __event__synthesize_thread(union perf_event *comm_event,
union perf_event *mmap_event,
union perf_event *fork_event,
@ -712,10 +717,10 @@ static int __event__synthesize_thread(union perf_event *comm_event,
struct perf_tool *tool, struct machine *machine, bool mmap_data)
{
char filename[PATH_MAX];
DIR *tasks;
struct dirent *dirent;
struct dirent **dirent;
pid_t tgid, ppid;
int rc = 0;
int i, n;
/* special case: only send one comm event using passed in pid */
if (!full) {
@ -747,18 +752,16 @@ static int __event__synthesize_thread(union perf_event *comm_event,
snprintf(filename, sizeof(filename), "%s/proc/%d/task",
machine->root_dir, pid);
tasks = opendir(filename);
if (tasks == NULL) {
pr_debug("couldn't open %s\n", filename);
return 0;
}
n = scandir(filename, &dirent, filter_task, alphasort);
if (n < 0)
return n;
while ((dirent = readdir(tasks)) != NULL) {
for (i = 0; i < n; i++) {
char *end;
pid_t _pid;
bool kernel_thread;
_pid = strtol(dirent->d_name, &end, 10);
_pid = strtol(dirent[i]->d_name, &end, 10);
if (*end)
continue;
@ -791,7 +794,10 @@ static int __event__synthesize_thread(union perf_event *comm_event,
}
}
closedir(tasks);
for (i = 0; i < n; i++)
zfree(&dirent[i]);
free(dirent);
return rc;
}
@ -976,7 +982,7 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
return 0;
snprintf(proc_path, sizeof(proc_path), "%s/proc", machine->root_dir);
n = scandir(proc_path, &dirent, 0, alphasort);
n = scandir(proc_path, &dirent, filter_task, alphasort);
if (n < 0)
return err;