Re: [PATCH v8] perf: __kmod_path__parse: deal with kernel module names in '[]' correctly

[Arnaldo Carvalho de Melo]

Em Wed, Jun 03, 2015 at 11:12:04AM +0200, Jiri Olsa escreveu:
> On Wed, Jun 03, 2015 at 08:52:21AM +0000, Wang Nan wrote:
> > Before patch ba92732e9808df679ddf75c5ea1c0caae6d7dce2 ('perf kmaps:
> > Check kmaps to make code more robust'), perf report and perf annotate
> > will segfault if trace data contains kernel module information like
> > this:
> 
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

Had to fix the merge with one hunk I had from a fix I made, please
check, full patch below, but the clash was in this loop:

+++ b/tools/perf/util/machine.c
@@ -1149,9 +1149,29 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
 		struct dso *dso;
 
 		list_for_each_entry(dso, &machine->dsos.head, node) {
-			if (!dso->kernel || is_kernel_module(dso->long_name))
+
+			/*
+			 * The cpumode passed to is_kernel_module is not the
+			 * cpumode of *this* event. If we insist on passing
+			 * correct cpumode to is_kernel_module, we should
+			 * record the cpumode when we adding this dso to the
+			 * linked list.
+			 *
+			 * However we don't really need passing correct
+			 * cpumode.  We know the correct cpumode must be kernel
+			 * mode (if not, we should not link it onto kernel_dsos
+			 * list).
+			 *
+			 * Therefore, we pass PERF_RECORD_MISC_CPUMODE_UNKNOWN.
+			 * is_kernel_module() treats it as a kernel cpumode.
+			 */
+
+			if (!dso->kernel ||
+			    is_kernel_module(dso->long_name,
+					     PERF_RECORD_MISC_CPUMODE_UNKNOWN))
 				continue;
 
+
 			kernel = dso;
 			break;
 		}
-
-------------------------------

I.e. before it was:

	if (dso->kernel && is_kernel_module(dso->long_name))


But then, since now there are !dso->kernel entries in this list, it
could get as the 'kernel' a user DSO. So I changed it to:

	if (!dso->kernel || is_kernel_module(dso->long_name))

To discard user and kernel module DSOs.

Applied the patch below, let me know if you disagree.

- Arnaldo