perf tools: Deal with kernel module names in '[]' correctly

Before patch ba92732e9808 ('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:

# perf report -D -i ./perf.data
...
0 0 0x188 [0x50]: PERF_RECORD_MMAP -1/0: [0xffffffbff1018000(0xf068000) @ 0]: x [test_module]
...

# perf report -i ./perf.data --objdump=/path/to/objdump --kallsyms=/path/to/kallsyms

perf: Segmentation fault
-------- backtrace --------
/path/to/perf[0x503478]
/lib64/libc.so.6(+0x3545f)[0x7fb201f3745f]
/path/to/perf[0x499b56]
/path/to/perf(dso__load_kallsyms+0x13c)[0x49b56c]
/path/to/perf(dso__load+0x72e)[0x49c21e]
/path/to/perf(map__load+0x6e)[0x4ae9ee]
/path/to/perf(thread__find_addr_map+0x24c)[0x47deec]
/path/to/perf(perf_event__preprocess_sample+0x88)[0x47e238]
/path/to/perf[0x43ad02]
/path/to/perf[0x4b55bc]
/path/to/perf(ordered_events__flush+0xca)[0x4b57ea]
/path/to/perf[0x4b1a01]
/path/to/perf(perf_session__process_events+0x3be)[0x4b428e]
/path/to/perf(cmd_report+0xf11)[0x43bfc1]
/path/to/perf[0x474702]
/path/to/perf(main+0x5f5)[0x42de95]
/lib64/libc.so.6(__libc_start_main+0xf4)[0x7fb201f23bd4]
/path/to/perf[0x42dfc4]

This is because __kmod_path__parse treats '[' leading names as kernel
name instead of names of kernel module.

If perf.data contains build information and the buildid of such modules
can be found, the dso->kernel of it will be set to DSO_TYPE_KERNEL by
__event_process_build_id(), not kernel module.

It will then be passed to dso__load() -> dso__load_kernel_sym() ->
dso__load_kcore() if --kallsyms is provided.

The refered patch adds NULL pointer checker to avoid segfault. However,
such kernel modules are still processed incorrectly.

This patch fixes __kmod_path__parse, makes it treat names like
'[test_module]' as kernel modules.

kmod-path.c is also update to reflect the above changes.

Signed-off-by: Wang Nan <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Zefan Li <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
[ Fixed the merged with 0443f36b0de0 ("perf machine: Fix the search
for the kernel DSO on the unified list" ]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/kmod-path.c

···
 	return 0;
 }
 
+static int test_is_kernel_module(const char *path, int cpumode, bool expect)
+{
+	TEST_ASSERT_VAL("is_kernel_module",
+			(!!is_kernel_module(path, cpumode)) == (!!expect));
+	pr_debug("%s (cpumode: %d) - is_kernel_module: %s\n",
+			path, cpumode, expect ? "true" : "false");
+	return 0;
+}
+
 #define T(path, an, ae, k, c, n, e) \
 	TEST_ASSERT_VAL("failed", !test(path, an, ae, k, c, n, e))
+
+#define M(path, c, e) \
+	TEST_ASSERT_VAL("failed", !test_is_kernel_module(path, c, e))
 
 int test__kmod_path__parse(void)
 {
···
 	T("/xxxx/xxxx/x-x.ko", false     , true      , true, false, NULL   , NULL);
 	T("/xxxx/xxxx/x-x.ko", true      , false     , true, false, "[x_x]", NULL);
 	T("/xxxx/xxxx/x-x.ko", false     , false     , true, false, NULL   , NULL);
+	M("/xxxx/xxxx/x-x.ko", PERF_RECORD_MISC_CPUMODE_UNKNOWN, true);
+	M("/xxxx/xxxx/x-x.ko", PERF_RECORD_MISC_KERNEL, true);
+	M("/xxxx/xxxx/x-x.ko", PERF_RECORD_MISC_USER, false);
 
 	/* path                alloc_name  alloc_ext   kmod  comp  name   ext */
 	T("/xxxx/xxxx/x.ko.gz", true     , true      , true, true, "[x]", "gz");
 	T("/xxxx/xxxx/x.ko.gz", false    , true      , true, true, NULL , "gz");
 	T("/xxxx/xxxx/x.ko.gz", true     , false     , true, true, "[x]", NULL);
 	T("/xxxx/xxxx/x.ko.gz", false    , false     , true, true, NULL , NULL);
+	M("/xxxx/xxxx/x.ko.gz", PERF_RECORD_MISC_CPUMODE_UNKNOWN, true);
+	M("/xxxx/xxxx/x.ko.gz", PERF_RECORD_MISC_KERNEL, true);
+	M("/xxxx/xxxx/x.ko.gz", PERF_RECORD_MISC_USER, false);
 
 	/* path              alloc_name  alloc_ext  kmod   comp  name    ext */
 	T("/xxxx/xxxx/x.gz", true      , true     , false, true, "x.gz" ,"gz");
 	T("/xxxx/xxxx/x.gz", false     , true     , false, true, NULL   ,"gz");
 	T("/xxxx/xxxx/x.gz", true      , false    , false, true, "x.gz" , NULL);
 	T("/xxxx/xxxx/x.gz", false     , false    , false, true, NULL   , NULL);
+	M("/xxxx/xxxx/x.gz", PERF_RECORD_MISC_CPUMODE_UNKNOWN, false);
+	M("/xxxx/xxxx/x.gz", PERF_RECORD_MISC_KERNEL, false);
+	M("/xxxx/xxxx/x.gz", PERF_RECORD_MISC_USER, false);
 
 	/* path   alloc_name  alloc_ext  kmod   comp  name     ext */
 	T("x.gz", true      , true     , false, true, "x.gz", "gz");
 	T("x.gz", false     , true     , false, true, NULL  , "gz");
 	T("x.gz", true      , false    , false, true, "x.gz", NULL);
 	T("x.gz", false     , false    , false, true, NULL  , NULL);
+	M("x.gz", PERF_RECORD_MISC_CPUMODE_UNKNOWN, false);
+	M("x.gz", PERF_RECORD_MISC_KERNEL, false);
+	M("x.gz", PERF_RECORD_MISC_USER, false);
 
 	/* path      alloc_name  alloc_ext  kmod  comp  name  ext */
 	T("x.ko.gz", true      , true     , true, true, "[x]", "gz");
 	T("x.ko.gz", false     , true     , true, true, NULL , "gz");
 	T("x.ko.gz", true      , false    , true, true, "[x]", NULL);
 	T("x.ko.gz", false     , false    , true, true, NULL , NULL);
+	M("x.ko.gz", PERF_RECORD_MISC_CPUMODE_UNKNOWN, true);
+	M("x.ko.gz", PERF_RECORD_MISC_KERNEL, true);
+	M("x.ko.gz", PERF_RECORD_MISC_USER, false);
+
+	/* path            alloc_name  alloc_ext  kmod  comp   name             ext */
+	T("[test_module]", true      , true     , true, false, "[test_module]", NULL);
+	T("[test_module]", false     , true     , true, false, NULL           , NULL);
+	T("[test_module]", true      , false    , true, false, "[test_module]", NULL);
+	T("[test_module]", false     , false    , true, false, NULL           , NULL);
+	M("[test_module]", PERF_RECORD_MISC_CPUMODE_UNKNOWN, true);
+	M("[test_module]", PERF_RECORD_MISC_KERNEL, true);
+	M("[test_module]", PERF_RECORD_MISC_USER, false);
+
+	/* path            alloc_name  alloc_ext  kmod  comp   name             ext */
+	T("[test.module]", true      , true     , true, false, "[test.module]", NULL);
+	T("[test.module]", false     , true     , true, false, NULL           , NULL);
+	T("[test.module]", true      , false    , true, false, "[test.module]", NULL);
+	T("[test.module]", false     , false    , true, false, NULL           , NULL);
+	M("[test.module]", PERF_RECORD_MISC_CPUMODE_UNKNOWN, true);
+	M("[test.module]", PERF_RECORD_MISC_KERNEL, true);
+	M("[test.module]", PERF_RECORD_MISC_USER, false);
+
+	/* path     alloc_name  alloc_ext  kmod   comp   name      ext */
+	T("[vdso]", true      , true     , false, false, "[vdso]", NULL);
+	T("[vdso]", false     , true     , false, false, NULL    , NULL);
+	T("[vdso]", true      , false    , false, false, "[vdso]", NULL);
+	T("[vdso]", false     , false    , false, false, NULL    , NULL);
+	M("[vdso]", PERF_RECORD_MISC_CPUMODE_UNKNOWN, false);
+	M("[vdso]", PERF_RECORD_MISC_KERNEL, false);
+	M("[vdso]", PERF_RECORD_MISC_USER, false);
+
+	/* path         alloc_name  alloc_ext  kmod   comp   name          ext */
+	T("[vsyscall]", true      , true     , false, false, "[vsyscall]", NULL);
+	T("[vsyscall]", false     , true     , false, false, NULL        , NULL);
+	T("[vsyscall]", true      , false    , false, false, "[vsyscall]", NULL);
+	T("[vsyscall]", false     , false    , false, false, NULL        , NULL);
+	M("[vsyscall]", PERF_RECORD_MISC_CPUMODE_UNKNOWN, false);
+	M("[vsyscall]", PERF_RECORD_MISC_KERNEL, false);
+	M("[vsyscall]", PERF_RECORD_MISC_USER, false);
+
+	/* path                alloc_name  alloc_ext  kmod   comp   name      ext */
+	T("[kernel.kallsyms]", true      , true     , false, false, "[kernel.kallsyms]", NULL);
+	T("[kernel.kallsyms]", false     , true     , false, false, NULL               , NULL);
+	T("[kernel.kallsyms]", true      , false    , false, false, "[kernel.kallsyms]", NULL);
+	T("[kernel.kallsyms]", false     , false    , false, false, NULL               , NULL);
+	M("[kernel.kallsyms]", PERF_RECORD_MISC_CPUMODE_UNKNOWN, false);
+	M("[kernel.kallsyms]", PERF_RECORD_MISC_KERNEL, false);
+	M("[kernel.kallsyms]", PERF_RECORD_MISC_USER, false);
 
 	return 0;
 }

tools/perf/util/dso.c

···
 	return false;
 }
 
-bool is_kernel_module(const char *pathname)
+bool is_kernel_module(const char *pathname, int cpumode)
 {
 	struct kmod_path m;
+	int mode = cpumode & PERF_RECORD_MISC_CPUMODE_MASK;
 
-	if (kmod_path__parse(&m, pathname))
-		return NULL;
+	WARN_ONCE(mode != cpumode,
+		  "Internal error: passing unmasked cpumode (%x) to is_kernel_module",
+		  cpumode);
+
+	switch (mode) {
+	case PERF_RECORD_MISC_USER:
+	case PERF_RECORD_MISC_HYPERVISOR:
+	case PERF_RECORD_MISC_GUEST_USER:
+		return false;
+	/* Treat PERF_RECORD_MISC_CPUMODE_UNKNOWN as kernel */
+	default:
+		if (kmod_path__parse(&m, pathname)) {
+			pr_err("Failed to check whether %s is a kernel module or not. Assume it is.",
+					pathname);
+			return true;
+		}
+	}
 
 	return m.kmod;
 }
···
 {
 	const char *name = strrchr(path, '/');
 	const char *ext  = strrchr(path, '.');
+	bool is_simple_name = false;
 
 	memset(m, 0x0, sizeof(*m));
 	name = name ? name + 1 : path;
 
+	/*
+	 * '.' is also a valid character for module name. For example:
+	 * [aaa.bbb] is a valid module name. '[' should have higher
+	 * priority than '.ko' suffix.
+	 *
+	 * The kernel names are from machine__mmap_name. Such
+	 * name should belong to kernel itself, not kernel module.
+	 */
+	if (name[0] == '[') {
+		is_simple_name = true;
+		if ((strncmp(name, "[kernel.kallsyms]", 17) == 0) ||
+		    (strncmp(name, "[guest.kernel.kallsyms", 22) == 0) ||
+		    (strncmp(name, "[vdso]", 6) == 0) ||
+		    (strncmp(name, "[vsyscall]", 10) == 0)) {
+			m->kmod = false;
+
+		} else
+			m->kmod = true;
+	}
+
 	/* No extension, just return name. */
-	if (ext == NULL) {
+	if ((ext == NULL) || is_simple_name) {
 		if (alloc_name) {
 			m->name = strdup(name);
 			return m->name ? 0 : -ENOMEM;

tools/perf/util/dso.h

···
 int dso__read_binary_type_filename(const struct dso *dso, enum dso_binary_type type,
 				   char *root_dir, char *filename, size_t size);
 bool is_supported_compression(const char *ext);
-bool is_kernel_module(const char *pathname);
+bool is_kernel_module(const char *pathname, int cpumode);
 bool decompress_to_file(const char *ext, const char *filename, int output_fd);
 bool dso__needs_decompress(struct dso *dso);
 

tools/perf/util/header.c

···
 {
 	int err = -1;
 	struct machine *machine;
-	u16 misc;
+	u16 cpumode;
 	struct dso *dso;
 	enum dso_kernel_type dso_type;
 
···
 	if (!machine)
 		goto out;
 
-	misc = bev->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;
+	cpumode = bev->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;
 
-	switch (misc) {
+	switch (cpumode) {
 	case PERF_RECORD_MISC_KERNEL:
 		dso_type = DSO_TYPE_KERNEL;
 		break;
···
 
 		dso__set_build_id(dso, &bev->build_id);
 
-		if (!is_kernel_module(filename))
+		if (!is_kernel_module(filename, cpumode))
 			dso->kernel = dso_type;
 
 		build_id__sprintf(dso->build_id, sizeof(dso->build_id),

tools/perf/util/machine.c

···
 		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;