perf kmaps: Check kmaps to make code more robust

This patch add checks in places where map__kmap is used to get kmaps
from struct kmap.

Error messages are added at map__kmap to warn invalid accessing of kmap
(for the case of !map->dso->kernel, kmap(map) does not exists at all).

Also, introduces map__kmaps() to warn uninitialized kmaps.

Reviewed-by: Ingo Molnar <[e-mail]>
Signed-off-by: Wang Nan <[e-mail]>
Cc: [e-mail]
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Zefan Li <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/machine.c

···
 			machine->vmlinux_maps[type]->unmap_ip =
 				identity__map_ip;
 		kmap = map__kmap(machine->vmlinux_maps[type]);
+		if (!kmap)
+			return -1;
+
 		kmap->kmaps = &machine->kmaps;
 		map_groups__insert(&machine->kmaps,
 				   machine->vmlinux_maps[type]);
···
 		kmap = map__kmap(machine->vmlinux_maps[type]);
 		map_groups__remove(&machine->kmaps,
 				   machine->vmlinux_maps[type]);
-		if (kmap->ref_reloc_sym) {
+		if (kmap && kmap->ref_reloc_sym) {
 			/*
 			 * ref_reloc_sym is shared among all maps, so free just
 			 * on one of them.

tools/perf/util/map.c

···
 		return rb_entry(next, struct map, rb_node);
 	return NULL;
 }
+
+struct kmap *map__kmap(struct map *map)
+{
+	if (!map->dso || !map->dso->kernel) {
+		pr_err("Internal error: map__kmap with a non-kernel map\n");
+		return NULL;
+	}
+	return (struct kmap *)(map + 1);
+}
+
+struct map_groups *map__kmaps(struct map *map)
+{
+	struct kmap *kmap = map__kmap(map);
+
+	if (!kmap || !kmap->kmaps) {
+		pr_err("Internal error: map__kmaps with a non-kernel map\n");
+		return NULL;
+	}
+	return kmap->kmaps;
+}

tools/perf/util/map.h

···
 
 void map_groups__put(struct map_groups *mg);
 
-static inline struct kmap *map__kmap(struct map *map)
-{
-	return (struct kmap *)(map + 1);
-}
+struct kmap *map__kmap(struct map *map);
+struct map_groups *map__kmaps(struct map *map);
 
 static inline u64 map__map_ip(struct map *map, u64 ip)
 {

tools/perf/util/probe-event.c

···
 		return NULL;
 
 	kmap = map__kmap(host_machine->vmlinux_maps[MAP__FUNCTION]);
+	if (!kmap)
+		return NULL;
 	return kmap->ref_reloc_sym;
 }
 

tools/perf/util/session.c

···
 
 	for (i = 0; i < MAP__NR_TYPES; ++i) {
 		struct kmap *kmap = map__kmap(maps[i]);
+
+		if (!kmap)
+			continue;
 		kmap->ref_reloc_sym = ref;
 	}
 

tools/perf/util/symbol-elf.c

···
 		  symbol_filter_t filter, int kmodule)
 {
 	struct kmap *kmap = dso->kernel ? map__kmap(map) : NULL;
+	struct map_groups *kmaps = kmap ? map__kmaps(map) : NULL;
 	struct map *curr_map = map;
 	struct dso *curr_dso = dso;
 	Elf_Data *symstrs, *secstrs;
···
 	Elf *elf;
 	int nr = 0;
 	bool remap_kernel = false, adjust_kernel_syms = false;
+
+	if (kmap && !kmaps)
+		return -1;
 
 	dso->symtab_type = syms_ss->type;
 	dso->is_64_bit = syms_ss->is_64_bit;
···
 					map->map_ip = map__map_ip;
 					map->unmap_ip = map__unmap_ip;
 					/* Ensure maps are correctly ordered */
-					map_groups__remove(kmap->kmaps, map);
-					map_groups__insert(kmap->kmaps, map);
+					if (kmaps) {
+						map_groups__remove(kmaps, map);
+						map_groups__insert(kmaps, map);
+					}
 				}
 
 				/*
···
 			snprintf(dso_name, sizeof(dso_name),
 				 "%s%s", dso->short_name, section_name);
 
-			curr_map = map_groups__find_by_name(kmap->kmaps, map->type, dso_name);
+			curr_map = map_groups__find_by_name(kmaps, map->type, dso_name);
 			if (curr_map == NULL) {
 				u64 start = sym.st_value;
 
···
 					curr_map->unmap_ip = identity__map_ip;
 				}
 				curr_dso->symtab_type = dso->symtab_type;
-				map_groups__insert(kmap->kmaps, curr_map);
+				map_groups__insert(kmaps, curr_map);
 				/*
 				 * The new DSO should go to the kernel DSOS
 				 */
···
 			 * We need to fixup this here too because we create new
 			 * maps here, for things like vsyscall sections.
 			 */
-			__map_groups__fixup_end(kmap->kmaps, map->type);
+			__map_groups__fixup_end(kmaps, map->type);
 		}
 	}
 	err = nr;

tools/perf/util/symbol.c

···
 static int dso__split_kallsyms_for_kcore(struct dso *dso, struct map *map,
 					 symbol_filter_t filter)
 {
-	struct map_groups *kmaps = map__kmap(map)->kmaps;
+	struct map_groups *kmaps = map__kmaps(map);
 	struct map *curr_map;
 	struct symbol *pos;
 	int count = 0, moved = 0;
 	struct rb_root *root = &dso->symbols[map->type];
 	struct rb_node *next = rb_first(root);
+
+	if (!kmaps)
+		return -1;
 
 	while (next) {
 		char *module;
···
 static int dso__split_kallsyms(struct dso *dso, struct map *map, u64 delta,
 			       symbol_filter_t filter)
 {
-	struct map_groups *kmaps = map__kmap(map)->kmaps;
-	struct machine *machine = kmaps->machine;
+	struct map_groups *kmaps = map__kmaps(map);
+	struct machine *machine;
 	struct map *curr_map = map;
 	struct symbol *pos;
 	int count = 0, moved = 0;
 	struct rb_root *root = &dso->symbols[map->type];
 	struct rb_node *next = rb_first(root);
 	int kernel_range = 0;
+
+	if (!kmaps)
+		return -1;
+
+	machine = kmaps->machine;
 
 	while (next) {
 		char *module;
···
 static int validate_kcore_modules(const char *kallsyms_filename,
 				  struct map *map)
 {
-	struct map_groups *kmaps = map__kmap(map)->kmaps;
+	struct map_groups *kmaps = map__kmaps(map);
 	char modules_filename[PATH_MAX];
+
+	if (!kmaps)
+		return -EINVAL;
 
 	if (!filename_from_kallsyms_filename(modules_filename, "modules",
 					     kallsyms_filename))
···
 				    struct map *map)
 {
 	struct kmap *kmap = map__kmap(map);
+
+	if (!kmap)
+		return -EINVAL;
 
 	if (kmap->ref_reloc_sym && kmap->ref_reloc_sym->name) {
 		u64 start;
···
 static int dso__load_kcore(struct dso *dso, struct map *map,
 			   const char *kallsyms_filename)
 {
-	struct map_groups *kmaps = map__kmap(map)->kmaps;
-	struct machine *machine = kmaps->machine;
+	struct map_groups *kmaps = map__kmaps(map);
+	struct machine *machine;
 	struct kcore_mapfn_data md;
 	struct map *old_map, *new_map, *replacement_map = NULL;
 	bool is_64_bit;
 	int err, fd;
 	char kcore_filename[PATH_MAX];
 	struct symbol *sym;
+
+	if (!kmaps)
+		return -EINVAL;
+
+	machine = kmaps->machine;
 
 	/* This function requires that the map is the kernel map */
 	if (map != machine->vmlinux_maps[map->type])
···
 {
 	struct kmap *kmap = map__kmap(map);
 	u64 addr;
+
+	if (!kmap)
+		return -1;
 
 	if (!kmap->ref_reloc_sym || !kmap->ref_reloc_sym->name)
 		return 0;