ANDROID: mm: add get_each_object_track function

Add and export get_each_object_track which helps in
looping through all the slab objects of a page
and gets the track structure of each object, also
make track_item and track structure public, these
will be used by the minidump module to get slab
owner info.

Bug: 177377077
Change-Id: Ic207fd26a122a5f1b014f4929760d064f7af0225
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>

mm/slab.h

@@ -91,6 +91,24 @@ struct kmem_cache *kmalloc_slab(size_t, gfp_t);
 
 gfp_t kmalloc_fix_flags(gfp_t flags);
 
+#ifdef CONFIG_SLUB
+/*
+ * Tracking user of a slab.
+ */
+#define TRACK_ADDRS_COUNT 16
+struct track {
+	unsigned long addr;	/* Called from address */
+#ifdef CONFIG_STACKTRACE
+	unsigned long addrs[TRACK_ADDRS_COUNT];	/* Called from address */
+#endif
+	int cpu;		/* Was running on cpu */
+	int pid;		/* Pid context */
+	unsigned long when;	/* When did the operation occur */
+};
+
+enum track_item { TRACK_ALLOC, TRACK_FREE };
+#endif
+
 /* Functions provided by the slab allocators */
 int __kmem_cache_create(struct kmem_cache *, slab_flags_t flags);
 
@@ -217,10 +235,21 @@ DECLARE_STATIC_KEY_TRUE(slub_debug_enabled);
 DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);
 #endif
 extern void print_tracking(struct kmem_cache *s, void *object);
+extern unsigned long get_each_object_track(struct kmem_cache *s,
+		struct page *page, enum track_item alloc,
+		int (*fn)(const struct kmem_cache *, const void *,
+		const struct track *, void *), void *private);
 #else
 static inline void print_tracking(struct kmem_cache *s, void *object)
 {
 }
+static inline unsigned long get_each_object_track(struct kmem_cache *s,
+		struct page *page, enum track_item alloc,
+		int (*fn)(const struct kmem_cache *, const void *,
+		const struct track *, void *), void *private)
+{
+	return 0;
+}
 #endif
 
 /*

mm/slub.c

@@ -200,22 +200,6 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
 /* Use cmpxchg_double */
 #define __CMPXCHG_DOUBLE	((slab_flags_t __force)0x40000000U)
 
-/*
- * Tracking user of a slab.
- */
-#define TRACK_ADDRS_COUNT 16
-struct track {
-	unsigned long addr;	/* Called from address */
-#ifdef CONFIG_STACKTRACE
-	unsigned long addrs[TRACK_ADDRS_COUNT];	/* Called from address */
-#endif
-	int cpu;		/* Was running on cpu */
-	int pid;		/* Pid context */
-	unsigned long when;	/* When did the operation occur */
-};
-
-enum track_item { TRACK_ALLOC, TRACK_FREE };
-
 #ifdef CONFIG_SYSFS
 static int sysfs_slab_add(struct kmem_cache *);
 static int sysfs_slab_alias(struct kmem_cache *, const char *);
@@ -576,6 +560,39 @@ static struct track *get_track(struct kmem_cache *s, void *object,
 	return kasan_reset_tag(p + alloc);
 }
 
+/*
+ * This function will be used to loop through all the slab objects in
+ * a page to give track structure for each object, the function fn will
+ * be using this track structure and extract required info into its private
+ * data, the return value will be the number of track structures that are
+ * processed.
+ */
+unsigned long get_each_object_track(struct kmem_cache *s,
+		struct page *page, enum track_item alloc,
+		int (*fn)(const struct kmem_cache *, const void *,
+		const struct track *, void *), void *private)
+{
+	void *p;
+	struct track *t;
+	int ret;
+	unsigned long num_track = 0;
+
+	if (!slub_debug || !(s->flags & SLAB_STORE_USER))
+		return 0;
+
+	slab_lock(page);
+	for_each_object(p, s, page_address(page), page->objects) {
+		t = get_track(s, p, alloc);
+		ret = fn(s, p, t, private);
+		if (ret < 0)
+			break;
+		num_track += 1;
+	}
+	slab_unlock(page);
+	return num_track;
+}
+EXPORT_SYMBOL_GPL(get_each_object_track);
+
 static void set_track(struct kmem_cache *s, void *object,
 			enum track_item alloc, unsigned long addr)
 {