mm: use stack_depot for recording kmemleak's backtrace

Using stack_depot to record kmemleak's backtrace which has been
implemented on slub for reducing redundant information.

[[email protected]: fix build - remove now-unused __save_stack_trace()]
[[email protected]: v3]
  Link: https://lkml.kernel.org/r/[email protected]
[[email protected]: fix v3 layout oddities]
[[email protected]: coding-style cleanups]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Zhaoyang Huang <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Cc: ke.wang <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Zhaoyang Huang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

lib/Kconfig.debug

@@ -728,6 +728,7 @@ config DEBUG_KMEMLEAK
 	select STACKTRACE if STACKTRACE_SUPPORT
 	select KALLSYMS
 	select CRC32
+	select STACKDEPOT
 	help
 	  Say Y here if you want to enable the memory leak
 	  detector. The memory allocation/freeing is traced in a way

mm/kmemleak.c

@@ -79,6 +79,7 @@
 #include <linux/mutex.h>
 #include <linux/rcupdate.h>
 #include <linux/stacktrace.h>
+#include <linux/stackdepot.h>
 #include <linux/cache.h>
 #include <linux/percpu.h>
 #include <linux/memblock.h>
@@ -159,8 +160,7 @@ struct kmemleak_object {
 	u32 checksum;
 	/* memory ranges to be scanned inside an object (empty for all) */
 	struct hlist_head area_list;
-	unsigned long trace[MAX_TRACE];
-	unsigned int trace_len;
+	depot_stack_handle_t trace_handle;
 	unsigned long jiffies;		/* creation timestamp */
 	pid_t pid;			/* pid of the current task */
 	char comm[TASK_COMM_LEN];	/* executable name */
@@ -346,18 +346,21 @@ static void print_unreferenced(struct seq_file *seq,
 			       struct kmemleak_object *object)
 {
 	int i;
+	unsigned long *entries;
+	unsigned int nr_entries;
 	unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
 
+	nr_entries = stack_depot_fetch(object->trace_handle, &entries);
 	warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
-		   object->pointer, object->size);
+			  object->pointer, object->size);
 	warn_or_seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
-		   object->comm, object->pid, object->jiffies,
-		   msecs_age / 1000, msecs_age % 1000);
+			   object->comm, object->pid, object->jiffies,
+			   msecs_age / 1000, msecs_age % 1000);
 	hex_dump_object(seq, object);
 	warn_or_seq_printf(seq, "  backtrace:\n");
 
-	for (i = 0; i < object->trace_len; i++) {
-		void *ptr = (void *)object->trace[i];
+	for (i = 0; i < nr_entries; i++) {
+		void *ptr = (void *)entries[i];
 		warn_or_seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
 	}
 }
@@ -370,15 +373,16 @@ static void print_unreferenced(struct seq_file *seq,
 static void dump_object_info(struct kmemleak_object *object)
 {
 	pr_notice("Object 0x%08lx (size %zu):\n",
-		  object->pointer, object->size);
+			object->pointer, object->size);
 	pr_notice("  comm \"%s\", pid %d, jiffies %lu\n",
-		  object->comm, object->pid, object->jiffies);
+			object->comm, object->pid, object->jiffies);
 	pr_notice("  min_count = %d\n", object->min_count);
 	pr_notice("  count = %d\n", object->count);
 	pr_notice("  flags = 0x%x\n", object->flags);
 	pr_notice("  checksum = %u\n", object->checksum);
 	pr_notice("  backtrace:\n");
-	stack_trace_print(object->trace, object->trace_len, 4);
+	if (object->trace_handle)
+		stack_depot_print(object->trace_handle);
 }
 
 /*
@@ -591,12 +595,18 @@ static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int ali
 	return object;
 }
 
-/*
- * Save stack trace to the given array of MAX_TRACE size.
- */
-static int __save_stack_trace(unsigned long *trace)
+static noinline depot_stack_handle_t set_track_prepare(void)
 {
-	return stack_trace_save(trace, MAX_TRACE, 2);
+	depot_stack_handle_t trace_handle;
+	unsigned long entries[MAX_TRACE];
+	unsigned int nr_entries;
+
+	if (!kmemleak_initialized)
+		return 0;
+	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
+	trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
+
+	return trace_handle;
 }
 
 /*
@@ -653,7 +663,7 @@ static void __create_object(unsigned long ptr, size_t size,
 	}
 
 	/* kernel backtrace */
-	object->trace_len = __save_stack_trace(object->trace);
+	object->trace_handle = set_track_prepare();
 
 	raw_spin_lock_irqsave(&kmemleak_lock, flags);
 
@@ -692,7 +702,6 @@ static void __create_object(unsigned long ptr, size_t size,
 	rb_link_node(&object->rb_node, rb_parent, link);
 	rb_insert_color(&object->rb_node, is_phys ? &object_phys_tree_root :
 					  &object_tree_root);
-
 	list_add_tail_rcu(&object->object_list, &object_list);
 out:
 	raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
@@ -1091,7 +1100,7 @@ void __ref kmemleak_update_trace(const void *ptr)
 	}
 
 	raw_spin_lock_irqsave(&object->lock, flags);
-	object->trace_len = __save_stack_trace(object->trace);
+	object->trace_handle = set_track_prepare();
 	raw_spin_unlock_irqrestore(&object->lock, flags);
 
 	put_object(object);
@@ -2084,6 +2093,7 @@ void __init kmemleak_init(void)
 	if (kmemleak_error)
 		return;
 
+	stack_depot_init();
 	jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
 	jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);