From: Zhaoyang Huang <redacted>

Kmemleak objects are reported each which could produce lot of redundant
backtrace informations. introduce a set of method to establish a hash
tree to sort the objects according to backtrace.

results:
[  579.075111]c6 [ T5491] kmemleak: unreferenced object 0xffffff80badd9e00 (size 128):
[  579.082734]c6 [ T5491] kmemleak:   comm "swapper/0", pid 1, jiffies 4294892470
[  579.096837]c6 [ T5491] kmemleak: unreferenced object 0xffffff80badd9d00 (size 128):
[  579.104435]c6 [ T5491] kmemleak:   comm "swapper/0", pid 1, jiffies 4294892470
[  579.118563]c6 [ T5491] kmemleak: unreferenced object 0xffffff80baddce80 (size 128):
[  579.126201]c6 [ T5491] kmemleak:   comm "swapper/0", pid 1, jiffies 4294892470
[  579.140303]c6 [ T5491] kmemleak: unreferenced object 0xffffff80baddcb00 (size 128):
[  579.147906]c6 [ T5491] kmemleak:   comm "swapper/0", pid 1, jiffies 4294892470
[  579.162032]c6 [ T5491] kmemleak: unreferenced object 0xffffff80bae74a80 (size 128):
[  579.169661]c6 [ T5491] kmemleak:   comm "swapper/0", pid 1, jiffies 4294892470
[  579.183775]c6 [ T5491] kmemleak: unreferenced object 0xffffff80bae74100 (size 128):
[  579.191374]c6 [ T5491] kmemleak:   comm "swapper/0", pid 1, jiffies 4294892471
[  579.205486]c6 [ T5491] kmemleak: unreferenced object 0xffffff80bae75880 (size 128):
[  579.213127]c6 [ T5491] kmemleak:   comm "swapper/0", pid 1, jiffies 4294892471
[  579.227743]c6 [ T5491] kmemleak:   backtrace:
[  579.232109]c6 [ T5491] kmemleak:     [<0000000066492d96>] __kmalloc_track_caller+0x1d4/0x3e0
[  579.240506]c6 [ T5491] kmemleak:     [<00000000e5400df8>] kstrdup_const+0x6c/0xa4
[  579.247930]c6 [ T5491] kmemleak:     [<00000000d7843951>] __kernfs_new_node+0x5c/0x1dc
[  579.255830]c6 [ T5491] kmemleak:     [<0000000073b5a7bd>] kernfs_new_node+0x60/0xc4
[  579.263436]c6 [ T5491] kmemleak:     [<000000002c7a48d5>] __kernfs_create_file+0x60/0xfc
[  579.271485]c6 [ T5491] kmemleak:     [<00000000260ae4a1>] cgroup_addrm_files+0x244/0x4b0
[  579.279534]c6 [ T5491] kmemleak:     [<00000000ec6bce51>] css_populate_dir+0xb4/0x13c
[  579.287324]c6 [ T5491] kmemleak:     [<000000005913d698>] cgroup_mkdir+0x1e0/0x31c
[  579.294859]c6 [ T5491] kmemleak:     [<0000000052605ead>] kernfs_iop_mkdir.llvm.8836999160598622324+0xb0/0x168
[  579.304817]c6 [ T5491] kmemleak:     [<0000000009665bc4>] vfs_mkdir+0xec/0x170
[  579.311990]c6 [ T5491] kmemleak:     [<000000003c9c94c1>] do_mkdirat+0xa4/0x168
[  579.319279]c6 [ T5491] kmemleak:     [<000000005dd5be19>] __arm64_sys_mkdirat+0x28/0x38
[  579.327242]c6 [ T5491] kmemleak:     [<000000005a0b9381>] el0_svc_common+0xb4/0x188
[  579.334868]c6 [ T5491] kmemleak:     [<0000000063586a51>] el0_svc_handler+0x2c/0x3c
[  579.342472]c6 [ T5491] kmemleak:     [<00000000edfd67aa>] el0_svc+0x8/0x100

Signed-off-by: Zhaoyang Huang <redacted>
---
 mm/kmemleak.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 97 insertions(+), 1 deletion(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 1eddc01..34134e5 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c

@@ -102,6 +102,8 @@
 #include <linux/kfence.h>
 #include <linux/kmemleak.h>
 #include <linux/memory_hotplug.h>
+#include <linux/jhash.h>
+#include <linux/random.h>

 /*
  * Kmemleak configuration and common defines.

@@ -143,6 +145,7 @@ struct kmemleak_object {
        unsigned int flags;             /* object status flags */
        struct list_head object_list;
        struct list_head gray_list;
+       struct list_head report_list;
        struct rb_node rb_node;
        struct rcu_head rcu;            /* object_list lockless traversal */
        /* object usage count; object freed when use_count == 0 */

@@ -161,11 +164,18 @@ struct kmemleak_object {
        struct hlist_head area_list;
        unsigned long trace[MAX_TRACE];
        unsigned int trace_len;
+       u32 trace_hash;
        unsigned long jiffies;          /* creation timestamp */
        pid_t pid;                      /* pid of the current task */
        char comm[TASK_COMM_LEN];       /* executable name */
 };

+struct kmemleak_report {
+       u32 trace_hash;
+       struct list_head report_list_head;
+       struct rb_node rb_node_report;
+       struct list_head *report_pos;
+};
 /* flag representing the memory block allocation status */
 #define OBJECT_ALLOCATED       (1 << 0)
 /* flag set after the first reporting of an unreference object */

@@ -195,10 +205,13 @@ struct kmemleak_object {
 static struct kmemleak_object mem_pool[CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE];
 static int mem_pool_free_count = ARRAY_SIZE(mem_pool);
 static LIST_HEAD(mem_pool_free_list);
+static struct kmemleak_report kr_pool[CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE];
+static int kr_pool_free_count = ARRAY_SIZE(kr_pool);
 /* search tree for object boundaries */
 static struct rb_root object_tree_root = RB_ROOT;
 /* search tree for object (with OBJECT_PHYS flag) boundaries */
 static struct rb_root object_phys_tree_root = RB_ROOT;
+static struct rb_root object_report_tree_root = RB_ROOT;
 /* protecting the access to object_list, object_tree_root (or object_phys_tree_root) */
 static DEFINE_RAW_SPINLOCK(kmemleak_lock);

@@ -241,6 +254,7 @@ struct kmemleak_object {

 static void kmemleak_disable(void);

+static u32 trace_seed;
 /*
  * Print a warning and dump the stack trace.
  */

@@ -423,6 +437,46 @@ static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
        return __lookup_object(ptr, alias, false);
 }

+void print_unreferenced_object_list(struct seq_file *seq)
+{
+       unsigned long flags;
+       struct kmemleak_object *object;
+       struct kmemleak_report *object_report;
+       int i;
+       struct rb_node *rb;
+       bool reported_flag = false;
+
+       rcu_read_lock();
+       raw_spin_lock_irqsave(&kmemleak_lock, flags);
+       for (rb = rb_first(&object_report_tree_root); rb; rb = rb_next(rb)) {
+               object_report = rb_entry(rb, struct kmemleak_report, rb_node_report);
+               if (object_report && !list_empty(&object_report->report_list_head)) {
+                       list_for_each_entry_rcu(object, &object_report->report_list_head, report_list) {
+                               raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
+                               raw_spin_lock_irqsave(&kmemleak_lock, flags);
+                               if (unreferenced_object(object) &&
+                                               (object->flags & OBJECT_REPORTED)) {
+                                       reported_flag = true;
+                                       warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
+                                                       object->pointer, object->size);
+                                       warn_or_seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
+                                                       object->comm, object->pid, object->jiffies);
+                               }
+                       }
+                       if (reported_flag) {
+                               warn_or_seq_printf(seq, "  backtrace:\n");
+                               object = list_prev_entry(object, report_list);
+                               for (i = 0; i < object->trace_len; i++) {
+                                       void *ptr = (void *)object->trace[i];
+                                       warn_or_seq_printf(seq, "    [<%p>] %pS\n", ptr, ptr);
+                               }
+                               reported_flag = false;
+                       }
+               }
+       }
+       raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
+       rcu_read_unlock();
+}
 /*
  * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
  * that once an object's use_count reached 0, the RCU freeing was already

@@ -568,6 +622,7 @@ static void __remove_object(struct kmemleak_object *object)
                                   &object_phys_tree_root :
                                   &object_tree_root);
        list_del_rcu(&object->object_list);
+       list_del_rcu(&object->report_list);
 }

 /*

@@ -610,9 +665,11 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,
 {
        unsigned long flags;
        struct kmemleak_object *object, *parent;
+       struct kmemleak_report *report, *report_parent;
        struct rb_node **link, *rb_parent;
        unsigned long untagged_ptr;
        unsigned long untagged_objp;
+       u32 trace_hash;

        object = mem_pool_alloc(gfp);
        if (!object) {

@@ -623,6 +680,7 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,

        INIT_LIST_HEAD(&object->object_list);
        INIT_LIST_HEAD(&object->gray_list);
+       INIT_LIST_HEAD(&object->report_list);
        INIT_HLIST_HEAD(&object->area_list);
        raw_spin_lock_init(&object->lock);
        atomic_set(&object->use_count, 1);

@@ -655,6 +713,7 @@ static struct kmemleak_object *__create_object(unsigned long ptr, size_t size,

        /* kernel backtrace */
        object->trace_len = __save_stack_trace(object->trace);
+       object->trace_hash = jhash2((const u32 *)object->trace, object->trace_len / sizeof(u32), trace_seed);

        raw_spin_lock_irqsave(&kmemleak_lock, flags);

@@ -694,8 +753,42 @@ static struct kmemleak_object *__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);
+
+       raw_spin_lock_irqsave(&kmemleak_lock, flags);
+       link = &object_report_tree_root.rb_node;
+       rb_parent = NULL;
+       while (*link) {
+               raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
+               raw_spin_lock_irqsave(&kmemleak_lock, flags);
+               rb_parent = *link;
+               report_parent = rb_entry(rb_parent, struct kmemleak_report, rb_node_report);
+               trace_hash = report_parent->trace_hash;
+               if (object->trace_hash < trace_hash)
+                       link = &report_parent->rb_node_report.rb_left;
+               else if (trace_hash < object->trace_hash)
+                       link = &report_parent->rb_node_report.rb_right;
+               else {
+                       list_add_tail_rcu(&object->report_list, &report_parent->report_list_head);
+                       goto out;
+               }
+       }
+       report = kr_pool_free_count ? &kr_pool[--kr_pool_free_count] : NULL;
+       if (!report)
+               goto out;
+       report->trace_hash = object->trace_hash;
+       /*
+        * report is the 1st node represent this trace_hash, init its list_head and
+        * insert it to object_report_tree_root
+        */
+       INIT_LIST_HEAD(&report->report_list_head);
+       /* record 1st object to the list*/
+       list_add_tail_rcu(&object->report_list, &report->report_list_head);
+       /* initialize the report_pos as report_list_head*/
+       report->report_pos = &report->report_list_head;
+       /* add the node to rb tree*/
+       rb_link_node(&report->rb_node_report, rb_parent, link);
+       rb_insert_color(&report->rb_node_report, &object_report_tree_root);
 out:
        raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
        return object;

@@ -1947,6 +2040,8 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
                kmemleak_scan();
        else if (strncmp(buf, "dump=", 5) == 0)
                ret = dump_str_object_info(buf + 5);
+       else if (strncmp(buf, "report", 6) == 0)
+               print_unreferenced_object_list(NULL);
        else
                ret = -EINVAL;

@@ -2080,6 +2175,7 @@ void __init kmemleak_init(void)
                create_object((unsigned long)__start_ro_after_init,
                              __end_ro_after_init - __start_ro_after_init,
                              KMEMLEAK_GREY, GFP_ATOMIC);
+       get_random_bytes(&trace_seed, 4);
 }

 /*
--

1.9.1