mm: Make mem_dump_obj() handle vmalloc() memory

This commit adds vmalloc() support to mem_dump_obj().  Note that the
vmalloc_dump_obj() function combines the checking and dumping, in
contrast with the split between kmem_valid_obj() and kmem_dump_obj().
The reason for the difference is that the checking in the vmalloc()
case involves acquiring a global lock, and redundant acquisitions of
global locks should be avoided, even on not-so-fast paths.

Note that this change causes on-stack variables to be reported as
vmalloc() storage from kernel_clone() or similar, depending on the degree
of inlining that your compiler does.  This is likely more helpful than
the earlier "non-paged (local) memory".

Cc: Andrew Morton <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: <[email protected]>
Reported-by: Andrii Nakryiko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

include/linux/vmalloc.h

@@ -246,4 +246,10 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
 int register_vmap_purge_notifier(struct notifier_block *nb);
 int unregister_vmap_purge_notifier(struct notifier_block *nb);
 
+#ifdef CONFIG_MMU
+bool vmalloc_dump_obj(void *object);
+#else
+static inline bool vmalloc_dump_obj(void *object) { return false; }
+#endif
+
 #endif /* _LINUX_VMALLOC_H */

mm/util.c

@@ -996,18 +996,20 @@ int __weak memcmp_pages(struct page *page1, struct page *page2)
  */
 void mem_dump_obj(void *object)
 {
+	if (kmem_valid_obj(object)) {
+		kmem_dump_obj(object);
+		return;
+	}
+	if (vmalloc_dump_obj(object))
+		return;
 	if (!virt_addr_valid(object)) {
 		if (object == NULL)
 			pr_cont(" NULL pointer.\n");
 		else if (object == ZERO_SIZE_PTR)
 			pr_cont(" zero-size pointer.\n");
 		else
-			pr_cont(" non-paged (local) memory.\n");
-		return;
-	}
-	if (kmem_valid_obj(object)) {
-		kmem_dump_obj(object);
+			pr_cont(" non-paged memory.\n");
 		return;
 	}
-	pr_cont(" non-slab memory.\n");
+	pr_cont(" non-slab/vmalloc memory.\n");
 }

mm/vmalloc.c

@@ -3448,6 +3448,18 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
 }
 #endif	/* CONFIG_SMP */
 
+bool vmalloc_dump_obj(void *object)
+{
+	struct vm_struct *vm;
+	void *objp = (void *)PAGE_ALIGN((unsigned long)object);
+
+	vm = find_vm_area(objp);
+	if (!vm)
+		return false;
+	pr_cont(" vmalloc allocated at %pS\n", vm->caller);
+	return true;
+}
+
 #ifdef CONFIG_PROC_FS
 static void *s_start(struct seq_file *m, loff_t *pos)
 	__acquires(&vmap_purge_lock)