[PATCH v2 sl-b 3/5] mm: Make mem_dump_obj() handle vmalloc() memory

paulmck
2020-12-09T01:13:15Z

From: "Paul E. McKenney" <paulmck@kernel.org>

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 <akpm@linux-foundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <linux-mm@kvack.org>
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/vmalloc.h | 6 ++++++
mm/util.c | 12 +++++++-----
mm/vmalloc.c | 12 ++++++++++++
3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 938eaf9..c89c2be 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -248,4 +248,10 @@ 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 */
diff --git a/mm/util.c b/mm/util.c
index 8c2449f..ee99a0a 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -984,6 +984,12 @@ 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");
@@ -993,10 +999,6 @@ void mem_dump_obj(void *object)
pr_cont(" non-paged (local) memory.\n");
return;
}
- if (kmem_valid_obj(object)) {
- kmem_dump_obj(object);
- return;
- }
- pr_cont(" non-slab memory.\n");
+ pr_cont(" non-slab/vmalloc memory.\n");
}
EXPORT_SYMBOL_GPL(mem_dump_obj);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 6ae491a..7421719 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3431,6 +3431,18 @@ 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)
--
2.9.5