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mm: kmemleak: make the tool tolerant to struct scan_area allocation failures

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Patch series "mm: kmemleak: Use a memory pool for kmemleak object
allocations", v3.

Following the discussions on v2 of this patch(set) [1], this series takes
slightly different approach:

- it implements its own simple memory pool that does not rely on the
  slab allocator

- drops the early log buffer logic entirely since it can now allocate
  metadata from the memory pool directly before kmemleak is fully
  initialised

- CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE option is renamed to
  CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE

- moves the kmemleak_init() call earlier (mm_init())

- to avoid a separate memory pool for struct scan_area, it makes the
  tool robust when such allocations fail as scan areas are rather an
  optimisation

[1] http://lkml.kernel.org/r/20190727132334.9184-1-catalin.marinas@arm.com

This patch (of 3):

Object scan areas are an optimisation aimed to decrease the false
positives and slightly improve the scanning time of large objects known to
only have a few specific pointers.  If a struct scan_area fails to
allocate, kmemleak can still function normally by scanning the full
object.

Introduce an OBJECT_FULL_SCAN flag and mark objects as such when scan_area
allocation fails.

Link: http://lkml.kernel.org/r/20190812160642.52134-2-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Catalin Marinas 2019-09-23 15:33:59 -07:00 committed by Linus Torvalds
parent b751c52bb5
commit dba82d9431
1 changed files with 10 additions and 6 deletions
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16
mm/kmemleak.c
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@ -168,6 +168,8 @@ struct kmemleak_object {
#define OBJECT_REPORTED (1 << 1)
/* flag set to not scan the object */
#define OBJECT_NO_SCAN (1 << 2)
/* flag set to fully scan the object when scan_area allocation failed */
#define OBJECT_FULL_SCAN (1 << 3)
#define HEX_PREFIX " "
/* number of bytes to print per line; must be 16 or 32 */
@ -773,12 +775,14 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
}
area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
if (!area) {
pr_warn("Cannot allocate a scan area\n");
goto out;
}
spin_lock_irqsave(&object->lock, flags);
if (!area) {
pr_warn_once("Cannot allocate a scan area, scanning the full object\n");
/* mark the object for full scan to avoid false positives */
object->flags |= OBJECT_FULL_SCAN;
goto out_unlock;
}
if (size == SIZE_MAX) {
size = object->pointer + object->size - ptr;
} else if (ptr + size > object->pointer + object->size) {
@ -795,7 +799,6 @@ static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
hlist_add_head(&area->node, &object->area_list);
out_unlock:
spin_unlock_irqrestore(&object->lock, flags);
out:
put_object(object);
}
@ -1408,7 +1411,8 @@ static void scan_object(struct kmemleak_object *object)
if (!(object->flags & OBJECT_ALLOCATED))
/* already freed object */
goto out;
if (hlist_empty(&object->area_list)) {
if (hlist_empty(&object->area_list) ||
object->flags & OBJECT_FULL_SCAN) {
void *start = (void *)object->pointer;
void *end = (void *)(object->pointer + object->size);
void *next;