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Date: Tue, 1 Jun 2010 13:25:09 +0300
From: Hiroshi DOYU <Hiroshi.DOYU@...ia.com>
To: linux-kernel@...r.kernel.org
Cc: catalin.marinas@....com, ext-phil.2.carmody@...ia.com,
linux-omap@...r.kernel.org, Hiroshi DOYU <Hiroshi.DOYU@...ia.com>
Subject: [PATCH v2 1/3] kmemleak: Fix false positives with special scan
From: Hiroshi DOYU <Hiroshi.DOYU@...ia.com>
There is a false positive case that a pointer is calculated by other
methods than the usual container_of macro. "kmemleak_ignore" can cover
such a false positive, but it would loose the advantage of memory leak
detection. This patch allows kmemleak to work with such false
positives by introducing a new special memory block with a specified
calculation formula. A client module can register its area with a
function, which kmemleak could scan and calculate a pointer with a
registered special function.
To avoid client being unloaded before unregistering special
conversion, module reference is introduced. This was pointed by Phil
Carmody.
A typical use case could be the IOMMU pagetable allocation which
stores pointers to the second level of page tables with some
conversion, for example, a physical address with attribution bits.
Signed-off-by: Hiroshi DOYU <Hiroshi.DOYU@...ia.com>
Acked-by: Phil Carmody <ext-phil.2.carmody@...ia.com>
---
include/linux/kmemleak.h | 5 ++
mm/kmemleak.c | 114 ++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 116 insertions(+), 3 deletions(-)
diff --git a/include/linux/kmemleak.h b/include/linux/kmemleak.h
index 99d9a67..1ff1cbc 100644
--- a/include/linux/kmemleak.h
+++ b/include/linux/kmemleak.h
@@ -35,6 +35,11 @@ extern void kmemleak_ignore(const void *ptr) __ref;
extern void kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp) __ref;
extern void kmemleak_no_scan(const void *ptr) __ref;
+extern int kmemleak_special_scan(const void *ptr, size_t size,
+ unsigned long (*fn)(void *, unsigned long), void *data,
+ struct module *owner) __ref;
+extern void kmemleak_no_special(const void *ptr) __ref;
+
static inline void kmemleak_alloc_recursive(const void *ptr, size_t size,
int min_count, unsigned long flags,
gfp_t gfp)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 2c0d032..872d5f3 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -249,6 +249,88 @@ static struct early_log
early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
static int crt_early_log __initdata;
+/* scan area which requires special conversion */
+struct special_block {
+ void *start;
+ void *end;
+ unsigned long (*fn)(void *, unsigned long);
+ void *data;
+ struct module *owner;
+};
+#define SPECIAL_MAX (PAGE_SIZE / sizeof(struct special_block))
+static struct special_block special_block[SPECIAL_MAX];
+static DEFINE_SPINLOCK(special_block_lock);
+
+int kmemleak_special_scan(const void *ptr, size_t size,
+ unsigned long (*fn)(void *, unsigned long), void *data,
+ struct module *owner)
+{
+ struct special_block *sp;
+ int i, err = 0;
+
+ if (!ptr || (size == 0) || !fn)
+ return -EINVAL;
+
+ spin_lock(&special_block_lock);
+
+ if (!try_module_get(owner)) {
+ err = -ENODEV;
+ goto err_module_get;
+ }
+
+ sp = special_block;
+ for (i = 0; i < SPECIAL_MAX; i++, sp++) {
+ if (!sp->start)
+ break;
+ }
+
+ if (i == SPECIAL_MAX) {
+ err = -ENOMEM;
+ goto err_no_entry;
+ }
+ sp->start = (void *)ptr;
+ sp->end = (void *)ptr + size;
+ sp->fn = fn;
+ sp->data = data;
+ sp->owner = owner;
+
+ spin_unlock(&special_block_lock);
+
+ return 0;
+
+err_no_entry:
+ module_put(owner);
+err_module_get:
+ spin_unlock(&special_block_lock);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(kmemleak_special_scan);
+
+void kmemleak_no_special(const void *ptr)
+{
+ int i;
+
+ spin_lock(&special_block_lock);
+
+ for (i = 0; i < SPECIAL_MAX; i++) {
+ struct special_block *sp;
+
+ sp = &special_block[i];
+ if (sp->start == ptr) {
+ module_put(sp->owner);
+ memset(sp, 0, sizeof(*sp));
+ break;
+ }
+ }
+
+ if (i == SPECIAL_MAX)
+ pr_warning("Couldn't find entry\n");
+
+ spin_unlock(&special_block_lock);
+}
+EXPORT_SYMBOL_GPL(kmemleak_no_special);
+
static void kmemleak_disable(void);
/*
@@ -983,8 +1065,9 @@ static int scan_should_stop(void)
* Scan a memory block (exclusive range) for valid pointers and add those
* found to the gray list.
*/
-static void scan_block(void *_start, void *_end,
- struct kmemleak_object *scanned, int allow_resched)
+static void __scan_block(void *_start, void *_end,
+ struct kmemleak_object *scanned, int allow_resched,
+ struct special_block *sp)
{
unsigned long *ptr;
unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
@@ -1005,7 +1088,10 @@ static void scan_block(void *_start, void *_end,
BYTES_PER_POINTER))
continue;
- pointer = *ptr;
+ if (sp && sp->fn)
+ pointer = sp->fn(sp->data, *ptr);
+ else
+ pointer = *ptr;
object = find_and_get_object(pointer, 1);
if (!object)
@@ -1048,6 +1134,26 @@ static void scan_block(void *_start, void *_end,
}
}
+static inline void scan_block(void *_start, void *_end,
+ struct kmemleak_object *scanned, int allow_resched)
+{
+ __scan_block(_start, _end, scanned, allow_resched, NULL);
+}
+
+/* Scan area which requires special conversion of address */
+static void scan_special_block(void)
+{
+ int i;
+ struct special_block *sp;
+
+ sp = special_block;
+ for (i = 0; i < ARRAY_SIZE(special_block); i++, sp++) {
+ if (!sp->start)
+ continue;
+ __scan_block(sp->start, sp->end, NULL, 1, sp);
+ }
+}
+
/*
* Scan a memory block corresponding to a kmemleak_object. A condition is
* that object->use_count >= 1.
@@ -1166,6 +1272,8 @@ static void kmemleak_scan(void)
scan_block(_sdata, _edata, NULL, 1);
scan_block(__bss_start, __bss_stop, NULL, 1);
+ scan_special_block();
+
#ifdef CONFIG_SMP
/* per-cpu sections scanning */
for_each_possible_cpu(i)
--
1.7.1.rc1
--
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