Messages in this thread | | | Subject | Re: WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (f6f6e1a4), by kmemleak's scan_block() | From | Catalin Marinas <> | Date | Tue, 25 Aug 2009 10:21:08 +0100 |
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On Tue, 2009-08-25 at 12:11 +0300, Pekka Enberg wrote: > On Tue, 2009-08-25 at 11:03 +0200, Vegard Nossum wrote: > > I don't know so much about the kmemleak internals, but this I can say > > about the kmemcheck part: According to your definition, an object is > > initialized if all the bytes of an object are initialized. > > > > Is it possible that because of this, if we have a partially > > uninitialized object, kmemleak will not record the pointers found in > > that object? If so, it might skip valid pointers, and deem an object > > unreferenced. Which could make kmemleak give false-positives. > > > > I think it would be better to ask kmemcheck on a per-pointer basis > > (i.e. for each pointer-sized word in the object), whether it is > > initialized or not. > > Yeah, makes sense.
I think this patch should work. With a few minor (aesthetic) things below and assuming that Ingo tests it (I don't have x86 hardware at hand now):
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> @@ -885,7 +886,8 @@ static void scan_block(void *_start, void *_end, > > for (ptr = start; ptr < end; ptr++) { > unsigned long flags; > - unsigned long pointer = *ptr; > + unsigned long pointer; > + > struct kmemleak_object *object;
An empty line here added which splits the local variables block.
> if (allow_resched) > @@ -893,6 +895,13 @@ static void scan_block(void *_start, void *_end, > if (scan_should_stop()) > break; > > + /* Don't scan uninitialized memory. */ > + if (!kmemcheck_is_obj_initialized((unsigned long) ptr, > + sizeof(unsigned long)))
There is a BYTES_PER_POINTER macro defined in the kmemleak.c file, you could use that instead of sizeof(unsigned long).
Thanks.
-- Catalin
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