Messages in this thread Patch in this message | | | Date | Wed, 25 Apr 2007 12:25:41 -0700 (PDT) | From | Christoph Lameter <> | Subject | BUILD_BUG_ON does not work |
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Here is a simple patch attempting to use BUILD_ON to fail if a too high slab size is requested. Currently we generate a link failure which makes it difficult to detect bad kmallocs.
However the BUILD_BUG_ON never triggers. kmalloc(64 *1024*1024, GFP_KERNEL) returns 0 and we get an alloc from the 8 byte kmalloc cache.
kmalloc_index() returns a constant result and thus index is constant. What do I need to do to make BUILD_BUG_ON trigger?
SLUB: Use BUILD_BUG_ON to flag too big slab caches
Do not generate a link failure instead abort compilation using BUILD_BUG_ON
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Index: linux-2.6.21-rc7-mm1/include/linux/slub_def.h =================================================================== --- linux-2.6.21-rc7-mm1.orig/include/linux/slub_def.h 2007-04-25 11:38:00.000000000 -0700 +++ linux-2.6.21-rc7-mm1/include/linux/slub_def.h 2007-04-25 11:38:14.000000000 -0700 @@ -140,17 +140,11 @@ static inline struct kmem_cache *kmalloc { int index = kmalloc_index(size); + BUILD_BUG_ON(index < 0); + if (index == 0) return NULL; - if (index < 0) { - /* - * Generate a link failure. Would be great if we could - * do something to stop the compile here. - */ - extern void __kmalloc_size_too_large(void); - __kmalloc_size_too_large(); - } return &kmalloc_caches[index]; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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