While studying the slab code, I found 2 strange things:
- kmalloc(size, ...); checks "size" validity only if size is a constant
known at compile-time.
- __kmalloc(...) contains code which is redundant with
kmem_find_general_cachep().
The following patch solves these two problems:
- It creates a (rather ugly) macro in kmalloc_sizes.h in order to check
kmalloc(size)'s validity at run-time in O(1).
- It replaces redundant code in __kmalloc() by a call to
kmem_find_general_cachep(). The debug checks are moved in the latter.
Please comment, as it is my first patch to the linux kernel.
Signed-off-by: Renaud Lienhart <[EMAIL PROTECTED]>
diff -Nrpu linux-2.6.11-orig/include/linux/kmalloc_sizes.h
linux-2.6.11-new/include/linux/kmalloc_sizes.h
--- linux-2.6.11-orig/include/linux/kmalloc_sizes.h 2005-03-02
08:38:20.000000000 +0100
+++ linux-2.6.11-new/include/linux/kmalloc_sizes.h 2005-03-06
21:34:34.000000000 +0100
@@ -19,15 +19,20 @@
CACHE(32768)
CACHE(65536)
CACHE(131072)
+#define MAX_KMALLOC 131072
#ifndef CONFIG_MMU
CACHE(262144)
CACHE(524288)
CACHE(1048576)
+#undef MAX_KMALLOC
+#define MAX_KMALLOC 1048576
#ifdef CONFIG_LARGE_ALLOCS
CACHE(2097152)
CACHE(4194304)
CACHE(8388608)
CACHE(16777216)
CACHE(33554432)
+#undef MAX_KMALLOC
+#define MAX_KMALLOC 33554432
#endif /* CONFIG_LARGE_ALLOCS */
#endif /* CONFIG_MMU */
diff -Nrpu linux-2.6.11-orig/include/linux/slab.h
linux-2.6.11-new/include/linux/slab.h
--- linux-2.6.11-orig/include/linux/slab.h 2005-03-02 08:38:33.000000000
+0100
+++ linux-2.6.11-new/include/linux/slab.h 2005-03-06 21:34:14.000000000
+0100
@@ -102,6 +102,8 @@ found:
malloc_sizes[i].cs_dmacachep :
malloc_sizes[i].cs_cachep, flags);
}
+ if (unlikely(size > MAX_KMALLOC))
+ return NULL;
return __kmalloc(size, flags);
}
diff -Nrpu linux-2.6.11-orig/mm/slab.c linux-2.6.11-new/mm/slab.c
--- linux-2.6.11-orig/mm/slab.c 2005-03-02 08:38:38.000000000 +0100
+++ linux-2.6.11-new/mm/slab.c 2005-03-06 21:33:58.000000000 +0100
@@ -507,7 +507,7 @@ static int slab_break_gfp_order = BREAK_
struct cache_sizes malloc_sizes[] = {
#define CACHE(x) { .cs_size = (x) },
#include <linux/kmalloc_sizes.h>
- { 0, }
+ CACHE(0)
#undef CACHE
};
@@ -584,19 +584,24 @@ static inline struct array_cache *ac_dat
return cachep->array[smp_processor_id()];
}
-static kmem_cache_t * kmem_find_general_cachep (size_t size, int gfpflags)
+static inline kmem_cache_t * kmem_find_general_cachep (size_t size, int
gfpflags)
{
struct cache_sizes *csizep = malloc_sizes;
- /* This function could be moved to the header file, and
- * made inline so consumers can quickly determine what
- * cache pointer they require.
- */
for ( ; csizep->cs_size; csizep++) {
if (size > csizep->cs_size)
continue;
break;
}
+#if DEBUG
+ /* we are a bit too optimistic and size > MAX_KMALLOC */
+ BUG_ON(csizep->cs_size == 0);
+ /* This happens if someone tries to call
+ * kmem_cache_create(), or __kmalloc(), before
+ * the generic caches are initialized.
+ */
+ BUG_ON(csizep->cs_cachep == NULL);
+#endif
return (gfpflags & GFP_DMA) ? csizep->cs_dmacachep : csizep->cs_cachep;
}
@@ -2453,22 +2458,10 @@ EXPORT_SYMBOL(kmem_cache_alloc_node);
*/
void * __kmalloc (size_t size, int flags)
{
- struct cache_sizes *csizep = malloc_sizes;
+ kmem_cache_t *cachep;
- for (; csizep->cs_size; csizep++) {
- if (size > csizep->cs_size)
- continue;
-#if DEBUG
- /* This happens if someone tries to call
- * kmem_cache_create(), or kmalloc(), before
- * the generic caches are initialized.
- */
- BUG_ON(csizep->cs_cachep == NULL);
-#endif
- return __cache_alloc(flags & GFP_DMA ?
- csizep->cs_dmacachep : csizep->cs_cachep, flags);
- }
- return NULL;
+ cachep = kmem_find_general_cachep(size, flags);
+ return __cache_alloc(cachep, flags);
}
EXPORT_SYMBOL(__kmalloc);
-
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