From: Benjamin LaHaise <bcrl@kvack.org>
The patch below makes kmalloc() fail at compile time for swapped flags and
size arguments when the flags are a constant. It will also fail at runtime
(non-constant flags) due to the size being too large.
This is done by adding a new flag, __GFP_VALID, which is checked for in
kmalloc(), that results in the size being too large.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
include/linux/gfp.h | 13 +++++++------
include/linux/slab.h | 4 ++++
2 files changed, 11 insertions(+), 6 deletions(-)
diff -puN include/linux/gfp.h~make-kmalloc-fail-for-swapped-size--gfp-flags include/linux/gfp.h
--- devel/include/linux/gfp.h~make-kmalloc-fail-for-swapped-size--gfp-flags 2005-07-26 00:15:49.000000000 -0700
+++ devel-akpm/include/linux/gfp.h 2005-07-26 00:15:49.000000000 -0700
@@ -40,6 +40,7 @@ struct vm_area_struct;
#define __GFP_ZERO 0x8000u /* Return zeroed page on success */
#define __GFP_NOMEMALLOC 0x10000u /* Don't use emergency reserves */
#define __GFP_NORECLAIM 0x20000u /* No realy zone reclaim during allocation */
+#define __GFP_VALID 0x80000000u /* valid GFP flags */
#define __GFP_BITS_SHIFT 20 /* Room for 20 __GFP_FOO bits */
#define __GFP_BITS_MASK ((1 << __GFP_BITS_SHIFT) - 1)
@@ -50,12 +51,12 @@ struct vm_area_struct;
__GFP_NOFAIL|__GFP_NORETRY|__GFP_NO_GROW|__GFP_COMP| \
__GFP_NOMEMALLOC|__GFP_NORECLAIM)
-#define GFP_ATOMIC (__GFP_HIGH)
-#define GFP_NOIO (__GFP_WAIT)
-#define GFP_NOFS (__GFP_WAIT | __GFP_IO)
-#define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS)
-#define GFP_USER (__GFP_WAIT | __GFP_IO | __GFP_FS)
-#define GFP_HIGHUSER (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HIGHMEM)
+#define GFP_ATOMIC (__GFP_VALID | __GFP_HIGH)
+#define GFP_NOIO (__GFP_VALID | __GFP_WAIT)
+#define GFP_NOFS (__GFP_VALID | __GFP_WAIT | __GFP_IO)
+#define GFP_KERNEL (__GFP_VALID | __GFP_WAIT | __GFP_IO | __GFP_FS)
+#define GFP_USER (__GFP_VALID | __GFP_WAIT | __GFP_IO | __GFP_FS)
+#define GFP_HIGHUSER (__GFP_VALID | __GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HIGHMEM)
/* Flag - indicates that the buffer will be suitable for DMA. Ignored on some
platforms, used as appropriate on others */
diff -puN include/linux/slab.h~make-kmalloc-fail-for-swapped-size--gfp-flags include/linux/slab.h
--- devel/include/linux/slab.h~make-kmalloc-fail-for-swapped-size--gfp-flags 2005-07-26 00:15:49.000000000 -0700
+++ devel-akpm/include/linux/slab.h 2005-07-26 00:15:49.000000000 -0700
@@ -78,6 +78,10 @@ extern void *__kmalloc(size_t, unsigned
static inline void *kmalloc(size_t size, unsigned int __nocast flags)
{
+ if (__builtin_constant_p(flags) && !(flags & __GFP_VALID)) {
+ extern void __your_kmalloc_flags_are_not_valid(void);
+ __your_kmalloc_flags_are_not_valid();
+ }
if (__builtin_constant_p(size)) {
int i = 0;
#define CACHE(x) \
_