Messages in this thread Patch in this message | | | Date | Thu, 09 Feb 2012 07:41:41 -0500 | From | Xi Wang <> | Subject | [PATCH RFC] slab: introduce knalloc/kxnalloc |
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This patch introduces knalloc/kxnalloc wrappers that perform integer overflow checks without zeroing the memory.
knalloc(n, size, flags) is the non-zeroing version of kcalloc(), which allocates n * size bytes.
kxnalloc(xsize, n, size, flags) allocates xsize + n * size bytes. It is useful to allocate a structure ending with a zero-length array, which is a commonly used pattern. For example, in posix_acl_alloc() to allocate a posix_acl object one could call
kxnalloc(sizeof(struct posix_acl), count, sizeof(struct posix_acl_entry), flags);
to avoid overflowing the allocation size.
Suggested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Xi Wang <xi.wang@gmail.com> --- I coined the name knalloc() for Andrew's wtf_do_i_call_this() in the previous email. A better name is welcome.
I additionally added kxnalloc() since it's a common idiom. --- include/linux/slab.h | 31 +++++++++++++++++++++++++++---- 1 files changed, 27 insertions(+), 4 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h index 573c809..e3a1e81 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -190,7 +190,8 @@ size_t ksize(const void *); #endif /** - * kcalloc - allocate memory for an array. The memory is set to zero. + * kxnalloc - allocate memory for an array with an extra header. + * @xsize: extra header size. * @n: number of elements. * @size: element size. * @flags: the type of memory to allocate. @@ -240,11 +241,33 @@ size_t ksize(const void *); * for general use, and so are not documented here. For a full list of * potential flags, always refer to linux/gfp.h. */ -static inline void *kcalloc(size_t n, size_t size, gfp_t flags) +static inline void *kxnalloc(size_t xsize, size_t n, size_t size, gfp_t flags) { - if (size != 0 && n > ULONG_MAX / size) + if (size != 0 && n > (ULONG_MAX - xsize) / size) return NULL; - return __kmalloc(n * size, flags | __GFP_ZERO); + return __kmalloc(xsize + n * size, flags); +} + +/** + * knalloc - allocate memory for an array. + * @n: number of elements. + * @size: element size. + * @flags: the type of memory to allocate (see kmalloc). + */ +static inline void *knalloc(size_t n, size_t size, gfp_t flags) +{ + return kxnalloc(0, n, size, flags); +} + +/** + * kcalloc - allocate memory for an array. The memory is set to zero. + * @n: number of elements. + * @size: element size. + * @flags: the type of memory to allocate (see kmalloc). + */ +static inline void *kcalloc(size_t n, size_t size, gfp_t flags) +{ + return knalloc(n, size, flags | __GFP_ZERO); } #if !defined(CONFIG_NUMA) && !defined(CONFIG_SLOB) -- 1.7.5.4
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