From: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> Subject: mm, slub: change run-time assertion in kmalloc_index() to compile-time Currently when size is not supported by kmalloc_index, compiler will generate a run-time BUG() while compile-time error is also possible, and better. So change BUG to BUILD_BUG_ON_MSG to make compile-time check possible. Also remove code that allocates more than 32MB because current implementation supports only up to 32MB. [42.hyeyoo@xxxxxxxxx: fix support for clang 10] Link: https://lkml.kernel.org/r/20210518181247.GA10062@hyeyoo [vbabka@xxxxxxx: fix false-positive assert in kernel/bpf/local_storage.c] Link: https://lkml.kernel.org/r/bea97388-01df-8eac-091b-a3c89b4a4a09@suse.czLink: https://lkml.kernel.org/r/20210511173448.GA54466@hyeyoo [elver@xxxxxxxxxx: kfence fix] Link: https://lkml.kernel.org/r/20210512195227.245000695c9014242e9a00e5@xxxxxxxxxxxxxxxxxxxx Signed-off-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Marco Elver <elver@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/slab.h | 17 ++++++++++++++--- mm/kfence/kfence_test.c | 5 +++-- mm/slab_common.c | 7 +++---- 3 files changed, 20 insertions(+), 9 deletions(-) --- a/include/linux/slab.h~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time +++ a/include/linux/slab.h @@ -346,8 +346,14 @@ static __always_inline enum kmalloc_cach * 1 = 65 .. 96 bytes * 2 = 129 .. 192 bytes * n = 2^(n-1)+1 .. 2^n + * + * Note: __kmalloc_index() is compile-time optimized, and not runtime optimized; + * typical usage is via kmalloc_index() and therefore evaluated at compile-time. + * Callers where !size_is_constant should only be test modules, where runtime + * overheads of __kmalloc_index() can be tolerated. Also see kmalloc_slab(). */ -static __always_inline unsigned int kmalloc_index(size_t size) +static __always_inline unsigned int __kmalloc_index(size_t size, + bool size_is_constant) { if (!size) return 0; @@ -382,12 +388,17 @@ static __always_inline unsigned int kmal if (size <= 8 * 1024 * 1024) return 23; if (size <= 16 * 1024 * 1024) return 24; if (size <= 32 * 1024 * 1024) return 25; - if (size <= 64 * 1024 * 1024) return 26; - BUG(); + + if ((IS_ENABLED(CONFIG_CC_IS_GCC) || CONFIG_CLANG_VERSION >= 110000) + && !IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES) && size_is_constant) + BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()"); + else + BUG(); /* Will never be reached. Needed because the compiler may complain */ return -1; } +#define kmalloc_index(s) __kmalloc_index(s, true) #endif /* !CONFIG_SLOB */ void *__kmalloc(size_t size, gfp_t flags) __assume_kmalloc_alignment __malloc; --- a/mm/kfence/kfence_test.c~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time +++ a/mm/kfence/kfence_test.c @@ -197,7 +197,7 @@ static void test_cache_destroy(void) static inline size_t kmalloc_cache_alignment(size_t size) { - return kmalloc_caches[kmalloc_type(GFP_KERNEL)][kmalloc_index(size)]->align; + return kmalloc_caches[kmalloc_type(GFP_KERNEL)][__kmalloc_index(size, false)]->align; } /* Must always inline to match stack trace against caller. */ @@ -267,7 +267,8 @@ static void *test_alloc(struct kunit *te if (is_kfence_address(alloc)) { struct page *page = virt_to_head_page(alloc); - struct kmem_cache *s = test_cache ?: kmalloc_caches[kmalloc_type(GFP_KERNEL)][kmalloc_index(size)]; + struct kmem_cache *s = test_cache ?: + kmalloc_caches[kmalloc_type(GFP_KERNEL)][__kmalloc_index(size, false)]; /* * Verify that various helpers return the right values --- a/mm/slab_common.c~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time +++ a/mm/slab_common.c @@ -754,8 +754,8 @@ struct kmem_cache *kmalloc_slab(size_t s /* * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time. - * kmalloc_index() supports up to 2^26=64MB, so the final entry of the table is - * kmalloc-67108864. + * kmalloc_index() supports up to 2^25=32MB, so the final entry of the table is + * kmalloc-32M. */ const struct kmalloc_info_struct kmalloc_info[] __initconst = { INIT_KMALLOC_INFO(0, 0), @@ -783,8 +783,7 @@ const struct kmalloc_info_struct kmalloc INIT_KMALLOC_INFO(4194304, 4M), INIT_KMALLOC_INFO(8388608, 8M), INIT_KMALLOC_INFO(16777216, 16M), - INIT_KMALLOC_INFO(33554432, 32M), - INIT_KMALLOC_INFO(67108864, 64M) + INIT_KMALLOC_INFO(33554432, 32M) }; /* _
