The patch titled
Subject: mm: move obj_to_index to include/linux/slab_def.h
has been added to the -mm tree. Its filename is
mm-move-obj_to_index-to-include-linux-slab_defh.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-move-obj_to_index-to-include-linux-slab_defh.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-move-obj_to_index-to-include-linux-slab_defh.patch
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------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: mm: move obj_to_index to include/linux/slab_def.h
While with SLUB we can actually preassign tags for caches with contructors
and store them in pointers in the freelist, SLAB doesn't allow that since
the freelist is stored as an array of indexes, so there are no pointers to
store the tags.
Instead we compute the tag twice, once when a slab is created before
calling the constructor and then again each time when an object is
allocated with kmalloc. Tag is computed simply by taking the lowest byte of
the index that corresponds to the object. However in kasan_kmalloc we only
have access to the objects pointer, so we need a way to find out which
index this object corresponds to.
This patch moves obj_to_index from slab.c to include/linux/slab_def.h to
be reused by KASAN.
Link: http://lkml.kernel.org/r/b68796c554fba66d5285274ea6356e642e18a9e5.1543337629.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/slab_def.h~mm-move-obj_to_index-to-include-linux-slab_defh
+++ a/include/linux/slab_def.h
@@ -104,4 +104,17 @@ static inline void *nearest_obj(struct k
return object;
}
+/*
+ * We want to avoid an expensive divide : (offset / cache->size)
+ * Using the fact that size is a constant for a particular cache,
+ * we can replace (offset / cache->size) by
+ * reciprocal_divide(offset, cache->reciprocal_buffer_size)
+ */
+static inline unsigned int obj_to_index(const struct kmem_cache *cache,
+ const struct page *page, void *obj)
+{
+ u32 offset = (obj - page->s_mem);
+ return reciprocal_divide(offset, cache->reciprocal_buffer_size);
+}
+
#endif /* _LINUX_SLAB_DEF_H */
--- a/mm/slab.c~mm-move-obj_to_index-to-include-linux-slab_defh
+++ a/mm/slab.c
@@ -406,19 +406,6 @@ static inline void *index_to_obj(struct
return page->s_mem + cache->size * idx;
}
-/*
- * We want to avoid an expensive divide : (offset / cache->size)
- * Using the fact that size is a constant for a particular cache,
- * we can replace (offset / cache->size) by
- * reciprocal_divide(offset, cache->reciprocal_buffer_size)
- */
-static inline unsigned int obj_to_index(const struct kmem_cache *cache,
- const struct page *page, void *obj)
-{
- u32 offset = (obj - page->s_mem);
- return reciprocal_divide(offset, cache->reciprocal_buffer_size);
-}
-
#define BOOT_CPUCACHE_ENTRIES 1
/* internal cache of cache description objs */
static struct kmem_cache kmem_cache_boot = {
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
kasan-mm-change-hooks-signatures.patch
kasan-slub-handle-pointer-tags-in-early_kmem_cache_node_alloc.patch
kasan-move-common-generic-and-tag-based-code-to-commonc.patch
kasan-rename-source-files-to-reflect-the-new-naming-scheme.patch
kasan-add-config_kasan_generic-and-config_kasan_sw_tags.patch
kasan-arm64-adjust-shadow-size-for-tag-based-mode.patch
kasan-rename-kasan_zero_page-to-kasan_early_shadow_page.patch
kasan-initialize-shadow-to-0xff-for-tag-based-mode.patch
arm64-move-untagged_addr-macro-from-uaccessh-to-memoryh.patch
kasan-add-tag-related-helper-functions.patch
kasan-arm64-untag-address-in-_virt_addr_is_linear.patch
kasan-preassign-tags-to-objects-with-ctors-or-slab_typesafe_by_rcu.patch
kasan-arm64-fix-up-fault-handling-logic.patch
kasan-arm64-enable-top-byte-ignore-for-the-kernel.patch
kasan-mm-perform-untagged-pointers-comparison-in-krealloc.patch
kasan-split-out-generic_reportc-from-reportc.patch
kasan-add-bug-reporting-routines-for-tag-based-mode.patch
mm-move-obj_to_index-to-include-linux-slab_defh.patch
kasan-add-hooks-implementation-for-tag-based-mode.patch
kasan-arm64-add-brk-handler-for-inline-instrumentation.patch
kasan-mm-arm64-tag-non-slab-memory-allocated-via-pagealloc.patch
kasan-add-__must_check-annotations-to-kasan-hooks.patch
kasan-arm64-select-have_arch_kasan_sw_tags.patch
kasan-update-documentation.patch
kasan-add-spdx-license-identifier-mark-to-source-files.patch
