The patch titled
Subject: kfence: test: fix for "mm, slub: change run-time assertion in kmalloc_index() to compile-time"
has been added to the -mm tree. Its filename is
mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix.patch
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------------------------------------------------------
From: Marco Elver <elver@xxxxxxxxxx>
Subject: kfence: test: fix for "mm, slub: change run-time assertion in kmalloc_index() to compile-time"
Enable using kmalloc_index() in allocator test modules again where the
size may be non-constant, while ensuring normal usage always passes a
constant size.
Split the definition into __kmalloc_index(size, size_is_constant), and a
definition of kmalloc_index(s), matching the old kmalloc_index()
interface, but that still requires size_is_constant==true. This ensures
that normal usage of kmalloc_index() always passes a constant size.
While the __-prefix should make it clearer that the function is to be used
with care, also rewrite the "Note" to highlight the restriction (and add a
hint to kmalloc_slab()).
The alternative considered here is to export kmalloc_slab(), but given it
is internal to mm/ and not in <linux/slab.h>, we should probably avoid
exporting it. Allocator test modules will work just fine by using
__kmalloc_index(s, false).
Link: https://lkml.kernel.org/r/20210512195227.245000695c9014242e9a00e5@xxxxxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/YJ0fN5Ul8i9e/3wC@xxxxxxxxxxxxxxxx
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/slab.h | 15 +++++++++++----
mm/kfence/kfence_test.c | 5 +++--
2 files changed, 14 insertions(+), 6 deletions(-)
--- a/include/linux/slab.h~mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix
+++ a/include/linux/slab.h
@@ -347,10 +347,13 @@ static __always_inline enum kmalloc_cach
* 2 = 129 .. 192 bytes
* n = 2^(n-1)+1 .. 2^n
*
- * Note: there's no need to optimize kmalloc_index because it's evaluated
- * in compile-time.
+ * 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;
@@ -386,11 +389,15 @@ static __always_inline unsigned int kmal
if (size <= 16 * 1024 * 1024) return 24;
if (size <= 32 * 1024 * 1024) return 25;
- BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
+ if (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-fix
+++ 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
_
Patches currently in -mm which might be from elver@xxxxxxxxxx are
mm-slub-change-run-time-assertion-in-kmalloc_index-to-compile-time-fix.patch
printk-introduce-dump_stack_lvl-fix.patch
