Hi David,
I have sucessfully tested the attached patch on Sparc32:sun4c.
Is there any chance of this getting sufficiantly tested on other
architectures to get in into v2.6.22 ?
Regards
Mark Fortescue.
From: Mark Fortescue <[email protected]>, David Woodhouse <[email protected]>
Verious alignment fixes in the SLAB alocator that increased the size
of the RedZone words failed to ensure that RedZone word 2 is aligned
on a 64bit boundary. This resulted in random invalid instruction
occourances on Sparc32 (sun4c).
These additional changes should ensure that the RedZone words are
correctly aligned on a 64bit boundary for architectures that require this.
Signed-off-by: Mark Fortescue <[email protected]>
---
Tested on Sparc32:sun4c
Additional testing desirable on PowerPC32, Sparc64, PowerPC64 and any
other platforms where alignment changes may be of concirn.
--- linux-2.6/mm/slab.c 2007-07-03 19:09:48.000000000 +0100
+++ linux-test/mm/slab.c 2007-07-04 04:14:15.000000000 +0100
@@ -137,6 +137,7 @@
/* Shouldn't this be in a header file somewhere? */
#define BYTES_PER_WORD sizeof(void *)
+#define RED_ZONE_ALIGN (max(__alignof__(void *), __alignof(unsigned long long)) - 1)
#ifndef cache_line_size
#define cache_line_size() L1_CACHE_BYTES
@@ -547,7 +548,7 @@ static unsigned long long *dbg_redzone2(
if (cachep->flags & SLAB_STORE_USER)
return (unsigned long long *)(objp + cachep->buffer_size -
sizeof(unsigned long long) -
- BYTES_PER_WORD);
+ max(BYTES_PER_WORD, __alignof__(unsigned long long)));
return (unsigned long long *) (objp + cachep->buffer_size -
sizeof(unsigned long long));
}
@@ -2178,7 +2179,8 @@ kmem_cache_create (const char *name, siz
* above the next power of two: caches with object sizes just above a
* power of two have a significant amount of internal fragmentation.
*/
- if (size < 4096 || fls(size - 1) == fls(size-1 + 3 * BYTES_PER_WORD))
+ if (size < 4096 || fls(size - 1) == fls(size-1 + 2 * sizeof(unsigned long long) +
+ max(BYTES_PER_WORD, __alignof__(unsigned long long))))
flags |= SLAB_RED_ZONE | SLAB_STORE_USER;
if (!(flags & SLAB_DESTROY_BY_RCU))
flags |= SLAB_POISON;
@@ -2197,9 +2199,9 @@ kmem_cache_create (const char *name, siz
* unaligned accesses for some archs when redzoning is used, and makes
* sure any on-slab bufctl's are also correctly aligned.
*/
- if (size & (BYTES_PER_WORD - 1)) {
- size += (BYTES_PER_WORD - 1);
- size &= ~(BYTES_PER_WORD - 1);
+ if (size & RED_ZONE_ALIGN) {
+ size += RED_ZONE_ALIGN;
+ size &= ~RED_ZONE_ALIGN;
}
/* calculate the final buffer alignment: */
@@ -2261,9 +2263,14 @@ kmem_cache_create (const char *name, siz
}
if (flags & SLAB_STORE_USER) {
/* user store requires one word storage behind the end of
- * the real object.
+ * the real object. But if the second red zone must be
+ * aligned 'better' than that, allow for it.
*/
- size += BYTES_PER_WORD;
+ if (flags & SLAB_RED_ZONE
+ && BYTES_PER_WORD < __alignof__(unsigned long long))
+ size += __alignof__(unsigned long long);
+ else
+ size += BYTES_PER_WORD;
}
#if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC)
if (size >= malloc_sizes[INDEX_L3 + 1].cs_size
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