iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

[POWERPC] Fix kernel stack allocation alignment

Browse Source 
The powerpc kernel stacks need to be naturally aligned, as they
contain the thread info at the bottom, which is obtained by
clearing the low bits of the stack pointer.

However, when using 64K pages, the stack is smaller than a page,
so we use kmalloc to allocate it, but that doesn't provide the
alignment guarantee we need.

It appeared to work so far... until one enables SLUB debugging
which then returns unaligned pointers.  Ooops...

This fixes it by using a slab cache with enforced alignment.  It
relies on my previous patch that adds a thread_info_cache_init()
callback.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Benjamin Herrenschmidt 2008-04-18 16:56:17 +10:00 committed by Paul Mackerras
parent 8c9843e57a
commit f6a616800e
2 changed files with 33 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
arch/powerpc/kernel/process.c
View File

@ -1033,3 +1033,34 @@ void ppc64_runlatch_off(void)
}
}
#endif
#if THREAD_SHIFT < PAGE_SHIFT
static struct kmem_cache *thread_info_cache;
struct thread_info *alloc_thread_info(struct task_struct *tsk)
{
struct thread_info *ti;
ti = kmem_cache_alloc(thread_info_cache, GFP_KERNEL);
if (unlikely(ti == NULL))
return NULL;
#ifdef CONFIG_DEBUG_STACK_USAGE
memset(ti, 0, THREAD_SIZE);
#endif
return ti;
}
void free_thread_info(struct thread_info *ti)
{
kmem_cache_free(thread_info_cache, ti);
}
void thread_info_cache_init(void)
{
thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
THREAD_SIZE, 0, NULL);
BUG_ON(thread_info_cache == NULL);
}
#endif /* THREAD_SHIFT < PAGE_SHIFT */

8
include/asm-powerpc/thread_info.h
View File

@ -80,12 +80,8 @@ struct thread_info {
#else /* THREAD_SHIFT < PAGE_SHIFT */
#ifdef CONFIG_DEBUG_STACK_USAGE
#define alloc_thread_info(tsk) kzalloc(THREAD_SIZE, GFP_KERNEL)
#else
#define alloc_thread_info(tsk) kmalloc(THREAD_SIZE, GFP_KERNEL)
#endif
#define free_thread_info(ti) kfree(ti)
extern struct thread_info *alloc_thread_info(struct task_struct *tsk);
extern void free_thread_info(struct thread_info *ti);
#endif /* THREAD_SHIFT < PAGE_SHIFT */