From f6a616800e68b61807d0f7bb0d5dc70665ef8046 Mon Sep 17 00:00:00 2001
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 18 Apr 2008 16:56:17 +1000
Subject: [PATCH] [POWERPC] Fix kernel stack allocation alignment
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>
---
arch/powerpc/kernel/process.c | 31 +++++++++++++++++++++++++++++++
include/asm-powerpc/thread_info.h | 8 ++------
2 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 703100d5e4589..6caad17ea72e6 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -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 */
diff --git a/include/asm-powerpc/thread_info.h b/include/asm-powerpc/thread_info.h
index 40d5f98c44fca..d030f5ce39ada 100644
--- a/include/asm-powerpc/thread_info.h
+++ b/include/asm-powerpc/thread_info.h
@@ -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 */
--
2.30.2