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Subject[PATCH 4.9 07/39] kaiser: stack map PAGE_SIZE at THREAD_SIZE-PAGE_SIZE
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hugh Dickins <hughd@google.com>


Kaiser only needs to map one page of the stack; and
kernel/fork.c did not build on powerpc (no __PAGE_KERNEL).
It's all cleaner if linux/kaiser.h provides kaiser_map_thread_stack()
and kaiser_unmap_thread_stack() wrappers around asm/kaiser.h's
kaiser_add_mapping() and kaiser_remove_mapping(). And use
linux/kaiser.h in init/main.c to avoid the #ifdefs there.

Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/kaiser.h | 40 +++++++++++++++++++++++++++++++++-------
init/main.c | 6 +-----
kernel/fork.c | 7 ++-----
3 files changed, 36 insertions(+), 17 deletions(-)

--- a/include/linux/kaiser.h
+++ b/include/linux/kaiser.h
@@ -1,26 +1,52 @@
-#ifndef _INCLUDE_KAISER_H
-#define _INCLUDE_KAISER_H
+#ifndef _LINUX_KAISER_H
+#define _LINUX_KAISER_H

#ifdef CONFIG_KAISER
#include <asm/kaiser.h>
+
+static inline int kaiser_map_thread_stack(void *stack)
+{
+ /*
+ * Map that page of kernel stack on which we enter from user context.
+ */
+ return kaiser_add_mapping((unsigned long)stack +
+ THREAD_SIZE - PAGE_SIZE, PAGE_SIZE, __PAGE_KERNEL);
+}
+
+static inline void kaiser_unmap_thread_stack(void *stack)
+{
+ /*
+ * Note: may be called even when kaiser_map_thread_stack() failed.
+ */
+ kaiser_remove_mapping((unsigned long)stack +
+ THREAD_SIZE - PAGE_SIZE, PAGE_SIZE);
+}
#else

/*
* These stubs are used whenever CONFIG_KAISER is off, which
- * includes architectures that support KAISER, but have it
- * disabled.
+ * includes architectures that support KAISER, but have it disabled.
*/

static inline void kaiser_init(void)
{
}
-static inline void kaiser_remove_mapping(unsigned long start, unsigned long size)
+static inline int kaiser_add_mapping(unsigned long addr,
+ unsigned long size, unsigned long flags)
+{
+ return 0;
+}
+static inline void kaiser_remove_mapping(unsigned long start,
+ unsigned long size)
{
}
-static inline int kaiser_add_mapping(unsigned long addr, unsigned long size, unsigned long flags)
+static inline int kaiser_map_thread_stack(void *stack)
{
return 0;
}
+static inline void kaiser_unmap_thread_stack(void *stack)
+{
+}

#endif /* !CONFIG_KAISER */
-#endif /* _INCLUDE_KAISER_H */
+#endif /* _LINUX_KAISER_H */
--- a/init/main.c
+++ b/init/main.c
@@ -80,15 +80,13 @@
#include <linux/integrity.h>
#include <linux/proc_ns.h>
#include <linux/io.h>
+#include <linux/kaiser.h>

#include <asm/io.h>
#include <asm/bugs.h>
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/cacheflush.h>
-#ifdef CONFIG_KAISER
-#include <asm/kaiser.h>
-#endif

static int kernel_init(void *);

@@ -476,9 +474,7 @@ static void __init mm_init(void)
pgtable_init();
vmalloc_init();
ioremap_huge_init();
-#ifdef CONFIG_KAISER
kaiser_init();
-#endif
}

asmlinkage __visible void __init start_kernel(void)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -212,12 +212,9 @@ static unsigned long *alloc_thread_stack
#endif
}

-extern void kaiser_remove_mapping(unsigned long start_addr, unsigned long size);
static inline void free_thread_stack(struct task_struct *tsk)
{
-#ifdef CONFIG_KAISER
- kaiser_remove_mapping((unsigned long)tsk->stack, THREAD_SIZE);
-#endif
+ kaiser_unmap_thread_stack(tsk->stack);
#ifdef CONFIG_VMAP_STACK
if (task_stack_vm_area(tsk)) {
unsigned long flags;
@@ -501,7 +498,7 @@ static struct task_struct *dup_task_stru
*/
tsk->stack = stack;

- err= kaiser_add_mapping((unsigned long)tsk->stack, THREAD_SIZE, __PAGE_KERNEL);
+ err= kaiser_map_thread_stack(tsk->stack);
if (err)
goto free_stack;
#ifdef CONFIG_VMAP_STACK

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