From f3ac60671954c8d413532627b1be13a76f394c49 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@kernel.org>
Date: Fri, 3 Feb 2017 22:59:33 +0100
Subject: sched/headers: Move task-stack related APIs from <linux/sched.h> to
 <linux/sched/task_stack.h>

Split out the task->stack related functionality, which is not really
part of the core scheduler APIs.

Only keep task_thread_info() because it's used by sched.h.

Update the code that uses those facilities.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/sched/task_stack.h | 104 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)

(limited to 'include/linux/sched/task_stack.h')

diff --git a/include/linux/sched/task_stack.h b/include/linux/sched/task_stack.h
index d2d578e85f7d..aaa5c2a6a0e9 100644
--- a/include/linux/sched/task_stack.h
+++ b/include/linux/sched/task_stack.h
@@ -1,7 +1,111 @@
 #ifndef _LINUX_SCHED_TASK_STACK_H
 #define _LINUX_SCHED_TASK_STACK_H
 
+/*
+ * task->stack (kernel stack) handling interfaces:
+ */
+
 #include <linux/sched.h>
 #include <linux/magic.h>
 
+#ifdef CONFIG_THREAD_INFO_IN_TASK
+
+/*
+ * When accessing the stack of a non-current task that might exit, use
+ * try_get_task_stack() instead.  task_stack_page will return a pointer
+ * that could get freed out from under you.
+ */
+static inline void *task_stack_page(const struct task_struct *task)
+{
+	return task->stack;
+}
+
+#define setup_thread_stack(new,old)	do { } while(0)
+
+static inline unsigned long *end_of_stack(const struct task_struct *task)
+{
+	return task->stack;
+}
+
+#elif !defined(__HAVE_THREAD_FUNCTIONS)
+
+#define task_stack_page(task)	((void *)(task)->stack)
+
+static inline void setup_thread_stack(struct task_struct *p, struct task_struct *org)
+{
+	*task_thread_info(p) = *task_thread_info(org);
+	task_thread_info(p)->task = p;
+}
+
+/*
+ * Return the address of the last usable long on the stack.
+ *
+ * When the stack grows down, this is just above the thread
+ * info struct. Going any lower will corrupt the threadinfo.
+ *
+ * When the stack grows up, this is the highest address.
+ * Beyond that position, we corrupt data on the next page.
+ */
+static inline unsigned long *end_of_stack(struct task_struct *p)
+{
+#ifdef CONFIG_STACK_GROWSUP
+	return (unsigned long *)((unsigned long)task_thread_info(p) + THREAD_SIZE) - 1;
+#else
+	return (unsigned long *)(task_thread_info(p) + 1);
+#endif
+}
+
+#endif
+
+#ifdef CONFIG_THREAD_INFO_IN_TASK
+static inline void *try_get_task_stack(struct task_struct *tsk)
+{
+	return atomic_inc_not_zero(&tsk->stack_refcount) ?
+		task_stack_page(tsk) : NULL;
+}
+
+extern void put_task_stack(struct task_struct *tsk);
+#else
+static inline void *try_get_task_stack(struct task_struct *tsk)
+{
+	return task_stack_page(tsk);
+}
+
+static inline void put_task_stack(struct task_struct *tsk) {}
+#endif
+
+#define task_stack_end_corrupted(task) \
+		(*(end_of_stack(task)) != STACK_END_MAGIC)
+
+static inline int object_is_on_stack(void *obj)
+{
+	void *stack = task_stack_page(current);
+
+	return (obj >= stack) && (obj < (stack + THREAD_SIZE));
+}
+
+extern void thread_stack_cache_init(void);
+
+#ifdef CONFIG_DEBUG_STACK_USAGE
+static inline unsigned long stack_not_used(struct task_struct *p)
+{
+	unsigned long *n = end_of_stack(p);
+
+	do { 	/* Skip over canary */
+# ifdef CONFIG_STACK_GROWSUP
+		n--;
+# else
+		n++;
+# endif
+	} while (!*n);
+
+# ifdef CONFIG_STACK_GROWSUP
+	return (unsigned long)end_of_stack(p) - (unsigned long)n;
+# else
+	return (unsigned long)n - (unsigned long)end_of_stack(p);
+# endif
+}
+#endif
+extern void set_task_stack_end_magic(struct task_struct *tsk);
+
 #endif /* _LINUX_SCHED_TASK_STACK_H */
-- 
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