[RFC/PATCH] Fix end_of_stack() and stack_not_used() for archs using CONFIG_STACK_GROWSUP

From: Chuck Ebbert
Date: Mon Sep 15 2014 - 00:23:15 EST


When looking at Aaron's patches adding extra checks of the stack canary, I
realized the code almost certainly never worked if the stack grows up. Something
like this is needed, I think.

Not-Signed-Off-By: Chuck Ebbert <cebbert.lkml@xxxxxxxxx>

---

Not even compile tested.

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5c2c885..da7f597 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2610,7 +2610,11 @@ static inline void setup_thread_stack(struct task_struct *p, struct task_struct

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
@@ -2629,13 +2633,21 @@ static inline unsigned long stack_not_used(struct task_struct *p)
{
unsigned long *n = end_of_stack(p);

+#ifdef CONFIG_STACK_GROWSUP
+ do { /* Skip over canary */
+ n--;
+ } while (!*n);
+
+ return (unsigned long)end_of_stack(p) - (unsigned long)n;
+#else
do { /* Skip over canary */
n++;
} while (!*n);

return (unsigned long)n - (unsigned long)end_of_stack(p);
-}
#endif
+}
+#endif /* CONFIG_DEBUG_STACK_USAGE */

/* set thread flags in other task's structures
* - see asm/thread_info.h for TIF_xxxx flags available


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/