um: adjust current_thread_info() for newer gcc versions

richardweinberger · torvalds · commit 534e3adbd22e · 2011-04-28T11:28:21.000-07:00
In some cases gcc &gt;= 4.5.2 will optimize away current_thread_info().  To
prevent gcc from doing so the stack address has to be obtained via inline
asm.

Signed-off-by: Richard Weinberger &lt;richard@nod.at&gt;
Acked-by: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
@@ -49,7 +49,10 @@ static inline struct thread_info *current_thread_info(void)
 {
 	struct thread_info *ti;
 	unsigned long mask = THREAD_SIZE - 1;
-	ti = (struct thread_info *) (((unsigned long) &ti) & ~mask);
+	void *p;
+
+	asm volatile ("" : "=r" (p) : "0" (&ti));
+	ti = (struct thread_info *) (((unsigned long)p) & ~mask);
 	return ti;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -49,7 +49,10 @@ static inline struct thread_info *current_thread_info(void)`
`49`	`49`	`{`
`50`	`50`	`struct thread_info *ti;`
`51`	`51`	`unsigned long mask = THREAD_SIZE - 1;`
`52`		`- ti = (struct thread_info *) (((unsigned long) &ti) & ~mask);`
	`52`	`+ void *p;`
	`53`	`+`
	`54`	`+ asm volatile ("" : "=r" (p) : "0" (&ti));`
	`55`	`+ ti = (struct thread_info *) (((unsigned long)p) & ~mask);`
`53`	`56`	`return ti;`
`54`	`57`	`}`
`55`	`58`