hexagon: work around compiler crash

Clang cannot translate the string "r30" into a valid register yet.

Link: ClangBuiltLinux#755
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Nick Desaulniers <[email protected]>
Suggested-by: Sid Manning <[email protected]>
Reviewed-by: Brian Cain <[email protected]>
Cc: Allison Randal <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Richard Fontana <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: nickdesaulniers

arch/hexagon/kernel/stacktrace.c

@@ -11,8 +11,6 @@
 #include <linux/thread_info.h>
 #include <linux/module.h>
 
-register unsigned long current_frame_pointer asm("r30");
-
 struct stackframe {
 	unsigned long fp;
 	unsigned long rets;
@@ -30,7 +28,7 @@ void save_stack_trace(struct stack_trace *trace)
 
 	low = (unsigned long)task_stack_page(current);
 	high = low + THREAD_SIZE;
-	fp = current_frame_pointer;
+	fp = (unsigned long)__builtin_frame_address(0);
 
 	while (fp >= low && fp <= (high - sizeof(*frame))) {
 		frame = (struct stackframe *)fp;