[MIPS] Make unwind_stack() can dig into interrupted context

If the PC was ret_from_irq or ret_from_exception, there will be no
more normal stackframe.  Instead of stopping the unwinding, use PC and
RA saved by an exception handler to continue unwinding into the
interrupted context.  This also simplifies the CONFIG_STACKTRACE code.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 6 insertions, 26 deletions

diff --git a/arch/mips/kernel/stacktrace.c b/arch/mips/kernel/stacktrace.c
index 676e6f69d24b..4aabe526a68e 100644
--- a/arch/mips/kernel/stacktrace.c
+++ b/arch/mips/kernel/stacktrace.c
@@ -31,23 +31,21 @@ static void save_raw_context_stack(struct stack_trace *trace,
 	}
 }
 
-static struct pt_regs * save_context_stack(struct stack_trace *trace,
+static void save_context_stack(struct stack_trace *trace,
 	struct task_struct *task, struct pt_regs *regs)
 {
 	unsigned long sp = regs->regs[29];
 #ifdef CONFIG_KALLSYMS
 	unsigned long ra = regs->regs[31];
 	unsigned long pc = regs->cp0_epc;
-	unsigned long stack_page =
-		(unsigned long)task_stack_page(task);
-	extern void ret_from_irq(void);
-	extern void ret_from_exception(void);
 
 	if (raw_show_trace || !__kernel_text_address(pc)) {
+		unsigned long stack_page =
+			(unsigned long)task_stack_page(task);
 		if (stack_page && sp >= stack_page &&
 		    sp <= stack_page + THREAD_SIZE - 32)
 			save_raw_context_stack(trace, sp);
-		return NULL;
+		return;
 	}
 	do {
 		if (trace->skip > 0)
@@ -56,25 +54,11 @@ static struct pt_regs * save_context_stack(struct stack_trace *trace,
 			trace->entries[trace->nr_entries++] = pc;
 		if (trace->nr_entries >= trace->max_entries)
 			break;
-		/*
-		 * If we reached the bottom of interrupt context,
-		 * return saved pt_regs.
-		 */
-		if (pc == (unsigned long)ret_from_irq ||
-		    pc == (unsigned long)ret_from_exception) {
-			if (stack_page && sp >= stack_page &&
-			    sp <= stack_page + THREAD_SIZE - 32)
-				return (struct pt_regs *)sp;
-			break;
-		}
-		pc = unwind_stack(task, &sp, pc, ra);
-		ra = 0;
+		pc = unwind_stack(task, &sp, pc, &ra);
 	} while (pc);
 #else
 	save_raw_context_stack(sp);
 #endif
-
-	return NULL;
 }
 
 /*
@@ -97,9 +81,5 @@ void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
 		prepare_frametrace(regs);
 	}
 
-	while (1) {
-		regs = save_context_stack(trace, task, regs);
-		if (!regs || trace->nr_entries >= trace->max_entries)
-			break;
-	}
+	save_context_stack(trace, task, regs);
 }