[PATCH 7/7] Allow unwind_stack() to return ra for leaf function

[Franck Bui-Huu <vagabon.xyz@gmail.com>]

Since get_frame_info() is more robust, unwind_stack() can
returns ra value for leaf functions.

Signed-off-by: Franck Bui-Huu <vagabon.xyz@gmail.com>
---
 arch/mips/kernel/process.c |   20 ++++++++++++--------
 arch/mips/kernel/traps.c   |   15 ++++++---------
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 539b23b..6377b17 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -445,14 +445,15 @@ #endif
 
 #ifdef CONFIG_KALLSYMS
 /* used by show_frametrace() */
-unsigned long unwind_stack(struct task_struct *task,
-			   unsigned long **sp, unsigned long pc)
+unsigned long unwind_stack(struct task_struct *task, unsigned long **sp,
+			   unsigned long pc, struct pt_regs *regs)
 {
 	unsigned long stack_page;
 	struct mips_frame_info info;
 	char *modname;
 	char namebuf[KSYM_NAME_LEN + 1];
 	unsigned long size, ofs;
+	int leaf;
 
 	stack_page = (unsigned long)task_stack_page(task);
 	if (!stack_page)
@@ -465,18 +466,21 @@ unsigned long unwind_stack(struct task_s
 
 	info.func = (void *)(pc - ofs);
 	info.func_size = ofs;	/* analyze from start to ofs */
-	if (get_frame_info(&info)) {
-		/* leaf or unknown */
-		*sp += info.frame_size / sizeof(long);
+	leaf = get_frame_info(&info);
+	if (leaf < 0)
 		return 0;
-	}
+
 	if ((unsigned long)*sp < stack_page ||
 	    (unsigned long)*sp + info.frame_size / sizeof(long) >
 	    stack_page + THREAD_SIZE - 32)
 		return 0;
 
-	pc = (*sp)[info.pc_offset];
+	if (leaf)
+		pc = regs->regs[31];
+	else
+		pc = (*sp)[info.pc_offset];
+
 	*sp += info.frame_size / sizeof(long);
-	return pc;
+	return __kernel_text_address(pc) ? pc : 0;
 }
 #endif
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 07191a6..78aed61 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -101,8 +101,9 @@ static int __init set_raw_show_trace(cha
 }
 __setup("raw_show_trace", set_raw_show_trace);
 
-extern unsigned long unwind_stack(struct task_struct *task,
-				  unsigned long **sp, unsigned long pc);
+extern unsigned long unwind_stack(struct task_struct *task, unsigned long **sp,
+				  unsigned long pc, struct pt_regs *regs);
+
 static void show_backtrace(struct task_struct *task, struct pt_regs *regs)
 {
 	unsigned long *sp = (long *)regs->regs[29];
@@ -114,14 +115,10 @@ static void show_backtrace(struct task_s
 		return;
 	}
 	printk("Call Trace:\n");
-	while (__kernel_text_address(pc)) {
+	do {
 		printk(" [<%0*lx>] ", 2 * sizeof(unsigned long), pc);
-		print_symbol("%s\n", pc);
-		pc = unwind_stack(task, &sp, pc);
-		if (top && pc == 0)
-			pc = regs->regs[31];	/* leaf? */
-		top = 0;
-	}
+ 		print_symbol("%s\n", pc);
+	} while ((pc = unwind_stack(task, &sp, pc, regs)));
 	printk("\n");
 }
 #else
-- 
1.4.2.rc2