[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