[MIPS] dump_stack() based on prologue code analysis

Instead of dump all possible address in the stack, unwind the stack frame
based on prologue code analysis, as like as get_wchan() does.  While the
code analysis might fail for some reason, there is a new kernel option
"raw_show_trace" to disable this feature.

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

2 files changed, 141 insertions, 23 deletions

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 7ab67f786bfe..8709a46a45c1 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -281,7 +281,7 @@ static struct mips_frame_info {
 } *schedule_frame, mfinfo[64];
 static int mfinfo_num;
 
-static int __init get_frame_info(struct mips_frame_info *info)
+static int get_frame_info(struct mips_frame_info *info)
 {
         int i;
         void *func = info->func;
@@ -329,14 +329,12 @@ static int __init get_frame_info(struct mips_frame_info *info)
                                 ip->i_format.simmediate / sizeof(long);
                 }
         }
-        if (info->pc_offset == -1 || info->frame_size == 0) {
-                if (func == schedule)
-                        printk("Can't analyze prologue code at %p\n", func);
-                info->pc_offset = -1;
-                info->frame_size = 0;
-        }
-
-        return 0;
+        if (info->frame_size && info->pc_offset >= 0) /* nested */
+                return 0;
+        if (info->pc_offset < 0) /* leaf */
+                return 1;
+        /* prologue seems boggus... */
+        return -1;
 }
 
 static int __init frame_info_init(void)
@@ -367,8 +365,15 @@ static int __init frame_info_init(void)
         mfinfo[0].func = schedule;
         schedule_frame = &mfinfo[0];
 #endif
-        for (i = 0; i < ARRAY_SIZE(mfinfo) && mfinfo[i].func; i++)
-                get_frame_info(&mfinfo[i]);
+        for (i = 0; i < ARRAY_SIZE(mfinfo) && mfinfo[i].func; i++) {
+                struct mips_frame_info *info = &mfinfo[i];
+                if (get_frame_info(info)) {
+                        /* leaf or unknown */
+                        if (info->func == schedule)
+                                printk("Can't analyze prologue code at %p\n",
+                                       info->func);
+                }
+        }
 
         mfinfo_num = i;
         return 0;
@@ -427,6 +432,8 @@ unsigned long get_wchan(struct task_struct *p)
                 if (i < 0)
                         break;
 
+                if (mfinfo[i].pc_offset < 0)
+                        break;
                 pc = ((unsigned long *)frame)[mfinfo[i].pc_offset];
                 if (!mfinfo[i].frame_size)
                         break;
@@ -437,3 +444,40 @@ unsigned long get_wchan(struct task_struct *p)
         return pc;
 }
 
+#ifdef CONFIG_KALLSYMS
+/* used by show_frametrace() */
+unsigned long unwind_stack(struct task_struct *task,
+                           unsigned long **sp, unsigned long pc)
+{
+        unsigned long stack_page;
+        struct mips_frame_info info;
+        char *modname;
+        char namebuf[KSYM_NAME_LEN + 1];
+        unsigned long size, ofs;
+
+        stack_page = (unsigned long)task_stack_page(task);
+        if (!stack_page)
+                return 0;
+
+        if (!kallsyms_lookup(pc, &size, &ofs, &modname, namebuf))
+                return 0;
+        if (ofs == 0)
+                return 0;
+
+        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);
+                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];
+        *sp += info.frame_size / sizeof(long);
+        return pc;
+}
+#endif
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index c6f70467e750..7aa9dfc57b81 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -98,24 +98,53 @@ static void show_trace(unsigned long *stack)
         printk("\n");
 }
 
+#ifdef CONFIG_KALLSYMS
+static int raw_show_trace;
+static int __init set_raw_show_trace(char *str)
+{
+        raw_show_trace = 1;
+        return 1;
+}
+__setup("raw_show_trace", set_raw_show_trace);
+
+extern unsigned long unwind_stack(struct task_struct *task,
+                                  unsigned long **sp, unsigned long pc);
+static void show_frametrace(struct task_struct *task, struct pt_regs *regs)
+{
+        const int field = 2 * sizeof(unsigned long);
+        unsigned long *stack = (long *)regs->regs[29];
+        unsigned long pc = regs->cp0_epc;
+        int top = 1;
+
+        if (raw_show_trace || !__kernel_text_address(pc)) {
+                show_trace(stack);
+                return;
+        }
+        printk("Call Trace:\n");
+        while (__kernel_text_address(pc)) {
+                printk(" [<%0*lx>] ", field, pc);
+                print_symbol("%s\n", pc);
+                pc = unwind_stack(task, &stack, pc);
+                if (top && pc == 0)
+                        pc = regs->regs[31];    /* leaf? */
+                top = 0;
+        }
+        printk("\n");
+}
+#else
+#define show_frametrace(task, r) show_trace((long *)(r)->regs[29]);
+#endif
+
 /*
  * This routine abuses get_user()/put_user() to reference pointers
  * with at least a bit of error checking ...
  */
-void show_stack(struct task_struct *task, unsigned long *sp)
+static void show_stacktrace(struct task_struct *task, struct pt_regs *regs)
 {
         const int field = 2 * sizeof(unsigned long);
         long stackdata;
         int i;
-        unsigned long *stack;
-
-        if (!sp) {
-                if (task && task != current)
-                        sp = (unsigned long *) task->thread.reg29;
-                else
-                        sp = (unsigned long *) &sp;
-        }
-        stack = sp;
+        unsigned long *sp = (unsigned long *)regs->regs[29];
 
         printk("Stack :");
         i = 0;
@@ -136,7 +165,44 @@ void show_stack(struct task_struct *task, unsigned long *sp)
                 i++;
         }
         printk("\n");
-        show_trace(stack);
+        show_frametrace(task, regs);
+}
+
+static noinline void prepare_frametrace(struct pt_regs *regs)
+{
+        __asm__ __volatile__(
+                "1: la $2, 1b\n\t"
+#ifdef CONFIG_64BIT
+                "sd $2, %0\n\t"
+                "sd $29, %1\n\t"
+                "sd $31, %2\n\t"
+#else
+                "sw $2, %0\n\t"
+                "sw $29, %1\n\t"
+                "sw $31, %2\n\t"
+#endif
+                : "=m" (regs->cp0_epc),
+                "=m" (regs->regs[29]), "=m" (regs->regs[31])
+                : : "memory");
+}
+
+void show_stack(struct task_struct *task, unsigned long *sp)
+{
+        struct pt_regs regs;
+        if (sp) {
+                regs.regs[29] = (unsigned long)sp;
+                regs.regs[31] = 0;
+                regs.cp0_epc = 0;
+        } else {
+                if (task && task != current) {
+                        regs.regs[29] = task->thread.reg29;
+                        regs.regs[31] = 0;
+                        regs.cp0_epc = task->thread.reg31;
+                } else {
+                        prepare_frametrace(&regs);
+                }
+        }
+        show_stacktrace(task, &regs);
 }
 
 /*
@@ -146,6 +212,14 @@ void dump_stack(void)
 {
         unsigned long stack;
 
+#ifdef CONFIG_KALLSYMS
+        if (!raw_show_trace) {
+                struct pt_regs regs;
+                prepare_frametrace(&regs);
+                show_frametrace(current, &regs);
+                return;
+        }
+#endif
         show_trace(&stack);
 }
 
@@ -265,7 +339,7 @@ void show_registers(struct pt_regs *regs)
         print_modules();
         printk("Process %s (pid: %d, threadinfo=%p, task=%p)\n",
                 current->comm, current->pid, current_thread_info(), current);
-        show_stack(current, (long *) regs->regs[29]);
+        show_stacktrace(current, regs);
         show_code((unsigned int *) regs->cp0_epc);
         printk("\n");
 }