[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>

1 files changed, 86 insertions, 12 deletions

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");
 }