m68knommu: add pretty back strace

With this patch and
 CONFIG_FRAME_POINTER=y
 CONFIG_KALLSYMS=y
The backtrace shows resolved function names and their numeric
address.

Signed-off-by: Sebastian Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 54 insertions, 34 deletions

diff --git a/arch/m68knommu/kernel/traps.c b/arch/m68knommu/kernel/traps.c
index 437a061d8b94..ec9aea652e79 100644
--- a/arch/m68knommu/kernel/traps.c
+++ b/arch/m68knommu/kernel/traps.c
@@ -28,6 +28,7 @@
 #include <linux/linkage.h>
 #include <linux/init.h>
 #include <linux/ptrace.h>
+#include <linux/kallsyms.h>
 
 #include <asm/setup.h>
 #include <asm/fpu.h>
@@ -102,56 +103,47 @@ asmlinkage void buserr_c(struct frame *fp)
         force_sig(SIGSEGV, current);
 }
 
-
 int kstack_depth_to_print = 48;
 
-void show_stack(struct task_struct *task, unsigned long *stack)
+static void __show_stack(struct task_struct *task, unsigned long *stack)
 {
         unsigned long *endstack, addr;
-        extern char _start, _etext;
+        unsigned long *last_stack;
         int i;
 
-        if (!stack) {
-                if (task)
-                        stack = (unsigned long *)task->thread.ksp;
-                else
-                        stack = (unsigned long *)&stack;
-        }
+        if (!stack)
+                stack = (unsigned long *)task->thread.ksp;
 
         addr = (unsigned long) stack;
         endstack = (unsigned long *) PAGE_ALIGN(addr);
 
         printk(KERN_EMERG "Stack from %08lx:", (unsigned long)stack);
         for (i = 0; i < kstack_depth_to_print; i++) {
-                if (stack + 1 > endstack)
+                if (stack + 1 + i > endstack)
                         break;
                 if (i % 8 == 0)
                         printk("\n" KERN_EMERG "       ");
-                printk(" %08lx", *stack++);
+                printk(" %08lx", *(stack + i));
         }
         printk("\n");
 
-        printk(KERN_EMERG "Call Trace:");
-        i = 0;
-        while (stack + 1 <= endstack) {
-                addr = *stack++;
-                /*
-                 * If the address is either in the text segment of the
-                 * kernel, or in the region which contains vmalloc'ed
-                 * memory, it *may* be the address of a calling
-                 * routine; if so, print it so that someone tracing
-                 * down the cause of the crash will be able to figure
-                 * out the call path that was taken.
-                 */
-                if (((addr >= (unsigned long) &_start) &&
-                     (addr <= (unsigned long) &_etext))) {
-                        if (i % 4 == 0)
-                                printk("\n" KERN_EMERG "       ");
-                        printk(" [<%08lx>]", addr);
-                        i++;
-                }
+#ifdef CONFIG_FRAME_POINTER
+        printk(KERN_EMERG "Call Trace:\n");
+
+        last_stack = stack - 1;
+        while (stack <= endstack && stack > last_stack) {
+
+                addr = *(stack + 1);
+                printk(KERN_EMERG " [%08lx] ", addr);
+                print_symbol(KERN_CONT "%s\n", addr);
+
+                last_stack = stack;
+                stack = (unsigned long *)*stack;
         }
         printk("\n");
+#else
+        printk(KERN_EMERG "CONFIG_FRAME_POINTER disabled, no symbolic call trace\n");
+#endif
 }
 
 void bad_super_trap(struct frame *fp)
@@ -298,19 +290,47 @@ asmlinkage void set_esp0(unsigned long ssp)
         current->thread.esp0 = ssp;
 }
 
-
 /*
  * The architecture-independent backtrace generator
  */
 void dump_stack(void)
 {
-        unsigned long stack;
+        /*
+         * We need frame pointers for this little trick, which works as follows:
+         *
+         * +------------+ 0x00
+         * | Next SP    |       -> 0x0c
+         * +------------+ 0x04
+         * | Caller     |
+         * +------------+ 0x08
+         * | Local vars |       -> our stack var
+         * +------------+ 0x0c
+         * | Next SP    |       -> 0x18, that is what we pass to show_stack()
+         * +------------+ 0x10
+         * | Caller     |
+         * +------------+ 0x14
+         * | Local vars |
+         * +------------+ 0x18
+         * | ...        |
+         * +------------+
+         */
 
-        show_stack(current, &stack);
-}
+        unsigned long *stack;
 
+        stack = (unsigned long *)&stack;
+        stack++;
+        __show_stack(current, stack);
+}
 EXPORT_SYMBOL(dump_stack);
 
+void show_stack(struct task_struct *task, unsigned long *stack)
+{
+        if (!stack && !task)
+                dump_stack();
+        else
+                __show_stack(task, stack);
+}
+
 #ifdef CONFIG_M68KFPU_EMU
 asmlinkage void fpemu_signal(int signal, int code, void *addr)
 {