microblaze: Stack trace support

This is working implemetation but the problem is that
Microblaze misses frame pointer that's why is there
big loop which trace and show all addresses which are in text.
It shows addresses which are in registers, etc.

This is problem and this is the reason why all Microblaze
traces are wrong. There is an option to do hacks and trace
the kernel code but this is too complicated.

Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/Kconfig

@@ -57,6 +57,9 @@ config GENERIC_GPIO
 config GENERIC_CSUM
 	def_bool y
 
+config STACKTRACE_SUPPORT
+	def_bool y
+
 config PCI
 	def_bool n
 

arch/microblaze/kernel/Makefile

@@ -16,5 +16,6 @@ obj-$(CONFIG_SELFMOD)		+= selfmod.o
 obj-$(CONFIG_HEART_BEAT)	+= heartbeat.o
 obj-$(CONFIG_MODULES)		+= microblaze_ksyms.o module.o
 obj-$(CONFIG_MMU)		+= misc.o
+obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 
 obj-y	+= entry$(MMU).o

arch/microblaze/kernel/stacktrace.c

@@ -0,0 +1,65 @@
+/*
+ * Stack trace support for Microblaze.
+ *
+ * Copyright (C) 2009 Michal Simek <monstr@monstr.eu>
+ * Copyright (C) 2009 PetaLogix
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+#include <linux/thread_info.h>
+#include <linux/ptrace.h>
+#include <linux/module.h>
+
+/* FIXME initial support */
+void save_stack_trace(struct stack_trace *trace)
+{
+	unsigned long *sp;
+	unsigned long addr;
+	asm("addik %0, r1, 0" : "=r" (sp));
+
+	while (!kstack_end(sp)) {
+		addr = *sp++;
+		if (__kernel_text_address(addr)) {
+			if (trace->skip > 0)
+				trace->skip--;
+			else
+				trace->entries[trace->nr_entries++] = addr;
+
+			if (trace->nr_entries >= trace->max_entries)
+				break;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+	unsigned int *sp;
+	unsigned long addr;
+
+	struct thread_info *ti = task_thread_info(tsk);
+
+	if (tsk == current)
+		asm("addik %0, r1, 0" : "=r" (sp));
+	else
+		sp = (unsigned int *)ti->cpu_context.r1;
+
+	while (!kstack_end(sp)) {
+		addr = *sp++;
+		if (__kernel_text_address(addr)) {
+			if (trace->skip > 0)
+				trace->skip--;
+			else
+				trace->entries[trace->nr_entries++] = addr;
+
+			if (trace->nr_entries >= trace->max_entries)
+				break;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_tsk);