xtensa: add stacktrace support

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/Kconfig

@@ -52,6 +52,9 @@ config HZ
 source "init/Kconfig"
 source "kernel/Kconfig.freezer"
 
+config STACKTRACE_SUPPORT
+	def_bool y
+
 config MMU
 	def_bool n
 

arch/xtensa/include/asm/stacktrace.h

@@ -0,0 +1,36 @@
+/*
+ * arch/xtensa/include/asm/stacktrace.h
+ *
+ * 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.
+ *
+ * Copyright (C) 2001 - 2013 Tensilica Inc.
+ */
+#ifndef _XTENSA_STACKTRACE_H
+#define _XTENSA_STACKTRACE_H
+
+#include <linux/sched.h>
+
+struct stackframe {
+	unsigned long pc;
+	unsigned long sp;
+};
+
+static __always_inline unsigned long *stack_pointer(struct task_struct *task)
+{
+	unsigned long *sp;
+
+	if (!task || task == current)
+		__asm__ __volatile__ ("mov %0, a1\n" : "=a"(sp));
+	else
+		sp = (unsigned long *)task->thread.sp;
+
+	return sp;
+}
+
+void walk_stackframe(unsigned long *sp,
+		int (*fn)(struct stackframe *frame, void *data),
+		void *data);
+
+#endif /* _XTENSA_STACKTRACE_H */

arch/xtensa/kernel/Makefile

@@ -4,9 +4,9 @@
 
 extra-y := head.o vmlinux.lds
 
-obj-y := align.o entry.o irq.o coprocessor.o process.o ptrace.o \
-	 setup.o signal.o syscall.o time.o traps.o vectors.o platform.o  \
-	 pci-dma.o
+obj-y := align.o coprocessor.o entry.o irq.o pci-dma.o platform.o process.o \
+	 ptrace.o setup.o signal.o stacktrace.o syscall.o time.o traps.o \
+	 vectors.o
 
 obj-$(CONFIG_KGDB) += xtensa-stub.o
 obj-$(CONFIG_PCI) += pci.o

arch/xtensa/kernel/stacktrace.c

@@ -0,0 +1,87 @@
+/*
+ * arch/xtensa/kernel/stacktrace.c
+ *
+ * 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.
+ *
+ * Copyright (C) 2001 - 2013 Tensilica Inc.
+ */
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+
+#include <asm/stacktrace.h>
+#include <asm/traps.h>
+
+void walk_stackframe(unsigned long *sp,
+		int (*fn)(struct stackframe *frame, void *data),
+		void *data)
+{
+	unsigned long a0, a1;
+	unsigned long sp_end;
+
+	a1 = (unsigned long)sp;
+	sp_end = ALIGN(a1, THREAD_SIZE);
+
+	spill_registers();
+
+	while (a1 < sp_end) {
+		struct stackframe frame;
+
+		sp = (unsigned long *)a1;
+
+		a0 = *(sp - 4);
+		a1 = *(sp - 3);
+
+		if (a1 <= (unsigned long)sp)
+			break;
+
+		frame.pc = MAKE_PC_FROM_RA(a0, a1);
+		frame.sp = a1;
+
+		if (fn(&frame, data))
+			return;
+	}
+}
+
+#ifdef CONFIG_STACKTRACE
+
+struct stack_trace_data {
+	struct stack_trace *trace;
+	unsigned skip;
+};
+
+static int stack_trace_cb(struct stackframe *frame, void *data)
+{
+	struct stack_trace_data *trace_data = data;
+	struct stack_trace *trace = trace_data->trace;
+
+	if (trace_data->skip) {
+		--trace_data->skip;
+		return 0;
+	}
+	if (!kernel_text_address(frame->pc))
+		return 0;
+
+	trace->entries[trace->nr_entries++] = frame->pc;
+	return trace->nr_entries >= trace->max_entries;
+}
+
+void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
+{
+	struct stack_trace_data trace_data = {
+		.trace = trace,
+		.skip = trace->skip,
+	};
+	walk_stackframe(stack_pointer(task), stack_trace_cb, &trace_data);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+void save_stack_trace(struct stack_trace *trace)
+{
+	save_stack_trace_tsk(current, trace);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+#endif

arch/xtensa/kernel/traps.c

@@ -11,7 +11,7 @@
  *
  * Essentially rewritten for the Xtensa architecture port.
  *
- * Copyright (C) 2001 - 2005 Tensilica Inc.
+ * Copyright (C) 2001 - 2013 Tensilica Inc.
  *
  * Joe Taylor	<joe@tensilica.com, joetylr@yahoo.com>
  * Chris Zankel	<chris@zankel.net>
@@ -32,6 +32,7 @@
 #include <linux/delay.h>
 #include <linux/hardirq.h>
 
+#include <asm/stacktrace.h>
 #include <asm/ptrace.h>
 #include <asm/timex.h>
 #include <asm/uaccess.h>
@@ -402,53 +403,25 @@ void show_regs(struct pt_regs * regs)
 		       regs->syscall);
 }
 
-static __always_inline unsigned long *stack_pointer(struct task_struct *task)
+static int show_trace_cb(struct stackframe *frame, void *data)
 {
-	unsigned long *sp;
-
-	if (!task || task == current)
-		__asm__ __volatile__ ("mov %0, a1\n" : "=a"(sp));
-	else
-		sp = (unsigned long *)task->thread.sp;
-
-	return sp;
+	if (kernel_text_address(frame->pc)) {
+		printk(" [<%08lx>] ", frame->pc);
+		print_symbol("%s\n", frame->pc);
+	}
+	return 0;
 }
 
 void show_trace(struct task_struct *task, unsigned long *sp)
 {
-	unsigned long a0, a1, pc;
-	unsigned long sp_start, sp_end;
-
-	if (sp)
-		a1 = (unsigned long)sp;
-	else
-		a1 = (unsigned long)stack_pointer(task);
-
-	sp_start = a1 & ~(THREAD_SIZE-1);
-	sp_end = sp_start + THREAD_SIZE;
+	if (!sp)
+		sp = stack_pointer(task);
 
 	printk("Call Trace:");
 #ifdef CONFIG_KALLSYMS
 	printk("\n");
 #endif
-	spill_registers();
-
-	while (a1 > sp_start && a1 < sp_end) {
-		sp = (unsigned long*)a1;
-
-		a0 = *(sp - 4);
-		a1 = *(sp - 3);
-
-		if (a1 <= (unsigned long) sp)
-			break;
-
-		pc = MAKE_PC_FROM_RA(a0, a1);
-
-		if (kernel_text_address(pc)) {
-			printk(" [<%08lx>] ", pc);
-			print_symbol("%s\n", pc);
-		}
-	}
+	walk_stackframe(sp, show_trace_cb, NULL);
 	printk("\n");
 }