xtensa: add stacktrace support

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

3 files changed, 101 insertions, 41 deletions

diff --git a/arch/xtensa/kernel/Makefile b/arch/xtensa/kernel/Makefile
index c433a56fbff9..1e7fc87a94bb 100644
--- a/arch/xtensa/kernel/Makefile
+++ b/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
diff --git a/arch/xtensa/kernel/stacktrace.c b/arch/xtensa/kernel/stacktrace.c
new file mode 100644
index 000000000000..e3aff9575183
--- /dev/null
+++ b/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
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 923db5c15278..cf065e165ceb 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/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");
 }