sysprof: kernel trace

add kernel backtracing to the sysprof tracer.

change the format of the data, so that type=0 means
beginning of stack trace, 1 means kernel address, 2 means user
address, and 3 means end of trace.

EIP addresses are no longer distinguished from return addresses,
mostly because sysprof userspace doesn't make use of it. It may be
worthwhile adding this back in though, just in case it becomes
interesting.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/trace/trace_sysprof.c

@@ -14,6 +14,8 @@
 #include <linux/irq.h>
 #include <linux/fs.h>
 
+#include <asm/stacktrace.h>
+
 #include "trace.h"
 
 static struct trace_array	*sysprof_trace;
@@ -52,6 +54,77 @@ static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
 	return ret;
 }
 
+struct backtrace_info {
+	struct trace_array_cpu	*data;
+	struct trace_array	*tr;
+	int			pos;
+};
+
+static void
+backtrace_warning_symbol(void *data, char *msg, unsigned long symbol)
+{
+	/* Ignore warnings */
+}
+
+static void backtrace_warning(void *data, char *msg)
+{
+	/* Ignore warnings */
+}
+
+static int backtrace_stack(void *data, char *name)
+{
+	/* Don't bother with IRQ stacks for now */
+	return -1;
+}
+
+static void backtrace_address(void *data, unsigned long addr, int reliable)
+{
+	struct backtrace_info *info = data;
+
+	if (info->pos < sample_max_depth && reliable) {
+		__trace_special(info->tr, info->data, 1, addr, 0);
+
+		info->pos++;
+	}
+}
+
+const static struct stacktrace_ops backtrace_ops = {
+	.warning		= backtrace_warning,
+	.warning_symbol		= backtrace_warning_symbol,
+	.stack			= backtrace_stack,
+	.address		= backtrace_address,
+};
+
+static struct pt_regs *
+trace_kernel(struct pt_regs *regs, struct trace_array *tr,
+	     struct trace_array_cpu *data)
+{
+	struct backtrace_info info;
+	unsigned long bp;
+	char *user_stack;
+	char *stack;
+
+	info.tr = tr;
+	info.data = data;
+	info.pos = 1;
+
+	__trace_special(info.tr, info.data, 1, regs->ip, 0);
+
+	stack = ((char *)regs + sizeof(struct pt_regs));
+#ifdef CONFIG_FRAME_POINTER
+	bp = regs->bp;
+#else
+	bp = 0;
+#endif
+
+	dump_trace(NULL, regs, (void *)stack, bp, &backtrace_ops, &info);
+
+	/* Now trace the user stack */
+	user_stack = ((char *)current->thread.sp0 - sizeof(struct pt_regs));
+
+	return (struct pt_regs *)user_stack;
+}
+
 static void timer_notify(struct pt_regs *regs, int cpu)
 {
 	struct trace_array_cpu *data;
@@ -74,17 +147,15 @@ static void timer_notify(struct pt_regs *regs, int cpu)
 	if (is_user && current->state != TASK_RUNNING)
 		return;
 
-	if (!is_user) {
-		/* kernel */
-		ftrace(tr, data, current->pid, 1, 0);
-		return;
+	__trace_special(tr, data, 0, 0, current->pid);
 
-	}
-
-	__trace_special(tr, data, 0, current->pid, regs->ip);
+	if (!is_user)
+		regs = trace_kernel(regs, tr, data);
 
 	fp = (void __user *)regs->bp;
 
+	__trace_special(tr, data, 2, regs->ip, 0);
+
 	for (i = 0; i < sample_max_depth; i++) {
 		frame.next_fp = 0;
 		frame.return_address = 0;
@@ -93,12 +164,12 @@ static void timer_notify(struct pt_regs *regs, int cpu)
 		if ((unsigned long)fp < regs->sp)
 			break;
 
-		__trace_special(tr, data, 1, frame.return_address,
+		__trace_special(tr, data, 2, frame.return_address,
 			      (unsigned long)fp);
 		fp = frame.next_fp;
 	}
 
-	__trace_special(tr, data, 2, current->pid, i);
+	__trace_special(tr, data, 3, current->pid, i);
 
 	/*
 	 * Special trace entry if we overflow the max depth: