parisc: add ftrace (function and graph tracer) functionality

This patch adds the ftrace debugging functionality to the parisc kernel.
It will currently only work with 64bit kernels, because the gcc options -pg
and -ffunction-sections can't be enabled at the same time and -ffunction-sections
is still needed to be able to link 32bit kernels.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>

1 files changed, 185 insertions, 0 deletions

diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
new file mode 100644
index 00000000000..9877372ffdb
--- /dev/null
+++ b/arch/parisc/kernel/ftrace.c
@@ -0,0 +1,185 @@
+/*
+ * Code for tracing calls in Linux kernel.
+ * Copyright (C) 2009 Helge Deller <deller@gmx.de>
+ *
+ * based on code for x86 which is:
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * future possible enhancements:
+ * 	- add CONFIG_DYNAMIC_FTRACE
+ *	- add CONFIG_STACK_TRACER
+ */
+
+#include <linux/init.h>
+#include <linux/ftrace.h>
+
+#include <asm/sections.h>
+#include <asm/ftrace.h>
+
+
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+/* Add a function return address to the trace stack on thread info.*/
+static int push_return_trace(unsigned long ret, unsigned long long time,
+				unsigned long func, int *depth)
+{
+	int index;
+
+	if (!current->ret_stack)
+		return -EBUSY;
+
+	/* The return trace stack is full */
+	if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
+		atomic_inc(&current->trace_overrun);
+		return -EBUSY;
+	}
+
+	index = ++current->curr_ret_stack;
+	barrier();
+	current->ret_stack[index].ret = ret;
+	current->ret_stack[index].func = func;
+	current->ret_stack[index].calltime = time;
+	*depth = index;
+
+	return 0;
+}
+
+/* Retrieve a function return address to the trace stack on thread info.*/
+static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
+{
+	int index;
+
+	index = current->curr_ret_stack;
+
+	if (unlikely(index < 0)) {
+		ftrace_graph_stop();
+		WARN_ON(1);
+		/* Might as well panic, otherwise we have no where to go */
+		*ret = (unsigned long)
+			dereference_function_descriptor(&panic);
+		return;
+	}
+
+	*ret = current->ret_stack[index].ret;
+	trace->func = current->ret_stack[index].func;
+	trace->calltime = current->ret_stack[index].calltime;
+	trace->overrun = atomic_read(&current->trace_overrun);
+	trace->depth = index;
+	barrier();
+	current->curr_ret_stack--;
+
+}
+
+/*
+ * Send the trace to the ring-buffer.
+ * @return the original return address.
+ */
+unsigned long ftrace_return_to_handler(unsigned long retval0,
+				       unsigned long retval1)
+{
+	struct ftrace_graph_ret trace;
+	unsigned long ret;
+
+	pop_return_trace(&trace, &ret);
+	trace.rettime = cpu_clock(raw_smp_processor_id());
+	ftrace_graph_return(&trace);
+
+	if (unlikely(!ret)) {
+		ftrace_graph_stop();
+		WARN_ON(1);
+		/* Might as well panic. What else to do? */
+		ret = (unsigned long)
+			dereference_function_descriptor(&panic);
+	}
+
+	/* HACK: we hand over the old functions' return values
+	   in %r23 and %r24. Assembly in entry.S will take care
+	   and move those to their final registers %ret0 and %ret1 */
+	asm( "copy %0, %%r23 \n\t"
+	     "copy %1, %%r24 \n" : : "r" (retval0), "r" (retval1) );
+
+	return ret;
+}
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+{
+	unsigned long old;
+	unsigned long long calltime;
+	struct ftrace_graph_ent trace;
+
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		return;
+
+	old = *parent;
+	*parent = (unsigned long)
+		  dereference_function_descriptor(&return_to_handler);
+
+	if (unlikely(!__kernel_text_address(old))) {
+		ftrace_graph_stop();
+		*parent = old;
+		WARN_ON(1);
+		return;
+	}
+
+	calltime = cpu_clock(raw_smp_processor_id());
+
+	if (push_return_trace(old, calltime,
+				self_addr, &trace.depth) == -EBUSY) {
+		*parent = old;
+		return;
+	}
+
+	trace.func = self_addr;
+
+	/* Only trace if the calling function expects to */
+	if (!ftrace_graph_entry(&trace)) {
+		current->curr_ret_stack--;
+		*parent = old;
+	}
+}
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+
+void ftrace_function_trampoline(unsigned long parent,
+				unsigned long self_addr,
+				unsigned long org_sp_gr3)
+{
+	extern ftrace_func_t ftrace_trace_function;
+
+	if (function_trace_stop)
+		return;
+
+	if (ftrace_trace_function != ftrace_stub) {
+		ftrace_trace_function(parent, self_addr);
+		return;
+	}
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	if (ftrace_graph_entry && ftrace_graph_return) {
+		unsigned long sp;
+		unsigned long *parent_rp;
+
+                asm volatile ("copy %%r30, %0" : "=r"(sp));
+		/* sanity check: is stack pointer which we got from
+		   assembler function in entry.S in a reasonable
+		   range compared to current stack pointer? */
+		if ((sp - org_sp_gr3) > 0x400)
+			return;
+
+		/* calculate pointer to %rp in stack */
+		parent_rp = (unsigned long *) org_sp_gr3 - 0x10;
+		/* sanity check: parent_rp should hold parent */
+		if (*parent_rp != parent)
+			return;
+		
+		prepare_ftrace_return(parent_rp, self_addr);
+		return;
+	}
+#endif
+}
+