sh: Function graph tracer support

Add both dynamic and static function graph tracer support for sh.

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/kernel/ftrace.c

@@ -16,11 +16,13 @@
 #include <linux/string.h>
 #include <linux/init.h>
 #include <linux/io.h>
+#include <linux/kernel.h>
 #include <asm/ftrace.h>
 #include <asm/cacheflush.h>
 #include <asm/unistd.h>
 #include <trace/syscall.h>
 
+#ifdef CONFIG_DYNAMIC_FTRACE
 static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
 
 static unsigned char ftrace_nop[4];
@@ -133,6 +135,126 @@ int __init ftrace_dyn_arch_init(void *data)
 
 	return 0;
 }
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+
+static int ftrace_mod(unsigned long ip, unsigned long old_addr,
+		      unsigned long new_addr)
+{
+	unsigned char code[MCOUNT_INSN_SIZE];
+
+	if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
+		return -EFAULT;
+
+	if (old_addr != __raw_readl((unsigned long *)code))
+		return -EINVAL;
+
+	__raw_writel(new_addr, ip);
+	return 0;
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+	unsigned long ip, old_addr, new_addr;
+
+	ip = (unsigned long)(&ftrace_graph_call) + GRAPH_INSN_OFFSET;
+	old_addr = (unsigned long)(&skip_trace);
+	new_addr = (unsigned long)(&ftrace_graph_caller);
+
+	return ftrace_mod(ip, old_addr, new_addr);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	unsigned long ip, old_addr, new_addr;
+
+	ip = (unsigned long)(&ftrace_graph_call) + GRAPH_INSN_OFFSET;
+	old_addr = (unsigned long)(&ftrace_graph_caller);
+	new_addr = (unsigned long)(&skip_trace);
+
+	return ftrace_mod(ip, old_addr, new_addr);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in the current thread info.
+ *
+ * This is the main routine for the function graph tracer. The function
+ * graph tracer essentially works like this:
+ *
+ * parent is the stack address containing self_addr's return address.
+ * We pull the real return address out of parent and store it in
+ * current's ret_stack. Then, we replace the return address on the stack
+ * with the address of return_to_handler. self_addr is the function that
+ * called mcount.
+ *
+ * When self_addr returns, it will jump to return_to_handler which calls
+ * ftrace_return_to_handler. ftrace_return_to_handler will pull the real
+ * return address off of current's ret_stack and jump to it.
+ */
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+{
+	unsigned long old;
+	int faulted, err;
+	struct ftrace_graph_ent trace;
+	unsigned long return_hooker = (unsigned long)&return_to_handler;
+
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		return;
+
+	/*
+	 * Protect against fault, even if it shouldn't
+	 * happen. This tool is too much intrusive to
+	 * ignore such a protection.
+	 */
+	__asm__ __volatile__(
+		"1:						\n\t"
+		"mov.l		@%2, %0				\n\t"
+		"2:						\n\t"
+		"mov.l		%3, @%2				\n\t"
+		"mov		#0, %1				\n\t"
+		"3:						\n\t"
+		".section .fixup, \"ax\"			\n\t"
+		"4:						\n\t"
+		"mov.l		5f, %0				\n\t"
+		"jmp		@%0				\n\t"
+		" mov		#1, %1				\n\t"
+		".balign 4					\n\t"
+		"5:	.long 3b				\n\t"
+		".previous					\n\t"
+		".section __ex_table,\"a\"			\n\t"
+		".long 1b, 4b					\n\t"
+		".long 2b, 4b					\n\t"
+		".previous					\n\t"
+		: "=&r" (old), "=r" (faulted)
+		: "r" (parent), "r" (return_hooker)
+	);
+
+	if (unlikely(faulted)) {
+		ftrace_graph_stop();
+		WARN_ON(1);
+		return;
+	}
+
+	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
+	if (err == -EBUSY) {
+		__raw_writel(old, parent);
+		return;
+	}
+
+	trace.func = self_addr;
+
+	/* Only trace if the calling function expects to */
+	if (!ftrace_graph_entry(&trace)) {
+		current->curr_ret_stack--;
+		__raw_writel(old, parent);
+	}
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
 #ifdef CONFIG_FTRACE_SYSCALLS