csky: Add kprobes supported

This patch enable kprobes, kretprobes, ftrace interface. It utilized
software breakpoint and single step debug exceptions, instructions
simulation on csky.

We use USR_BKPT replace origin instruction, and the kprobe handler
prepares an excutable memory slot for out-of-line execution with a
copy of the original instruction being probed. Most of instructions
could be executed by single-step, but some instructions need origin
pc value to execute and we need software simulate these instructions.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>

arch/csky/mm/fault.c

@@ -18,6 +18,7 @@
 #include <linux/extable.h>
 #include <linux/uaccess.h>
 #include <linux/perf_event.h>
+#include <linux/kprobes.h>
 
 #include <asm/hardirq.h>
 #include <asm/mmu_context.h>
@@ -53,6 +54,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
 	int fault;
 	unsigned long address = mmu_meh & PAGE_MASK;
 
+	if (kprobe_page_fault(regs, tsk->thread.trap_no))
+		return;
+
 	si_code = SEGV_MAPERR;
 
 #ifndef CONFIG_CPU_HAS_TLBI