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>

1 files changed, 19 insertions, 0 deletions

diff --git a/arch/csky/kernel/probes/kprobes_trampoline.S b/arch/csky/kernel/probes/kprobes_trampoline.S
new file mode 100644
index 000000000000..b1fe3af24f03
--- /dev/null
+++ b/arch/csky/kernel/probes/kprobes_trampoline.S
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#include <linux/linkage.h>
+
+#include <abi/entry.h>
+
+ENTRY(kretprobe_trampoline)
+	SAVE_REGS_FTRACE
+
+	mov	a0, sp /* pt_regs */
+
+	jbsr	trampoline_probe_handler
+
+	/* use the result as the return-address */
+	mov	lr, a0
+
+	RESTORE_REGS_FTRACE
+	rts
+ENDPROC(kretprobe_trampoline)