riscv: add macro to get instruction length

Extract the calculation of instruction length for common use.
Signed-off-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/include/asm/bug.h

@@ -19,6 +19,14 @@
 #define __BUG_INSN_32	_UL(0x00100073) /* ebreak */
 #define __BUG_INSN_16	_UL(0x9002) /* c.ebreak */
 
+#define GET_INSN_LENGTH(insn)						\
+({									\
+	unsigned long __len;						\
+	__len = ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) ?	\
+		4UL : 2UL;						\
+	__len;								\
+})
+
 typedef u32 bug_insn_t;
 
 #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS

arch/riscv/kernel/traps.c

@@ -118,7 +118,8 @@ static inline unsigned long get_break_insn_length(unsigned long pc)
 
 	if (probe_kernel_address((bug_insn_t *)pc, insn))
 		return 0;
-	return (((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) ? 4UL : 2UL);
+
+	return GET_INSN_LENGTH(insn);
 }
 
 asmlinkage __visible void do_trap_break(struct pt_regs *regs)