add a comment describing how this was created

ok deraadt@

diff --git a/sys/arch/riscv64/riscv64/db_instruction.h b/sys/arch/riscv64/riscv64/db_instruction.h
index 96b8737..eb74220 100644 (file)
--- a/sys/arch/riscv64/riscv64/db_instruction.h
+++ b/sys/arch/riscv64/riscv64/db_instruction.h
@@ -1,3 +1,13 @@
+/*     $OpenBSD: db_instruction.h,v 1.2 2021/05/12 01:24:32 jsg Exp $  */
+
+/*
+ * https://github.com/riscv/riscv-opcodes
+ * 7d1a0e3153c37cd180be9e95f331f32c225d9257
+ *
+ * db_instruction.h: $(ALL_OPCODES) parse_opcodes
+ *     cat $(ALL_OPCODES) | python3 ./parse_opcodes -c > $@
+ */
+
 /* Automatically generated by parse_opcodes.  */
 #ifndef RISCV_ENCODING_H
 #define RISCV_ENCODING_H