From e817eab93a21b67f02b737b37322f820c9496c38 Mon Sep 17 00:00:00 2001
From: dv <dv@openbsd.org>
Date: Sat, 2 Sep 2023 19:28:46 +0000
Subject: [PATCH] btrace(8): allow empty statements in probes.

Allows for probes like `BEGIN {}`, in parity with bpftrace.

Also fixes an incorrect syntax error parsing argN builtins in
subsequent probes after an empty BEGIN block.

ok mpi@
---
 regress/usr.sbin/btrace/Makefile       |  4 ++--
 regress/usr.sbin/btrace/empty-stmts.bt | 18 ++++++++++++++++++
 regress/usr.sbin/btrace/empty-stmts.ok |  0
 usr.sbin/btrace/bt_parse.y             |  3 ++-
 4 files changed, 22 insertions(+), 3 deletions(-)
 create mode 100644 regress/usr.sbin/btrace/empty-stmts.bt
 create mode 100644 regress/usr.sbin/btrace/empty-stmts.ok

diff --git a/regress/usr.sbin/btrace/Makefile b/regress/usr.sbin/btrace/Makefile
index e1d39991082..a5b37cbab83 100644
--- a/regress/usr.sbin/btrace/Makefile
+++ b/regress/usr.sbin/btrace/Makefile
@@ -1,4 +1,4 @@
-# $OpenBSD: Makefile,v 1.28 2023/08/28 21:23:46 dv Exp $
+# $OpenBSD: Makefile,v 1.29 2023/09/02 19:28:46 dv Exp $
 
 BTRACE?=		 /usr/sbin/btrace
 ALLOWDT!=		sysctl -n kern.allowdt 2>/dev/null
@@ -14,7 +14,7 @@ BT_LANG_SCRIPTS=	arithm beginend beginend-argn boolean comments delete \
 BT_ARG_LANG_SCRIPTS=	staticv str
 
 # scripts that use kernel probes
-BT_KERN_SCRIPTS=	filters mapoverwrite multiprobe
+BT_KERN_SCRIPTS=	empty-stmts filters mapoverwrite multiprobe
 
 REGRESS_EXPECTED_FAILURES=	run-maxoperand
 
diff --git a/regress/usr.sbin/btrace/empty-stmts.bt b/regress/usr.sbin/btrace/empty-stmts.bt
new file mode 100644
index 00000000000..87cd947d5e8
--- /dev/null
+++ b/regress/usr.sbin/btrace/empty-stmts.bt
@@ -0,0 +1,18 @@
+// Test support for empty statement lists.
+BEGIN
+{
+      exit();
+}
+
+syscall:open:return
+{
+}
+
+syscall:close:return
+/comm != "ksh"/
+{
+}
+
+END
+{
+}
\ No newline at end of file
diff --git a/regress/usr.sbin/btrace/empty-stmts.ok b/regress/usr.sbin/btrace/empty-stmts.ok
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/usr.sbin/btrace/bt_parse.y b/usr.sbin/btrace/bt_parse.y
index b2c3bef3b80..b2c3e65854b 100644
--- a/usr.sbin/btrace/bt_parse.y
+++ b/usr.sbin/btrace/bt_parse.y
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bt_parse.y,v 1.51 2023/08/28 21:23:46 dv Exp $	*/
+/*	$OpenBSD: bt_parse.y,v 1.52 2023/09/02 19:28:46 dv Exp $	*/
 
 /*
  * Copyright (c) 2019-2021 Martin Pieuchot <mpi@openbsd.org>
@@ -266,6 +266,7 @@ block	: action
 	;
 
 action	: '{' stmtlist '}'		{ $$ = $2; }
+	| '{' '}'			{ $$ = NULL; }
 	;
 
 %%
-- 
2.20.1