provide ffs, gcc generates calls to it, even when __builtin_ffs() is used.

ok deraadt@

2 files changed, 42 insertions, 2 deletions

diff --git a/libexec/ld.so/Makefile b/libexec/ld.so/Makefile
index 6de38637dd5..50228d66ff3 100644
--- a/libexec/ld.so/Makefile
+++ b/libexec/ld.so/Makefile
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile,v 1.71 2017/12/08 05:30:16 deraadt Exp $
+#	$OpenBSD: Makefile,v 1.72 2018/01/30 20:15:25 otto Exp $
 
 SUBDIR=ldconfig ldd
 MAN=	ld.so.1
@@ -19,7 +19,7 @@ VPATH=${.CURDIR}/../../lib/libc/string
 SRCS=	ldasm.S boot.c loader.c resolve.c dlfcn.c dl_printf.c rtld_machine.c
 SRCS+=	path.c util.c sod.c strsep.c strtol.c dir.c library_subr.c
 SRCS+=	dl_realpath.c dl_uname.c dl_dirname.c strlcat.c strlen.c trace.c
-SRCS+=	malloc.c reallocarray.c tib.c
+SRCS+=	malloc.c reallocarray.c tib.c ffs.c
 
 syscall=__syscall close exit fstat __getcwd getdents getentropy getthrid \
 	issetugid mprotect munmap open pledge read readlink sendsyslog \
diff --git a/libexec/ld.so/ffs.c b/libexec/ld.so/ffs.c
new file mode 100644
index 00000000000..8c5e6240f5d
--- /dev/null
+++ b/libexec/ld.so/ffs.c
@@ -0,0 +1,40 @@
+/*	$OpenBSD: ffs.c,v 1.1 2018/01/30 20:15:25 otto Exp $	*/
+
+/*
+ * Public domain.
+ * Written by Dale Rahn.
+ */
+
+#include <string.h>
+
+/*
+ * ffs -- vax ffs instruction
+ */
+int
+ffs(int mask)
+{
+	int bit;
+	unsigned int r = mask;
+	static const signed char t[16] = {
+		-28, 1, 2, 1,
+		  3, 1, 2, 1,
+		  4, 1, 2, 1,
+		  3, 1, 2, 1
+	};
+
+	bit = 0;
+	if (!(r & 0xffff)) {
+		bit += 16;
+		r >>= 16;
+	}
+	if (!(r & 0xff)) {
+		bit += 8;
+		r >>= 8;
+	}
+	if (!(r & 0xf)) {
+		bit += 4;
+		r >>= 4;
+	}
+
+	return (bit + t[ r & 0xf ]);
+}