Reduce the number of used syscalls by using sendmsg() instead of writev()

We relied on sendmsg() anyway for the MSG_NO_SIGNAL version of the calls,
thus it is a good idea to avoid calling writev() and use sendmsg(). That
way we reduce the number of calls required for seccomp.

2 files changed, 7 insertions, 5 deletions

diff --git a/lib/system.c b/lib/system.c
index aabe4c0fbc..f5f9c76ece 100644
--- a/lib/system.c
+++ b/lib/system.c
@@ -129,8 +129,13 @@ ssize_t
 system_writev(gnutls_transport_ptr_t ptr, const giovec_t * iovec,
 	      int iovec_cnt)
 {
-	return writev(GNUTLS_POINTER_TO_INT(ptr), (struct iovec *) iovec,
-		      iovec_cnt);
+	struct msghdr hdr;
+
+	memset(&hdr, 0, sizeof(hdr));
+	hdr.msg_iov = (struct iovec *)iovec;
+	hdr.msg_iovlen = iovec_cnt;
+
+	return sendmsg(GNUTLS_POINTER_TO_INT(ptr), &hdr, 0);
 }
 #endif
 
diff --git a/tests/seccomp.c b/tests/seccomp.c
index 557d71ac2d..8427fd9f7b 100644
--- a/tests/seccomp.c
+++ b/tests/seccomp.c
@@ -67,9 +67,6 @@ int disable_system_calls(void)
 	ADD_SYSCALL(sendto, 0);
 	ADD_SYSCALL(recvfrom, 0);
 
-	/* writev() is used explicitly */
-	ADD_SYSCALL(writev, 0);
-
 	/* to read from /dev/urandom */
 	ADD_SYSCALL(read, 0);
 	ADD_SYSCALL(getrandom, 0);