Fix existing CI test for memfd_create()

The test was failing (after hanging for several hours) because of a
hard-coded assumption about which file descriptor would be returned
by memfd_create(). The actual file descriptor gets printed by the
test program though, so read this and use it instead. (Adjust the
test program so that this is not printed until the file is ready.)

Resolve compiler warnings about implicit function declarations, by
using the #include statements listed in the kernel.org man-pages.

tests/memory/memfd_create/runtest.sh

@@ -38,11 +38,12 @@ fi
 
 function sanity_memfd_create()
 {
-    rlRun "./t_memfd_create memf 1024 gswS &"
-    rlRun "./t_get_seals /proc/$!/fd/3 > seals"
+    rlRun "coproc ./t_memfd_create memf 1024 gswS"
+    rlRun "read -u ${COPROC[0]} MEMFD_PATH"
+    rlRun "./t_get_seals $MEMFD_PATH > ./seals"
     rlRun "cat ./seals"
     rlAssertGrep "SEAL GROW WRITE SHRINK" ./seals
-    rlRun "pkill t_memfd_create"
+    rlRun "kill $COPROC_PID"
 }
 
 

tests/memory/memfd_create/t_get_seals.c

@@ -16,8 +16,9 @@
  *
  */
 
-#include <linux/fcntl.h>
+#define _GNU_SOURCE
 #include <unistd.h>
+#include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>

tests/memory/memfd_create/t_memfd_create.c

@@ -16,11 +16,12 @@
  *
  */
 
-#include <linux/memfd.h>
-#include <linux/fcntl.h>
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
 #include <sys/syscall.h>
 #include <stdlib.h>
-#include <unistd.h>
 #include <string.h>
 #include <stdio.h>
 
@@ -66,10 +67,6 @@ int main(int argc, char *argv[])
 	if (write(fd, message, strlen(message)) <= 0)
 		errExit("write");
 
-	//printf("PID: %ld; fd: %d; /proc/%ld/fd/%d\n",
-	//        (long) getpid(), fd, (long) getpid(), fd);
-	printf("/proc/%ld/fd/%d\n", (long) getpid(), fd);
-
 	/* Code to map the file and populate the mapping with data
 	   omitted */
 
@@ -92,6 +89,13 @@ int main(int argc, char *argv[])
 			errExit("fcntl");
 	}
 
+	/* Output the pathname of (a symbolic link to) the file
+	   created by memfd_create() */
+
+	printf("/proc/%ld/fd/%d\n", (long) getpid(), fd);
+
+	fflush(stdout);
+
 	/* Keep running, so that the file created by memfd_create()
 	   continues to exist */