From f1e56f54b25e178e813ab44b6e449c55675841bb Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Fri, 30 Aug 2019 00:14:43 -0500
Subject: [PATCH] test_util: use MAP_ANONYMOUS instead of /dev/zero

Apparently, mmap'ing /dev/zero fails on macOS.  So contrary to the
intent, it's not actually portable.  Switch to MAP_ANONYMOUS instead,
with a fallback to MAP_ANON if it's not defined.
---
 programs/test_util.c | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/programs/test_util.c b/programs/test_util.c
index 8bd88e6..2ff8b83 100644
--- a/programs/test_util.c
+++ b/programs/test_util.c
@@ -25,6 +25,16 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
+#ifndef _WIN32
+/* for MAP_ANONYMOUS or MAP_ANON, which unfortunately aren't part of POSIX... */
+#  undef _POSIX_C_SOURCE
+#  ifdef __APPLE__
+#    define _DARWIN_C_SOURCE
+#  elif defined(__linux__)
+#    define _GNU_SOURCE
+#  endif
+#endif
+
 #include "test_util.h"
 
 #include <fcntl.h>
@@ -37,6 +47,10 @@
 #  include <sys/time.h>
 #endif
 
+#ifndef MAP_ANONYMOUS
+#  define MAP_ANONYMOUS MAP_ANON
+#endif
+
 /* Abort with an error message */
 _noreturn void
 assertion_failed(const char *expr, const char *file, int line)
@@ -68,8 +82,6 @@ alloc_guarded_buffer(size_t size, u8 **start_ret, u8 **end_ret)
 	u8 *start, *end;
 #ifdef _WIN32
 	DWORD oldProtect;
-#else
-	int fd;
 #endif
 
 	*start_ret = NULL;
@@ -95,20 +107,11 @@ alloc_guarded_buffer(size_t size, u8 **start_ret, u8 **end_ret)
 		return -1;
 	}
 #else
-	/*
-	 * Allocate buffer and guard pages.
-	 * For portability, use /dev/zero instead of MAP_ANONYMOUS.
-	 */
-	fd = open("/dev/zero", O_RDONLY);
-	if (fd < 0) {
-		msg_errno("Unable to open /dev/zero");
-		return -1;
-	}
-	base_addr = mmap(NULL, (nr_pages + 2) * pagesize,
-			 PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
-	close(fd);
+	/* Allocate buffer and guard pages. */
+	base_addr = mmap(NULL, (nr_pages + 2) * pagesize, PROT_READ|PROT_WRITE,
+			 MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
 	if (base_addr == (u8 *)MAP_FAILED) {
-		msg_errno("Unable to allocate memory (unable to mmap /dev/zero)");
+		msg_errno("Unable to allocate memory (anonymous mmap)");
 		return -1;
 	}
 	start = base_addr + pagesize;