lib/replace: test for incoherent mmap.

We test for other mmap features here, and both tdb1 and tdb2 want this check.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

3 files changed, 97 insertions, 0 deletions

diff --git a/lib/replace/libreplace.m4 b/lib/replace/libreplace.m4
index ca0c6846ab..e14fadabf1 100644
--- a/lib/replace/libreplace.m4
+++ b/lib/replace/libreplace.m4
@@ -107,6 +107,13 @@ if test x"$libreplace_cv_HAVE_MREMAP" = x"yes"; then
     AC_DEFINE(HAVE_MREMAP,1,[Whether mremap works])
 fi
 
+AC_CACHE_CHECK([for incoherent mmap],libreplace_cv_HAVE_INCOHERENT_MMAP,[
+AC_TRY_RUN([#include "$libreplacedir/test/incoherent_mmap.c"],
+           libreplace_cv_HAVE_INCOHERENT_MMAP=yes,libreplace_cv_HAVE_INCOHERENT_MMAP=no,libreplace_cv_HAVE_INCOHERENT_MMAP=cross)])
+if test x"$libreplace_cv_HAVE_INCOHERENT_MMAP" = x"yes"; then
+    AC_DEFINE(HAVE_INCOHERENT_MMAP,1,[Whether mmap is incoherent against write])
+fi
+
 
 AC_CHECK_HEADERS(sys/syslog.h syslog.h)
 AC_CHECK_HEADERS(sys/time.h time.h)
diff --git a/lib/replace/test/incoherent_mmap.c b/lib/replace/test/incoherent_mmap.c
new file mode 100644
index 0000000000..ee288fd806
--- /dev/null
+++ b/lib/replace/test/incoherent_mmap.c
@@ -0,0 +1,83 @@
+/* In OpenBSD, if you write to a file, another process doesn't see it
+ * in its mmap.  Returns with exit status 0 if that is the case, 1 if
+ * it's coherent, and other if there's a problem. */
+#include <err.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#define DATA "coherent.mmap"
+
+int main(int argc, char *argv[])
+{
+	int tochild[2], toparent[2];
+	int fd;
+	volatile unsigned char *map;
+	unsigned char *page;
+        const char *fname = argv[1];
+	char c = 0;
+
+	if (pipe(tochild) != 0 || pipe(toparent) != 0)
+		err(2, "Creating pipe");
+
+	if (!fname)
+		fname = DATA;
+
+	fd = open(fname, O_RDWR|O_CREAT|O_TRUNC, 0600);
+	if (fd < 0)
+		err(2, "opening %s", fname);
+	unlink(fname);
+
+	switch (fork()) {
+	case -1:
+		err(2, "Fork");
+	case 0:
+		close(tochild[1]);
+		close(toparent[0]);
+
+		/* Wait for parent to create file. */
+		if (read(tochild[0], &c, 1) != 1)
+			err(2, "reading from parent");
+
+		/* Alter first byte. */
+		pwrite(fd, &c, 1, 0);
+
+		if (write(toparent[1], &c, 1) != 1)
+			err(2, "writing to parent");
+		exit(0);
+
+	default:
+		close(tochild[0]);
+		close(toparent[1]);
+
+		/* Create a file and mmap it. */
+		page = malloc(getpagesize());
+		memset(page, 0x42, getpagesize());
+		if (write(fd, page, getpagesize()) != getpagesize())
+			err(2, "writing first page");
+		map = mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE,
+			   MAP_SHARED, fd, 0);
+		if (map == MAP_FAILED)
+			err(2, "mapping file");
+
+		if (*map != 0x42)
+			errx(2, "first byte isn't 0x42!");
+
+		/* Tell child to alter file. */
+		if (write(tochild[1], &c, 1) != 1)
+			err(2, "writing to child");
+
+		if (read(toparent[0], &c, 1) != 1)
+			err(2, "reading from child");
+
+		if (*map)
+			errx(0, "mmap incoherent: first byte isn't 0.");
+
+		exit(1);
+	}
+}
diff --git a/lib/replace/wscript b/lib/replace/wscript
index 36c2f0f3e1..63944c3800 100644
--- a/lib/replace/wscript
+++ b/lib/replace/wscript
@@ -299,6 +299,13 @@ def configure(conf):
                     addmain=False,
                     msg="Checking for C99 vsnprintf")
 
+    # OpenBSD (and I've heard HPUX) doesn't sync between mmap and write.
+    # FIXME: Anything other than a 0 or 1 exit code should abort configure!
+    conf.CHECK_CODE('#include "test/incoherent_mmap.c"',
+                    addmain=False, add_headers=False, execute=True,
+                    define='HAVE_INCOHERENT_MMAP',
+                    msg="Checking for HAVE_INCOHERENT_MMAP")
+
     conf.SAMBA_BUILD_ENV()
 
     conf.CHECK_CODE('''