Change the C wrappers for mmap/lseek/pread/pwrite/truncate/ftruncate to

call the pad-less versions of the corresponding syscalls if the running
kernel supports it.  Check kern.osreldate once per program and cache the
result to select the appropriate syscall.  This maintains userland
compatability with kernel.old's from quite a while back.

Approved by:  re (kensmith)

1 files changed, 61 insertions, 0 deletions

diff --git a/lib/libc/gen/__getosreldate.c b/lib/libc/gen/__getosreldate.c
new file mode 100644
index 000000000000..69aac07ea7f5
--- /dev/null
+++ b/lib/libc/gen/__getosreldate.c
@@ -0,0 +1,61 @@
+/*-
+ * Copyright (c) 2007 Peter Wemm
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/sysctl.h>
+
+/*
+ * This is private to libc.  It is intended for wrapping syscall stubs in order
+ * to avoid having to put SIGSYS signal handlers in place to test for presence
+ * of new syscalls.  This caches the result in order to be as quick as possible.
+ *
+ * Use getosreldate(3) for public use as it respects the $OSVERSION environment
+ * variable.
+ */
+
+int
+__getosreldate(void)
+{
+	static int osreldate;
+	size_t len;
+	int oid[2];
+	int error, osrel;
+
+	if (osreldate != 0)
+		return (osreldate);
+	
+	oid[0] = CTL_KERN;
+	oid[1] = KERN_OSRELDATE;
+	osrel = 0;
+	len = sizeof(osrel);
+	error = sysctl(oid, 2, &osrel, &len, NULL, 0);
+	if (error == 0 && osrel > 0 && len == sizeof(osrel))
+		osreldate = osrel;
+	return (osreldate);
+}