Linux 6.8 compat: implement strlcpy fallback

Linux has removed strlcpy in favour of strscpy. This implements a
fallback implementation of strlcpy for this case.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #15805

config/kernel-strlcpy.m4

@@ -0,0 +1,47 @@
+dnl #
+dnl # 6.8.x replaced strlcpy with strscpy. Check for both so we can provide
+dnl # appropriate fallbacks.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_SRC_STRLCPY], [
+	ZFS_LINUX_TEST_SRC([kernel_has_strlcpy], [
+		#include <linux/string.h>
+	], [
+		const char *src = "goodbye";
+		char dst[32];
+		size_t len;
+		len = strlcpy(dst, src, sizeof (dst));
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_SRC_STRSCPY], [
+	ZFS_LINUX_TEST_SRC([kernel_has_strscpy], [
+		#include <linux/string.h>
+	], [
+		const char *src = "goodbye";
+		char dst[32];
+		ssize_t len;
+		len = strscpy(dst, src, sizeof (dst));
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_STRLCPY], [
+	AC_MSG_CHECKING([whether strlcpy() exists])
+	ZFS_LINUX_TEST_RESULT([kernel_has_strlcpy], [
+		AC_MSG_RESULT([yes])
+		AC_DEFINE(HAVE_KERNEL_STRLCPY, 1,
+			[strlcpy() exists])
+	], [
+		AC_MSG_RESULT([no])
+	])
+])
+
+AC_DEFUN([ZFS_AC_KERNEL_STRSCPY], [
+	AC_MSG_CHECKING([whether strscpy() exists])
+	ZFS_LINUX_TEST_RESULT([kernel_has_strscpy], [
+		AC_MSG_RESULT([yes])
+		AC_DEFINE(HAVE_KERNEL_STRSCPY, 1,
+			[strscpy() exists])
+	], [
+		AC_MSG_RESULT([no])
+	])
+])

config/kernel.m4

@@ -149,6 +149,8 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_SYSFS
 	ZFS_AC_KERNEL_SRC_SET_SPECIAL_STATE
 	ZFS_AC_KERNEL_SRC_STANDALONE_LINUX_STDARG
+	ZFS_AC_KERNEL_SRC_STRLCPY
+	ZFS_AC_KERNEL_SRC_STRSCPY
 	ZFS_AC_KERNEL_SRC_PAGEMAP_FOLIO_WAIT_BIT
 	ZFS_AC_KERNEL_SRC_ADD_DISK
 	ZFS_AC_KERNEL_SRC_KTHREAD
@@ -294,6 +296,8 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_SYSFS
 	ZFS_AC_KERNEL_SET_SPECIAL_STATE
 	ZFS_AC_KERNEL_STANDALONE_LINUX_STDARG
+	ZFS_AC_KERNEL_STRLCPY
+	ZFS_AC_KERNEL_STRSCPY
 	ZFS_AC_KERNEL_PAGEMAP_FOLIO_WAIT_BIT
 	ZFS_AC_KERNEL_ADD_DISK
 	ZFS_AC_KERNEL_KTHREAD

include/os/linux/spl/sys/string.h

@@ -1 +1,50 @@
+/*
+ *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
+ *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
+ *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
+ *  UCRL-CODE-235197
+ *
+ *  This file is part of the SPL, Solaris Porting Layer.
+ *
+ *  The SPL is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License as published by the
+ *  Free Software Foundation; either version 2 of the License, or (at your
+ *  option) any later version.
+ *
+ *  The SPL is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _SPL_STRING_H
+#define	_SPL_STRING_H
+
 #include <linux/string.h>
+
+/* Fallbacks for kernel missing strlcpy */
+#ifndef HAVE_KERNEL_STRLCPY
+
+#if defined(HAVE_KERNEL_STRSCPY)
+/*
+ * strscpy is strlcpy, but returns an error on truncation. strlcpy is defined
+ * to return strlen(src), so detect error and override it.
+ */
+static inline size_t
+strlcpy(char *dest, const char *src, size_t size)
+{
+	ssize_t ret = strscpy(dest, src, size);
+	if (likely(ret > 0))
+		return ((size_t)ret);
+	return (strlen(src));
+}
+#else
+#error "no strlcpy fallback available"
+#endif
+
+#endif /* HAVE_KERNEL_STRLCPY */
+
+#endif /* _SPL_STRING_H */

module/os/linux/spl/spl-kmem-cache.c

@@ -28,6 +28,7 @@
 #include <sys/timer.h>
 #include <sys/vmem.h>
 #include <sys/wait.h>
+#include <sys/string.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/prefetch.h>

module/os/linux/spl/spl-kstat.c

@@ -32,6 +32,7 @@
 #include <sys/vmem.h>
 #include <sys/cmn_err.h>
 #include <sys/sysmacros.h>
+#include <sys/string.h>
 
 static kmutex_t kstat_module_lock;
 static struct list_head kstat_module_list;

module/os/linux/spl/spl-thread.c

@@ -26,6 +26,7 @@
 #include <sys/thread.h>
 #include <sys/kmem.h>
 #include <sys/tsd.h>
+#include <sys/string.h>
 
 /*
  * Thread interfaces

module/os/linux/spl/spl-zone.c

@@ -30,6 +30,7 @@
 #include <linux/file.h>
 #include <linux/magic.h>
 #include <sys/zone.h>
+#include <sys/string.h>
 
 #if defined(CONFIG_USER_NS)
 #include <linux/statfs.h>