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
(cherry picked from commit 7466e09a49)

include/os/linux/spl/sys/Makefile.am

@@ -34,6 +34,7 @@ KERNEL_H = \
 	signal.h \
 	simd.h \
 	stat.h \
+	string.h \
 	strings.h \
 	sunddi.h \
 	sysmacros.h \

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

@@ -0,0 +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 */