1 files changed, 67 insertions, 0 deletions
diff --git a/lib/copy-file-range.c b/lib/copy-file-range.c
new file mode 100644
index 0000000..1ec7f4d
--- /dev/null
+++ b/lib/copy-file-range.c
@@ -0,0 +1,67 @@
+/* Stub for copy_file_range
+   Copyright 2019-2022 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   This file 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 Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include <unistd.h>
+
+#include <errno.h>
+
+#if defined __linux__ && HAVE_COPY_FILE_RANGE
+# include <sys/utsname.h>
+#endif
+
+ssize_t
+copy_file_range (int infd, off_t *pinoff,
+                 int outfd, off_t *poutoff,
+                 size_t length, unsigned int flags)
+{
+#undef copy_file_range
+
+#if defined __linux__ && HAVE_COPY_FILE_RANGE
+  /* The implementation of copy_file_range (which first appeared in
+     Linux kernel release 4.5) had many issues before release 5.3
+     <https://lwn.net/Articles/789527/>, so fail with ENOSYS for Linux
+     kernels 5.2 and earlier.
+
+     This workaround, and the configure-time check for Linux, can be
+     removed when such kernels (released March 2016 through September
+     2019) are no longer a consideration.  As of January 2021, the
+     furthest-future planned kernel EOL is December 2024 for kernel
+     release 4.19.  */
+
+    static signed char ok;
+
+    if (! ok)
+      {
+        struct utsname name;
+        uname (&name);
+        char *p = name.release;
+        ok = ((p[1] != '.' || '5' < p[0]
+               || (p[0] == '5' && (p[3] != '.' || '2' < p[2])))
+              ? 1 : -1);
+      }
+
+    if (0 < ok)
+      return copy_file_range (infd, pinoff, outfd, poutoff, length, flags);
+#endif
+
+  /* There is little need to emulate copy_file_range with read+write,
+     since programs that use copy_file_range must fall back on
+     read+write anyway.  */
+  errno = ENOSYS;
+  return -1;
+}