v4.19.13 snapshot.
diff --git a/lib/kasprintf.c b/lib/kasprintf.c
new file mode 100644
index 0000000..bacf7b8
--- /dev/null
+++ b/lib/kasprintf.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/lib/kasprintf.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ */
+
+#include <stdarg.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/string.h>
+
+/* Simplified asprintf. */
+char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap)
+{
+ unsigned int first, second;
+ char *p;
+ va_list aq;
+
+ va_copy(aq, ap);
+ first = vsnprintf(NULL, 0, fmt, aq);
+ va_end(aq);
+
+ p = kmalloc_track_caller(first+1, gfp);
+ if (!p)
+ return NULL;
+
+ second = vsnprintf(p, first+1, fmt, ap);
+ WARN(first != second, "different return values (%u and %u) from vsnprintf(\"%s\", ...)",
+ first, second, fmt);
+
+ return p;
+}
+EXPORT_SYMBOL(kvasprintf);
+
+/*
+ * If fmt contains no % (or is exactly %s), use kstrdup_const. If fmt
+ * (or the sole vararg) points to rodata, we will then save a memory
+ * allocation and string copy. In any case, the return value should be
+ * freed using kfree_const().
+ */
+const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list ap)
+{
+ if (!strchr(fmt, '%'))
+ return kstrdup_const(fmt, gfp);
+ if (!strcmp(fmt, "%s"))
+ return kstrdup_const(va_arg(ap, const char*), gfp);
+ return kvasprintf(gfp, fmt, ap);
+}
+EXPORT_SYMBOL(kvasprintf_const);
+
+char *kasprintf(gfp_t gfp, const char *fmt, ...)
+{
+ va_list ap;
+ char *p;
+
+ va_start(ap, fmt);
+ p = kvasprintf(gfp, fmt, ap);
+ va_end(ap);
+
+ return p;
+}
+EXPORT_SYMBOL(kasprintf);