From: Baskov Evgeniy <baskov@ispras.ru>

Command line needs to be combined in both compressed and uncompressed
kernel from built-in and boot command line strings, which requires
non-trivial logic depending on CONFIG_CMDLINE_BOOL and
CONFIG_CMDLINE_OVERRIDE.

Add a helper function to avoid code duplication.

Signed-off-by: Baskov Evgeniy <baskov@ispras.ru>

 create mode 100644 arch/x86/include/asm/shared/setup-cmdline.h

diff --git a/arch/x86/include/asm/shared/setup-cmdline.h b/arch/x86/include/asm/shared/setup-cmdline.h
new file mode 100644
index 000000000000..b8bb19e63ec2
--- /dev/null
+++ b/arch/x86/include/asm/shared/setup-cmdline.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_X86_SETUP_CMDLINE_H
+#define _ASM_X86_SETUP_CMDLINE_H
+
+#define _SETUP
+#include <asm/setup.h> /* For COMMAND_LINE_SIZE */
+#undef _SETUP
+
+#include <linux/string.h>
+
+#ifdef CONFIG_CMDLINE_BOOL
+#define COMMAND_LINE_INIT CONFIG_CMDLINE
+#else
+#define COMMAND_LINE_INIT ""
+#endif
+
+/*
+ * command_line and boot_command_line are expected to be at most
+ * COMMAND_LINE_SIZE length. command_line needs to be initialized
+ * with COMMAND_LINE_INIT.
+ */
+
+static inline void resolve_cmdline(char *command_line,
+				   const char *boot_command_line)
+{
+#ifdef CONFIG_CMDLINE_BOOL
+	if (!IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) {
+		/* Append boot loader cmdline to builtin */
+		strlcat(command_line, " ", COMMAND_LINE_SIZE);
+		strlcat(command_line, boot_command_line, COMMAND_LINE_SIZE);
+	}
+#else
+	strscpy(command_line, boot_command_line, COMMAND_LINE_SIZE);
+#endif
+}
+
+#endif /* _ASM_X86_SETUP_CMDLINE_H */
-- 
2.35.1