fs/proc: Skip bootloader comment if no embedded kernel parameters

If the "bootconfig" kernel command-line argument was specified or if
the kernel was built with CONFIG_BOOT_CONFIG_FORCE, but if there are
no embedded kernel parameter, omit the "# Parameters from bootloader:"
comment from the /proc/bootconfig file.  This will cause automation
to fall back to the /proc/cmdline file, which will be identical to the
comment in this no-embedded-kernel-parameters case.

Link: https://lore.kernel.org/all/20240409044358.1156477-2-paulmck@kernel.org/

Fixes: 8b8ce6c75430 ("fs/proc: remove redundant comments from /proc/bootconfig")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: stable@vger.kernel.org
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

fs/proc/bootconfig.c

@@ -63,7 +63,7 @@ static int __init copy_xbc_key_value_list(char *dst, size_t size)
 			dst += ret;
 		}
 	}
-	if (ret >= 0 && boot_command_line[0]) {
+	if (cmdline_has_extra_options() && ret >= 0 && boot_command_line[0]) {
 		ret = snprintf(dst, rest(dst, end), "# Parameters from bootloader:\n# %s\n",
 			       boot_command_line);
 		if (ret > 0)

include/linux/bootconfig.h

@@ -10,6 +10,7 @@
 #ifdef __KERNEL__
 #include <linux/kernel.h>
 #include <linux/types.h>
+bool __init cmdline_has_extra_options(void);
 #else /* !__KERNEL__ */
 /*
  * NOTE: This is only for tools/bootconfig, because tools/bootconfig will

init/main.c

@@ -487,6 +487,11 @@ static int __init warn_bootconfig(char *str)
 
 early_param("bootconfig", warn_bootconfig);
 
+bool __init cmdline_has_extra_options(void)
+{
+	return extra_command_line || extra_init_args;
+}
+
 /* Change NUL term back to "=", to make "param" the whole string. */
 static void __init repair_env_string(char *param, char *val)
 {