x86/setup: Parse the builtin command line before merging

Commit in Fixes was added as a catch-all for cases where the cmdline is
parsed before being merged with the builtin one.

And promptly one issue appeared, see Link below. The microcode loader
really needs to parse it that early, but the merging happens later.

Reshuffling the early boot nightmare^W code to handle that properly would
be a painful exercise for another day so do the chicken thing and parse the
builtin cmdline too before it has been merged.

Fixes: 0c40b1c7 ("x86/setup: Warn when option parsing is done too early")
Reported-by: Mike Lothian <mike@fireburn.co.uk>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240730152108.GAZqkE5Dfi9AuKllRw@fat_crate.local
Link: https://lore.kernel.org/r/20240722152330.GCZp55ck8E_FT4kPnC@fat_crate.local

arch/x86/include/asm/cmdline.h

@@ -2,6 +2,10 @@
 #ifndef _ASM_X86_CMDLINE_H
 #define _ASM_X86_CMDLINE_H
 
+#include <asm/setup.h>
+
+extern char builtin_cmdline[COMMAND_LINE_SIZE];
+
 int cmdline_find_option_bool(const char *cmdline_ptr, const char *option);
 int cmdline_find_option(const char *cmdline_ptr, const char *option,
 			char *buffer, int bufsize);

arch/x86/kernel/setup.c

@@ -164,7 +164,7 @@ unsigned long saved_video_mode;
 
 static char __initdata command_line[COMMAND_LINE_SIZE];
 #ifdef CONFIG_CMDLINE_BOOL
-static char __initdata builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
+char builtin_cmdline[COMMAND_LINE_SIZE] = CONFIG_CMDLINE;
 bool builtin_cmdline_added __ro_after_init;
 #endif
 

arch/x86/lib/cmdline.c

@@ -207,18 +207,29 @@ __cmdline_find_option(const char *cmdline, int max_cmdline_size,
 
 int cmdline_find_option_bool(const char *cmdline, const char *option)
 {
-	if (IS_ENABLED(CONFIG_CMDLINE_BOOL))
-		WARN_ON_ONCE(!builtin_cmdline_added);
+	int ret;
 
-	return __cmdline_find_option_bool(cmdline, COMMAND_LINE_SIZE, option);
+	ret = __cmdline_find_option_bool(cmdline, COMMAND_LINE_SIZE, option);
+	if (ret > 0)
+		return ret;
+
+	if (IS_ENABLED(CONFIG_CMDLINE_BOOL) && !builtin_cmdline_added)
+		return __cmdline_find_option_bool(builtin_cmdline, COMMAND_LINE_SIZE, option);
+
+	return ret;
 }
 
 int cmdline_find_option(const char *cmdline, const char *option, char *buffer,
 			int bufsize)
 {
-	if (IS_ENABLED(CONFIG_CMDLINE_BOOL))
-		WARN_ON_ONCE(!builtin_cmdline_added);
+	int ret;
+
+	ret = __cmdline_find_option(cmdline, COMMAND_LINE_SIZE, option, buffer, bufsize);
+	if (ret > 0)
+		return ret;
+
+	if (IS_ENABLED(CONFIG_CMDLINE_BOOL) && !builtin_cmdline_added)
+		return __cmdline_find_option(builtin_cmdline, COMMAND_LINE_SIZE, option, buffer, bufsize);
 
-	return __cmdline_find_option(cmdline, COMMAND_LINE_SIZE, option,
-				     buffer, bufsize);
+	return ret;
 }