x86/microcode: Do not select FW_LOADER

The x86 microcode support works just fine without FW_LOADER. In fact,
these days most people load microcode early during boot so FW_LOADER
never gets into the picture anyway.

As almost everyone on x86 needs to enable MICROCODE, this by extension
means that FW_LOADER is always built into the kernel even if nothing
uses it. The FW_LOADER system is about two thousand lines long and
contains user-space facing interfaces that could potentially provide an
entry point into the kernel (or beyond).

Remove the unnecessary select of FW_LOADER by MICROCODE. People who need
the FW_LOADER capability can still enable it.

 [ bp: Massage a bit. ]

Signed-off-by: Herbert Xu <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

Author: herbertx

arch/x86/Kconfig

@@ -1292,7 +1292,6 @@ config MICROCODE
 	bool "CPU microcode loading support"
 	default y
 	depends on CPU_SUP_AMD || CPU_SUP_INTEL
-	select FW_LOADER
 	help
 	  If you say Y here, you will be able to update the microcode on
 	  Intel and AMD processors. The Intel support is for the IA32 family,
@@ -1314,7 +1313,6 @@ config MICROCODE_INTEL
 	bool "Intel microcode loading support"
 	depends on MICROCODE
 	default MICROCODE
-	select FW_LOADER
 	help
 	  This options enables microcode patch loading support for Intel
 	  processors.
@@ -1326,7 +1324,6 @@ config MICROCODE_INTEL
 config MICROCODE_AMD
 	bool "AMD microcode loading support"
 	depends on MICROCODE
-	select FW_LOADER
 	help
 	  If you select this option, microcode patch loading support for AMD
 	  processors will be enabled.

arch/x86/kernel/cpu/microcode/core.c

@@ -145,7 +145,6 @@ extern struct builtin_fw __end_builtin_fw[];
 
 bool get_builtin_firmware(struct cpio_data *cd, const char *name)
 {
-#ifdef CONFIG_FW_LOADER
 	struct builtin_fw *b_fw;
 
 	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
@@ -155,7 +154,6 @@ bool get_builtin_firmware(struct cpio_data *cd, const char *name)
 			return true;
 		}
 	}
-#endif
 	return false;
 }