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Commit 65cef131 authored by Borislav Petkov's avatar Borislav Petkov Committed by H. Peter Anvin
Browse files

x86, microcode: Add a disable chicken bit 



Add a cmdline param which disables the microcode loader. This is useful
mostly in debugging situations where we want to turn off microcode
loading, both early from the initrd and late, as a means to be able to
rule out its influence on the machine.

Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1400525957-11525-3-git-send-email-bp@alien8.de


Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 1b1ded57

arch/x86/include/asm/microcode.h

+1 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ struct cpu_signature { 
struct device;



enum ucode_state { UCODE_ERROR, UCODE_OK, UCODE_NFOUND };

extern bool dis_ucode_ldr;



struct microcode_ops {

	enum ucode_state (*request_microcode_user) (int cpu,

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

+6 −0
Original line number Diff line number Diff line
@@ -97,6 +97,9 @@ MODULE_LICENSE("GPL"); 


static struct microcode_ops	*microcode_ops;



bool dis_ucode_ldr;

module_param(dis_ucode_ldr, bool, 0);



/*

 * Synchronization.

 *
@@ -546,6 +549,9 @@ static int __init microcode_init(void) 
	struct cpuinfo_x86 *c = &cpu_data(0);

	int error;



	if (dis_ucode_ldr)

		return 0;



	if (c->x86_vendor == X86_VENDOR_INTEL)

		microcode_ops = init_intel_microcode();

	else if (c->x86_vendor == X86_VENDOR_AMD)

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

+37 −0
Original line number Diff line number Diff line
@@ -17,9 +17,11 @@ 
 *	2 of the License, or (at your option) any later version.

 */

#include <linux/module.h>

#include <asm/microcode.h>

#include <asm/microcode_intel.h>

#include <asm/microcode_amd.h>

#include <asm/processor.h>

#include <asm/cmdline.h>



#define QCHAR(a, b, c, d) ((a) + ((b) << 8) + ((c) << 16) + ((d) << 24))

#define CPUID_INTEL1 QCHAR('G', 'e', 'n', 'u')
@@ -72,10 +74,33 @@ static int x86_family(void) 
	return x86;

}



static bool __init check_loader_disabled_bsp(void)

{

#ifdef CONFIG_X86_32

	const char *cmdline = (const char *)__pa_nodebug(boot_command_line);

	const char *opt	    = "dis_ucode_ldr";

	const char *option  = (const char *)__pa_nodebug(opt);

	bool *res = (bool *)__pa_nodebug(&dis_ucode_ldr);



#else /* CONFIG_X86_64 */

	const char *cmdline = boot_command_line;

	const char *option  = "dis_ucode_ldr";

	bool *res = &dis_ucode_ldr;

#endif



	if (cmdline_find_option_bool(cmdline, option))

		*res = true;



	return *res;

}



void __init load_ucode_bsp(void)

{

	int vendor, x86;



	if (check_loader_disabled_bsp())

		return;



	if (!have_cpuid_p())

		return;
@@ -96,10 +121,22 @@ void __init load_ucode_bsp(void) 
	}

}



static bool check_loader_disabled_ap(void)

{

#ifdef CONFIG_X86_32

	return __pa_nodebug(dis_ucode_ldr);

#else

	return dis_ucode_ldr;

#endif

}



void load_ucode_ap(void)

{

	int vendor, x86;



	if (check_loader_disabled_ap())

		return;



	if (!have_cpuid_p())

		return;