Change in coreboot[master]: cpu/x86/entry16.S: Make Intel CBnT TOCTOU safe

[Angel Pons (Code Review)]

Attention is currently required from: Christian Walter, Arthur Heymans, Kyösti Mälkki, Patrick Rudolph.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/54010 )

Change subject: cpu/x86/entry16.S: Make Intel CBnT TOCTOU safe
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Patch Set 2:

(1 comment)

File src/cpu/x86/entry16.S:

https://review.coreboot.org/c/coreboot/+/54010/comment/52b01468_63ea9d1b 
PS2, Line 135: 2:
> Since %ebx is not used, how about: […]

Looks like CMOVcc does not work with immediates...

movl	$0x60000001, %ebx /* CD, NW, PE = 1 */
 #if CONFIG(INTEL_CBNT_SUPPORT)
 #include <cpu/intel/msr.h>
    /* Do not disable caching if the BootGuard ACM has set up CAR */
    movl	$MSR_BOOT_GUARD_SACM_INFO, %ecx
    rdmsr
    movl	$0x01, %edx /* PE = 1 */
    test	$B_BOOT_GUARD_SACM_INFO_NEM_ENABLED, %eax
    cmovne	%edx, %ebx
 #endif
    movl	%cr0, %eax
    andl	$0x7FFAFFD1, %eax /* PG,AM,WP,NE,TS,EM,MP = 0 */
    orl	%ebx, %eax
    movl	%eax, %cr0

Alternatively, use a jump