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security/intel/txt: Fix variable MTRR handling 

The MSR macros were treated as memory addresses and the loops had
off-by-one errors. This resulted in a CPU exception before GETSEC, and
another exception after GETSEC (once the first exception was fixed).

Tested on Asrock B85M Pro4, ACM complains about the missing TPM and
resets the platform. When the `getsec` instruction is commented-out, the
board is able to boot normally, without any exceptions nor corruption.

Change-Id: Ib5d23cf9885401f3ec69b0f14cea7bad77eee19a
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44183
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
This commit is contained in:
Angel Pons 2020-08-04 19:22:01 +02:00
parent bf9bc50ec1
commit 2f1739ada8
1 changed files with 47 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

95
src/security/intel/txt/getsec_enteraccs.S
View File

@ -27,46 +27,6 @@
wrmsr
.endm
/* Variable MTRR index is passed through %ebx */
.macro PUSH_VAR_MTRR
movl %ebx, %ecx
shll %ecx
addl MTRR_PHYS_BASE(0), %ecx
rdmsr
push %eax
push %edx
incl %ecx /* MTRR_PHYS_MASK */
rdmsr
push %eax
push %edx
.endm
.macro POP_VAR_MTRR
movl %ebx, %ecx
shll %ecx
addl MTRR_PHYS_MASK(0), %ecx
pop %edx
pop %eax
wrmsr
decl %ecx /* MTRR_PHYS_BASE */
pop %edx
pop %eax
wrmsr
.endm
.macro CLEAR_VAR_MTRR
movl %ebx, %ecx
shll %ecx
addl MTRR_PHYS_BASE(0), %ecx
xorl %edx, %edx
xorl %eax, %eax
wrmsr
incl %ecx /* MTRR_PHYS_MASK */
xorl %edx, %edx
xorl %eax, %eax
wrmsr
.endm
.align 4
.text
@ -111,12 +71,23 @@ getsec_enteraccs:
PUSH_MSR MTRR_FIX_4K_F8000
/* Push variable MTRRs in ascending order */
xorl %ebx, %ebx
jmp cond_push_var_mtrrs
body_push_var_mtrrs:
PUSH_VAR_MTRR
movl %ebx, %ecx
shll %ecx
addl $(MTRR_PHYS_BASE(0)), %ecx
rdmsr
push %eax
push %edx
incl %ecx /* MTRR_PHYS_MASK */
rdmsr
push %eax
push %edx
incl %ebx
cond_push_var_mtrrs:
@ -125,7 +96,7 @@ cond_push_var_mtrrs:
rdmsr
andl $(0xff), %eax
cmp %ebx, %eax
jge body_push_var_mtrrs
jg body_push_var_mtrrs
/*
* Disable cache.
@ -168,10 +139,24 @@ cond_push_var_mtrrs:
andl $(0xff), %eax
movl %eax, %ebx
xorl %eax, %eax
xorl %edx, %edx
jmp cond_clear_var_mtrrs
body_clear_var_mtrrs:
CLEAR_VAR_MTRR
decl %ebx
movl %ebx, %ecx
shll %ecx
addl $(MTRR_PHYS_BASE(0)), %ecx
wrmsr
incl %ecx /* MTRR_PHYS_MASK */
wrmsr
cond_clear_var_mtrrs:
cmpl $0, %ebx
jnz body_clear_var_mtrrs
/*
@ -266,19 +251,33 @@ body_clear_var_mtrrs:
orl $(CR0_CD | CR0_NW), %eax
movl %eax, %cr0
/* Restore MTTRs */
/* Pop variable MTRRs in descending order */
movl $(MTRR_CAP_MSR), %ecx
rdmsr
andl $(0xff), %eax
movl %eax, %ebx
jmp cond_pop_var_mtrrs
body_pop_var_mtrrs:
POP_VAR_MTRR
decl %ebx
jnz body_pop_var_mtrrs
movl %ebx, %ecx
shll %ecx
addl $(MTRR_PHYS_MASK(0)), %ecx
pop %edx
pop %eax
wrmsr
decl %ecx /* MTRR_PHYS_BASE */
pop %edx
pop %eax
wrmsr
cond_pop_var_mtrrs:
cmpl $0, %ebx
jne body_pop_var_mtrrs
POP_MSR MTRR_FIX_4K_F8000
POP_MSR MTRR_FIX_4K_F0000
@ -301,7 +300,7 @@ body_pop_var_mtrrs:
/* Enable cache */
movl %cr0, %eax
andl $(~(CR0_CD | CR0_NW)), %eax
movl %eax, %cr0
movl %eax, %cr0
/* Pop GDT */
addl $8, %esp