Change in coreboot[master]: arch/x86/postcar: Use a separate stack for C execution

[Felix Held (Code Review)]

Felix Held has submitted this change. ( https://review.coreboot.org/c/coreboot/+/54298 )

Change subject: arch/x86/postcar: Use a separate stack for C execution
......................................................................

arch/x86/postcar: Use a separate stack for C execution

Add a stack in .bss for C execution. This will make it easier to move
the setup of MTRRs in C code.

Change-Id: I67cbc988051036b1a0519cec9ed614acede31fd7
Signed-off-by: Arthur Heymans 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54298
Tested-by: build bot (Jenkins) 
Reviewed-by: Subrata Banik 
Reviewed-by: Raul Rangel 
---
M src/arch/x86/exit_car.S
M src/drivers/intel/fsp1_1/exit_car.S
M src/soc/intel/common/block/cpu/car/exit_car_fsp.S
3 files changed, 16 insertions(+), 2 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Raul Rangel: Looks good to me, approved
  Subrata Banik: Looks good to me, but someone else must approve

diff --git a/src/arch/x86/exit_car.S b/src/arch/x86/exit_car.S
index 9b89ffb..d3954d3 100644
--- a/src/arch/x86/exit_car.S
+++ b/src/arch/x86/exit_car.S
@@ -35,6 +35,18 @@
 .endm
 #endif

+/* Place the stack in the bss section. It's not necessary to define it in the
+ * the linker script. */
+	.section .bss, "aw", @nobits
+.global _stack
+.global _estack
+.global _stack_size
+
+_stack:
+.space CONFIG_STACK_SIZE
+_estack:
+.set _stack_size, _estack - _stack
+
 .text
 .global _start
 _start:
@@ -174,8 +186,10 @@
    wrmsr
 #endif /* CONFIG_SOC_SETS_MSRS */

+	movl	$_estack, %esp
    /* Align stack to 16 bytes at call instruction. */
    andl	$0xfffffff0, %esp
+
    /* Call into main for postcar. */
    call main
    /* Should never return. */
diff --git a/src/drivers/intel/fsp1_1/exit_car.S b/src/drivers/intel/fsp1_1/exit_car.S
index dbdd3e6..2671de5 100644
--- a/src/drivers/intel/fsp1_1/exit_car.S
+++ b/src/drivers/intel/fsp1_1/exit_car.S
@@ -7,7 +7,7 @@

pop	%ebx
    /* Move the stack pointer to real RAM */
-	movl	post_car_stack_top, %esp
+	movl	_estack, %esp
    /* Align the stack 16 bytes */
    andl	$0xfffffff0, %esp

diff --git a/src/soc/intel/common/block/cpu/car/exit_car_fsp.S b/src/soc/intel/common/block/cpu/car/exit_car_fsp.S
index 4b90628..4d35447 100644
--- a/src/soc/intel/common/block/cpu/car/exit_car_fsp.S
+++ b/src/soc/intel/common/block/cpu/car/exit_car_fsp.S
@@ -17,7 +17,7 @@
 chipset_teardown_car:

/* Set up new stack. */
-	mov	post_car_stack_top, %esp
+	mov	_estack, %esp
    /* Align the stack. */
    andl	$0xfffffff0, %esp