src/arch/x86/assembly_entry.S

/*
 * This file is part of the coreboot project.
 *
 * Copyright 2016 Google Inc.
 * Copyright (C) 2016 Intel Corp.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <rules.h>

/*
 *Take the path where CAR_GLOBAL variables just need to be cleared when
 * verstage runs directly after bootblock.
 */
#define ROMSTAGE_AFTER_VERSTAGE \
	(IS_ENABLED(CONFIG_SEPARATE_VERSTAGE) && \
		IS_ENABLED(CONFIG_VBOOT_STARTS_IN_BOOTBLOCK) && ENV_ROMSTAGE)

#if IS_ENABLED(CONFIG_C_ENVIRONMENT_BOOTBLOCK) || ROMSTAGE_AFTER_VERSTAGE

/*
 * This path is for stages that are post bootblock when employing
 * CONFIG_C_ENVIRONMENT_BOOTBLOCK or any intermediate stage succeeding
 * the first stage to initialize protected mode. There's no need to re-load
 * the gdt, etc as all those settings are cached within the processor. In
 * order to continue with C code execution one needs to set stack pointer and
 * clear CAR_GLOBAL variables that are stage specific.
 */
.section ".text._start", "ax", @progbits
.global _start
_start:

/* _car_stack_end symbol is only valid when bootblock does CAR setup. */
#if IS_ENABLED(CONFIG_C_ENVIRONMENT_BOOTBLOCK)
	/* reset stack pointer to CAR stack */
	mov	$_car_stack_end, %esp
#endif

	/* clear CAR_GLOBAL area as it is not shared */
	cld
	xor	%eax, %eax
	movl	$(_car_global_end), %ecx
	movl	$(_car_global_start), %edi
	sub	%edi, %ecx
	rep	stosl

#if ((ENV_VERSTAGE && IS_ENABLED(CONFIG_VERSTAGE_DEBUG_SPINLOOP)) \
	|| (ENV_ROMSTAGE && IS_ENABLED(CONFIG_ROMSTAGE_DEBUG_SPINLOOP)))

	/* Wait for a JTAG debugger to break in and set EBX non-zero */
	xor	%ebx, %ebx

debug_spinloop:
	cmp	$0, %ebx
	jz	debug_spinloop
#endif

	jmp	car_stage_entry

/* This is here for linking purposes. */
.weak car_stage_entry
car_stage_entry:
1:
	jmp	1b

#else

/* This file assembles the start of the romstage program by the order of the
 * includes. Thus, it's extremely important that one pays very careful
 * attention to the order of the includes. */

#include <arch/x86/prologue.inc>
#include <cpu/x86/32bit/entry32.inc>
#include <cpu/x86/fpu_enable.inc>
#if IS_ENABLED(CONFIG_SSE)
#include <cpu/x86/sse_enable.inc>
#endif

/*
 * The assembly.inc is generated based on the requirements of the mainboard.
 * For example, for ROMCC boards the MAINBOARDDIR/romstage.c would be
 * processed by ROMCC and added. In non-ROMCC boards the chipsets'
 * cache-as-ram setup files would be here.
 */
#include <generated/assembly.inc>

#endif