diff options
Diffstat (limited to 'qemu/roms/u-boot/arch/x86/cpu/start16.S')
| -rw-r--r-- | qemu/roms/u-boot/arch/x86/cpu/start16.S | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/qemu/roms/u-boot/arch/x86/cpu/start16.S b/qemu/roms/u-boot/arch/x86/cpu/start16.S new file mode 100644 index 000000000..8b9b327cd --- /dev/null +++ b/qemu/roms/u-boot/arch/x86/cpu/start16.S @@ -0,0 +1,130 @@ +/* + * U-boot - x86 Startup Code + * + * (C) Copyright 2008-2011 + * Graeme Russ, <graeme.russ@gmail.com> + * + * (C) Copyright 2002,2003 + * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se> + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <asm/global_data.h> +#include <asm/processor-flags.h> + +#define BOOT_SEG 0xffff0000 /* linear segment of boot code */ +#define a32 .byte 0x67; +#define o32 .byte 0x66; + +.section .start16, "ax" +.code16 +.globl start16 +start16: + /* Set the Cold Boot / Hard Reset flag */ + movl $GD_FLG_COLD_BOOT, %ebx + + /* + * First we let the BSP do some early initialization + * this code have to map the flash to its final position + */ + jmp board_init16 +.globl board_init16_ret +board_init16_ret: + + /* Turn of cache (this might require a 486-class CPU) */ + movl %cr0, %eax + orl $(X86_CR0_NW | X86_CR0_CD), %eax + movl %eax, %cr0 + wbinvd + + /* load the temporary Global Descriptor Table */ +o32 cs lidt idt_ptr +o32 cs lgdt gdt_ptr + + /* Now, we enter protected mode */ + movl %cr0, %eax + orl $X86_CR0_PE, %eax + movl %eax, %cr0 + + /* Flush the prefetch queue */ + jmp ff +ff: + /* Finally jump to the 32bit initialization code */ + movw $code32start, %ax + movw %ax, %bp +o32 cs ljmp *(%bp) + + /* 48-bit far pointer */ +code32start: + .long _start /* offset */ + .word 0x10 /* segment */ + +idt_ptr: + .word 0 /* limit */ + .long 0 /* base */ + +/* + * The following Global Descriptor Table is just enough to get us into + * 'Flat Protected Mode' - It will be discarded as soon as the final + * GDT is setup in a safe location in RAM + */ +gdt_ptr: + .word 0x20 /* limit (32 bytes = 4 GDT entries) */ + .long BOOT_SEG + gdt /* base */ + +/* Some CPUs are picky about GDT alignment... */ +.align 16 +gdt: + /* + * The GDT table ... + * + * Selector Type + * 0x00 NULL + * 0x08 Unused + * 0x10 32bit code + * 0x18 32bit data/stack + */ + /* The NULL Desciptor - Mandatory */ + .word 0x0000 /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x00 /* access */ + .byte 0x00 /* flags + limit_high */ + .byte 0x00 /* base_high */ + + /* Unused Desciptor - (matches Linux) */ + .word 0x0000 /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x00 /* access */ + .byte 0x00 /* flags + limit_high */ + .byte 0x00 /* base_high */ + + /* + * The Code Segment Descriptor: + * - Base = 0x00000000 + * - Size = 4GB + * - Access = Present, Ring 0, Exec (Code), Readable + * - Flags = 4kB Granularity, 32-bit + */ + .word 0xffff /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x9b /* access */ + .byte 0xcf /* flags + limit_high */ + .byte 0x00 /* base_high */ + + /* + * The Data Segment Descriptor: + * - Base = 0x00000000 + * - Size = 4GB + * - Access = Present, Ring 0, Non-Exec (Data), Writable + * - Flags = 4kB Granularity, 32-bit + */ + .word 0xffff /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x93 /* access */ + .byte 0xcf /* flags + limit_high */ + .byte 0x00 /* base_high */ |