| /* SPDX-License-Identifier: GPL-2.0+ */ |
| /* |
| * 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> |
| */ |
| |
| #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: |
| /* Save BIST */ |
| movl %eax, %ecx |
| |
| xorl %eax, %eax |
| movl %eax, %cr3 /* Invalidate TLB */ |
| |
| /* Turn off 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 restore BIST and jump to the 32-bit initialization code */ |
| movw $code32start, %ax |
| movw %ax, %bp |
| movl %ecx, %eax |
| 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 0x1f /* limit (31 bytes = 4 GDT entries - 1) */ |
| .long BOOT_SEG + gdt_rom /* base */ |
| |
| /* Some CPUs are picky about GDT alignment... */ |
| .align 16 |
| .globl gdt_rom |
| gdt_rom: |
| /* |
| * 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 */ |
