X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=arch%2Fx86%2Fcpu%2Fstart16.S;h=5eb17f15c906f8a085f43161163a0668508c6745;hb=d46f2a68e64b14a54a120a4bab0781f8e11f07dd;hp=f1b9d0a0c9719f0c9946bc4243c43802a529323d;hpb=fea25720013f84427a0ba8833a38614fcaf488ba;p=oweals%2Fu-boot.git diff --git a/arch/x86/cpu/start16.S b/arch/x86/cpu/start16.S index f1b9d0a0c9..5eb17f15c9 100644 --- a/arch/x86/cpu/start16.S +++ b/arch/x86/cpu/start16.S @@ -1,29 +1,13 @@ /* - * U-boot - x86 Startup Code + * U-Boot - x86 Startup Code * * (C) Copyright 2008-2011 * Graeme Russ, * * (C) Copyright 2002,2003 - * Daniel Engström, Omicron Ceti AB, + * Daniel Engström, Omicron Ceti AB, * - * See file CREDITS for list of people who contributed to this - * project. - * - * 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; either version 2 of - * the License, or (at your option) any later version. - * - * 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. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place, Suite 330, Boston, - * MA 02111-1307 USA + * SPDX-License-Identifier: GPL-2.0+ */ #include @@ -37,20 +21,18 @@ .code16 .globl start16 start16: + /* Save BIST */ + movl %eax, %ecx + /* 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: + xorl %eax, %eax + movl %eax, %cr3 /* Invalidate TLB */ - /* Turn of cache (this might require a 486-class CPU) */ + /* Turn off cache (this might require a 486-class CPU) */ movl %cr0, %eax - orl $(X86_CR0_NW & X86_CR0_CD), %eax + orl $(X86_CR0_NW | X86_CR0_CD), %eax movl %eax, %cr0 wbinvd @@ -66,9 +48,11 @@ o32 cs lgdt gdt_ptr /* Flush the prefetch queue */ jmp ff ff: - /* Finally jump to the 32bit initialization code */ + + /* 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 */ @@ -80,16 +64,21 @@ 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 - */ + /* + * 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 */ + .word 0x1f /* limit (31 bytes = 4 GDT entries - 1) */ + .long BOOT_SEG + gdt_rom /* base */ - /* The GDT table ... + /* Some CPUs are picky about GDT alignment... */ + .align 16 +.globl gdt_rom +gdt_rom: + /* + * The GDT table ... * * Selector Type * 0x00 NULL @@ -97,17 +86,46 @@ gdt_ptr: * 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 */ -gdt: - .word 0, 0, 0, 0 /* NULL */ - .word 0, 0, 0, 0 /* unused */ + /* 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 */ - .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ - .word 0 /* base address = 0 */ - .word 0x9B00 /* code read/exec */ - .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ + /* + * 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 */ - .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ - .word 0x0 /* base address = 0 */ - .word 0x9300 /* data read/write */ - .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ + /* + * 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 */