/* * U-boot - i386 Startup Code * * Copyright (c) 2002 Omicron Ceti AB, Daniel Engström * * 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 */ #include #include .section .text .code32 .globl _start .type _start, @function .globl _i386boot_start _i386boot_start: /* * This is the fail safe 32-bit bootstrap entry point. The * following code is not executed from a cold-reset (actually, a * lot of it is, but from real-mode after cold reset. It is * repeated here to put the board into a state as close to cold * reset as necessary) */ cli cld /* Turn of cache (this might require a 486-class CPU) */ movl %cr0, %eax orl $0x60000000,%eax movl %eax, %cr0 wbinvd /* Tell 32-bit code it is being entered from an in-RAM copy */ movw $0x0000, %bx _start: /* This is the 32-bit cold-reset entry point */ movl $0x18,%eax /* Load our segement registes, the * gdt have already been loaded by start16.S */ movw %ax,%fs movw %ax,%ds movw %ax,%gs movw %ax,%es movw %ax,%ss /* Clear the interupt vectors */ lidt blank_idt_ptr /* * Skip low-level board and memory initialization if not starting * from cold-reset. This allows us to do a fail safe boot-strap * into a new build of U-Boot from a known-good boot flash */ movw $0x0001, %ax cmpw %ax, %bx jne mem_init_ret /* We call a few functions in the board support package * since we have no stack yet we'll have to use %ebp * to store the return address */ /* Early platform init (setup gpio, etc ) */ mov $early_board_init_ret, %ebp jmp early_board_init early_board_init_ret: /* The __port80 entry-point should be usabe by now */ /* so we try to indicate progress */ movw $0x01, %ax movl $.progress0, %ebp jmp show_boot_progress_asm .progress0: /* size memory */ mov $mem_init_ret, %ebp jmp mem_init mem_init_ret: /* fetch memory size (into %eax) */ mov $get_mem_size_ret, %ebp jmp get_mem_size get_mem_size_ret: /* * We are now in 'Flat Protected Mode' and we know how much memory * the board has. The (temporary) Global Descriptor Table is not * in a 'Safe' place (it is either in Flash which can be erased or * reprogrammed or in a fail-safe boot-strap image which could be * over-written). * * Move the final gdt to a safe place (top of RAM) and load it. * This is not a trivial excercise - the lgdt instruction does not * have a register operand (memory only) and we may well be * running from Flash, so self modifying code will not work here. * To overcome this, we copy a stub into upper memory along with * the GDT. */ /* Reduce upper memory limit by (Stub + GDT Pointer + GDT) */ subl $(end_gdt_setup - start_gdt_setup), %eax /* Copy the GDT and Stub */ movl $start_gdt_setup, %esi movl %eax, %edi movl $(end_gdt_setup - start_gdt_setup), %ecx shrl $2, %ecx cld rep movsl /* write the lgdt 'parameter' */ subl $(jmp_instr - start_gdt_setup - 4), %ebp addl %eax, %ebp movl $(gdt_ptr - start_gdt_setup), %ebx addl %eax, %ebx movl %ebx, (%ebp) /* write the gdt address into the pointer */ movl $(gdt_addr - start_gdt_setup), %ebp addl %eax, %ebp movl $(gdt - start_gdt_setup), %ebx addl %eax, %ebx movl %ebx, (%ebp) /* Save the return address */ movl $load_gdt_ret, %ebp /* Load the new (safe) Global Descriptor Table */ jmp *%eax load_gdt_ret: /* Check we have enough memory for stack */ movl $CONFIG_SYS_STACK_SIZE, %ecx cmpl %ecx, %eax jae mem_ok /* indicate (lack of) progress */ movw $0x81, %ax movl $.progress0a, %ebp jmp show_boot_progress_asm .progress0a: jmp die mem_ok: /* Set stack pointer to upper memory limit*/ movl %eax, %esp /* indicate progress */ movw $0x02, %ax movl $.progress1, %ebp jmp show_boot_progress_asm .progress1: /* Test the stack */ pushl $0 popl %eax cmpl $0, %eax jne no_stack push $0x55aa55aa popl %ebx cmpl $0x55aa55aa, %ebx je stack_ok no_stack: /* indicate (lack of) progress */ movw $0x82, %ax movl $.progress1a, %ebp jmp show_boot_progress_asm .progress1a: jmp die stack_ok: /* indicate progress */ movw $0x03, %ax movl $.progress2, %ebp jmp show_boot_progress_asm .progress2: wbinvd /* Get upper memory limit */ movl %esp, %ecx subl $CONFIG_SYS_STACK_SIZE, %ecx /* Create a Stack Frame */ pushl %ebp movl %esp, %ebp /* stack_limit parameter */ pushl %ecx call board_init_f /* Enter, U-boot! */ /* indicate (lack of) progress */ movw $0x85, %ax movl $.progress4a, %ebp jmp show_boot_progress_asm .progress4a: die: hlt jmp die hlt blank_idt_ptr: .word 0 /* limit */ .long 0 /* base */ .align 4 start_gdt_setup: lgdt gdt_ptr jmp_instr: jmp *%ebp .align 4 gdt_ptr: .word 0x30 /* limit (48 bytes = 6 GDT entries) */ gdt_addr: .long gdt /* base */ /* The GDT table ... * * Selector Type * 0x00 NULL * 0x08 Unused * 0x10 32bit code * 0x18 32bit data/stack * 0x20 16bit code * 0x28 16bit data/stack */ .align 4 gdt: .word 0, 0, 0, 0 /* NULL */ .word 0, 0, 0, 0 /* unused */ .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) */ .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) */ .word 0xFFFF /* 64kb */ .word 0 /* base address = 0 */ .word 0x9b00 /* data read/write */ .word 0x0010 /* granularity = 1 (+5th nibble of limit) */ .word 0xFFFF /* 64kb */ .word 0 /* base address = 0 */ .word 0x9300 /* data read/write */ .word 0x0010 /* granularity = 1 (+5th nibble of limit) */ end_gdt_setup: