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/*
* U-boot - i386 Startup Code
*
* Copyright (c) 2002 Omicron Ceti AB, Daniel Engström <denaiel@omicron.se>
*
* 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 <config.h>
#include <version.h>
.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:
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