diff options
Diffstat (limited to 'util/x86emu/x86_asm.S')
| -rw-r--r-- | util/x86emu/x86_asm.S | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/util/x86emu/x86_asm.S b/util/x86emu/x86_asm.S new file mode 100644 index 0000000000..988b596878 --- /dev/null +++ b/util/x86emu/x86_asm.S @@ -0,0 +1,345 @@ +/* + * This file is part of the coreboot project. + * + * Copyright (C) 2009 coresystems GmbH + * + * 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; version 2 of the License. + * + * 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. + */ + +#define REALMODE_BASE 0x500 +#define RELOCATED(x) (x - __realmode_code + REALMODE_BASE) + +/* CR0 bits */ +#define PE (1 << 0) + +/* This is the intXX interrupt handler stub code. It gets copied + * to the IDT and to some fixed addresses in the F segment. Before + * the code can used, it gets patched up by the C function copying + * it: byte 3 (the $0 in movb $0, %al) is overwritten with the int#. + */ + + .code16 + .globl __idt_handler +__idt_handler: + pushal + movb $0, %al /* This instruction gets modified */ + ljmp $0, $__interrupt_handler_16bit + .globl __idt_handler_size +__idt_handler_size = ( . - __idt_handler) + + +/* In order to be independent of coreboot's position in RAM + * we relocate a part of the code to the low megabyte, so the + * CPU can use it in real-mode. This code lives at __realmode_code. + */ + .globl __realmode_code +__realmode_code: + +/* Realmode IDT pointer structure. */ + .globl __realmode_idt +__realmode_idt = RELOCATED(.) + .word 1023 /* 16-bit limit */ + .long 0 /* 24-bit base */ + .word 0 + +/* Preserve old stack */ +__stack = RELOCATED(.) + .long 0 + + .code32 + .globl __run_optionrom +__run_optionrom = RELOCATED(.) + /* save all registers to the stack */ + pushal + + /* Move the protected mode stack to a safe place */ + mov %esp, __stack + + /* Get devfn into %ecx */ + movl %esp, %ebp + // FIXME: Should this function be called with regparm=0? + movl 8(%ebp), %ecx + + /* Activate the right segment descriptor real mode. */ + ljmp $0x28, $RELOCATED(1f) +1: +.code16 + /* 16 bit code from here on... */ + + /* Load the segment registers w/ properly configured + * segment descriptors. They will retain these + * configurations (limits, writability, etc.) once + * protected mode is turned off. + */ + mov $0x30, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov %ax, %ss + + /* Turn off protection */ + movl %cr0, %eax + andl $~PE, %eax + movl %eax, %cr0 + + /* Now really going into real mode */ + ljmp $0, $RELOCATED(1f) +1: + /* Setup a stack: Put the stack at the end of page zero. + * That way we can easily share it between real and + * protected, since the 16-bit ESP at segment 0 will + * work for any case. */ + mov $0x0, %ax + mov %ax, %ss + movl $0x1000, %eax + movl %eax, %esp + + /* Load our 16 bit idt */ + xor %ax, %ax + mov %ax, %ds + lidt __realmode_idt + + /* Set all segments to 0x0000, ds to 0x0040 */ + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov $0x40, %ax + mov %ax, %ds + mov %cx, %ax // restore ax + + /* ************************************ */ + // TODO this will not work for non-VGA option ROMs + /* run VGA BIOS at 0xc000:0003 */ + lcall $0xc000, $0x0003 + /* ************************************ */ + + /* If we got here, just about done. + * Need to get back to protected mode + */ + movl %cr0, %eax + orl $PE, %eax + movl %eax, %cr0 + + /* Now that we are in protected mode + * jump to a 32 bit code segment. + */ + data32 ljmp $0x10, $RELOCATED(1f) +1: + .code32 + movw $0x18, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov %ax, %ss + + /* restore proper idt */ + lidt idtarg + + /* and exit */ + mov __stack, %esp + popal + ret + + .globl __run_interrupt +__run_interrupt = RELOCATED(.) + + /* paranoia -- does ecx get saved? not sure. This is + * the easiest safe thing to do. */ + pushal + /* save the stack */ + mov %esp, __stack + + + /* This configures CS properly for real mode. */ + ljmp $0x28, $RELOCATED(1f) +1: + .code16 /* 16 bit code from here on... */ + + // CONFIG_DEBUG + movb $0xec, %al + outb %al, $0x80 + + /* Load the segment registers w/ properly configured segment + * descriptors. They will retain these configurations (limits, + * writability, etc.) once protected mode is turned off. + */ + mov $0x30, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov %ax, %ss + + /* Turn off protected mode */ + movl %cr0, %eax + andl $~PE, %eax + movl %eax, %cr0 + + /* Now really going into real mode */ + data32 ljmp $0, $RELOCATED(1f) +1: + + /* put the stack at the end of page zero. + * that way we can easily share it between real and protected, + * since the 16-bit ESP at segment 0 will work for any case. + */ + /* setup a stack */ + mov $0x0, %ax + mov %ax, %ss + movl $0x1000, %eax + movl %eax, %esp + + /* Load 16-bit intXX IDT */ + xor %ax, %ax + mov %ax, %ds + lidt __realmode_idt + + /* Set all segments to 0x0000 */ + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + + /* Call VGA BIOS int10 function 0x4f14 to enable main console + * Epia-M does not always autosence the main console so forcing + * it on is good. + */ + + /* Ask VGA option rom to enable main console */ + movw $0x4f14,%ax + movw $0x8003,%bx + movw $1, %cx + movw $0, %dx + movw $0, %di + int $0x10 + + /* Ok, the job is done, now go back to protected mode coreboot */ + movl %cr0, %eax + orl $PE, %eax + movl %eax, %cr0 + + /* Now that we are in protected mode jump to a 32-bit code segment. */ + data32 ljmp $0x10, $RELOCATED(1f) +1: + .code32 + movw $0x18, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov %ax, %ss + + /* restore coreboot's 32-bit IDT */ + lidt idtarg + + /* Exit */ + mov __stack, %esp + popal + ret + +/* This is the 16-bit interrupt entry point called by the IDT stub code. + * Before this code code is called, %eax is pushed to the stack, and the + * interrupt number is loaded into %al + */ + .code16 +__interrupt_handler_16bit = RELOCATED(.) + push %ds + push %es + push %fs + push %gs + + /* Clean up the interrupt number. We could have done this in the stub, + * but it would have cost 2 more bytes per stub entry. + */ + andl $0xff, %eax + pushl %eax /* ... and make it the first parameter */ + + /* Switch to protected mode */ + movl %cr0, %eax + orl $PE, %eax + movl %eax, %cr0 + + /* ... and jump to a 32 bit code segment. */ + data32 ljmp $0x10, $RELOCATED(1f) +1: + .code32 + movw $0x18, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov %ax, %ss + + lidt idtarg + + /* Call the C interrupt handler */ + movl $interrupt_handler, %eax + call *%eax + + /* Now return to real mode ... */ + ljmp $0x28, $RELOCATED(1f) +1: + .code16 + /* Load the segment registers with properly configured segment + * descriptors. They will retain these configurations (limits, + * writability, etc.) once protected mode is turned off. + */ + mov $0x30, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov %ax, %ss + + /* Disable Protected Mode */ + movl %cr0, %eax + andl $~PE, %eax + movl %eax, %cr0 + + /* Now really going into real mode */ + ljmp $0, $RELOCATED(1f) +1: + /* Restore real-mode stack segment */ + mov $0x0, %ax + mov %ax, %ss + + /* Restore 16-bit IDT */ + xor %ax, %ax + mov %ax, %ds + lidt __realmode_idt + + /* Set up our segment registers to segment 0x0000 */ + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov $0x40, %ax + mov %ax, %ds + + /* Restore all registers, including those + * manipulated by the C handler + */ + popl %eax + pop %gs + pop %fs + pop %es + pop %ds + popal + iret + + .globl __realmode_code_size +__realmode_code_size = (. - __realmode_code) + + .code32 |