diff options
Diffstat (limited to 'sys/boot/i386/pxeldr/pxeldr.S')
| -rw-r--r-- | sys/boot/i386/pxeldr/pxeldr.S | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/sys/boot/i386/pxeldr/pxeldr.S b/sys/boot/i386/pxeldr/pxeldr.S new file mode 100644 index 0000000..fa93c9c --- /dev/null +++ b/sys/boot/i386/pxeldr/pxeldr.S @@ -0,0 +1,287 @@ +# +# Copyright (c) 2000 John Baldwin +# All rights reserved. +# +# Redistribution and use in source and binary forms are freely +# permitted provided that the above copyright notice and this +# paragraph and the following disclaimer are duplicated in all +# such forms. +# +# This software is provided "AS IS" and without any express or +# implied warranties, including, without limitation, the implied +# warranties of merchantability and fitness for a particular +# purpose. +# + +# $FreeBSD$ + +# +# This simple program is a preloader for the normal boot3 loader. It is simply +# prepended to the beginning of a fully built and btxld'd loader. It then +# copies the loader to the address boot2 normally loads it, emulates the +# boot[12] environment (protected mode, a bootinfo struct, etc.), and then jumps +# to the start of btxldr to start the boot process. This method allows a stock +# /boot/loader to be booted over the network via PXE w/o having to write a +# separate PXE-aware client just to load the loader. +# + +# +# Memory locations. +# + .set MEM_PAGE_SIZE,0x1000 # memory page size, 4k + .set MEM_ARG,0x900 # Arguments at start + .set MEM_ARG_BTX,0xa100 # Where we move them to so the + # BTX client can see them + .set MEM_ARG_SIZE,0x18 # Size of the arguments + .set MEM_BTX_ADDRESS,0x9000 # where BTX lives + .set MEM_BTX_ENTRY,0x9010 # where BTX starts to execute + .set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader + .set MEM_BTX_CLIENT,0xa000 # where BTX clients live + .set MEM_BIOS_KEYBOARD,0x496 # BDA byte with keyboard bit +# +# a.out header fields +# + .set AOUT_TEXT,0x04 # text segment size + .set AOUT_DATA,0x08 # data segment size + .set AOUT_BSS,0x0c # zero'd BSS size + .set AOUT_SYMBOLS,0x10 # symbol table + .set AOUT_ENTRY,0x14 # entry point + .set AOUT_HEADER,MEM_PAGE_SIZE # size of the a.out header +# +# Flags for kargs->bootflags +# + .set KARGS_FLAGS_PXE,0x2 # flag to indicate booting from + # PXE loader +# +# Boot howto bits +# + .set RB_SERIAL,0x1000 # serial console +# +# Segment selectors. +# + .set SEL_SDATA,0x8 # Supervisor data + .set SEL_RDATA,0x10 # Real mode data + .set SEL_SCODE,0x18 # PM-32 code + .set SEL_SCODE16,0x20 # PM-16 code +# +# BTX constants +# + .set INT_SYS,0x30 # BTX syscall interrupt +# +# Bit in MEM_BIOS_KEYBOARD that is set if an enhanced keyboard is present +# + .set KEYBOARD_BIT,0x10 +# +# We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry +# point) +# + .code16 + .globl start + .org 0x0, 0x0 +# +# BTX program loader for PXE network booting +# +start: cld # string ops inc + xorw %ax, %ax # zero %ax + movw %ax, %ss # setup the + movw $start, %sp # stack + movw %es, %cx # save PXENV+ segment + movw %ax, %ds # setup the + movw %ax, %es # data segments + andl $0xffff, %ecx # clear upper words + andl $0xffff, %ebx # of %ebx and %ecx + shll $4, %ecx # calculate the offset of + addl %ebx, %ecx # the PXENV+ struct and + pushl %ecx # save it on the stack + movw $welcome_msg, %si # %ds:(%si) -> welcome message + callw putstr # display the welcome message +# +# Setup the arguments that the loader is expecting from boot[12] +# + movw $bootinfo_msg, %si # %ds:(%si) -> boot args message + callw putstr # display the message + movw $MEM_ARG, %bx # %ds:(%bx) -> boot args + movw %bx, %di # %es:(%di) -> boot args + xorl %eax, %eax # zero %eax + movw $(MEM_ARG_SIZE/4), %cx # Size of arguments in 32-bit + # dwords + rep # Clear the arguments + stosl # to zero + orb $KARGS_FLAGS_PXE, 0x8(%bx) # kargs->bootflags |= + # KARGS_FLAGS_PXE + popl 0xc(%bx) # kargs->pxeinfo = *PXENV+ +ifdef(`ALWAYS_SERIAL',` +# +# set the RBX_SERIAL bit in the howto byte. + orl $RB_SERIAL, (%bx) # enable serial console +') +ifdef(`PROBE_KEYBOARD',` +# +# Look at the BIOS data area to see if we have an enhanced keyboard. If not, +# set the RBX_SERIAL bit in the howto byte. + testb $KEYBOARD_BIT, MEM_BIOS_KEYBOARD # keyboard present? + jnz keyb # yes, so skip + orl $RB_SERIAL, (%bx) # enable serial console +keyb: +') +# +# Turn on the A20 address line +# + callw seta20 # Turn A20 on +# +# Relocate the loader and BTX using a very lazy protected mode +# + movw $relocate_msg, %si # Display the + callw putstr # relocation message + movl end+AOUT_ENTRY, %edi # %edi is the destination + movl $(end+AOUT_HEADER), %esi # %esi is + # the start of the text + # segment + movl end+AOUT_TEXT, %ecx # %ecx = length of the text + # segment + lgdt gdtdesc # setup our own gdt + cli # turn off interrupts + movl %cr0, %eax # Turn on + orb $0x1, %al # protected + movl %eax, %cr0 # mode + ljmp $SEL_SCODE,$pm_start # long jump to clear the + # instruction pre-fetch queue + .code32 +pm_start: movw $SEL_SDATA, %ax # Initialize + movw %ax, %ds # %ds and + movw %ax, %es # %es to a flat selector + rep # Relocate the + movsb # text segment + addl $(MEM_PAGE_SIZE - 1), %edi # pad %edi out to a new page + andl $~(MEM_PAGE_SIZE - 1), %edi # for the data segment + movl end+AOUT_DATA, %ecx # size of the data segment + rep # Relocate the + movsb # data segment + movl end+AOUT_BSS, %ecx # size of the bss + xorl %eax, %eax # zero %eax + addb $3, %cl # round %ecx up to + shrl $2, %ecx # a multiple of 4 + rep # zero the + stosl # bss + movl end+AOUT_ENTRY, %esi # %esi -> relocated loader + addl $MEM_BTX_OFFSET, %esi # %esi -> BTX in the loader + movl $MEM_BTX_ADDRESS, %edi # %edi -> where BTX needs to go + movzwl 0xa(%esi), %ecx # %ecx -> length of BTX + rep # Relocate + movsb # BTX + ljmp $SEL_SCODE16,$pm_16 # Jump to 16-bit PM + .code16 +pm_16: movw $SEL_RDATA, %ax # Initialize + movw %ax, %ds # %ds and + movw %ax, %es # %es to a real mode selector + movl %cr0, %eax # Turn off + andb $~0x1, %al # protected + movl %eax, %cr0 # mode + ljmp $0,$pm_end # Long jump to clear the + # instruction pre-fetch queue +pm_end: sti # Turn interrupts back on now +# +# Copy the BTX client to MEM_BTX_CLIENT +# + xorw %ax, %ax # zero %ax and set + movw %ax, %ds # %ds and %es + movw %ax, %es # to segment 0 + movw $MEM_BTX_CLIENT, %di # Prepare to relocate + movw $btx_client, %si # the simple btx client + movw $(btx_client_end-btx_client), %cx # length of btx client + rep # Relocate the + movsb # simple BTX client +# +# Copy the boot[12] args to where the BTX client can see them +# + movw $MEM_ARG, %si # where the args are at now + movw $MEM_ARG_BTX, %di # where the args are moving to + movw $(MEM_ARG_SIZE/4), %cx # size of the arguments in longs + rep # Relocate + movsl # the words +# +# Save the entry point so the client can get to it later on +# + movl end+AOUT_ENTRY, %eax # load the entry point + stosl # add it to the end of the + # arguments +# +# Now we just start up BTX and let it do the rest +# + movw $jump_message, %si # Display the + callw putstr # jump message + ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point + +# +# Display a null-terminated string +# +putstr: lodsb # load %al from %ds:(%si) + testb %al,%al # stop at null + jnz putc # if the char != null, output it + retw # return when null is hit +putc: movw $0x7,%bx # attribute for output + movb $0xe,%ah # BIOS: put_char + int $0x10 # call BIOS, print char in %al + jmp putstr # keep looping + +# +# Enable A20 +# +seta20: cli # Disable interrupts +seta20.1: inb $0x64,%al # Get status + testb $0x2,%al # Busy? + jnz seta20.1 # Yes + movb $0xd1,%al # Command: Write + outb %al,$0x64 # output port +seta20.2: inb $0x64,%al # Get status + testb $0x2,%al # Busy? + jnz seta20.2 # Yes + movb $0xdf,%al # Enable + outb %al,$0x60 # A20 + sti # Enable interrupts + retw # To caller + +# +# BTX client to start btxldr +# + .code32 +btx_client: movl $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi + # %ds:(%esi) -> end + # of boot[12] args + movl $(MEM_ARG_SIZE/4), %ecx # Number of words to push + std # Go backwards +push_arg: lodsl # Read argument + pushl %eax # Push it onto the stack + loop push_arg # Push all of the arguments + cld # In case anyone depends on this + pushl MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE # Entry point of + # the loader + pushl %eax # Emulate a near call + movl $0x1, %eax # 'exec' system call + int $INT_SYS # BTX system call +btx_client_end: + .code16 + + .p2align 4 +# +# Global descriptor table. +# +gdt: .word 0x0,0x0,0x0,0x0 # Null entry + .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA + .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA + .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE (32-bit) + .word 0xffff,0x0,0x9a00,0x8f # SEL_SCODE16 (16-bit) +gdt.1: +# +# Pseudo-descriptors. +# +gdtdesc: .word gdt.1-gdt-1 # Limit + .long gdt # Base + +welcome_msg: .asciz "PXE Loader 1.00\r\n\n" +bootinfo_msg: .asciz "Building the boot loader arguments\r\n" +relocate_msg: .asciz "Relocating the loader and the BTX\r\n" +jump_message: .asciz "Starting the BTX loader\r\n" + + .p2align 4 +end: |
