1/* 2 * Copyright (c) 2000 John Baldwin 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD$ 27 */ 28 29/* 30 * This simple program is a preloader for the normal boot3 loader. It is simply 31 * prepended to the beginning of a fully built and btxld'd loader. It then 32 * copies the loader to the address boot2 normally loads it, emulates the 33 * boot[12] environment (protected mode, a bootinfo struct, etc.), and then jumps 34 * to the start of btxldr to start the boot process. This method allows a stock 35 * /boot/loader to be booted over the network via PXE w/o having to write a 36 * separate PXE-aware client just to load the loader. 37 */ 38 39#include <sys/reboot.h> 40#include <bootargs.h> 41 42/* 43 * Memory locations. 44 */ 45 .set MEM_PAGE_SIZE,0x1000 # memory page size, 4k 46 .set MEM_ARG,0x900 # Arguments at start 47 .set MEM_ARG_BTX,0xa100 # Where we move them to so the 48 # BTX client can see them 49 .set MEM_ARG_SIZE,0x18 # Size of the arguments 50 .set MEM_BTX_ADDRESS,0x9000 # where BTX lives 51 .set MEM_BTX_ENTRY,0x9010 # where BTX starts to execute 52 .set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader 53 .set MEM_BTX_CLIENT,0xa000 # where BTX clients live 54 .set MEM_BIOS_KEYBOARD,0x496 # BDA byte with keyboard bit 55/* 56 * a.out header fields 57 */ 58 .set AOUT_TEXT,0x04 # text segment size 59 .set AOUT_DATA,0x08 # data segment size 60 .set AOUT_BSS,0x0c # zero'd BSS size 61 .set AOUT_SYMBOLS,0x10 # symbol table 62 .set AOUT_ENTRY,0x14 # entry point 63 .set AOUT_HEADER,MEM_PAGE_SIZE # size of the a.out header 64/* 65 * Segment selectors. 66 */ 67 .set SEL_SDATA,0x8 # Supervisor data 68 .set SEL_RDATA,0x10 # Real mode data 69 .set SEL_SCODE,0x18 # PM-32 code 70 .set SEL_SCODE16,0x20 # PM-16 code 71/* 72 * BTX constants 73 */ 74 .set INT_SYS,0x30 # BTX syscall interrupt 75/* 76 * Bit in MEM_BIOS_KEYBOARD that is set if an enhanced keyboard is present 77 */ 78 .set KEYBOARD_BIT,0x10 79/* 80 * We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry 81 * point) 82 */ 83 .code16 84 .globl start 85 .org 0x0, 0x0 86/* 87 * BTX program loader for PXE network booting 88 */ 89start: cld # string ops inc 90 xorw %ax, %ax # zero %ax 91 movw %ax, %ss # setup the 92 movw $start, %sp # stack 93 movw %es, %cx # save PXENV+ segment 94 movw %ax, %ds # setup the 95 movw %ax, %es # data segments 96 andl $0xffff, %ecx # clear upper words 97 andl $0xffff, %ebx # of %ebx and %ecx 98 shll $4, %ecx # calculate the offset of 99 addl %ebx, %ecx # the PXENV+ struct and 100 pushl %ecx # save it on the stack 101 movw $welcome_msg, %si # %ds:(%si) -> welcome message 102 callw putstr # display the welcome message 103/* 104 * Setup the arguments that the loader is expecting from boot[12] 105 */ 106 movw $bootinfo_msg, %si # %ds:(%si) -> boot args message 107 callw putstr # display the message 108 movw $MEM_ARG, %bx # %ds:(%bx) -> boot args 109 movw %bx, %di # %es:(%di) -> boot args 110 xorl %eax, %eax # zero %eax 111 movw $(MEM_ARG_SIZE/4), %cx # Size of arguments in 32-bit 112 # dwords 113 rep # Clear the arguments 114 stosl # to zero 115 orb $KARGS_FLAGS_PXE, 0x8(%bx) # kargs->bootflags |= 116 # KARGS_FLAGS_PXE 117 popl 0xc(%bx) # kargs->pxeinfo = *PXENV+ 118#ifdef ALWAYS_SERIAL 119/* 120 * set the RBX_SERIAL bit in the howto byte. 121 */ 122 orl $RB_SERIAL, (%bx) # enable serial console 123#endif 124#ifdef PROBE_KEYBOARD 125/* 126 * Look at the BIOS data area to see if we have an enhanced keyboard. If not, 127 * set the RBX_DUAL and RBX_SERIAL bits in the howto byte. 128 */ 129 testb $KEYBOARD_BIT, MEM_BIOS_KEYBOARD # keyboard present? 130 jnz keyb # yes, so skip 131 orl $(RB_MULTIPLE | RB_SERIAL), (%bx) # enable serial console 132keyb: 133#endif 134/* 135 * Turn on the A20 address line 136 */ 137 callw seta20 # Turn A20 on 138/* 139 * Relocate the loader and BTX using a very lazy protected mode 140 */ 141 movw $relocate_msg, %si # Display the 142 callw putstr # relocation message 143 movl end+AOUT_ENTRY, %edi # %edi is the destination 144 movl $(end+AOUT_HEADER), %esi # %esi is 145 # the start of the text 146 # segment 147 movl end+AOUT_TEXT, %ecx # %ecx = length of the text 148 # segment 149 lgdt gdtdesc # setup our own gdt 150 cli # turn off interrupts 151 movl %cr0, %eax # Turn on 152 orb $0x1, %al # protected 153 movl %eax, %cr0 # mode 154 ljmp $SEL_SCODE,$pm_start # long jump to clear the 155 # instruction pre-fetch queue 156 .code32 157pm_start: movw $SEL_SDATA, %ax # Initialize 158 movw %ax, %ds # %ds and 159 movw %ax, %es # %es to a flat selector 160 rep # Relocate the 161 movsb # text segment 162 addl $(MEM_PAGE_SIZE - 1), %edi # pad %edi out to a new page 163 andl $~(MEM_PAGE_SIZE - 1), %edi # for the data segment 164 movl end+AOUT_DATA, %ecx # size of the data segment 165 rep # Relocate the 166 movsb # data segment 167 movl end+AOUT_BSS, %ecx # size of the bss 168 xorl %eax, %eax # zero %eax 169 addb $3, %cl # round %ecx up to 170 shrl $2, %ecx # a multiple of 4 171 rep # zero the 172 stosl # bss 173 movl end+AOUT_ENTRY, %esi # %esi -> relocated loader 174 addl $MEM_BTX_OFFSET, %esi # %esi -> BTX in the loader 175 movl $MEM_BTX_ADDRESS, %edi # %edi -> where BTX needs to go 176 movzwl 0xa(%esi), %ecx # %ecx -> length of BTX 177 rep # Relocate 178 movsb # BTX 179 ljmp $SEL_SCODE16,$pm_16 # Jump to 16-bit PM 180 .code16 181pm_16: movw $SEL_RDATA, %ax # Initialize 182 movw %ax, %ds # %ds and 183 movw %ax, %es # %es to a real mode selector 184 movl %cr0, %eax # Turn off 185 andb $~0x1, %al # protected 186 movl %eax, %cr0 # mode 187 ljmp $0,$pm_end # Long jump to clear the 188 # instruction pre-fetch queue 189pm_end: sti # Turn interrupts back on now 190/* 191 * Copy the BTX client to MEM_BTX_CLIENT 192 */ 193 xorw %ax, %ax # zero %ax and set 194 movw %ax, %ds # %ds and %es 195 movw %ax, %es # to segment 0 196 movw $MEM_BTX_CLIENT, %di # Prepare to relocate 197 movw $btx_client, %si # the simple btx client 198 movw $(btx_client_end-btx_client), %cx # length of btx client 199 rep # Relocate the 200 movsb # simple BTX client 201/* 202 * Copy the boot[12] args to where the BTX client can see them 203 */ 204 movw $MEM_ARG, %si # where the args are at now 205 movw $MEM_ARG_BTX, %di # where the args are moving to 206 movw $(MEM_ARG_SIZE/4), %cx # size of the arguments in longs 207 rep # Relocate 208 movsl # the words 209/* 210 * Save the entry point so the client can get to it later on 211 */ 212 movl end+AOUT_ENTRY, %eax # load the entry point 213 stosl # add it to the end of the 214 # arguments 215/* 216 * Now we just start up BTX and let it do the rest 217 */ 218 movw $jump_message, %si # Display the 219 callw putstr # jump message 220 ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point 221 222/* 223 * Display a null-terminated string 224 */ 225putstr: lodsb # load %al from %ds:(%si) 226 testb %al,%al # stop at null 227 jnz putc # if the char != null, output it 228 retw # return when null is hit 229putc: movw $0x7,%bx # attribute for output 230 movb $0xe,%ah # BIOS: put_char 231 int $0x10 # call BIOS, print char in %al 232 jmp putstr # keep looping 233 234/* 235 * Enable A20. Put an upper limit on the amount of time we wait for the 236 * keyboard controller to get ready (65K x ISA access time). If 237 * we wait more than that amount, the hardware is probably 238 * legacy-free and simply doesn't have a keyboard controller. 239 * Thus, the A20 line is already enabled. 240 */ 241seta20: cli # Disable interrupts 242 xor %cx,%cx # Clear 243seta20.1: inc %cx # Increment, overflow? 244 jz seta20.3 # Yes 245 inb $0x64,%al # Get status 246 testb $0x2,%al # Busy? 247 jnz seta20.1 # Yes 248 movb $0xd1,%al # Command: Write 249 outb %al,$0x64 # output port 250seta20.2: inb $0x64,%al # Get status 251 testb $0x2,%al # Busy? 252 jnz seta20.2 # Yes 253 movb $0xdf,%al # Enable 254 outb %al,$0x60 # A20 255seta20.3: sti # Enable interrupts 256 retw # To caller 257 258/* 259 * BTX client to start btxldr 260 */ 261 .code32 262btx_client: movl $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi 263 # %ds:(%esi) -> end 264 # of boot[12] args 265 movl $(MEM_ARG_SIZE/4), %ecx # Number of words to push 266 std # Go backwards 267push_arg: lodsl # Read argument 268 pushl %eax # Push it onto the stack 269 loop push_arg # Push all of the arguments 270 cld # In case anyone depends on this 271 pushl MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE # Entry point of 272 # the loader 273 pushl %eax # Emulate a near call 274 movl $0x1, %eax # 'exec' system call 275 int $INT_SYS # BTX system call 276btx_client_end: 277 .code16 278 279 .p2align 4 280/* 281 * Global descriptor table. 282 */ 283gdt: .word 0x0,0x0,0x0,0x0 # Null entry 284 .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA 285 .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA 286 .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE (32-bit) 287 .word 0xffff,0x0,0x9a00,0x8f # SEL_SCODE16 (16-bit) 288gdt.1: 289/* 290 * Pseudo-descriptors. 291 */ 292gdtdesc: .word gdt.1-gdt-1 # Limit 293 .long gdt # Base 294 295welcome_msg: .asciz "PXE Loader 1.00\r\n\n" 296bootinfo_msg: .asciz "Building the boot loader arguments\r\n" 297relocate_msg: .asciz "Relocating the loader and the BTX\r\n" 298jump_message: .asciz "Starting the BTX loader\r\n" 299 300 .p2align 4 301end: 302