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