Fully synchronize sys/boot from FreeBSD-5.x, but add / to the module path
[dragonfly.git] / sys / boot / pc32 / pxeldr / pxeldr.S
CommitLineData
984263bc
MD
1#
2# Copyright (c) 2000 John Baldwin
3# All rights reserved.
4#
5# Redistribution and use in source and binary forms are freely
6# permitted provided that the above copyright notice and this
7# paragraph and the following disclaimer are duplicated in all
8# such forms.
9#
10# This software is provided "AS IS" and without any express or
11# implied warranties, including, without limitation, the implied
12# warranties of merchantability and fitness for a particular
13# purpose.
14#
15
5ee58eed
MD
16# $FreeBSD: src/sys/boot/i386/pxeldr/pxeldr.s,v 1.9 2003/09/03 08:12:20 phk Exp $
17# $DragonFly: src/sys/boot/pc32/pxeldr/pxeldr.S,v 1.3 2003/11/10 06:08:37 dillon Exp $
984263bc
MD
18
19#
20# This simple program is a preloader for the normal boot3 loader. It is simply
21# prepended to the beginning of a fully built and btxld'd loader. It then
22# copies the loader to the address boot2 normally loads it, emulates the
23# boot[12] environment (protected mode, a bootinfo struct, etc.), and then jumps
24# to the start of btxldr to start the boot process. This method allows a stock
25# /boot/loader to be booted over the network via PXE w/o having to write a
26# separate PXE-aware client just to load the loader.
27#
28
29#
30# Memory locations.
31#
32 .set MEM_PAGE_SIZE,0x1000 # memory page size, 4k
33 .set MEM_ARG,0x900 # Arguments at start
34 .set MEM_ARG_BTX,0xa100 # Where we move them to so the
35 # BTX client can see them
36 .set MEM_ARG_SIZE,0x18 # Size of the arguments
37 .set MEM_BTX_ADDRESS,0x9000 # where BTX lives
38 .set MEM_BTX_ENTRY,0x9010 # where BTX starts to execute
39 .set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader
40 .set MEM_BTX_CLIENT,0xa000 # where BTX clients live
41 .set MEM_BIOS_KEYBOARD,0x496 # BDA byte with keyboard bit
42#
43# a.out header fields
44#
45 .set AOUT_TEXT,0x04 # text segment size
46 .set AOUT_DATA,0x08 # data segment size
47 .set AOUT_BSS,0x0c # zero'd BSS size
48 .set AOUT_SYMBOLS,0x10 # symbol table
49 .set AOUT_ENTRY,0x14 # entry point
50 .set AOUT_HEADER,MEM_PAGE_SIZE # size of the a.out header
51#
52# Flags for kargs->bootflags
53#
54 .set KARGS_FLAGS_PXE,0x2 # flag to indicate booting from
55 # PXE loader
56#
57# Boot howto bits
58#
59 .set RB_SERIAL,0x1000 # serial console
60#
61# Segment selectors.
62#
63 .set SEL_SDATA,0x8 # Supervisor data
64 .set SEL_RDATA,0x10 # Real mode data
65 .set SEL_SCODE,0x18 # PM-32 code
66 .set SEL_SCODE16,0x20 # PM-16 code
67#
68# BTX constants
69#
70 .set INT_SYS,0x30 # BTX syscall interrupt
71#
72# Bit in MEM_BIOS_KEYBOARD that is set if an enhanced keyboard is present
73#
74 .set KEYBOARD_BIT,0x10
75#
76# We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry
77# point)
78#
79 .code16
80 .globl start
81 .org 0x0, 0x0
82#
83# BTX program loader for PXE network booting
84#
85start: cld # string ops inc
86 xorw %ax, %ax # zero %ax
87 movw %ax, %ss # setup the
88 movw $start, %sp # stack
89 movw %es, %cx # save PXENV+ segment
90 movw %ax, %ds # setup the
91 movw %ax, %es # data segments
92 andl $0xffff, %ecx # clear upper words
93 andl $0xffff, %ebx # of %ebx and %ecx
94 shll $4, %ecx # calculate the offset of
95 addl %ebx, %ecx # the PXENV+ struct and
96 pushl %ecx # save it on the stack
97 movw $welcome_msg, %si # %ds:(%si) -> welcome message
98 callw putstr # display the welcome message
99#
100# Setup the arguments that the loader is expecting from boot[12]
101#
102 movw $bootinfo_msg, %si # %ds:(%si) -> boot args message
103 callw putstr # display the message
104 movw $MEM_ARG, %bx # %ds:(%bx) -> boot args
105 movw %bx, %di # %es:(%di) -> boot args
106 xorl %eax, %eax # zero %eax
107 movw $(MEM_ARG_SIZE/4), %cx # Size of arguments in 32-bit
108 # dwords
109 rep # Clear the arguments
110 stosl # to zero
111 orb $KARGS_FLAGS_PXE, 0x8(%bx) # kargs->bootflags |=
112 # KARGS_FLAGS_PXE
113 popl 0xc(%bx) # kargs->pxeinfo = *PXENV+
5ee58eed
MD
114ifdef(`ALWAYS_SERIAL',`
115#
116# set the RBX_SERIAL bit in the howto byte.
117 orl $RB_SERIAL, (%bx) # enable serial console
118')
984263bc
MD
119ifdef(`PROBE_KEYBOARD',`
120#
121# Look at the BIOS data area to see if we have an enhanced keyboard. If not,
122# set the RBX_SERIAL bit in the howto byte.
123 testb $KEYBOARD_BIT, MEM_BIOS_KEYBOARD # keyboard present?
124 jnz keyb # yes, so skip
125 orl $RB_SERIAL, (%bx) # enable serial console
126keyb:
127')
128#
129# Turn on the A20 address line
130#
131 callw seta20 # Turn A20 on
132#
133# Relocate the loader and BTX using a very lazy protected mode
134#
135 movw $relocate_msg, %si # Display the
136 callw putstr # relocation message
137 movl end+AOUT_ENTRY, %edi # %edi is the destination
138 movl $(end+AOUT_HEADER), %esi # %esi is
139 # the start of the text
140 # segment
141 movl end+AOUT_TEXT, %ecx # %ecx = length of the text
142 # segment
143 lgdt gdtdesc # setup our own gdt
144 cli # turn off interrupts
145 movl %cr0, %eax # Turn on
146 orb $0x1, %al # protected
147 movl %eax, %cr0 # mode
148 ljmp $SEL_SCODE,$pm_start # long jump to clear the
149 # instruction pre-fetch queue
150 .code32
151pm_start: movw $SEL_SDATA, %ax # Initialize
152 movw %ax, %ds # %ds and
153 movw %ax, %es # %es to a flat selector
154 rep # Relocate the
155 movsb # text segment
156 addl $(MEM_PAGE_SIZE - 1), %edi # pad %edi out to a new page
157 andl $~(MEM_PAGE_SIZE - 1), %edi # for the data segment
158 movl end+AOUT_DATA, %ecx # size of the data segment
159 rep # Relocate the
160 movsb # data segment
161 movl end+AOUT_BSS, %ecx # size of the bss
162 xorl %eax, %eax # zero %eax
163 addb $3, %cl # round %ecx up to
164 shrl $2, %ecx # a multiple of 4
165 rep # zero the
166 stosl # bss
167 movl end+AOUT_ENTRY, %esi # %esi -> relocated loader
168 addl $MEM_BTX_OFFSET, %esi # %esi -> BTX in the loader
169 movl $MEM_BTX_ADDRESS, %edi # %edi -> where BTX needs to go
170 movzwl 0xa(%esi), %ecx # %ecx -> length of BTX
171 rep # Relocate
172 movsb # BTX
173 ljmp $SEL_SCODE16,$pm_16 # Jump to 16-bit PM
174 .code16
175pm_16: movw $SEL_RDATA, %ax # Initialize
176 movw %ax, %ds # %ds and
177 movw %ax, %es # %es to a real mode selector
178 movl %cr0, %eax # Turn off
179 andb $~0x1, %al # protected
180 movl %eax, %cr0 # mode
181 ljmp $0,$pm_end # Long jump to clear the
182 # instruction pre-fetch queue
183pm_end: sti # Turn interrupts back on now
184#
185# Copy the BTX client to MEM_BTX_CLIENT
186#
187 xorw %ax, %ax # zero %ax and set
188 movw %ax, %ds # %ds and %es
189 movw %ax, %es # to segment 0
190 movw $MEM_BTX_CLIENT, %di # Prepare to relocate
191 movw $btx_client, %si # the simple btx client
192 movw $(btx_client_end-btx_client), %cx # length of btx client
193 rep # Relocate the
194 movsb # simple BTX client
195#
196# Copy the boot[12] args to where the BTX client can see them
197#
198 movw $MEM_ARG, %si # where the args are at now
199 movw $MEM_ARG_BTX, %di # where the args are moving to
200 movw $(MEM_ARG_SIZE/4), %cx # size of the arguments in longs
201 rep # Relocate
202 movsl # the words
203#
204# Save the entry point so the client can get to it later on
205#
206 movl end+AOUT_ENTRY, %eax # load the entry point
207 stosl # add it to the end of the
208 # arguments
209#
210# Now we just start up BTX and let it do the rest
211#
212 movw $jump_message, %si # Display the
213 callw putstr # jump message
214 ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point
215
216#
217# Display a null-terminated string
218#
219putstr: lodsb # load %al from %ds:(%si)
220 testb %al,%al # stop at null
221 jnz putc # if the char != null, output it
222 retw # return when null is hit
223putc: movw $0x7,%bx # attribute for output
224 movb $0xe,%ah # BIOS: put_char
225 int $0x10 # call BIOS, print char in %al
226 jmp putstr # keep looping
227
228#
229# Enable A20
230#
231seta20: cli # Disable interrupts
232seta20.1: inb $0x64,%al # Get status
233 testb $0x2,%al # Busy?
234 jnz seta20.1 # Yes
235 movb $0xd1,%al # Command: Write
236 outb %al,$0x64 # output port
237seta20.2: inb $0x64,%al # Get status
238 testb $0x2,%al # Busy?
239 jnz seta20.2 # Yes
240 movb $0xdf,%al # Enable
241 outb %al,$0x60 # A20
242 sti # Enable interrupts
243 retw # To caller
244
245#
246# BTX client to start btxldr
247#
248 .code32
249btx_client: movl $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi
250 # %ds:(%esi) -> end
251 # of boot[12] args
252 movl $(MEM_ARG_SIZE/4), %ecx # Number of words to push
253 std # Go backwards
254push_arg: lodsl # Read argument
255 pushl %eax # Push it onto the stack
256 loop push_arg # Push all of the arguments
257 cld # In case anyone depends on this
258 pushl MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE # Entry point of
259 # the loader
260 pushl %eax # Emulate a near call
261 movl $0x1, %eax # 'exec' system call
262 int $INT_SYS # BTX system call
263btx_client_end:
264 .code16
265
266 .p2align 4
267#
268# Global descriptor table.
269#
270gdt: .word 0x0,0x0,0x0,0x0 # Null entry
271 .word 0xffff,0x0,0x9200,0xcf # SEL_SDATA
272 .word 0xffff,0x0,0x9200,0x0 # SEL_RDATA
273 .word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE (32-bit)
274 .word 0xffff,0x0,0x9a00,0x8f # SEL_SCODE16 (16-bit)
275gdt.1:
276#
277# Pseudo-descriptors.
278#
279gdtdesc: .word gdt.1-gdt-1 # Limit
280 .long gdt # Base
281
282welcome_msg: .asciz "PXE Loader 1.00\r\n\n"
283bootinfo_msg: .asciz "Building the boot loader arguments\r\n"
284relocate_msg: .asciz "Relocating the loader and the BTX\r\n"
285jump_message: .asciz "Starting the BTX loader\r\n"
286
287 .p2align 4
288end: