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H. Peter Anvin62607312007-07-11 12:18:54 -07001/*
2 * header.S
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * Based on bootsect.S and setup.S
7 * modified by more people than can be counted
8 *
9 * Rewritten as a common file by H. Peter Anvin (Apr 2007)
10 *
11 * BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment
12 * addresses must be multiplied by 16 to obtain their respective linear
13 * addresses. To avoid confusion, linear addresses are written using leading
14 * hex while segment addresses are written as segment:offset.
15 *
16 */
17
18#include <asm/segment.h>
Sam Ravnborg273b2812009-10-18 00:52:28 +020019#include <generated/utsrelease.h>
H. Peter Anvin62607312007-07-11 12:18:54 -070020#include <asm/boot.h>
21#include <asm/e820.h>
Jeremy Fitzhardinge0341c142009-02-13 11:14:01 -080022#include <asm/page_types.h>
H. Peter Anvin62607312007-07-11 12:18:54 -070023#include <asm/setup.h>
24#include "boot.h"
H. Peter Anvin77d1a492009-05-11 14:21:12 -070025#include "voffset.h"
26#include "zoffset.h"
H. Peter Anvin62607312007-07-11 12:18:54 -070027
H. Peter Anvin62607312007-07-11 12:18:54 -070028BOOTSEG = 0x07C0 /* original address of boot-sector */
H. Peter Anvin5e47c472009-03-11 10:55:33 -070029SYSSEG = 0x1000 /* historical load address >> 4 */
H. Peter Anvin62607312007-07-11 12:18:54 -070030
31#ifndef SVGA_MODE
32#define SVGA_MODE ASK_VGA
33#endif
34
35#ifndef RAMDISK
36#define RAMDISK 0
37#endif
38
39#ifndef ROOT_RDONLY
40#define ROOT_RDONLY 1
41#endif
42
43 .code16
44 .section ".bstext", "ax"
45
46 .global bootsect_start
47bootsect_start:
48
49 # Normalize the start address
50 ljmp $BOOTSEG, $start2
51
52start2:
53 movw %cs, %ax
54 movw %ax, %ds
55 movw %ax, %es
56 movw %ax, %ss
57 xorw %sp, %sp
58 sti
59 cld
60
61 movw $bugger_off_msg, %si
62
63msg_loop:
64 lodsb
65 andb %al, %al
66 jz bs_die
67 movb $0xe, %ah
68 movw $7, %bx
69 int $0x10
70 jmp msg_loop
71
72bs_die:
73 # Allow the user to press a key, then reboot
74 xorw %ax, %ax
75 int $0x16
76 int $0x19
77
78 # int 0x19 should never return. In case it does anyway,
79 # invoke the BIOS reset code...
80 ljmp $0xf000,$0xfff0
81
82 .section ".bsdata", "a"
83bugger_off_msg:
84 .ascii "Direct booting from floppy is no longer supported.\r\n"
85 .ascii "Please use a boot loader program instead.\r\n"
86 .ascii "\n"
87 .ascii "Remove disk and press any key to reboot . . .\r\n"
88 .byte 0
89
90
91 # Kernel attributes; used by setup. This is part 1 of the
92 # header, from the old boot sector.
93
94 .section ".header", "a"
95 .globl hdr
96hdr:
H. Peter Anvin5e47c472009-03-11 10:55:33 -070097setup_sects: .byte 0 /* Filled in by build.c */
H. Peter Anvin62607312007-07-11 12:18:54 -070098root_flags: .word ROOT_RDONLY
H. Peter Anvin5e47c472009-03-11 10:55:33 -070099syssize: .long 0 /* Filled in by build.c */
100ram_size: .word 0 /* Obsolete */
H. Peter Anvin62607312007-07-11 12:18:54 -0700101vid_mode: .word SVGA_MODE
H. Peter Anvin5e47c472009-03-11 10:55:33 -0700102root_dev: .word 0 /* Filled in by build.c */
H. Peter Anvin62607312007-07-11 12:18:54 -0700103boot_flag: .word 0xAA55
104
105 # offset 512, entry point
106
107 .globl _start
108_start:
109 # Explicitly enter this as bytes, or the assembler
110 # tries to generate a 3-byte jump here, which causes
111 # everything else to push off to the wrong offset.
112 .byte 0xeb # short (2-byte) jump
113 .byte start_of_setup-1f
1141:
115
116 # Part 2 of the header, from the old setup.S
117
118 .ascii "HdrS" # header signature
H. Peter Anvin37ba7ab2009-05-11 15:56:08 -0700119 .word 0x020a # header version number (>= 0x0105)
H. Peter Anvin62607312007-07-11 12:18:54 -0700120 # or else old loadlin-1.5 will fail)
121 .globl realmode_swtch
122realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
H. Peter Anvin5e47c472009-03-11 10:55:33 -0700123start_sys_seg: .word SYSSEG # obsolete and meaningless, but just
124 # in case something decided to "use" it
H. Peter Anvin62607312007-07-11 12:18:54 -0700125 .word kernel_version-512 # pointing to kernel version string
126 # above section of header is compatible
127 # with loadlin-1.5 (header v1.5). Don't
128 # change it.
129
H. Peter Anvin5e47c472009-03-11 10:55:33 -0700130type_of_loader: .byte 0 # 0 means ancient bootloader, newer
131 # bootloaders know to change this.
H. Peter Anvin62607312007-07-11 12:18:54 -0700132 # See Documentation/i386/boot.txt for
133 # assigned ids
134
135# flags, unused bits must be zero (RFU) bit within loadflags
136loadflags:
137LOADED_HIGH = 1 # If set, the kernel is loaded high
138CAN_USE_HEAP = 0x80 # If set, the loader also has set
139 # heap_end_ptr to tell how much
140 # space behind setup.S can be used for
141 # heap purposes.
142 # Only the loader knows what is free
H. Peter Anvin62607312007-07-11 12:18:54 -0700143 .byte LOADED_HIGH
H. Peter Anvin62607312007-07-11 12:18:54 -0700144
145setup_move_size: .word 0x8000 # size to move, when setup is not
146 # loaded at 0x90000. We will move setup
147 # to 0x90000 then just before jumping
148 # into the kernel. However, only the
149 # loader knows how much data behind
150 # us also needs to be loaded.
151
152code32_start: # here loaders can put a different
153 # start address for 32-bit code.
H. Peter Anvin62607312007-07-11 12:18:54 -0700154 .long 0x100000 # 0x100000 = default for big kernel
H. Peter Anvin62607312007-07-11 12:18:54 -0700155
156ramdisk_image: .long 0 # address of loaded ramdisk image
157 # Here the loader puts the 32-bit
158 # address where it loaded the image.
159 # This only will be read by the kernel.
160
161ramdisk_size: .long 0 # its size in bytes
162
163bootsect_kludge:
164 .long 0 # obsolete
165
H. Peter Anvin6b6815c2007-10-25 16:11:33 -0700166heap_end_ptr: .word _end+STACK_SIZE-512
167 # (Header version 0x0201 or later)
H. Peter Anvin62607312007-07-11 12:18:54 -0700168 # space from here (exclusive) down to
169 # end of setup code can be used by setup
170 # for local heap purposes.
171
H. Peter Anvin50312962009-05-07 16:54:11 -0700172ext_loader_ver:
173 .byte 0 # Extended boot loader version
174ext_loader_type:
175 .byte 0 # Extended boot loader type
176
H. Peter Anvin62607312007-07-11 12:18:54 -0700177cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
178 # If nonzero, a 32-bit pointer
179 # to the kernel command line.
180 # The command line should be
181 # located between the start of
182 # setup and the end of low
183 # memory (0xa0000), or it may
184 # get overwritten before it
185 # gets read. If this field is
186 # used, there is no longer
187 # anything magical about the
188 # 0x90000 segment; the setup
189 # can be located anywhere in
190 # low memory 0x10000 or higher.
191
H. Peter Anvincf8fa922008-01-30 13:32:51 +0100192ramdisk_max: .long 0x7fffffff
H. Peter Anvin62607312007-07-11 12:18:54 -0700193 # (Header version 0x0203 or later)
194 # The highest safe address for
195 # the contents of an initrd
H. Peter Anvincf8fa922008-01-30 13:32:51 +0100196 # The current kernel allows up to 4 GB,
197 # but leave it at 2 GB to avoid
198 # possible bootloader bugs.
H. Peter Anvin62607312007-07-11 12:18:54 -0700199
200kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
201 #required for protected mode
202 #kernel
203#ifdef CONFIG_RELOCATABLE
204relocatable_kernel: .byte 1
205#else
206relocatable_kernel: .byte 0
207#endif
H. Peter Anvin37ba7ab2009-05-11 15:56:08 -0700208min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
H. Peter Anvin62607312007-07-11 12:18:54 -0700209pad3: .word 0
210
211cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
212 #added with boot protocol
213 #version 2.06
214
Rusty Russella24e7852007-10-21 16:41:35 -0700215hardware_subarch: .long 0 # subarchitecture, added with 2.07
216 # default to 0 for normal x86 PC
217
218hardware_subarch_data: .quad 0
219
H. Peter Anvin77d1a492009-05-11 14:21:12 -0700220payload_offset: .long ZO_input_data
221payload_length: .long ZO_z_input_len
Ian Campbell099e1372008-02-13 20:54:58 +0000222
Huang, Ying8b664aa2008-03-28 10:49:44 +0800223setup_data: .quad 0 # 64-bit physical pointer to
224 # single linked list of
225 # struct setup_data
226
H. Peter Anvin37ba7ab2009-05-11 15:56:08 -0700227pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
228
H. Peter Anvinc6ac4c12009-05-20 11:26:09 -0700229#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
H. Peter Anvin37ba7ab2009-05-11 15:56:08 -0700230#define VO_INIT_SIZE (VO__end - VO__text)
231#if ZO_INIT_SIZE > VO_INIT_SIZE
232#define INIT_SIZE ZO_INIT_SIZE
233#else
234#define INIT_SIZE VO_INIT_SIZE
235#endif
236init_size: .long INIT_SIZE # kernel initialization size
237
H. Peter Anvin62607312007-07-11 12:18:54 -0700238# End of setup header #####################################################
239
H. Peter Anvin7a734e72009-04-01 18:08:28 -0700240 .section ".entrytext", "ax"
H. Peter Anvin62607312007-07-11 12:18:54 -0700241start_of_setup:
242#ifdef SAFE_RESET_DISK_CONTROLLER
243# Reset the disk controller.
244 movw $0x0000, %ax # Reset disk controller
245 movb $0x80, %dl # All disks
246 int $0x13
247#endif
248
H. Peter Anvin62607312007-07-11 12:18:54 -0700249# Force %es = %ds
250 movw %ds, %ax
251 movw %ax, %es
252 cld
253
Jens Rottmann16252da2007-11-27 12:35:13 +0100254# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
255# which happened to work by accident for the old code. Recalculate the stack
256# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
257# stack behind its own code, so we can't blindly put it directly past the heap.
H. Peter Anvin6b6815c2007-10-25 16:11:33 -0700258
H. Peter Anvin6b6815c2007-10-25 16:11:33 -0700259 movw %ss, %dx
260 cmpw %ax, %dx # %ds == %ss?
261 movw %sp, %dx
Jens Rottmann16252da2007-11-27 12:35:13 +0100262 je 2f # -> assume %sp is reasonably set
H. Peter Anvin6b6815c2007-10-25 16:11:33 -0700263
Jens Rottmann16252da2007-11-27 12:35:13 +0100264 # Invalid %ss, make up a new stack
265 movw $_end, %dx
266 testb $CAN_USE_HEAP, loadflags
267 jz 1f
268 movw heap_end_ptr, %dx
2691: addw $STACK_SIZE, %dx
270 jnc 2f
271 xorw %dx, %dx # Prevent wraparound
272
2732: # Now %dx should point to the end of our stack space
H. Peter Anvin6b6815c2007-10-25 16:11:33 -0700274 andw $~3, %dx # dword align (might as well...)
275 jnz 3f
276 movw $0xfffc, %dx # Make sure we're not zero
Jens Rottmann16252da2007-11-27 12:35:13 +01002773: movw %ax, %ss
H. Peter Anvin6b6815c2007-10-25 16:11:33 -0700278 movzwl %dx, %esp # Clear upper half of %esp
279 sti # Now we should have a working stack
280
281# We will have entered with %cs = %ds+0x20, normalize %cs so
282# it is on par with the other segments.
283 pushw %ds
284 pushw $6f
285 lretw
2866:
H. Peter Anvin62607312007-07-11 12:18:54 -0700287
288# Check signature at end of setup
289 cmpl $0x5a5aaa55, setup_sig
290 jne setup_bad
291
292# Zero the bss
293 movw $__bss_start, %di
294 movw $_end+3, %cx
295 xorl %eax, %eax
296 subw %di, %cx
297 shrw $2, %cx
298 rep; stosl
299
300# Jump to C code (should not return)
301 calll main
302
303# Setup corrupt somehow...
304setup_bad:
305 movl $setup_corrupt, %eax
306 calll puts
307 # Fall through...
308
309 .globl die
310 .type die, @function
311die:
312 hlt
313 jmp die
314
Paul Bollebbc15f42007-09-10 23:39:02 +0200315 .size die, .-die
H. Peter Anvin62607312007-07-11 12:18:54 -0700316
317 .section ".initdata", "a"
318setup_corrupt:
319 .byte 7
H. Peter Anvin8b608d22007-07-26 16:10:22 -0700320 .string "No setup signature found...\n"