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62607313 PA |
1 | /* |
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> | |
19 | #include <linux/utsrelease.h> | |
20 | #include <asm/boot.h> | |
21 | #include <asm/e820.h> | |
22 | #include <asm/page.h> | |
23 | #include <asm/setup.h> | |
24 | #include "boot.h" | |
25 | ||
26 | SETUPSECTS = 4 /* default nr of setup-sectors */ | |
27 | BOOTSEG = 0x07C0 /* original address of boot-sector */ | |
28 | SYSSEG = DEF_SYSSEG /* system loaded at 0x10000 (65536) */ | |
29 | SYSSIZE = DEF_SYSSIZE /* system size: # of 16-byte clicks */ | |
30 | /* to be loaded */ | |
31 | ROOT_DEV = 0 /* ROOT_DEV is now written by "build" */ | |
32 | SWAP_DEV = 0 /* SWAP_DEV is now written by "build" */ | |
33 | ||
34 | #ifndef SVGA_MODE | |
35 | #define SVGA_MODE ASK_VGA | |
36 | #endif | |
37 | ||
38 | #ifndef RAMDISK | |
39 | #define RAMDISK 0 | |
40 | #endif | |
41 | ||
42 | #ifndef ROOT_RDONLY | |
43 | #define ROOT_RDONLY 1 | |
44 | #endif | |
45 | ||
46 | .code16 | |
47 | .section ".bstext", "ax" | |
48 | ||
49 | .global bootsect_start | |
50 | bootsect_start: | |
51 | ||
52 | # Normalize the start address | |
53 | ljmp $BOOTSEG, $start2 | |
54 | ||
55 | start2: | |
56 | movw %cs, %ax | |
57 | movw %ax, %ds | |
58 | movw %ax, %es | |
59 | movw %ax, %ss | |
60 | xorw %sp, %sp | |
61 | sti | |
62 | cld | |
63 | ||
64 | movw $bugger_off_msg, %si | |
65 | ||
66 | msg_loop: | |
67 | lodsb | |
68 | andb %al, %al | |
69 | jz bs_die | |
70 | movb $0xe, %ah | |
71 | movw $7, %bx | |
72 | int $0x10 | |
73 | jmp msg_loop | |
74 | ||
75 | bs_die: | |
76 | # Allow the user to press a key, then reboot | |
77 | xorw %ax, %ax | |
78 | int $0x16 | |
79 | int $0x19 | |
80 | ||
81 | # int 0x19 should never return. In case it does anyway, | |
82 | # invoke the BIOS reset code... | |
83 | ljmp $0xf000,$0xfff0 | |
84 | ||
85 | .section ".bsdata", "a" | |
86 | bugger_off_msg: | |
87 | .ascii "Direct booting from floppy is no longer supported.\r\n" | |
88 | .ascii "Please use a boot loader program instead.\r\n" | |
89 | .ascii "\n" | |
90 | .ascii "Remove disk and press any key to reboot . . .\r\n" | |
91 | .byte 0 | |
92 | ||
93 | ||
94 | # Kernel attributes; used by setup. This is part 1 of the | |
95 | # header, from the old boot sector. | |
96 | ||
97 | .section ".header", "a" | |
98 | .globl hdr | |
99 | hdr: | |
100 | setup_sects: .byte SETUPSECTS | |
101 | root_flags: .word ROOT_RDONLY | |
102 | syssize: .long SYSSIZE | |
103 | ram_size: .word RAMDISK | |
104 | vid_mode: .word SVGA_MODE | |
105 | root_dev: .word ROOT_DEV | |
106 | boot_flag: .word 0xAA55 | |
107 | ||
108 | # offset 512, entry point | |
109 | ||
110 | .globl _start | |
111 | _start: | |
112 | # Explicitly enter this as bytes, or the assembler | |
113 | # tries to generate a 3-byte jump here, which causes | |
114 | # everything else to push off to the wrong offset. | |
115 | .byte 0xeb # short (2-byte) jump | |
116 | .byte start_of_setup-1f | |
117 | 1: | |
118 | ||
119 | # Part 2 of the header, from the old setup.S | |
120 | ||
121 | .ascii "HdrS" # header signature | |
a24e7851 | 122 | .word 0x0207 # header version number (>= 0x0105) |
62607313 PA |
123 | # or else old loadlin-1.5 will fail) |
124 | .globl realmode_swtch | |
125 | realmode_swtch: .word 0, 0 # default_switch, SETUPSEG | |
126 | start_sys_seg: .word SYSSEG | |
127 | .word kernel_version-512 # pointing to kernel version string | |
128 | # above section of header is compatible | |
129 | # with loadlin-1.5 (header v1.5). Don't | |
130 | # change it. | |
131 | ||
132 | type_of_loader: .byte 0 # = 0, old one (LILO, Loadlin, | |
133 | # Bootlin, SYSLX, bootsect...) | |
134 | # See Documentation/i386/boot.txt for | |
135 | # assigned ids | |
136 | ||
137 | # flags, unused bits must be zero (RFU) bit within loadflags | |
138 | loadflags: | |
139 | LOADED_HIGH = 1 # If set, the kernel is loaded high | |
140 | CAN_USE_HEAP = 0x80 # If set, the loader also has set | |
141 | # heap_end_ptr to tell how much | |
142 | # space behind setup.S can be used for | |
143 | # heap purposes. | |
144 | # Only the loader knows what is free | |
145 | #ifndef __BIG_KERNEL__ | |
146 | .byte 0 | |
147 | #else | |
148 | .byte LOADED_HIGH | |
149 | #endif | |
150 | ||
151 | setup_move_size: .word 0x8000 # size to move, when setup is not | |
152 | # loaded at 0x90000. We will move setup | |
153 | # to 0x90000 then just before jumping | |
154 | # into the kernel. However, only the | |
155 | # loader knows how much data behind | |
156 | # us also needs to be loaded. | |
157 | ||
158 | code32_start: # here loaders can put a different | |
159 | # start address for 32-bit code. | |
160 | #ifndef __BIG_KERNEL__ | |
161 | .long 0x1000 # 0x1000 = default for zImage | |
162 | #else | |
163 | .long 0x100000 # 0x100000 = default for big kernel | |
164 | #endif | |
165 | ||
166 | ramdisk_image: .long 0 # address of loaded ramdisk image | |
167 | # Here the loader puts the 32-bit | |
168 | # address where it loaded the image. | |
169 | # This only will be read by the kernel. | |
170 | ||
171 | ramdisk_size: .long 0 # its size in bytes | |
172 | ||
173 | bootsect_kludge: | |
174 | .long 0 # obsolete | |
175 | ||
6b6815c6 PA |
176 | heap_end_ptr: .word _end+STACK_SIZE-512 |
177 | # (Header version 0x0201 or later) | |
62607313 PA |
178 | # space from here (exclusive) down to |
179 | # end of setup code can be used by setup | |
180 | # for local heap purposes. | |
181 | ||
182 | pad1: .word 0 | |
183 | cmd_line_ptr: .long 0 # (Header version 0x0202 or later) | |
184 | # If nonzero, a 32-bit pointer | |
185 | # to the kernel command line. | |
186 | # The command line should be | |
187 | # located between the start of | |
188 | # setup and the end of low | |
189 | # memory (0xa0000), or it may | |
190 | # get overwritten before it | |
191 | # gets read. If this field is | |
192 | # used, there is no longer | |
193 | # anything magical about the | |
194 | # 0x90000 segment; the setup | |
195 | # can be located anywhere in | |
196 | # low memory 0x10000 or higher. | |
197 | ||
198 | ramdisk_max: .long (-__PAGE_OFFSET-(512 << 20)-1) & 0x7fffffff | |
199 | # (Header version 0x0203 or later) | |
200 | # The highest safe address for | |
201 | # the contents of an initrd | |
202 | ||
203 | kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment | |
204 | #required for protected mode | |
205 | #kernel | |
206 | #ifdef CONFIG_RELOCATABLE | |
207 | relocatable_kernel: .byte 1 | |
208 | #else | |
209 | relocatable_kernel: .byte 0 | |
210 | #endif | |
211 | pad2: .byte 0 | |
212 | pad3: .word 0 | |
213 | ||
214 | cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, | |
215 | #added with boot protocol | |
216 | #version 2.06 | |
217 | ||
a24e7851 RR |
218 | hardware_subarch: .long 0 # subarchitecture, added with 2.07 |
219 | # default to 0 for normal x86 PC | |
220 | ||
221 | hardware_subarch_data: .quad 0 | |
222 | ||
62607313 PA |
223 | # End of setup header ##################################################### |
224 | ||
225 | .section ".inittext", "ax" | |
226 | start_of_setup: | |
227 | #ifdef SAFE_RESET_DISK_CONTROLLER | |
228 | # Reset the disk controller. | |
229 | movw $0x0000, %ax # Reset disk controller | |
230 | movb $0x80, %dl # All disks | |
231 | int $0x13 | |
232 | #endif | |
233 | ||
62607313 PA |
234 | # Force %es = %ds |
235 | movw %ds, %ax | |
236 | movw %ax, %es | |
237 | cld | |
238 | ||
16252da6 JR |
239 | # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds, |
240 | # which happened to work by accident for the old code. Recalculate the stack | |
241 | # pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the | |
242 | # stack behind its own code, so we can't blindly put it directly past the heap. | |
6b6815c6 | 243 | |
6b6815c6 PA |
244 | movw %ss, %dx |
245 | cmpw %ax, %dx # %ds == %ss? | |
246 | movw %sp, %dx | |
16252da6 JR |
247 | je 2f # -> assume %sp is reasonably set |
248 | ||
249 | # Invalid %ss, make up a new stack | |
250 | movw $_end, %dx | |
251 | testb $CAN_USE_HEAP, loadflags | |
252 | jz 1f | |
253 | movw heap_end_ptr, %dx | |
254 | 1: addw $STACK_SIZE, %dx | |
255 | jnc 2f | |
256 | xorw %dx, %dx # Prevent wraparound | |
6b6815c6 | 257 | |
16252da6 | 258 | 2: # Now %dx should point to the end of our stack space |
6b6815c6 PA |
259 | andw $~3, %dx # dword align (might as well...) |
260 | jnz 3f | |
261 | movw $0xfffc, %dx # Make sure we're not zero | |
16252da6 | 262 | 3: movw %ax, %ss |
6b6815c6 PA |
263 | movzwl %dx, %esp # Clear upper half of %esp |
264 | sti # Now we should have a working stack | |
265 | ||
266 | # We will have entered with %cs = %ds+0x20, normalize %cs so | |
267 | # it is on par with the other segments. | |
268 | pushw %ds | |
269 | pushw $6f | |
270 | lretw | |
271 | 6: | |
62607313 PA |
272 | |
273 | # Check signature at end of setup | |
274 | cmpl $0x5a5aaa55, setup_sig | |
275 | jne setup_bad | |
276 | ||
277 | # Zero the bss | |
278 | movw $__bss_start, %di | |
279 | movw $_end+3, %cx | |
280 | xorl %eax, %eax | |
281 | subw %di, %cx | |
282 | shrw $2, %cx | |
283 | rep; stosl | |
284 | ||
285 | # Jump to C code (should not return) | |
286 | calll main | |
287 | ||
288 | # Setup corrupt somehow... | |
289 | setup_bad: | |
290 | movl $setup_corrupt, %eax | |
291 | calll puts | |
292 | # Fall through... | |
293 | ||
294 | .globl die | |
295 | .type die, @function | |
296 | die: | |
297 | hlt | |
298 | jmp die | |
299 | ||
bbc15f46 | 300 | .size die, .-die |
62607313 PA |
301 | |
302 | .section ".initdata", "a" | |
303 | setup_corrupt: | |
304 | .byte 7 | |
8b608d2f | 305 | .string "No setup signature found...\n" |