Commit | Line | Data |
---|---|---|
b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
62607313 PA |
2 | /* |
3 | * header.S | |
4 | * | |
5 | * Copyright (C) 1991, 1992 Linus Torvalds | |
6 | * | |
7 | * Based on bootsect.S and setup.S | |
8 | * modified by more people than can be counted | |
9 | * | |
10 | * Rewritten as a common file by H. Peter Anvin (Apr 2007) | |
11 | * | |
12 | * BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment | |
13 | * addresses must be multiplied by 16 to obtain their respective linear | |
14 | * addresses. To avoid confusion, linear addresses are written using leading | |
15 | * hex while segment addresses are written as segment:offset. | |
16 | * | |
17 | */ | |
a3326a0d | 18 | #include <linux/pe.h> |
62607313 | 19 | #include <asm/segment.h> |
62607313 | 20 | #include <asm/boot.h> |
0341c14d | 21 | #include <asm/page_types.h> |
62607313 | 22 | #include <asm/setup.h> |
09c205af | 23 | #include <asm/bootparam.h> |
62607313 | 24 | #include "boot.h" |
77d1a499 PA |
25 | #include "voffset.h" |
26 | #include "zoffset.h" | |
62607313 | 27 | |
62607313 | 28 | BOOTSEG = 0x07C0 /* original address of boot-sector */ |
5e47c478 | 29 | SYSSEG = 0x1000 /* historical load address >> 4 */ |
62607313 PA |
30 | |
31 | #ifndef SVGA_MODE | |
32 | #define SVGA_MODE ASK_VGA | |
33 | #endif | |
34 | ||
62607313 PA |
35 | #ifndef ROOT_RDONLY |
36 | #define ROOT_RDONLY 1 | |
37 | #endif | |
38 | ||
39 | .code16 | |
40 | .section ".bstext", "ax" | |
41 | ||
42 | .global bootsect_start | |
43 | bootsect_start: | |
291f3632 MF |
44 | #ifdef CONFIG_EFI_STUB |
45 | # "MZ", MS-DOS header | |
a3326a0d | 46 | .word MZ_MAGIC |
291f3632 | 47 | #endif |
62607313 PA |
48 | |
49 | # Normalize the start address | |
50 | ljmp $BOOTSEG, $start2 | |
51 | ||
52 | start2: | |
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 | ||
63 | msg_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 | ||
72 | bs_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 | ||
291f3632 | 82 | #ifdef CONFIG_EFI_STUB |
29636a5c | 83 | .org 0x38 |
291f3632 MF |
84 | # |
85 | # Offset to the PE header. | |
86 | # | |
29636a5c | 87 | .long LINUX_PE_MAGIC |
291f3632 MF |
88 | .long pe_header |
89 | #endif /* CONFIG_EFI_STUB */ | |
90 | ||
62607313 PA |
91 | .section ".bsdata", "a" |
92 | bugger_off_msg: | |
c7fb93ec | 93 | .ascii "Use a boot loader.\r\n" |
62607313 | 94 | .ascii "\n" |
c7fb93ec | 95 | .ascii "Remove disk and press any key to reboot...\r\n" |
62607313 PA |
96 | .byte 0 |
97 | ||
291f3632 MF |
98 | #ifdef CONFIG_EFI_STUB |
99 | pe_header: | |
a3326a0d | 100 | .long PE_MAGIC |
291f3632 MF |
101 | |
102 | coff_header: | |
103 | #ifdef CONFIG_X86_32 | |
a3326a0d AB |
104 | .set image_file_add_flags, IMAGE_FILE_32BIT_MACHINE |
105 | .set pe_opt_magic, PE_OPT_MAGIC_PE32 | |
106 | .word IMAGE_FILE_MACHINE_I386 | |
291f3632 | 107 | #else |
a3326a0d AB |
108 | .set image_file_add_flags, 0 |
109 | .set pe_opt_magic, PE_OPT_MAGIC_PE32PLUS | |
110 | .word IMAGE_FILE_MACHINE_AMD64 | |
291f3632 | 111 | #endif |
97aa2765 | 112 | .word section_count # nr_sections |
291f3632 MF |
113 | .long 0 # TimeDateStamp |
114 | .long 0 # PointerToSymbolTable | |
115 | .long 1 # NumberOfSymbols | |
116 | .word section_table - optional_header # SizeOfOptionalHeader | |
a3326a0d AB |
117 | .word IMAGE_FILE_EXECUTABLE_IMAGE | \ |
118 | image_file_add_flags | \ | |
119 | IMAGE_FILE_DEBUG_STRIPPED | \ | |
120 | IMAGE_FILE_LINE_NUMS_STRIPPED # Characteristics | |
291f3632 MF |
121 | |
122 | optional_header: | |
a3326a0d | 123 | .word pe_opt_magic |
291f3632 MF |
124 | .byte 0x02 # MajorLinkerVersion |
125 | .byte 0x14 # MinorLinkerVersion | |
126 | ||
127 | # Filled in by build.c | |
128 | .long 0 # SizeOfCode | |
129 | ||
130 | .long 0 # SizeOfInitializedData | |
131 | .long 0 # SizeOfUninitializedData | |
132 | ||
133 | # Filled in by build.c | |
134 | .long 0x0000 # AddressOfEntryPoint | |
135 | ||
e31be363 | 136 | .long 0x0200 # BaseOfCode |
291f3632 MF |
137 | #ifdef CONFIG_X86_32 |
138 | .long 0 # data | |
139 | #endif | |
140 | ||
141 | extra_header_fields: | |
26725192 AS |
142 | # PE specification requires ImageBase to be 64k aligned |
143 | .set image_base, (LOAD_PHYSICAL_ADDR + 0xffff) & ~0xffff | |
291f3632 | 144 | #ifdef CONFIG_X86_32 |
26725192 | 145 | .long image_base # ImageBase |
291f3632 | 146 | #else |
26725192 | 147 | .quad image_base # ImageBase |
291f3632 | 148 | #endif |
fa5c3501 | 149 | .long 0x20 # SectionAlignment |
743628e8 | 150 | .long 0x20 # FileAlignment |
291f3632 MF |
151 | .word 0 # MajorOperatingSystemVersion |
152 | .word 0 # MinorOperatingSystemVersion | |
148d3f71 AB |
153 | .word LINUX_EFISTUB_MAJOR_VERSION # MajorImageVersion |
154 | .word LINUX_EFISTUB_MINOR_VERSION # MinorImageVersion | |
291f3632 MF |
155 | .word 0 # MajorSubsystemVersion |
156 | .word 0 # MinorSubsystemVersion | |
157 | .long 0 # Win32VersionValue | |
158 | ||
159 | # | |
160 | # The size of the bzImage is written in tools/build.c | |
161 | # | |
162 | .long 0 # SizeOfImage | |
163 | ||
164 | .long 0x200 # SizeOfHeaders | |
165 | .long 0 # CheckSum | |
a3326a0d | 166 | .word IMAGE_SUBSYSTEM_EFI_APPLICATION # Subsystem (EFI application) |
ca209f8b | 167 | #ifdef CONFIG_EFI_DXE_MEM_ATTRIBUTES |
24b72bb1 PJ |
168 | .word IMAGE_DLL_CHARACTERISTICS_NX_COMPAT # DllCharacteristics |
169 | #else | |
291f3632 | 170 | .word 0 # DllCharacteristics |
24b72bb1 | 171 | #endif |
291f3632 MF |
172 | #ifdef CONFIG_X86_32 |
173 | .long 0 # SizeOfStackReserve | |
174 | .long 0 # SizeOfStackCommit | |
175 | .long 0 # SizeOfHeapReserve | |
176 | .long 0 # SizeOfHeapCommit | |
177 | #else | |
178 | .quad 0 # SizeOfStackReserve | |
179 | .quad 0 # SizeOfStackCommit | |
180 | .quad 0 # SizeOfHeapReserve | |
181 | .quad 0 # SizeOfHeapCommit | |
182 | #endif | |
183 | .long 0 # LoaderFlags | |
a3326a0d | 184 | .long (section_table - .) / 8 # NumberOfRvaAndSizes |
291f3632 MF |
185 | |
186 | .quad 0 # ExportTable | |
187 | .quad 0 # ImportTable | |
188 | .quad 0 # ResourceTable | |
189 | .quad 0 # ExceptionTable | |
190 | .quad 0 # CertificationTable | |
191 | .quad 0 # BaseRelocationTable | |
192 | ||
193 | # Section table | |
194 | section_table: | |
743628e8 JJ |
195 | # |
196 | # The offset & size fields are filled in by build.c. | |
197 | # | |
198 | .ascii ".setup" | |
291f3632 MF |
199 | .byte 0 |
200 | .byte 0 | |
201 | .long 0 | |
202 | .long 0x0 # startup_{32,64} | |
203 | .long 0 # Size of initialized data | |
204 | # on disk | |
205 | .long 0x0 # startup_{32,64} | |
206 | .long 0 # PointerToRelocations | |
207 | .long 0 # PointerToLineNumbers | |
208 | .word 0 # NumberOfRelocations | |
209 | .word 0 # NumberOfLineNumbers | |
a3326a0d AB |
210 | .long IMAGE_SCN_CNT_CODE | \ |
211 | IMAGE_SCN_MEM_READ | \ | |
212 | IMAGE_SCN_MEM_EXECUTE | \ | |
213 | IMAGE_SCN_ALIGN_16BYTES # Characteristics | |
291f3632 MF |
214 | |
215 | # | |
216 | # The EFI application loader requires a relocation section | |
743628e8 JJ |
217 | # because EFI applications must be relocatable. The .reloc |
218 | # offset & size fields are filled in by build.c. | |
291f3632 MF |
219 | # |
220 | .ascii ".reloc" | |
221 | .byte 0 | |
222 | .byte 0 | |
2e064b1e JJ |
223 | .long 0 |
224 | .long 0 | |
225 | .long 0 # SizeOfRawData | |
226 | .long 0 # PointerToRawData | |
291f3632 MF |
227 | .long 0 # PointerToRelocations |
228 | .long 0 # PointerToLineNumbers | |
229 | .word 0 # NumberOfRelocations | |
230 | .word 0 # NumberOfLineNumbers | |
a3326a0d AB |
231 | .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ |
232 | IMAGE_SCN_MEM_READ | \ | |
233 | IMAGE_SCN_MEM_DISCARDABLE | \ | |
234 | IMAGE_SCN_ALIGN_1BYTES # Characteristics | |
743628e8 | 235 | |
97aa2765 AB |
236 | #ifdef CONFIG_EFI_MIXED |
237 | # | |
238 | # The offset & size fields are filled in by build.c. | |
239 | # | |
240 | .asciz ".compat" | |
241 | .long 0 | |
242 | .long 0x0 | |
243 | .long 0 # Size of initialized data | |
244 | # on disk | |
245 | .long 0x0 | |
246 | .long 0 # PointerToRelocations | |
247 | .long 0 # PointerToLineNumbers | |
248 | .word 0 # NumberOfRelocations | |
249 | .word 0 # NumberOfLineNumbers | |
a3326a0d AB |
250 | .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ |
251 | IMAGE_SCN_MEM_READ | \ | |
252 | IMAGE_SCN_MEM_DISCARDABLE | \ | |
253 | IMAGE_SCN_ALIGN_1BYTES # Characteristics | |
97aa2765 AB |
254 | #endif |
255 | ||
743628e8 JJ |
256 | # |
257 | # The offset & size fields are filled in by build.c. | |
258 | # | |
259 | .ascii ".text" | |
260 | .byte 0 | |
261 | .byte 0 | |
262 | .byte 0 | |
263 | .long 0 | |
264 | .long 0x0 # startup_{32,64} | |
265 | .long 0 # Size of initialized data | |
266 | # on disk | |
267 | .long 0x0 # startup_{32,64} | |
268 | .long 0 # PointerToRelocations | |
269 | .long 0 # PointerToLineNumbers | |
270 | .word 0 # NumberOfRelocations | |
271 | .word 0 # NumberOfLineNumbers | |
a3326a0d AB |
272 | .long IMAGE_SCN_CNT_CODE | \ |
273 | IMAGE_SCN_MEM_READ | \ | |
274 | IMAGE_SCN_MEM_EXECUTE | \ | |
275 | IMAGE_SCN_ALIGN_16BYTES # Characteristics | |
743628e8 | 276 | |
97aa2765 | 277 | .set section_count, (. - section_table) / 40 |
291f3632 | 278 | #endif /* CONFIG_EFI_STUB */ |
62607313 PA |
279 | |
280 | # Kernel attributes; used by setup. This is part 1 of the | |
281 | # header, from the old boot sector. | |
282 | ||
283 | .section ".header", "a" | |
09c205af PA |
284 | .globl sentinel |
285 | sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */ | |
286 | ||
62607313 PA |
287 | .globl hdr |
288 | hdr: | |
5e47c478 | 289 | setup_sects: .byte 0 /* Filled in by build.c */ |
62607313 | 290 | root_flags: .word ROOT_RDONLY |
5e47c478 PA |
291 | syssize: .long 0 /* Filled in by build.c */ |
292 | ram_size: .word 0 /* Obsolete */ | |
62607313 | 293 | vid_mode: .word SVGA_MODE |
5e47c478 | 294 | root_dev: .word 0 /* Filled in by build.c */ |
62607313 PA |
295 | boot_flag: .word 0xAA55 |
296 | ||
297 | # offset 512, entry point | |
298 | ||
299 | .globl _start | |
300 | _start: | |
301 | # Explicitly enter this as bytes, or the assembler | |
302 | # tries to generate a 3-byte jump here, which causes | |
303 | # everything else to push off to the wrong offset. | |
304 | .byte 0xeb # short (2-byte) jump | |
305 | .byte start_of_setup-1f | |
306 | 1: | |
307 | ||
308 | # Part 2 of the header, from the old setup.S | |
309 | ||
310 | .ascii "HdrS" # header signature | |
b3c72fc9 | 311 | .word 0x020f # header version number (>= 0x0105) |
62607313 PA |
312 | # or else old loadlin-1.5 will fail) |
313 | .globl realmode_swtch | |
314 | realmode_swtch: .word 0, 0 # default_switch, SETUPSEG | |
5e47c478 PA |
315 | start_sys_seg: .word SYSSEG # obsolete and meaningless, but just |
316 | # in case something decided to "use" it | |
62607313 PA |
317 | .word kernel_version-512 # pointing to kernel version string |
318 | # above section of header is compatible | |
319 | # with loadlin-1.5 (header v1.5). Don't | |
320 | # change it. | |
321 | ||
5e47c478 PA |
322 | type_of_loader: .byte 0 # 0 means ancient bootloader, newer |
323 | # bootloaders know to change this. | |
ff61f079 | 324 | # See Documentation/arch/x86/boot.rst for |
62607313 PA |
325 | # assigned ids |
326 | ||
327 | # flags, unused bits must be zero (RFU) bit within loadflags | |
328 | loadflags: | |
09c205af | 329 | .byte LOADED_HIGH # The kernel is to be loaded high |
62607313 PA |
330 | |
331 | setup_move_size: .word 0x8000 # size to move, when setup is not | |
332 | # loaded at 0x90000. We will move setup | |
333 | # to 0x90000 then just before jumping | |
334 | # into the kernel. However, only the | |
335 | # loader knows how much data behind | |
336 | # us also needs to be loaded. | |
337 | ||
338 | code32_start: # here loaders can put a different | |
339 | # start address for 32-bit code. | |
62607313 | 340 | .long 0x100000 # 0x100000 = default for big kernel |
62607313 PA |
341 | |
342 | ramdisk_image: .long 0 # address of loaded ramdisk image | |
343 | # Here the loader puts the 32-bit | |
344 | # address where it loaded the image. | |
345 | # This only will be read by the kernel. | |
346 | ||
347 | ramdisk_size: .long 0 # its size in bytes | |
348 | ||
349 | bootsect_kludge: | |
350 | .long 0 # obsolete | |
351 | ||
6b6815c6 PA |
352 | heap_end_ptr: .word _end+STACK_SIZE-512 |
353 | # (Header version 0x0201 or later) | |
62607313 PA |
354 | # space from here (exclusive) down to |
355 | # end of setup code can be used by setup | |
356 | # for local heap purposes. | |
357 | ||
5031296c PA |
358 | ext_loader_ver: |
359 | .byte 0 # Extended boot loader version | |
360 | ext_loader_type: | |
361 | .byte 0 # Extended boot loader type | |
362 | ||
62607313 PA |
363 | cmd_line_ptr: .long 0 # (Header version 0x0202 or later) |
364 | # If nonzero, a 32-bit pointer | |
365 | # to the kernel command line. | |
366 | # The command line should be | |
367 | # located between the start of | |
368 | # setup and the end of low | |
369 | # memory (0xa0000), or it may | |
370 | # get overwritten before it | |
371 | # gets read. If this field is | |
372 | # used, there is no longer | |
373 | # anything magical about the | |
374 | # 0x90000 segment; the setup | |
375 | # can be located anywhere in | |
376 | # low memory 0x10000 or higher. | |
377 | ||
3e920b53 | 378 | initrd_addr_max: .long 0x7fffffff |
62607313 PA |
379 | # (Header version 0x0203 or later) |
380 | # The highest safe address for | |
381 | # the contents of an initrd | |
cf8fa920 PA |
382 | # The current kernel allows up to 4 GB, |
383 | # but leave it at 2 GB to avoid | |
384 | # possible bootloader bugs. | |
62607313 PA |
385 | |
386 | kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment | |
387 | #required for protected mode | |
388 | #kernel | |
389 | #ifdef CONFIG_RELOCATABLE | |
390 | relocatable_kernel: .byte 1 | |
391 | #else | |
392 | relocatable_kernel: .byte 0 | |
393 | #endif | |
37ba7ab5 | 394 | min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment |
09c205af PA |
395 | |
396 | xloadflags: | |
397 | #ifdef CONFIG_X86_64 | |
398 | # define XLF0 XLF_KERNEL_64 /* 64-bit kernel */ | |
399 | #else | |
400 | # define XLF0 0 | |
401 | #endif | |
ee92d815 | 402 | |
745c5167 | 403 | #if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64) |
ee92d815 YL |
404 | /* kernel/boot_param/ramdisk could be loaded above 4g */ |
405 | # define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G | |
406 | #else | |
407 | # define XLF1 0 | |
408 | #endif | |
409 | ||
cc3fdda2 | 410 | #ifdef CONFIG_EFI_HANDOVER_PROTOCOL |
7d453eee MF |
411 | # ifdef CONFIG_EFI_MIXED |
412 | # define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64) | |
09c205af | 413 | # else |
7d453eee MF |
414 | # ifdef CONFIG_X86_64 |
415 | # define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */ | |
416 | # else | |
417 | # define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */ | |
418 | # endif | |
09c205af PA |
419 | # endif |
420 | #else | |
421 | # define XLF23 0 | |
422 | #endif | |
456a29dd | 423 | |
2965faa5 | 424 | #if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE) |
456a29dd DY |
425 | # define XLF4 XLF_EFI_KEXEC |
426 | #else | |
427 | # define XLF4 0 | |
428 | #endif | |
429 | ||
f2d08c5d BH |
430 | #ifdef CONFIG_X86_64 |
431 | #ifdef CONFIG_X86_5LEVEL | |
432 | #define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED) | |
433 | #else | |
434 | #define XLF56 XLF_5LEVEL | |
435 | #endif | |
436 | #else | |
437 | #define XLF56 0 | |
438 | #endif | |
439 | ||
440 | .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56 | |
62607313 PA |
441 | |
442 | cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, | |
443 | #added with boot protocol | |
444 | #version 2.06 | |
445 | ||
a24e7851 RR |
446 | hardware_subarch: .long 0 # subarchitecture, added with 2.07 |
447 | # default to 0 for normal x86 PC | |
448 | ||
449 | hardware_subarch_data: .quad 0 | |
450 | ||
77d1a499 PA |
451 | payload_offset: .long ZO_input_data |
452 | payload_length: .long ZO_z_input_len | |
099e1377 | 453 | |
8b664aa6 HY |
454 | setup_data: .quad 0 # 64-bit physical pointer to |
455 | # single linked list of | |
456 | # struct setup_data | |
457 | ||
37ba7ab5 PA |
458 | pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr |
459 | ||
4252db10 BH |
460 | # |
461 | # Getting to provably safe in-place decompression is hard. Worst case | |
462 | # behaviours need to be analyzed. Here let's take the decompression of | |
463 | # a gzip-compressed kernel as example, to illustrate it: | |
464 | # | |
465 | # The file layout of gzip compressed kernel is: | |
466 | # | |
467 | # magic[2] | |
468 | # method[1] | |
469 | # flags[1] | |
470 | # timestamp[4] | |
471 | # extraflags[1] | |
472 | # os[1] | |
473 | # compressed data blocks[N] | |
474 | # crc[4] orig_len[4] | |
475 | # | |
476 | # ... resulting in +18 bytes overhead of uncompressed data. | |
477 | # | |
478 | # (For more information, please refer to RFC 1951 and RFC 1952.) | |
479 | # | |
480 | # Files divided into blocks | |
481 | # 1 bit (last block flag) | |
482 | # 2 bits (block type) | |
483 | # | |
484 | # 1 block occurs every 32K -1 bytes or when there 50% compression | |
485 | # has been achieved. The smallest block type encoding is always used. | |
486 | # | |
487 | # stored: | |
488 | # 32 bits length in bytes. | |
489 | # | |
490 | # fixed: | |
491 | # magic fixed tree. | |
492 | # symbols. | |
493 | # | |
494 | # dynamic: | |
495 | # dynamic tree encoding. | |
496 | # symbols. | |
497 | # | |
498 | # | |
499 | # The buffer for decompression in place is the length of the uncompressed | |
500 | # data, plus a small amount extra to keep the algorithm safe. The | |
501 | # compressed data is placed at the end of the buffer. The output pointer | |
502 | # is placed at the start of the buffer and the input pointer is placed | |
503 | # where the compressed data starts. Problems will occur when the output | |
504 | # pointer overruns the input pointer. | |
505 | # | |
506 | # The output pointer can only overrun the input pointer if the input | |
507 | # pointer is moving faster than the output pointer. A condition only | |
508 | # triggered by data whose compressed form is larger than the uncompressed | |
509 | # form. | |
510 | # | |
511 | # The worst case at the block level is a growth of the compressed data | |
512 | # of 5 bytes per 32767 bytes. | |
513 | # | |
514 | # The worst case internal to a compressed block is very hard to figure. | |
515 | # The worst case can at least be bounded by having one bit that represents | |
516 | # 32764 bytes and then all of the rest of the bytes representing the very | |
517 | # very last byte. | |
518 | # | |
519 | # All of which is enough to compute an amount of extra data that is required | |
520 | # to be safe. To avoid problems at the block level allocating 5 extra bytes | |
521 | # per 32767 bytes of data is sufficient. To avoid problems internal to a | |
522 | # block adding an extra 32767 bytes (the worst case uncompressed block size) | |
523 | # is sufficient, to ensure that in the worst case the decompressed data for | |
524 | # block will stop the byte before the compressed data for a block begins. | |
525 | # To avoid problems with the compressed data's meta information an extra 18 | |
526 | # bytes are needed. Leading to the formula: | |
527 | # | |
d607251b | 528 | # extra_bytes = (uncompressed_size >> 12) + 32768 + 18 |
4252db10 BH |
529 | # |
530 | # Adding 8 bytes per 32K is a bit excessive but much easier to calculate. | |
531 | # Adding 32768 instead of 32767 just makes for round numbers. | |
4252db10 BH |
532 | # |
533 | # Above analysis is for decompressing gzip compressed kernel only. Up to | |
534 | # now 6 different decompressor are supported all together. And among them | |
535 | # xz stores data in chunks and has maximum chunk of 64K. Hence safety | |
536 | # margin should be updated to cover all decompressors so that we don't | |
537 | # need to deal with each of them separately. Please check | |
538 | # the description in lib/decompressor_xxx.c for specific information. | |
539 | # | |
540 | # extra_bytes = (uncompressed_size >> 12) + 65536 + 128 | |
5746f055 JS |
541 | # |
542 | # LZ4 is even worse: data that cannot be further compressed grows by 0.4%, | |
543 | # or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as | |
544 | # the size-dependent part now grows so fast. | |
545 | # | |
546 | # extra_bytes = (uncompressed_size >> 8) + 65536 | |
0fe4f4ef NT |
547 | # |
548 | # ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22 | |
549 | # byte fixed overhead but has a maximum block size of 128K, so it needs a | |
550 | # larger margin. | |
551 | # | |
552 | # extra_bytes = (uncompressed_size >> 8) + 131072 | |
4252db10 | 553 | |
0fe4f4ef | 554 | #define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072) |
d607251b YL |
555 | #if ZO_z_output_len > ZO_z_input_len |
556 | # define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \ | |
557 | ZO_z_input_len) | |
558 | #else | |
559 | # define ZO_z_extract_offset ZO_z_extra_bytes | |
560 | #endif | |
561 | ||
562 | /* | |
563 | * The extract_offset has to be bigger than ZO head section. Otherwise when | |
564 | * the head code is running to move ZO to the end of the buffer, it will | |
565 | * overwrite the head code itself. | |
566 | */ | |
567 | #if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset | |
568 | # define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095) | |
569 | #else | |
570 | # define ZO_z_min_extract_offset ((ZO_z_extract_offset + 4095) & ~4095) | |
571 | #endif | |
572 | ||
573 | #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset) | |
574 | ||
37ba7ab5 PA |
575 | #define VO_INIT_SIZE (VO__end - VO__text) |
576 | #if ZO_INIT_SIZE > VO_INIT_SIZE | |
d607251b | 577 | # define INIT_SIZE ZO_INIT_SIZE |
37ba7ab5 | 578 | #else |
d607251b | 579 | # define INIT_SIZE VO_INIT_SIZE |
37ba7ab5 | 580 | #endif |
d607251b | 581 | |
37ba7ab5 | 582 | init_size: .long INIT_SIZE # kernel initialization size |
86134a1b | 583 | handover_offset: .long 0 # Filled in by build.c |
2c33c27f | 584 | kernel_info_offset: .long 0 # Filled in by build.c |
37ba7ab5 | 585 | |
62607313 PA |
586 | # End of setup header ##################################################### |
587 | ||
7a734e7d | 588 | .section ".entrytext", "ax" |
62607313 | 589 | start_of_setup: |
62607313 PA |
590 | # Force %es = %ds |
591 | movw %ds, %ax | |
592 | movw %ax, %es | |
593 | cld | |
594 | ||
16252da6 JR |
595 | # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds, |
596 | # which happened to work by accident for the old code. Recalculate the stack | |
597 | # pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the | |
598 | # stack behind its own code, so we can't blindly put it directly past the heap. | |
6b6815c6 | 599 | |
6b6815c6 PA |
600 | movw %ss, %dx |
601 | cmpw %ax, %dx # %ds == %ss? | |
602 | movw %sp, %dx | |
16252da6 JR |
603 | je 2f # -> assume %sp is reasonably set |
604 | ||
605 | # Invalid %ss, make up a new stack | |
606 | movw $_end, %dx | |
607 | testb $CAN_USE_HEAP, loadflags | |
608 | jz 1f | |
609 | movw heap_end_ptr, %dx | |
610 | 1: addw $STACK_SIZE, %dx | |
611 | jnc 2f | |
612 | xorw %dx, %dx # Prevent wraparound | |
6b6815c6 | 613 | |
16252da6 | 614 | 2: # Now %dx should point to the end of our stack space |
6b6815c6 PA |
615 | andw $~3, %dx # dword align (might as well...) |
616 | jnz 3f | |
617 | movw $0xfffc, %dx # Make sure we're not zero | |
16252da6 | 618 | 3: movw %ax, %ss |
6b6815c6 PA |
619 | movzwl %dx, %esp # Clear upper half of %esp |
620 | sti # Now we should have a working stack | |
621 | ||
622 | # We will have entered with %cs = %ds+0x20, normalize %cs so | |
623 | # it is on par with the other segments. | |
624 | pushw %ds | |
625 | pushw $6f | |
626 | lretw | |
627 | 6: | |
62607313 PA |
628 | |
629 | # Check signature at end of setup | |
630 | cmpl $0x5a5aaa55, setup_sig | |
631 | jne setup_bad | |
632 | ||
633 | # Zero the bss | |
634 | movw $__bss_start, %di | |
635 | movw $_end+3, %cx | |
636 | xorl %eax, %eax | |
637 | subw %di, %cx | |
638 | shrw $2, %cx | |
639 | rep; stosl | |
640 | ||
641 | # Jump to C code (should not return) | |
642 | calll main | |
643 | ||
644 | # Setup corrupt somehow... | |
645 | setup_bad: | |
646 | movl $setup_corrupt, %eax | |
647 | calll puts | |
648 | # Fall through... | |
649 | ||
650 | .globl die | |
651 | .type die, @function | |
652 | die: | |
653 | hlt | |
654 | jmp die | |
655 | ||
bbc15f46 | 656 | .size die, .-die |
62607313 PA |
657 | |
658 | .section ".initdata", "a" | |
659 | setup_corrupt: | |
660 | .byte 7 | |
8b608d2f | 661 | .string "No setup signature found...\n" |