1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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 | */ |
18 | #include <linux/pe.h> |
19 | #include <asm/segment.h> |
20 | #include <asm/boot.h> |
21 | #include <asm/page_types.h> |
22 | #include <asm/setup.h> |
23 | #include <asm/bootparam.h> |
24 | #include "boot.h" |
25 | #include "voffset.h" |
26 | #include "zoffset.h" |
27 | |
28 | BOOTSEG = 0x07C0 /* original address of boot-sector */ |
29 | SYSSEG = 0x1000 /* historical load address >> 4 */ |
30 | |
31 | #ifndef SVGA_MODE |
32 | #define SVGA_MODE ASK_VGA |
33 | #endif |
34 | |
35 | #ifndef ROOT_RDONLY |
36 | #define ROOT_RDONLY 1 |
37 | #endif |
38 | |
39 | .set salign, 0x1000 |
40 | .set falign, 0x200 |
41 | |
42 | .code16 |
43 | .section ".bstext" , "ax" |
44 | #ifdef CONFIG_EFI_STUB |
45 | # "MZ", MS-DOS header |
46 | .word MZ_MAGIC |
47 | .org 0x38 |
48 | # |
49 | # Offset to the PE header. |
50 | # |
51 | .long LINUX_PE_MAGIC |
52 | .long pe_header |
53 | pe_header: |
54 | .long PE_MAGIC |
55 | |
56 | coff_header: |
57 | #ifdef CONFIG_X86_32 |
58 | .set image_file_add_flags, IMAGE_FILE_32BIT_MACHINE |
59 | .set pe_opt_magic, PE_OPT_MAGIC_PE32 |
60 | .word IMAGE_FILE_MACHINE_I386 |
61 | #else |
62 | .set image_file_add_flags, 0 |
63 | .set pe_opt_magic, PE_OPT_MAGIC_PE32PLUS |
64 | .word IMAGE_FILE_MACHINE_AMD64 |
65 | #endif |
66 | .word section_count # nr_sections |
67 | .long 0 # TimeDateStamp |
68 | .long 0 # PointerToSymbolTable |
69 | .long 1 # NumberOfSymbols |
70 | .word section_table - optional_header # SizeOfOptionalHeader |
71 | .word IMAGE_FILE_EXECUTABLE_IMAGE | \ |
72 | image_file_add_flags | \ |
73 | IMAGE_FILE_DEBUG_STRIPPED | \ |
74 | IMAGE_FILE_LINE_NUMS_STRIPPED # Characteristics |
75 | |
76 | optional_header: |
77 | .word pe_opt_magic |
78 | .byte 0x02 # MajorLinkerVersion |
79 | .byte 0x14 # MinorLinkerVersion |
80 | |
81 | .long ZO__data # SizeOfCode |
82 | |
83 | .long ZO__end - ZO__data # SizeOfInitializedData |
84 | .long 0 # SizeOfUninitializedData |
85 | |
86 | .long setup_size + ZO_efi_pe_entry # AddressOfEntryPoint |
87 | |
88 | .long setup_size # BaseOfCode |
89 | #ifdef CONFIG_X86_32 |
90 | .long 0 # data |
91 | #endif |
92 | |
93 | extra_header_fields: |
94 | #ifdef CONFIG_X86_32 |
95 | .long 0 # ImageBase |
96 | #else |
97 | .quad 0 # ImageBase |
98 | #endif |
99 | .long salign # SectionAlignment |
100 | .long falign # FileAlignment |
101 | .word 0 # MajorOperatingSystemVersion |
102 | .word 0 # MinorOperatingSystemVersion |
103 | .word LINUX_EFISTUB_MAJOR_VERSION # MajorImageVersion |
104 | .word LINUX_EFISTUB_MINOR_VERSION # MinorImageVersion |
105 | .word 0 # MajorSubsystemVersion |
106 | .word 0 # MinorSubsystemVersion |
107 | .long 0 # Win32VersionValue |
108 | |
109 | .long setup_size + ZO__end + pecompat_vsize |
110 | # SizeOfImage |
111 | |
112 | .long salign # SizeOfHeaders |
113 | .long 0 # CheckSum |
114 | .word IMAGE_SUBSYSTEM_EFI_APPLICATION # Subsystem (EFI application) |
115 | #ifdef CONFIG_EFI_DXE_MEM_ATTRIBUTES |
116 | .word IMAGE_DLL_CHARACTERISTICS_NX_COMPAT # DllCharacteristics |
117 | #else |
118 | .word 0 # DllCharacteristics |
119 | #endif |
120 | #ifdef CONFIG_X86_32 |
121 | .long 0 # SizeOfStackReserve |
122 | .long 0 # SizeOfStackCommit |
123 | .long 0 # SizeOfHeapReserve |
124 | .long 0 # SizeOfHeapCommit |
125 | #else |
126 | .quad 0 # SizeOfStackReserve |
127 | .quad 0 # SizeOfStackCommit |
128 | .quad 0 # SizeOfHeapReserve |
129 | .quad 0 # SizeOfHeapCommit |
130 | #endif |
131 | .long 0 # LoaderFlags |
132 | .long (section_table - .) / 8 # NumberOfRvaAndSizes |
133 | |
134 | .quad 0 # ExportTable |
135 | .quad 0 # ImportTable |
136 | .quad 0 # ResourceTable |
137 | .quad 0 # ExceptionTable |
138 | .quad 0 # CertificationTable |
139 | .quad 0 # BaseRelocationTable |
140 | |
141 | # Section table |
142 | section_table: |
143 | .ascii ".setup" |
144 | .byte 0 |
145 | .byte 0 |
146 | .long setup_size - salign # VirtualSize |
147 | .long salign # VirtualAddress |
148 | .long pecompat_fstart - salign # SizeOfRawData |
149 | .long salign # PointerToRawData |
150 | |
151 | .long 0, 0, 0 |
152 | .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ |
153 | IMAGE_SCN_MEM_READ | \ |
154 | IMAGE_SCN_MEM_DISCARDABLE # Characteristics |
155 | |
156 | #ifdef CONFIG_EFI_MIXED |
157 | .asciz ".compat" |
158 | |
159 | .long 8 # VirtualSize |
160 | .long setup_size + ZO__end # VirtualAddress |
161 | .long pecompat_fsize # SizeOfRawData |
162 | .long pecompat_fstart # PointerToRawData |
163 | |
164 | .long 0, 0, 0 |
165 | .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ |
166 | IMAGE_SCN_MEM_READ | \ |
167 | IMAGE_SCN_MEM_DISCARDABLE # Characteristics |
168 | |
169 | /* |
170 | * Put the IA-32 machine type and the associated entry point address in |
171 | * the .compat section, so loaders can figure out which other execution |
172 | * modes this image supports. |
173 | */ |
174 | .pushsection ".pecompat" , "a" , @progbits |
175 | .balign falign |
176 | .set pecompat_vsize, salign |
177 | .globl pecompat_fstart |
178 | pecompat_fstart: |
179 | .byte 0x1 # Version |
180 | .byte 8 # Size |
181 | .word IMAGE_FILE_MACHINE_I386 # PE machine type |
182 | .long setup_size + ZO_efi32_pe_entry # Entrypoint |
183 | .popsection |
184 | #else |
185 | .set pecompat_vsize, 0 |
186 | .set pecompat_fstart, setup_size |
187 | #endif |
188 | .ascii ".text" |
189 | .byte 0 |
190 | .byte 0 |
191 | .byte 0 |
192 | .long ZO__data |
193 | .long setup_size |
194 | .long ZO__data # Size of initialized data |
195 | # on disk |
196 | .long setup_size |
197 | .long 0 # PointerToRelocations |
198 | .long 0 # PointerToLineNumbers |
199 | .word 0 # NumberOfRelocations |
200 | .word 0 # NumberOfLineNumbers |
201 | .long IMAGE_SCN_CNT_CODE | \ |
202 | IMAGE_SCN_MEM_READ | \ |
203 | IMAGE_SCN_MEM_EXECUTE # Characteristics |
204 | |
205 | .ascii ".data\0\0\0" |
206 | .long ZO__end - ZO__data # VirtualSize |
207 | .long setup_size + ZO__data # VirtualAddress |
208 | .long ZO__edata - ZO__data # SizeOfRawData |
209 | .long setup_size + ZO__data # PointerToRawData |
210 | |
211 | .long 0, 0, 0 |
212 | .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ |
213 | IMAGE_SCN_MEM_READ | \ |
214 | IMAGE_SCN_MEM_WRITE # Characteristics |
215 | |
216 | .set section_count, (. - section_table) / 40 |
217 | #endif /* CONFIG_EFI_STUB */ |
218 | |
219 | # Kernel attributes; used by setup. This is part 1 of the |
220 | # header, from the old boot sector. |
221 | |
222 | .section ".header" , "a" |
223 | .globl sentinel |
224 | sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */ |
225 | |
226 | .globl hdr |
227 | hdr: |
228 | .byte setup_sects - 1 |
229 | root_flags: .word ROOT_RDONLY |
230 | syssize: .long ZO__edata / 16 |
231 | ram_size: .word 0 /* Obsolete */ |
232 | vid_mode: .word SVGA_MODE |
233 | root_dev: .word 0 /* Default to major/minor 0/0 */ |
234 | boot_flag: .word 0xAA55 |
235 | |
236 | # offset 512, entry point |
237 | |
238 | .globl _start |
239 | _start: |
240 | # Explicitly enter this as bytes, or the assembler |
241 | # tries to generate a 3-byte jump here, which causes |
242 | # everything else to push off to the wrong offset. |
243 | .byte 0xeb # short (2-byte) jump |
244 | .byte start_of_setup-1f |
245 | 1: |
246 | |
247 | # Part 2 of the header, from the old setup.S |
248 | |
249 | .ascii "HdrS" # header signature |
250 | .word 0x020f # header version number (>= 0x0105) |
251 | # or else old loadlin-1.5 will fail) |
252 | .globl realmode_swtch |
253 | realmode_swtch: .word 0, 0 # default_switch, SETUPSEG |
254 | start_sys_seg: .word SYSSEG # obsolete and meaningless, but just |
255 | # in case something decided to "use" it |
256 | .word kernel_version-512 # pointing to kernel version string |
257 | # above section of header is compatible |
258 | # with loadlin-1.5 (header v1.5). Don't |
259 | # change it. |
260 | |
261 | type_of_loader: .byte 0 # 0 means ancient bootloader, newer |
262 | # bootloaders know to change this. |
263 | # See Documentation/arch/x86/boot.rst for |
264 | # assigned ids |
265 | |
266 | # flags, unused bits must be zero (RFU) bit within loadflags |
267 | loadflags: |
268 | .byte LOADED_HIGH # The kernel is to be loaded high |
269 | |
270 | setup_move_size: .word 0x8000 # size to move, when setup is not |
271 | # loaded at 0x90000. We will move setup |
272 | # to 0x90000 then just before jumping |
273 | # into the kernel. However, only the |
274 | # loader knows how much data behind |
275 | # us also needs to be loaded. |
276 | |
277 | code32_start: # here loaders can put a different |
278 | # start address for 32-bit code. |
279 | .long 0x100000 # 0x100000 = default for big kernel |
280 | |
281 | ramdisk_image: .long 0 # address of loaded ramdisk image |
282 | # Here the loader puts the 32-bit |
283 | # address where it loaded the image. |
284 | # This only will be read by the kernel. |
285 | |
286 | ramdisk_size: .long 0 # its size in bytes |
287 | |
288 | bootsect_kludge: |
289 | .long 0 # obsolete |
290 | |
291 | heap_end_ptr: .word _end+STACK_SIZE-512 |
292 | # (Header version 0x0201 or later) |
293 | # space from here (exclusive) down to |
294 | # end of setup code can be used by setup |
295 | # for local heap purposes. |
296 | |
297 | ext_loader_ver: |
298 | .byte 0 # Extended boot loader version |
299 | ext_loader_type: |
300 | .byte 0 # Extended boot loader type |
301 | |
302 | cmd_line_ptr: .long 0 # (Header version 0x0202 or later) |
303 | # If nonzero, a 32-bit pointer |
304 | # to the kernel command line. |
305 | # The command line should be |
306 | # located between the start of |
307 | # setup and the end of low |
308 | # memory (0xa0000), or it may |
309 | # get overwritten before it |
310 | # gets read. If this field is |
311 | # used, there is no longer |
312 | # anything magical about the |
313 | # 0x90000 segment; the setup |
314 | # can be located anywhere in |
315 | # low memory 0x10000 or higher. |
316 | |
317 | initrd_addr_max: .long 0x7fffffff |
318 | # (Header version 0x0203 or later) |
319 | # The highest safe address for |
320 | # the contents of an initrd |
321 | # The current kernel allows up to 4 GB, |
322 | # but leave it at 2 GB to avoid |
323 | # possible bootloader bugs. |
324 | |
325 | kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment |
326 | #required for protected mode |
327 | #kernel |
328 | #ifdef CONFIG_RELOCATABLE |
329 | relocatable_kernel: .byte 1 |
330 | #else |
331 | relocatable_kernel: .byte 0 |
332 | #endif |
333 | min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment |
334 | |
335 | xloadflags: |
336 | #ifdef CONFIG_X86_64 |
337 | # define XLF0 XLF_KERNEL_64 /* 64-bit kernel */ |
338 | #else |
339 | # define XLF0 0 |
340 | #endif |
341 | |
342 | #if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64) |
343 | /* kernel/boot_param/ramdisk could be loaded above 4g */ |
344 | # define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G |
345 | #else |
346 | # define XLF1 0 |
347 | #endif |
348 | |
349 | #ifdef CONFIG_EFI_HANDOVER_PROTOCOL |
350 | # ifdef CONFIG_EFI_MIXED |
351 | # define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64) |
352 | # else |
353 | # ifdef CONFIG_X86_64 |
354 | # define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */ |
355 | # else |
356 | # define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */ |
357 | # endif |
358 | # endif |
359 | #else |
360 | # define XLF23 0 |
361 | #endif |
362 | |
363 | #if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE) |
364 | # define XLF4 XLF_EFI_KEXEC |
365 | #else |
366 | # define XLF4 0 |
367 | #endif |
368 | |
369 | #ifdef CONFIG_X86_64 |
370 | #ifdef CONFIG_X86_5LEVEL |
371 | #define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED) |
372 | #else |
373 | #define XLF56 XLF_5LEVEL |
374 | #endif |
375 | #else |
376 | #define XLF56 0 |
377 | #endif |
378 | |
379 | .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56 |
380 | |
381 | cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, |
382 | #added with boot protocol |
383 | #version 2.06 |
384 | |
385 | hardware_subarch: .long 0 # subarchitecture, added with 2.07 |
386 | # default to 0 for normal x86 PC |
387 | |
388 | hardware_subarch_data: .quad 0 |
389 | |
390 | payload_offset: .long ZO_input_data |
391 | payload_length: .long ZO_z_input_len |
392 | |
393 | setup_data: .quad 0 # 64-bit physical pointer to |
394 | # single linked list of |
395 | # struct setup_data |
396 | |
397 | pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr |
398 | |
399 | # |
400 | # Getting to provably safe in-place decompression is hard. Worst case |
401 | # behaviours need to be analyzed. Here let's take the decompression of |
402 | # a gzip-compressed kernel as example, to illustrate it: |
403 | # |
404 | # The file layout of gzip compressed kernel is: |
405 | # |
406 | # magic[2] |
407 | # method[1] |
408 | # flags[1] |
409 | # timestamp[4] |
410 | # extraflags[1] |
411 | # os[1] |
412 | # compressed data blocks[N] |
413 | # crc[4] orig_len[4] |
414 | # |
415 | # ... resulting in +18 bytes overhead of uncompressed data. |
416 | # |
417 | # (For more information, please refer to RFC 1951 and RFC 1952.) |
418 | # |
419 | # Files divided into blocks |
420 | # 1 bit (last block flag) |
421 | # 2 bits (block type) |
422 | # |
423 | # 1 block occurs every 32K -1 bytes or when there 50% compression |
424 | # has been achieved. The smallest block type encoding is always used. |
425 | # |
426 | # stored: |
427 | # 32 bits length in bytes. |
428 | # |
429 | # fixed: |
430 | # magic fixed tree. |
431 | # symbols. |
432 | # |
433 | # dynamic: |
434 | # dynamic tree encoding. |
435 | # symbols. |
436 | # |
437 | # |
438 | # The buffer for decompression in place is the length of the uncompressed |
439 | # data, plus a small amount extra to keep the algorithm safe. The |
440 | # compressed data is placed at the end of the buffer. The output pointer |
441 | # is placed at the start of the buffer and the input pointer is placed |
442 | # where the compressed data starts. Problems will occur when the output |
443 | # pointer overruns the input pointer. |
444 | # |
445 | # The output pointer can only overrun the input pointer if the input |
446 | # pointer is moving faster than the output pointer. A condition only |
447 | # triggered by data whose compressed form is larger than the uncompressed |
448 | # form. |
449 | # |
450 | # The worst case at the block level is a growth of the compressed data |
451 | # of 5 bytes per 32767 bytes. |
452 | # |
453 | # The worst case internal to a compressed block is very hard to figure. |
454 | # The worst case can at least be bounded by having one bit that represents |
455 | # 32764 bytes and then all of the rest of the bytes representing the very |
456 | # very last byte. |
457 | # |
458 | # All of which is enough to compute an amount of extra data that is required |
459 | # to be safe. To avoid problems at the block level allocating 5 extra bytes |
460 | # per 32767 bytes of data is sufficient. To avoid problems internal to a |
461 | # block adding an extra 32767 bytes (the worst case uncompressed block size) |
462 | # is sufficient, to ensure that in the worst case the decompressed data for |
463 | # block will stop the byte before the compressed data for a block begins. |
464 | # To avoid problems with the compressed data's meta information an extra 18 |
465 | # bytes are needed. Leading to the formula: |
466 | # |
467 | # extra_bytes = (uncompressed_size >> 12) + 32768 + 18 |
468 | # |
469 | # Adding 8 bytes per 32K is a bit excessive but much easier to calculate. |
470 | # Adding 32768 instead of 32767 just makes for round numbers. |
471 | # |
472 | # Above analysis is for decompressing gzip compressed kernel only. Up to |
473 | # now 6 different decompressor are supported all together. And among them |
474 | # xz stores data in chunks and has maximum chunk of 64K. Hence safety |
475 | # margin should be updated to cover all decompressors so that we don't |
476 | # need to deal with each of them separately. Please check |
477 | # the description in lib/decompressor_xxx.c for specific information. |
478 | # |
479 | # extra_bytes = (uncompressed_size >> 12) + 65536 + 128 |
480 | # |
481 | # LZ4 is even worse: data that cannot be further compressed grows by 0.4%, |
482 | # or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as |
483 | # the size-dependent part now grows so fast. |
484 | # |
485 | # extra_bytes = (uncompressed_size >> 8) + 65536 |
486 | # |
487 | # ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22 |
488 | # byte fixed overhead but has a maximum block size of 128K, so it needs a |
489 | # larger margin. |
490 | # |
491 | # extra_bytes = (uncompressed_size >> 8) + 131072 |
492 | |
493 | #define ((ZO_z_output_len >> 8) + 131072) |
494 | #if ZO_z_output_len > ZO_z_input_len |
495 | # define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \ |
496 | ZO_z_input_len) |
497 | #else |
498 | # define ZO_z_extra_bytes |
499 | #endif |
500 | |
501 | /* |
502 | * The extract_offset has to be bigger than ZO head section. Otherwise when |
503 | * the head code is running to move ZO to the end of the buffer, it will |
504 | * overwrite the head code itself. |
505 | */ |
506 | #if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset |
507 | # define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095) |
508 | #else |
509 | # define ((ZO_z_extract_offset + 4095) & ~4095) |
510 | #endif |
511 | |
512 | #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset) |
513 | |
514 | #define VO_INIT_SIZE (VO__end - VO__text) |
515 | #if ZO_INIT_SIZE > VO_INIT_SIZE |
516 | # define INIT_SIZE ZO_INIT_SIZE |
517 | #else |
518 | # define INIT_SIZE VO_INIT_SIZE |
519 | #endif |
520 | |
521 | .macro __handover_offset |
522 | #ifndef CONFIG_EFI_HANDOVER_PROTOCOL |
523 | .long 0 |
524 | #elif !defined(CONFIG_X86_64) |
525 | .long ZO_efi32_stub_entry |
526 | #else |
527 | /* Yes, this is really how we defined it :( */ |
528 | .long ZO_efi64_stub_entry - 0x200 |
529 | #ifdef CONFIG_EFI_MIXED |
530 | .if ZO_efi32_stub_entry != ZO_efi64_stub_entry - 0x200 |
531 | .error "32-bit and 64-bit EFI entry points do not match" |
532 | .endif |
533 | #endif |
534 | #endif |
535 | .endm |
536 | |
537 | init_size: .long INIT_SIZE # kernel initialization size |
538 | handover_offset: __handover_offset |
539 | kernel_info_offset: .long ZO_kernel_info |
540 | |
541 | # End of setup header ##################################################### |
542 | |
543 | .section ".entrytext" , "ax" |
544 | start_of_setup: |
545 | # Force %es = %ds |
546 | movw %ds, %ax |
547 | movw %ax, %es |
548 | cld |
549 | |
550 | # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds, |
551 | # which happened to work by accident for the old code. Recalculate the stack |
552 | # pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the |
553 | # stack behind its own code, so we can't blindly put it directly past the heap. |
554 | |
555 | movw %ss, %dx |
556 | cmpw %ax, %dx # %ds == %ss? |
557 | movw %sp, %dx |
558 | je 2f # -> assume %sp is reasonably set |
559 | |
560 | # Invalid %ss, make up a new stack |
561 | movw $_end, %dx |
562 | testb $CAN_USE_HEAP, loadflags |
563 | jz 1f |
564 | movw heap_end_ptr, %dx |
565 | 1: addw $STACK_SIZE, %dx |
566 | jnc 2f |
567 | xorw %dx, %dx # Prevent wraparound |
568 | |
569 | 2: # Now %dx should point to the end of our stack space |
570 | andw $~3, %dx # dword align (might as well...) |
571 | jnz 3f |
572 | movw $0xfffc, %dx # Make sure we're not zero |
573 | 3: movw %ax, %ss |
574 | movzwl %dx, %esp # Clear upper half of %esp |
575 | sti # Now we should have a working stack |
576 | |
577 | # We will have entered with %cs = %ds+0x20, normalize %cs so |
578 | # it is on par with the other segments. |
579 | pushw %ds |
580 | pushw $6f |
581 | lretw |
582 | 6: |
583 | |
584 | # Check signature at end of setup |
585 | cmpl $0x5a5aaa55, setup_sig |
586 | jne setup_bad |
587 | |
588 | # Zero the bss |
589 | movw $__bss_start, %di |
590 | movw $_end+3, %cx |
591 | xorl %eax, %eax |
592 | subw %di, %cx |
593 | shrw $2, %cx |
594 | rep; stosl |
595 | |
596 | # Jump to C code (should not return) |
597 | calll main |
598 | |
599 | # Setup corrupt somehow... |
600 | setup_bad: |
601 | movl $setup_corrupt, %eax |
602 | calll puts |
603 | # Fall through... |
604 | |
605 | .globl die |
606 | .type die, @function |
607 | die: |
608 | hlt |
609 | jmp die |
610 | |
611 | .size die, .-die |
612 | |
613 | .section ".initdata" , "a" |
614 | setup_corrupt: |
615 | .byte 7 |
616 | .string "No setup signature found...\n" |
617 | |