| blob | b5c79f43359bcde2c4c3c5ed796e8780f7979774 |
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"
28 BOOTSEG = 0x07C0 /* original address of boot-sector */
29 SYSSEG = 0x1000 /* historical load address >> 4 */
31 #ifndef SVGA_MODE
32 #define SVGA_MODE ASK_VGA
33 #endif
35 #ifndef ROOT_RDONLY
36 #define ROOT_RDONLY 1
37 #endif
39 .set salign, 0x1000
40 .set falign, 0x200
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
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
76 optional_header:
77 .word pe_opt_magic
78 .byte 0x02 # MajorLinkerVersion
79 .byte 0x14 # MinorLinkerVersion
81 .long ZO__data # SizeOfCode
83 .long ZO__end - ZO__data # SizeOfInitializedData
84 .long 0 # SizeOfUninitializedData
86 .long setup_size + ZO_efi_pe_entry # AddressOfEntryPoint
88 .long setup_size # BaseOfCode
89 #ifdef CONFIG_X86_32
90 .long 0 # data
91 #endif
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
109 .long setup_size + ZO__end # SizeOfImage
111 .long salign # SizeOfHeaders
112 .long 0 # CheckSum
113 .word IMAGE_SUBSYSTEM_EFI_APPLICATION # Subsystem (EFI application)
114 .word IMAGE_DLL_CHARACTERISTICS_NX_COMPAT # DllCharacteristics
115 #ifdef CONFIG_X86_32
116 .long 0 # SizeOfStackReserve
117 .long 0 # SizeOfStackCommit
118 .long 0 # SizeOfHeapReserve
119 .long 0 # SizeOfHeapCommit
120 #else
121 .quad 0 # SizeOfStackReserve
122 .quad 0 # SizeOfStackCommit
123 .quad 0 # SizeOfHeapReserve
124 .quad 0 # SizeOfHeapCommit
125 #endif
126 .long 0 # LoaderFlags
127 .long (section_table - .) / 8 # NumberOfRvaAndSizes
129 .quad 0 # ExportTable
130 .quad 0 # ImportTable
131 .quad 0 # ResourceTable
132 .quad 0 # ExceptionTable
133 .quad 0 # CertificationTable
134 .quad 0 # BaseRelocationTable
136 # Section table
137 section_table:
138 .ascii ".setup"
139 .byte 0
140 .byte 0
141 .long pecompat_fstart - salign # VirtualSize
142 .long salign # VirtualAddress
143 .long pecompat_fstart - salign # SizeOfRawData
144 .long salign # PointerToRawData
146 .long 0, 0, 0
147 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
148 IMAGE_SCN_MEM_READ | \
149 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
151 #ifdef CONFIG_EFI_MIXED
152 .asciz ".compat"
154 .long pecompat_fsize # VirtualSize
155 .long pecompat_fstart # VirtualAddress
156 .long pecompat_fsize # SizeOfRawData
157 .long pecompat_fstart # PointerToRawData
159 .long 0, 0, 0
160 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
161 IMAGE_SCN_MEM_READ | \
162 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
164 /*
165 * Put the IA-32 machine type and the associated entry point address in
166 * the .compat section, so loaders can figure out which other execution
167 * modes this image supports.
168 */
169 .pushsection ".pecompat", "a", @progbits
170 .balign salign
171 .globl pecompat_fstart
172 pecompat_fstart:
173 .byte 0x1 # Version
174 .byte 8 # Size
175 .word IMAGE_FILE_MACHINE_I386 # PE machine type
176 .long setup_size + ZO_efi32_pe_entry # Entrypoint
177 .byte 0x0 # Sentinel
178 .popsection
179 #else
180 .set pecompat_fstart, setup_size
181 #endif
182 .ascii ".text"
183 .byte 0
184 .byte 0
185 .byte 0
186 .long ZO__data
187 .long setup_size
188 .long ZO__data # Size of initialized data
189 # on disk
190 .long setup_size
191 .long 0 # PointerToRelocations
192 .long 0 # PointerToLineNumbers
193 .word 0 # NumberOfRelocations
194 .word 0 # NumberOfLineNumbers
195 .long IMAGE_SCN_CNT_CODE | \
196 IMAGE_SCN_MEM_READ | \
197 IMAGE_SCN_MEM_EXECUTE # Characteristics
199 .ascii ".data\0\0\0"
200 .long ZO__end - ZO__data # VirtualSize
201 .long setup_size + ZO__data # VirtualAddress
202 .long ZO__edata - ZO__data # SizeOfRawData
203 .long setup_size + ZO__data # PointerToRawData
205 .long 0, 0, 0
206 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
207 IMAGE_SCN_MEM_READ | \
208 IMAGE_SCN_MEM_WRITE # Characteristics
210 .set section_count, (. - section_table) / 40
211 #endif /* CONFIG_EFI_STUB */
213 # Kernel attributes; used by setup. This is part 1 of the
214 # header, from the old boot sector.
216 .section ".header", "a"
217 .globl sentinel
218 sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */
220 .globl hdr
221 hdr:
222 .byte setup_sects - 1
223 root_flags: .word ROOT_RDONLY
224 syssize: .long ZO__edata / 16
225 ram_size: .word 0 /* Obsolete */
226 vid_mode: .word SVGA_MODE
227 root_dev: .word 0 /* Default to major/minor 0/0 */
228 boot_flag: .word 0xAA55
230 # offset 512, entry point
232 .globl _start
233 _start:
234 # Explicitly enter this as bytes, or the assembler
235 # tries to generate a 3-byte jump here, which causes
236 # everything else to push off to the wrong offset.
237 .byte 0xeb # short (2-byte) jump
238 .byte start_of_setup-1f
239 1:
241 # Part 2 of the header, from the old setup.S
243 .ascii "HdrS" # header signature
244 .word 0x020f # header version number (>= 0x0105)
245 # or else old loadlin-1.5 will fail)
246 .globl realmode_swtch
247 realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
248 start_sys_seg: .word SYSSEG # obsolete and meaningless, but just
249 # in case something decided to "use" it
250 .word kernel_version-512 # pointing to kernel version string
251 # above section of header is compatible
252 # with loadlin-1.5 (header v1.5). Don't
253 # change it.
255 type_of_loader: .byte 0 # 0 means ancient bootloader, newer
256 # bootloaders know to change this.
257 # See Documentation/arch/x86/boot.rst for
258 # assigned ids
260 # flags, unused bits must be zero (RFU) bit within loadflags
261 loadflags:
262 .byte LOADED_HIGH # The kernel is to be loaded high
264 setup_move_size: .word 0x8000 # size to move, when setup is not
265 # loaded at 0x90000. We will move setup
266 # to 0x90000 then just before jumping
267 # into the kernel. However, only the
268 # loader knows how much data behind
269 # us also needs to be loaded.
271 code32_start: # here loaders can put a different
272 # start address for 32-bit code.
273 .long 0x100000 # 0x100000 = default for big kernel
275 ramdisk_image: .long 0 # address of loaded ramdisk image
276 # Here the loader puts the 32-bit
277 # address where it loaded the image.
278 # This only will be read by the kernel.
280 ramdisk_size: .long 0 # its size in bytes
282 bootsect_kludge:
283 .long 0 # obsolete
285 heap_end_ptr: .word _end+STACK_SIZE-512
286 # (Header version 0x0201 or later)
287 # space from here (exclusive) down to
288 # end of setup code can be used by setup
289 # for local heap purposes.
291 ext_loader_ver:
292 .byte 0 # Extended boot loader version
293 ext_loader_type:
294 .byte 0 # Extended boot loader type
296 cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
297 # If nonzero, a 32-bit pointer
298 # to the kernel command line.
299 # The command line should be
300 # located between the start of
301 # setup and the end of low
302 # memory (0xa0000), or it may
303 # get overwritten before it
304 # gets read. If this field is
305 # used, there is no longer
306 # anything magical about the
307 # 0x90000 segment; the setup
308 # can be located anywhere in
309 # low memory 0x10000 or higher.
311 initrd_addr_max: .long 0x7fffffff
312 # (Header version 0x0203 or later)
313 # The highest safe address for
314 # the contents of an initrd
315 # The current kernel allows up to 4 GB,
316 # but leave it at 2 GB to avoid
317 # possible bootloader bugs.
319 kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
320 #required for protected mode
321 #kernel
322 #ifdef CONFIG_RELOCATABLE
323 relocatable_kernel: .byte 1
324 #else
325 relocatable_kernel: .byte 0
326 #endif
327 min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
329 xloadflags:
330 #ifdef CONFIG_X86_64
331 # define XLF0 XLF_KERNEL_64 /* 64-bit kernel */
332 #else
333 # define XLF0 0
334 #endif
336 #if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64)
337 /* kernel/boot_param/ramdisk could be loaded above 4g */
338 # define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G
339 #else
340 # define XLF1 0
341 #endif
343 #ifdef CONFIG_EFI_HANDOVER_PROTOCOL
344 # ifdef CONFIG_EFI_MIXED
345 # define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64)
346 # else
347 # ifdef CONFIG_X86_64
348 # define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */
349 # else
350 # define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */
351 # endif
352 # endif
353 #else
354 # define XLF23 0
355 #endif
357 #if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE)
358 # define XLF4 XLF_EFI_KEXEC
359 #else
360 # define XLF4 0
361 #endif
363 #ifdef CONFIG_X86_64
364 #ifdef CONFIG_X86_5LEVEL
365 #define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED)
366 #else
367 #define XLF56 XLF_5LEVEL
368 #endif
369 #else
370 #define XLF56 0
371 #endif
373 .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56
375 cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
376 #added with boot protocol
377 #version 2.06
379 hardware_subarch: .long 0 # subarchitecture, added with 2.07
380 # default to 0 for normal x86 PC
382 hardware_subarch_data: .quad 0
384 payload_offset: .long ZO_input_data
385 payload_length: .long ZO_z_input_len
387 setup_data: .quad 0 # 64-bit physical pointer to
388 # single linked list of
389 # struct setup_data
391 pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
393 #
394 # Getting to provably safe in-place decompression is hard. Worst case
395 # behaviours need to be analyzed. Here let's take the decompression of
396 # a gzip-compressed kernel as example, to illustrate it:
397 #
398 # The file layout of gzip compressed kernel is:
399 #
400 # magic[2]
401 # method[1]
402 # flags[1]
403 # timestamp[4]
404 # extraflags[1]
405 # os[1]
406 # compressed data blocks[N]
407 # crc[4] orig_len[4]
408 #
409 # ... resulting in +18 bytes overhead of uncompressed data.
410 #
411 # (For more information, please refer to RFC 1951 and RFC 1952.)
412 #
413 # Files divided into blocks
414 # 1 bit (last block flag)
415 # 2 bits (block type)
416 #
417 # 1 block occurs every 32K -1 bytes or when there 50% compression
418 # has been achieved. The smallest block type encoding is always used.
419 #
420 # stored:
421 # 32 bits length in bytes.
422 #
423 # fixed:
424 # magic fixed tree.
425 # symbols.
426 #
427 # dynamic:
428 # dynamic tree encoding.
429 # symbols.
430 #
431 #
432 # The buffer for decompression in place is the length of the uncompressed
433 # data, plus a small amount extra to keep the algorithm safe. The
434 # compressed data is placed at the end of the buffer. The output pointer
435 # is placed at the start of the buffer and the input pointer is placed
436 # where the compressed data starts. Problems will occur when the output
437 # pointer overruns the input pointer.
438 #
439 # The output pointer can only overrun the input pointer if the input
440 # pointer is moving faster than the output pointer. A condition only
441 # triggered by data whose compressed form is larger than the uncompressed
442 # form.
443 #
444 # The worst case at the block level is a growth of the compressed data
445 # of 5 bytes per 32767 bytes.
446 #
447 # The worst case internal to a compressed block is very hard to figure.
448 # The worst case can at least be bounded by having one bit that represents
449 # 32764 bytes and then all of the rest of the bytes representing the very
450 # very last byte.
451 #
452 # All of which is enough to compute an amount of extra data that is required
453 # to be safe. To avoid problems at the block level allocating 5 extra bytes
454 # per 32767 bytes of data is sufficient. To avoid problems internal to a
455 # block adding an extra 32767 bytes (the worst case uncompressed block size)
456 # is sufficient, to ensure that in the worst case the decompressed data for
457 # block will stop the byte before the compressed data for a block begins.
458 # To avoid problems with the compressed data's meta information an extra 18
459 # bytes are needed. Leading to the formula:
460 #
461 # extra_bytes = (uncompressed_size >> 12) + 32768 + 18
462 #
463 # Adding 8 bytes per 32K is a bit excessive but much easier to calculate.
464 # Adding 32768 instead of 32767 just makes for round numbers.
465 #
466 # Above analysis is for decompressing gzip compressed kernel only. Up to
467 # now 6 different decompressor are supported all together. And among them
468 # xz stores data in chunks and has maximum chunk of 64K. Hence safety
469 # margin should be updated to cover all decompressors so that we don't
470 # need to deal with each of them separately. Please check
471 # the description in lib/decompressor_xxx.c for specific information.
472 #
473 # extra_bytes = (uncompressed_size >> 12) + 65536 + 128
474 #
475 # LZ4 is even worse: data that cannot be further compressed grows by 0.4%,
476 # or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as
477 # the size-dependent part now grows so fast.
478 #
479 # extra_bytes = (uncompressed_size >> 8) + 65536
480 #
481 # ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22
482 # byte fixed overhead but has a maximum block size of 128K, so it needs a
483 # larger margin.
484 #
485 # extra_bytes = (uncompressed_size >> 8) + 131072
487 #define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072)
488 #if ZO_z_output_len > ZO_z_input_len
489 # define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \
490 ZO_z_input_len)
491 #else
492 # define ZO_z_extract_offset ZO_z_extra_bytes
493 #endif
495 /*
496 * The extract_offset has to be bigger than ZO head section. Otherwise when
497 * the head code is running to move ZO to the end of the buffer, it will
498 * overwrite the head code itself.
499 */
500 #if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset
501 # define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095)
502 #else
503 # define ZO_z_min_extract_offset ((ZO_z_extract_offset + 4095) & ~4095)
504 #endif
506 #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset)
508 #define VO_INIT_SIZE (VO__end - VO__text)
509 #if ZO_INIT_SIZE > VO_INIT_SIZE
510 # define INIT_SIZE ZO_INIT_SIZE
511 #else
512 # define INIT_SIZE VO_INIT_SIZE
513 #endif
515 .macro __handover_offset
516 #ifndef CONFIG_EFI_HANDOVER_PROTOCOL
517 .long 0
518 #elif !defined(CONFIG_X86_64)
519 .long ZO_efi32_stub_entry
520 #else
521 /* Yes, this is really how we defined it :( */
522 .long ZO_efi64_stub_entry - 0x200
523 #ifdef CONFIG_EFI_MIXED
524 .if ZO_efi32_stub_entry != ZO_efi64_stub_entry - 0x200
525 .error "32-bit and 64-bit EFI entry points do not match"
526 .endif
527 #endif
528 #endif
529 .endm
531 init_size: .long INIT_SIZE # kernel initialization size
532 handover_offset: __handover_offset
533 kernel_info_offset: .long ZO_kernel_info
535 # End of setup header #####################################################
537 .section ".entrytext", "ax"
538 start_of_setup:
539 # Force %es = %ds
540 movw %ds, %ax
541 movw %ax, %es
542 cld
544 # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
545 # which happened to work by accident for the old code. Recalculate the stack
546 # pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
547 # stack behind its own code, so we can't blindly put it directly past the heap.
549 movw %ss, %dx
550 cmpw %ax, %dx # %ds == %ss?
551 movw %sp, %dx
552 je 2f # -> assume %sp is reasonably set
554 # Invalid %ss, make up a new stack
555 movw $_end, %dx
556 testb $CAN_USE_HEAP, loadflags
557 jz 1f
558 movw heap_end_ptr, %dx
559 1: addw $STACK_SIZE, %dx
560 jnc 2f
561 xorw %dx, %dx # Prevent wraparound
563 2: # Now %dx should point to the end of our stack space
564 andw $~3, %dx # dword align (might as well...)
565 jnz 3f
566 movw $0xfffc, %dx # Make sure we're not zero
567 3: movw %ax, %ss
568 movzwl %dx, %esp # Clear upper half of %esp
569 sti # Now we should have a working stack
571 # We will have entered with %cs = %ds+0x20, normalize %cs so
572 # it is on par with the other segments.
573 pushw %ds
574 pushw $6f
575 lretw
576 6:
578 # Check signature at end of setup
579 cmpl $0x5a5aaa55, setup_sig
580 jne setup_bad
582 # Zero the bss
583 movw $__bss_start, %di
584 movw $_end+3, %cx
585 xorl %eax, %eax
586 subw %di, %cx
587 shrw $2, %cx
588 rep; stosl
590 # Jump to C code (should not return)
591 calll main
593 # Setup corrupt somehow...
594 setup_bad:
595 movl $setup_corrupt, %eax
596 calll puts
597 # Fall through...
599 .globl die
600 .type die, @function
601 die:
602 hlt
603 jmp die
605 .size die, .-die
607 .section ".initdata", "a"
608 setup_corrupt:
609 .byte 7
610 .string "No setup signature found...\n"