1 /* SPDX-License-Identifier: GPL-2.0 */
5 * Copyright (C) 1991, 1992 Linus Torvalds
7 * Based on bootsect.S and setup.S
8 * modified by more people than can be counted
10 * Rewritten as a common file by H. Peter Anvin (Apr 2007)
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.
19 #include <asm/segment.h>
21 #include <asm/page_types.h>
22 #include <asm/setup.h>
23 #include <asm/bootparam.h>
28 BOOTSEG = 0x07C0 /* original address of boot-sector */
29 SYSSEG = 0x1000 /* historical load address >> 4 */
32 #define SVGA_MODE ASK_VGA
43 .section ".bstext", "ax"
44 #ifdef CONFIG_EFI_STUB
49 # Offset to the PE header.
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
62 .set image_file_add_flags, 0
63 .set pe_opt_magic, PE_OPT_MAGIC_PE32PLUS
64 .word IMAGE_FILE_MACHINE_AMD64
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
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
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
113 .word IMAGE_SUBSYSTEM_EFI_APPLICATION # Subsystem (EFI application)
114 #ifdef CONFIG_EFI_DXE_MEM_ATTRIBUTES
115 .word IMAGE_DLL_CHARACTERISTICS_NX_COMPAT # DllCharacteristics
117 .word 0 # DllCharacteristics
120 .long 0 # SizeOfStackReserve
121 .long 0 # SizeOfStackCommit
122 .long 0 # SizeOfHeapReserve
123 .long 0 # SizeOfHeapCommit
125 .quad 0 # SizeOfStackReserve
126 .quad 0 # SizeOfStackCommit
127 .quad 0 # SizeOfHeapReserve
128 .quad 0 # SizeOfHeapCommit
130 .long 0 # LoaderFlags
131 .long (section_table - .) / 8 # NumberOfRvaAndSizes
133 .quad 0 # ExportTable
134 .quad 0 # ImportTable
135 .quad 0 # ResourceTable
136 .quad 0 # ExceptionTable
137 .quad 0 # CertificationTable
138 .quad 0 # BaseRelocationTable
145 .long pecompat_fstart - salign # VirtualSize
146 .long salign # VirtualAddress
147 .long pecompat_fstart - salign # SizeOfRawData
148 .long salign # PointerToRawData
151 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
152 IMAGE_SCN_MEM_READ | \
153 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
155 #ifdef CONFIG_EFI_MIXED
158 .long pecompat_fsize # VirtualSize
159 .long pecompat_fstart # VirtualAddress
160 .long pecompat_fsize # SizeOfRawData
161 .long pecompat_fstart # PointerToRawData
164 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
165 IMAGE_SCN_MEM_READ | \
166 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
169 * Put the IA-32 machine type and the associated entry point address in
170 * the .compat section, so loaders can figure out which other execution
171 * modes this image supports.
173 .pushsection ".pecompat", "a", @progbits
175 .globl pecompat_fstart
179 .word IMAGE_FILE_MACHINE_I386 # PE machine type
180 .long setup_size + ZO_efi32_pe_entry # Entrypoint
184 .set pecompat_fstart, setup_size
192 .long ZO__data # Size of initialized data
195 .long 0 # PointerToRelocations
196 .long 0 # PointerToLineNumbers
197 .word 0 # NumberOfRelocations
198 .word 0 # NumberOfLineNumbers
199 .long IMAGE_SCN_CNT_CODE | \
200 IMAGE_SCN_MEM_READ | \
201 IMAGE_SCN_MEM_EXECUTE # Characteristics
204 .long ZO__end - ZO__data # VirtualSize
205 .long setup_size + ZO__data # VirtualAddress
206 .long ZO__edata - ZO__data # SizeOfRawData
207 .long setup_size + ZO__data # PointerToRawData
210 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
211 IMAGE_SCN_MEM_READ | \
212 IMAGE_SCN_MEM_WRITE # Characteristics
214 .set section_count, (. - section_table) / 40
215 #endif /* CONFIG_EFI_STUB */
217 # Kernel attributes; used by setup. This is part 1 of the
218 # header, from the old boot sector.
220 .section ".header", "a"
222 sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */
226 .byte setup_sects - 1
227 root_flags: .word ROOT_RDONLY
228 syssize: .long ZO__edata / 16
229 ram_size: .word 0 /* Obsolete */
230 vid_mode: .word SVGA_MODE
231 root_dev: .word 0 /* Default to major/minor 0/0 */
232 boot_flag: .word 0xAA55
234 # offset 512, entry point
238 # Explicitly enter this as bytes, or the assembler
239 # tries to generate a 3-byte jump here, which causes
240 # everything else to push off to the wrong offset.
241 .byte 0xeb # short (2-byte) jump
242 .byte start_of_setup-1f
245 # Part 2 of the header, from the old setup.S
247 .ascii "HdrS" # header signature
248 .word 0x020f # header version number (>= 0x0105)
249 # or else old loadlin-1.5 will fail)
250 .globl realmode_swtch
251 realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
252 start_sys_seg: .word SYSSEG # obsolete and meaningless, but just
253 # in case something decided to "use" it
254 .word kernel_version-512 # pointing to kernel version string
255 # above section of header is compatible
256 # with loadlin-1.5 (header v1.5). Don't
259 type_of_loader: .byte 0 # 0 means ancient bootloader, newer
260 # bootloaders know to change this.
261 # See Documentation/arch/x86/boot.rst for
264 # flags, unused bits must be zero (RFU) bit within loadflags
266 .byte LOADED_HIGH # The kernel is to be loaded high
268 setup_move_size: .word 0x8000 # size to move, when setup is not
269 # loaded at 0x90000. We will move setup
270 # to 0x90000 then just before jumping
271 # into the kernel. However, only the
272 # loader knows how much data behind
273 # us also needs to be loaded.
275 code32_start: # here loaders can put a different
276 # start address for 32-bit code.
277 .long 0x100000 # 0x100000 = default for big kernel
279 ramdisk_image: .long 0 # address of loaded ramdisk image
280 # Here the loader puts the 32-bit
281 # address where it loaded the image.
282 # This only will be read by the kernel.
284 ramdisk_size: .long 0 # its size in bytes
289 heap_end_ptr: .word _end+STACK_SIZE-512
290 # (Header version 0x0201 or later)
291 # space from here (exclusive) down to
292 # end of setup code can be used by setup
293 # for local heap purposes.
296 .byte 0 # Extended boot loader version
298 .byte 0 # Extended boot loader type
300 cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
301 # If nonzero, a 32-bit pointer
302 # to the kernel command line.
303 # The command line should be
304 # located between the start of
305 # setup and the end of low
306 # memory (0xa0000), or it may
307 # get overwritten before it
308 # gets read. If this field is
309 # used, there is no longer
310 # anything magical about the
311 # 0x90000 segment; the setup
312 # can be located anywhere in
313 # low memory 0x10000 or higher.
315 initrd_addr_max: .long 0x7fffffff
316 # (Header version 0x0203 or later)
317 # The highest safe address for
318 # the contents of an initrd
319 # The current kernel allows up to 4 GB,
320 # but leave it at 2 GB to avoid
321 # possible bootloader bugs.
323 kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
324 #required for protected mode
326 #ifdef CONFIG_RELOCATABLE
327 relocatable_kernel: .byte 1
329 relocatable_kernel: .byte 0
331 min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
335 # define XLF0 XLF_KERNEL_64 /* 64-bit kernel */
340 #if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64)
341 /* kernel/boot_param/ramdisk could be loaded above 4g */
342 # define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G
347 #ifdef CONFIG_EFI_HANDOVER_PROTOCOL
348 # ifdef CONFIG_EFI_MIXED
349 # define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64)
351 # ifdef CONFIG_X86_64
352 # define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */
354 # define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */
361 #if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE)
362 # define XLF4 XLF_EFI_KEXEC
368 #ifdef CONFIG_X86_5LEVEL
369 #define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED)
371 #define XLF56 XLF_5LEVEL
377 .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56
379 cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
380 #added with boot protocol
383 hardware_subarch: .long 0 # subarchitecture, added with 2.07
384 # default to 0 for normal x86 PC
386 hardware_subarch_data: .quad 0
388 payload_offset: .long ZO_input_data
389 payload_length: .long ZO_z_input_len
391 setup_data: .quad 0 # 64-bit physical pointer to
392 # single linked list of
395 pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
398 # Getting to provably safe in-place decompression is hard. Worst case
399 # behaviours need to be analyzed. Here let's take the decompression of
400 # a gzip-compressed kernel as example, to illustrate it:
402 # The file layout of gzip compressed kernel is:
410 # compressed data blocks[N]
413 # ... resulting in +18 bytes overhead of uncompressed data.
415 # (For more information, please refer to RFC 1951 and RFC 1952.)
417 # Files divided into blocks
418 # 1 bit (last block flag)
419 # 2 bits (block type)
421 # 1 block occurs every 32K -1 bytes or when there 50% compression
422 # has been achieved. The smallest block type encoding is always used.
425 # 32 bits length in bytes.
432 # dynamic tree encoding.
436 # The buffer for decompression in place is the length of the uncompressed
437 # data, plus a small amount extra to keep the algorithm safe. The
438 # compressed data is placed at the end of the buffer. The output pointer
439 # is placed at the start of the buffer and the input pointer is placed
440 # where the compressed data starts. Problems will occur when the output
441 # pointer overruns the input pointer.
443 # The output pointer can only overrun the input pointer if the input
444 # pointer is moving faster than the output pointer. A condition only
445 # triggered by data whose compressed form is larger than the uncompressed
448 # The worst case at the block level is a growth of the compressed data
449 # of 5 bytes per 32767 bytes.
451 # The worst case internal to a compressed block is very hard to figure.
452 # The worst case can at least be bounded by having one bit that represents
453 # 32764 bytes and then all of the rest of the bytes representing the very
456 # All of which is enough to compute an amount of extra data that is required
457 # to be safe. To avoid problems at the block level allocating 5 extra bytes
458 # per 32767 bytes of data is sufficient. To avoid problems internal to a
459 # block adding an extra 32767 bytes (the worst case uncompressed block size)
460 # is sufficient, to ensure that in the worst case the decompressed data for
461 # block will stop the byte before the compressed data for a block begins.
462 # To avoid problems with the compressed data's meta information an extra 18
463 # bytes are needed. Leading to the formula:
465 # extra_bytes = (uncompressed_size >> 12) + 32768 + 18
467 # Adding 8 bytes per 32K is a bit excessive but much easier to calculate.
468 # Adding 32768 instead of 32767 just makes for round numbers.
470 # Above analysis is for decompressing gzip compressed kernel only. Up to
471 # now 6 different decompressor are supported all together. And among them
472 # xz stores data in chunks and has maximum chunk of 64K. Hence safety
473 # margin should be updated to cover all decompressors so that we don't
474 # need to deal with each of them separately. Please check
475 # the description in lib/decompressor_xxx.c for specific information.
477 # extra_bytes = (uncompressed_size >> 12) + 65536 + 128
479 # LZ4 is even worse: data that cannot be further compressed grows by 0.4%,
480 # or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as
481 # the size-dependent part now grows so fast.
483 # extra_bytes = (uncompressed_size >> 8) + 65536
485 # ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22
486 # byte fixed overhead but has a maximum block size of 128K, so it needs a
489 # extra_bytes = (uncompressed_size >> 8) + 131072
491 #define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072)
492 #if ZO_z_output_len > ZO_z_input_len
493 # define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \
496 # define ZO_z_extract_offset ZO_z_extra_bytes
500 * The extract_offset has to be bigger than ZO head section. Otherwise when
501 * the head code is running to move ZO to the end of the buffer, it will
502 * overwrite the head code itself.
504 #if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset
505 # define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095)
507 # define ZO_z_min_extract_offset ((ZO_z_extract_offset + 4095) & ~4095)
510 #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset)
512 #define VO_INIT_SIZE (VO__end - VO__text)
513 #if ZO_INIT_SIZE > VO_INIT_SIZE
514 # define INIT_SIZE ZO_INIT_SIZE
516 # define INIT_SIZE VO_INIT_SIZE
519 .macro __handover_offset
520 #ifndef CONFIG_EFI_HANDOVER_PROTOCOL
522 #elif !defined(CONFIG_X86_64)
523 .long ZO_efi32_stub_entry
525 /* Yes, this is really how we defined it :( */
526 .long ZO_efi64_stub_entry - 0x200
527 #ifdef CONFIG_EFI_MIXED
528 .if ZO_efi32_stub_entry != ZO_efi64_stub_entry - 0x200
529 .error "32-bit and 64-bit EFI entry points do not match"
535 init_size: .long INIT_SIZE # kernel initialization size
536 handover_offset: __handover_offset
537 kernel_info_offset: .long ZO_kernel_info
539 # End of setup header #####################################################
541 .section ".entrytext", "ax"
548 # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
549 # which happened to work by accident for the old code. Recalculate the stack
550 # pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
551 # stack behind its own code, so we can't blindly put it directly past the heap.
554 cmpw %ax, %dx # %ds == %ss?
556 je 2f # -> assume %sp is reasonably set
558 # Invalid %ss, make up a new stack
560 testb $CAN_USE_HEAP, loadflags
562 movw heap_end_ptr, %dx
563 1: addw $STACK_SIZE, %dx
565 xorw %dx, %dx # Prevent wraparound
567 2: # Now %dx should point to the end of our stack space
568 andw $~3, %dx # dword align (might as well...)
570 movw $0xfffc, %dx # Make sure we're not zero
572 movzwl %dx, %esp # Clear upper half of %esp
573 sti # Now we should have a working stack
575 # We will have entered with %cs = %ds+0x20, normalize %cs so
576 # it is on par with the other segments.
582 # Check signature at end of setup
583 cmpl $0x5a5aaa55, setup_sig
587 movw $__bss_start, %di
594 # Jump to C code (should not return)
597 # Setup corrupt somehow...
599 movl $setup_corrupt, %eax
611 .section ".initdata", "a"
614 .string "No setup signature found...\n"