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.
57 .set image_file_add_flags, IMAGE_FILE_32BIT_MACHINE
58 .set pe_opt_magic, PE_OPT_MAGIC_PE32
59 .word IMAGE_FILE_MACHINE_I386
61 .set image_file_add_flags, 0
62 .set pe_opt_magic, PE_OPT_MAGIC_PE32PLUS
63 .word IMAGE_FILE_MACHINE_AMD64
65 .word section_count # nr_sections
66 .long 0 # TimeDateStamp
67 .long 0 # PointerToSymbolTable
68 .long 1 # NumberOfSymbols
69 .word section_table - optional_header # SizeOfOptionalHeader
70 .word IMAGE_FILE_EXECUTABLE_IMAGE | \
71 image_file_add_flags | \
72 IMAGE_FILE_DEBUG_STRIPPED | \
73 IMAGE_FILE_LINE_NUMS_STRIPPED # Characteristics
77 .byte 0x02 # MajorLinkerVersion
78 .byte 0x14 # MinorLinkerVersion
80 .long ZO__data # SizeOfCode
82 .long ZO__end - ZO__data # SizeOfInitializedData
83 .long 0 # SizeOfUninitializedData
85 .long setup_size + ZO_efi_pe_entry # AddressOfEntryPoint
87 .long setup_size # BaseOfCode
98 .long salign # SectionAlignment
99 .long falign # FileAlignment
100 .word 0 # MajorOperatingSystemVersion
101 .word 0 # MinorOperatingSystemVersion
102 .word LINUX_EFISTUB_MAJOR_VERSION # MajorImageVersion
103 .word LINUX_EFISTUB_MINOR_VERSION # MinorImageVersion
104 .word 0 # MajorSubsystemVersion
105 .word 0 # MinorSubsystemVersion
106 .long 0 # Win32VersionValue
108 .long setup_size + ZO__end # SizeOfImage
110 .long salign # SizeOfHeaders
112 .word IMAGE_SUBSYSTEM_EFI_APPLICATION # Subsystem (EFI application)
113 #ifdef CONFIG_EFI_DXE_MEM_ATTRIBUTES
114 .word IMAGE_DLL_CHARACTERISTICS_NX_COMPAT # DllCharacteristics
116 .word 0 # DllCharacteristics
119 .long 0 # SizeOfStackReserve
120 .long 0 # SizeOfStackCommit
121 .long 0 # SizeOfHeapReserve
122 .long 0 # SizeOfHeapCommit
124 .quad 0 # SizeOfStackReserve
125 .quad 0 # SizeOfStackCommit
126 .quad 0 # SizeOfHeapReserve
127 .quad 0 # SizeOfHeapCommit
129 .long 0 # LoaderFlags
130 .long (section_table - .) / 8 # NumberOfRvaAndSizes
132 .quad 0 # ExportTable
133 .quad 0 # ImportTable
134 .quad 0 # ResourceTable
135 .quad 0 # ExceptionTable
136 .quad 0 # CertificationTable
137 .quad 0 # BaseRelocationTable
144 .long pecompat_fstart - salign # VirtualSize
145 .long salign # VirtualAddress
146 .long pecompat_fstart - salign # SizeOfRawData
147 .long salign # PointerToRawData
150 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
151 IMAGE_SCN_MEM_READ | \
152 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
154 #ifdef CONFIG_EFI_MIXED
157 .long pecompat_fsize # VirtualSize
158 .long pecompat_fstart # VirtualAddress
159 .long pecompat_fsize # SizeOfRawData
160 .long pecompat_fstart # PointerToRawData
163 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
164 IMAGE_SCN_MEM_READ | \
165 IMAGE_SCN_MEM_DISCARDABLE # Characteristics
168 * Put the IA-32 machine type and the associated entry point address in
169 * the .compat section, so loaders can figure out which other execution
170 * modes this image supports.
172 .pushsection ".pecompat", "a", @progbits
174 .globl pecompat_fstart
178 .word IMAGE_FILE_MACHINE_I386 # PE machine type
179 .long setup_size + ZO_efi32_pe_entry # Entrypoint
183 .set pecompat_fstart, setup_size
191 .long ZO__data # Size of initialized data
194 .long 0 # PointerToRelocations
195 .long 0 # PointerToLineNumbers
196 .word 0 # NumberOfRelocations
197 .word 0 # NumberOfLineNumbers
198 .long IMAGE_SCN_CNT_CODE | \
199 IMAGE_SCN_MEM_READ | \
200 IMAGE_SCN_MEM_EXECUTE # Characteristics
203 .long ZO__end - ZO__data # VirtualSize
204 .long setup_size + ZO__data # VirtualAddress
205 .long ZO__edata - ZO__data # SizeOfRawData
206 .long setup_size + ZO__data # PointerToRawData
209 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
210 IMAGE_SCN_MEM_READ | \
211 IMAGE_SCN_MEM_WRITE # Characteristics
213 .set section_count, (. - section_table) / 40
214 #endif /* CONFIG_EFI_STUB */
216 # Kernel attributes; used by setup. This is part 1 of the
217 # header, from the old boot sector.
219 .section ".header", "a"
221 sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */
225 .byte setup_sects - 1
226 root_flags: .word ROOT_RDONLY
227 syssize: .long ZO__edata / 16
228 ram_size: .word 0 /* Obsolete */
229 vid_mode: .word SVGA_MODE
230 root_dev: .word 0 /* Default to major/minor 0/0 */
231 boot_flag: .word 0xAA55
233 # offset 512, entry point
237 # Explicitly enter this as bytes, or the assembler
238 # tries to generate a 3-byte jump here, which causes
239 # everything else to push off to the wrong offset.
240 .byte 0xeb # short (2-byte) jump
241 .byte start_of_setup-1f
244 # Part 2 of the header, from the old setup.S
246 .ascii "HdrS" # header signature
247 .word 0x020f # header version number (>= 0x0105)
248 # or else old loadlin-1.5 will fail)
249 .globl realmode_swtch
250 realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
251 start_sys_seg: .word SYSSEG # obsolete and meaningless, but just
252 # in case something decided to "use" it
253 .word kernel_version-512 # pointing to kernel version string
254 # above section of header is compatible
255 # with loadlin-1.5 (header v1.5). Don't
258 type_of_loader: .byte 0 # 0 means ancient bootloader, newer
259 # bootloaders know to change this.
260 # See Documentation/x86/boot.rst for
263 # flags, unused bits must be zero (RFU) bit within loadflags
265 .byte LOADED_HIGH # The kernel is to be loaded high
267 setup_move_size: .word 0x8000 # size to move, when setup is not
268 # loaded at 0x90000. We will move setup
269 # to 0x90000 then just before jumping
270 # into the kernel. However, only the
271 # loader knows how much data behind
272 # us also needs to be loaded.
274 code32_start: # here loaders can put a different
275 # start address for 32-bit code.
276 .long 0x100000 # 0x100000 = default for big kernel
278 ramdisk_image: .long 0 # address of loaded ramdisk image
279 # Here the loader puts the 32-bit
280 # address where it loaded the image.
281 # This only will be read by the kernel.
283 ramdisk_size: .long 0 # its size in bytes
288 heap_end_ptr: .word _end+STACK_SIZE-512
289 # (Header version 0x0201 or later)
290 # space from here (exclusive) down to
291 # end of setup code can be used by setup
292 # for local heap purposes.
295 .byte 0 # Extended boot loader version
297 .byte 0 # Extended boot loader type
299 cmd_line_ptr: .long 0 # (Header version 0x0202 or later)
300 # If nonzero, a 32-bit pointer
301 # to the kernel command line.
302 # The command line should be
303 # located between the start of
304 # setup and the end of low
305 # memory (0xa0000), or it may
306 # get overwritten before it
307 # gets read. If this field is
308 # used, there is no longer
309 # anything magical about the
310 # 0x90000 segment; the setup
311 # can be located anywhere in
312 # low memory 0x10000 or higher.
314 initrd_addr_max: .long 0x7fffffff
315 # (Header version 0x0203 or later)
316 # The highest safe address for
317 # the contents of an initrd
318 # The current kernel allows up to 4 GB,
319 # but leave it at 2 GB to avoid
320 # possible bootloader bugs.
322 kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment
323 #required for protected mode
325 #ifdef CONFIG_RELOCATABLE
326 relocatable_kernel: .byte 1
328 relocatable_kernel: .byte 0
330 min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment
334 # define XLF0 XLF_KERNEL_64 /* 64-bit kernel */
339 #if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64)
340 /* kernel/boot_param/ramdisk could be loaded above 4g */
341 # define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G
346 #ifdef CONFIG_EFI_HANDOVER_PROTOCOL
347 # ifdef CONFIG_EFI_MIXED
348 # define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64)
350 # ifdef CONFIG_X86_64
351 # define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */
353 # define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */
360 #if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE)
361 # define XLF4 XLF_EFI_KEXEC
367 #ifdef CONFIG_X86_5LEVEL
368 #define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED)
370 #define XLF56 XLF_5LEVEL
376 .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56
378 cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line,
379 #added with boot protocol
382 hardware_subarch: .long 0 # subarchitecture, added with 2.07
383 # default to 0 for normal x86 PC
385 hardware_subarch_data: .quad 0
387 payload_offset: .long ZO_input_data
388 payload_length: .long ZO_z_input_len
390 setup_data: .quad 0 # 64-bit physical pointer to
391 # single linked list of
394 pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr
397 # Getting to provably safe in-place decompression is hard. Worst case
398 # behaviours need to be analyzed. Here let's take the decompression of
399 # a gzip-compressed kernel as example, to illustrate it:
401 # The file layout of gzip compressed kernel is:
409 # compressed data blocks[N]
412 # ... resulting in +18 bytes overhead of uncompressed data.
414 # (For more information, please refer to RFC 1951 and RFC 1952.)
416 # Files divided into blocks
417 # 1 bit (last block flag)
418 # 2 bits (block type)
420 # 1 block occurs every 32K -1 bytes or when there 50% compression
421 # has been achieved. The smallest block type encoding is always used.
424 # 32 bits length in bytes.
431 # dynamic tree encoding.
435 # The buffer for decompression in place is the length of the uncompressed
436 # data, plus a small amount extra to keep the algorithm safe. The
437 # compressed data is placed at the end of the buffer. The output pointer
438 # is placed at the start of the buffer and the input pointer is placed
439 # where the compressed data starts. Problems will occur when the output
440 # pointer overruns the input pointer.
442 # The output pointer can only overrun the input pointer if the input
443 # pointer is moving faster than the output pointer. A condition only
444 # triggered by data whose compressed form is larger than the uncompressed
447 # The worst case at the block level is a growth of the compressed data
448 # of 5 bytes per 32767 bytes.
450 # The worst case internal to a compressed block is very hard to figure.
451 # The worst case can at least be bounded by having one bit that represents
452 # 32764 bytes and then all of the rest of the bytes representing the very
455 # All of which is enough to compute an amount of extra data that is required
456 # to be safe. To avoid problems at the block level allocating 5 extra bytes
457 # per 32767 bytes of data is sufficient. To avoid problems internal to a
458 # block adding an extra 32767 bytes (the worst case uncompressed block size)
459 # is sufficient, to ensure that in the worst case the decompressed data for
460 # block will stop the byte before the compressed data for a block begins.
461 # To avoid problems with the compressed data's meta information an extra 18
462 # bytes are needed. Leading to the formula:
464 # extra_bytes = (uncompressed_size >> 12) + 32768 + 18
466 # Adding 8 bytes per 32K is a bit excessive but much easier to calculate.
467 # Adding 32768 instead of 32767 just makes for round numbers.
469 # Above analysis is for decompressing gzip compressed kernel only. Up to
470 # now 6 different decompressor are supported all together. And among them
471 # xz stores data in chunks and has maximum chunk of 64K. Hence safety
472 # margin should be updated to cover all decompressors so that we don't
473 # need to deal with each of them separately. Please check
474 # the description in lib/decompressor_xxx.c for specific information.
476 # extra_bytes = (uncompressed_size >> 12) + 65536 + 128
478 # LZ4 is even worse: data that cannot be further compressed grows by 0.4%,
479 # or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as
480 # the size-dependent part now grows so fast.
482 # extra_bytes = (uncompressed_size >> 8) + 65536
484 # ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22
485 # byte fixed overhead but has a maximum block size of 128K, so it needs a
488 # extra_bytes = (uncompressed_size >> 8) + 131072
490 #define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072)
491 #if ZO_z_output_len > ZO_z_input_len
492 # define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \
495 # define ZO_z_extract_offset ZO_z_extra_bytes
499 * The extract_offset has to be bigger than ZO head section. Otherwise when
500 * the head code is running to move ZO to the end of the buffer, it will
501 * overwrite the head code itself.
503 #if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset
504 # define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095)
506 # define ZO_z_min_extract_offset ((ZO_z_extract_offset + 4095) & ~4095)
509 #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset)
511 #define VO_INIT_SIZE (VO__end - VO__text)
512 #if ZO_INIT_SIZE > VO_INIT_SIZE
513 # define INIT_SIZE ZO_INIT_SIZE
515 # define INIT_SIZE VO_INIT_SIZE
518 .macro __handover_offset
519 #ifndef CONFIG_EFI_HANDOVER_PROTOCOL
521 #elif !defined(CONFIG_X86_64)
522 .long ZO_efi32_stub_entry
524 /* Yes, this is really how we defined it :( */
525 .long ZO_efi64_stub_entry - 0x200
526 #ifdef CONFIG_EFI_MIXED
527 .if ZO_efi32_stub_entry != ZO_efi64_stub_entry - 0x200
528 .error "32-bit and 64-bit EFI entry points do not match"
534 init_size: .long INIT_SIZE # kernel initialization size
535 handover_offset: __handover_offset
536 kernel_info_offset: .long ZO_kernel_info
538 # End of setup header #####################################################
540 .section ".entrytext", "ax"
547 # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
548 # which happened to work by accident for the old code. Recalculate the stack
549 # pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the
550 # stack behind its own code, so we can't blindly put it directly past the heap.
553 cmpw %ax, %dx # %ds == %ss?
555 je 2f # -> assume %sp is reasonably set
557 # Invalid %ss, make up a new stack
559 testb $CAN_USE_HEAP, loadflags
561 movw heap_end_ptr, %dx
562 1: addw $STACK_SIZE, %dx
564 xorw %dx, %dx # Prevent wraparound
566 2: # Now %dx should point to the end of our stack space
567 andw $~3, %dx # dword align (might as well...)
569 movw $0xfffc, %dx # Make sure we're not zero
571 movzwl %dx, %esp # Clear upper half of %esp
572 sti # Now we should have a working stack
574 # We will have entered with %cs = %ds+0x20, normalize %cs so
575 # it is on par with the other segments.
581 # Check signature at end of setup
582 cmpl $0x5a5aaa55, setup_sig
586 movw $__bss_start, %di
593 # Jump to C code (should not return)
596 # Setup corrupt somehow...
598 movl $setup_corrupt, %eax
610 .section ".initdata", "a"
613 .string "No setup signature found...\n"