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 28BOOTSEG = 0x07C0 /* original address of boot-sector */ 29SYSSEG = 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 53pe_header: 54 .long PE_MAGIC 55 56coff_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 76optional_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 93extra_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 # SizeOfImage 110 111 .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 128 129 .quad 0 # ExportTable 130 .quad 0 # ImportTable 131 .quad 0 # ResourceTable 132 .quad 0 # ExceptionTable 133 .quad 0 # CertificationTable 134 .quad 0 # BaseRelocationTable 135 136 # Section table 137section_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 145 146 .long 0, 0, 0 147 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ 148 IMAGE_SCN_MEM_READ | \ 149 IMAGE_SCN_MEM_DISCARDABLE # Characteristics 150 151#ifdef CONFIG_EFI_MIXED 152 .asciz ".compat" 153 154 .long pecompat_fsize # VirtualSize 155 .long pecompat_fstart # VirtualAddress 156 .long pecompat_fsize # SizeOfRawData 157 .long pecompat_fstart # PointerToRawData 158 159 .long 0, 0, 0 160 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ 161 IMAGE_SCN_MEM_READ | \ 162 IMAGE_SCN_MEM_DISCARDABLE # Characteristics 163 164 /* 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 172pecompat_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 198 199 .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 204 205 .long 0, 0, 0 206 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ 207 IMAGE_SCN_MEM_READ | \ 208 IMAGE_SCN_MEM_WRITE # Characteristics 209 210 .set section_count, (. - section_table) / 40 211#endif /* CONFIG_EFI_STUB */ 212 213 # Kernel attributes; used by setup. This is part 1 of the 214 # header, from the old boot sector. 215 216 .section ".header", "a" 217 .globl sentinel 218sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */ 219 220 .globl hdr 221hdr: 222 .byte setup_sects - 1 223root_flags: .word ROOT_RDONLY 224syssize: .long ZO__edata / 16 225ram_size: .word 0 /* Obsolete */ 226vid_mode: .word SVGA_MODE 227root_dev: .word 0 /* Default to major/minor 0/0 */ 228boot_flag: .word 0xAA55 229 230 # offset 512, entry point 231 232 .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 2391: 240 241 # Part 2 of the header, from the old setup.S 242 243 .ascii "HdrS" # header signature 244 .word 0x020f # header version number (>= 0x0105) 245 # or else old loadlin-1.5 will fail) 246 .globl realmode_swtch 247realmode_swtch: .word 0, 0 # default_switch, SETUPSEG 248start_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. 254 255type_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 259 260# flags, unused bits must be zero (RFU) bit within loadflags 261loadflags: 262 .byte LOADED_HIGH # The kernel is to be loaded high 263 264setup_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. 270 271code32_start: # here loaders can put a different 272 # start address for 32-bit code. 273 .long 0x100000 # 0x100000 = default for big kernel 274 275ramdisk_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. 279 280ramdisk_size: .long 0 # its size in bytes 281 282bootsect_kludge: 283 .long 0 # obsolete 284 285heap_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. 290 291ext_loader_ver: 292 .byte 0 # Extended boot loader version 293ext_loader_type: 294 .byte 0 # Extended boot loader type 295 296cmd_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. 310 311initrd_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. 318 319kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment 320 #required for protected mode 321 #kernel 322#ifdef CONFIG_RELOCATABLE 323relocatable_kernel: .byte 1 324#else 325relocatable_kernel: .byte 0 326#endif 327min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment 328 329xloadflags: 330#ifdef CONFIG_X86_64 331# define XLF0 XLF_KERNEL_64 /* 64-bit kernel */ 332#else 333# define XLF0 0 334#endif 335 336#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 342 343#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 356 357#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 362 363#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 372 373 .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56 374 375cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, 376 #added with boot protocol 377 #version 2.06 378 379hardware_subarch: .long 0 # subarchitecture, added with 2.07 380 # default to 0 for normal x86 PC 381 382hardware_subarch_data: .quad 0 383 384payload_offset: .long ZO_input_data 385payload_length: .long ZO_z_input_len 386 387setup_data: .quad 0 # 64-bit physical pointer to 388 # single linked list of 389 # struct setup_data 390 391pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr 392 393# 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 486 487#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 494 495/* 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 505 506#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset) 507 508#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 514 515 .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 530 531init_size: .long INIT_SIZE # kernel initialization size 532handover_offset: __handover_offset 533kernel_info_offset: .long ZO_kernel_info 534 535# End of setup header ##################################################### 536 537 .section ".entrytext", "ax" 538start_of_setup: 539# Force %es = %ds 540 movw %ds, %ax 541 movw %ax, %es 542 cld 543 544# 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. 548 549 movw %ss, %dx 550 cmpw %ax, %dx # %ds == %ss? 551 movw %sp, %dx 552 je 2f # -> assume %sp is reasonably set 553 554 # 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 5591: addw $STACK_SIZE, %dx 560 jnc 2f 561 xorw %dx, %dx # Prevent wraparound 562 5632: # 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 5673: movw %ax, %ss 568 movzwl %dx, %esp # Clear upper half of %esp 569 sti # Now we should have a working stack 570 571# 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 5766: 577 578# Check signature at end of setup 579 cmpl $0x5a5aaa55, setup_sig 580 jne setup_bad 581 582# 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 589 590# Jump to C code (should not return) 591 calll main 592 593# Setup corrupt somehow... 594setup_bad: 595 movl $setup_corrupt, %eax 596 calll puts 597 # Fall through... 598 599 .globl die 600 .type die, @function 601die: 602 hlt 603 jmp die 604 605 .size die, .-die 606 607 .section ".initdata", "a" 608setup_corrupt: 609 .byte 7 610 .string "No setup signature found...\n" 611