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 IMAGE_DOS_SIGNATURE 47 .org 0x38 48 # 49 # Offset to the PE header. 50 # 51 .long LINUX_PE_MAGIC 52 .long pe_header 53pe_header: 54 .long IMAGE_NT_SIGNATURE 55 56coff_header: 57#ifdef CONFIG_X86_32 58 .set image_file_add_flags, IMAGE_FILE_32BIT_MACHINE 59 .set pe_opt_magic, IMAGE_NT_OPTIONAL_HDR32_MAGIC 60 .word IMAGE_FILE_MACHINE_I386 61#else 62 .set image_file_add_flags, 0 63 .set pe_opt_magic, IMAGE_NT_OPTIONAL_HDR64_MAGIC 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_DLLCHARACTERISTICS_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\0\0\0" 183 .long textsize # VirtualSize 184 .long setup_size # VirtualAddress 185 .long textsize # SizeOfRawData 186 .long setup_size # PointerToRawData 187 .long 0 # PointerToRelocations 188 .long 0 # PointerToLineNumbers 189 .word 0 # NumberOfRelocations 190 .word 0 # NumberOfLineNumbers 191 .long IMAGE_SCN_CNT_CODE | \ 192 IMAGE_SCN_MEM_READ | \ 193 IMAGE_SCN_MEM_EXECUTE # Characteristics 194 195#ifdef CONFIG_EFI_SBAT 196 .ascii ".sbat\0\0\0" 197 .long ZO__esbat - ZO__sbat # VirtualSize 198 .long setup_size + ZO__sbat # VirtualAddress 199 .long ZO__esbat - ZO__sbat # SizeOfRawData 200 .long setup_size + ZO__sbat # PointerToRawData 201 202 .long 0, 0, 0 203 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ 204 IMAGE_SCN_MEM_READ | \ 205 IMAGE_SCN_MEM_DISCARDABLE # Characteristics 206 207 .set textsize, ZO__sbat 208#else 209 .set textsize, ZO__data 210#endif 211 212 .ascii ".data\0\0\0" 213 .long ZO__end - ZO__data # VirtualSize 214 .long setup_size + ZO__data # VirtualAddress 215 .long ZO__edata - ZO__data # SizeOfRawData 216 .long setup_size + ZO__data # PointerToRawData 217 218 .long 0, 0, 0 219 .long IMAGE_SCN_CNT_INITIALIZED_DATA | \ 220 IMAGE_SCN_MEM_READ | \ 221 IMAGE_SCN_MEM_WRITE # Characteristics 222 223 .set section_count, (. - section_table) / 40 224#endif /* CONFIG_EFI_STUB */ 225 226 # Kernel attributes; used by setup. This is part 1 of the 227 # header, from the old boot sector. 228 229 .section ".header", "a" 230 .globl sentinel 231sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */ 232 233 .globl hdr 234hdr: 235 .byte setup_sects - 1 236root_flags: .word ROOT_RDONLY 237syssize: .long ZO__edata / 16 238ram_size: .word 0 /* Obsolete */ 239vid_mode: .word SVGA_MODE 240root_dev: .word 0 /* Default to major/minor 0/0 */ 241boot_flag: .word 0xAA55 242 243 # offset 512, entry point 244 245 .globl _start 246_start: 247 # Explicitly enter this as bytes, or the assembler 248 # tries to generate a 3-byte jump here, which causes 249 # everything else to push off to the wrong offset. 250 .byte 0xeb # short (2-byte) jump 251 .byte start_of_setup-1f 2521: 253 254 # Part 2 of the header, from the old setup.S 255 256 .ascii "HdrS" # header signature 257 .word 0x020f # header version number (>= 0x0105) 258 # or else old loadlin-1.5 will fail) 259 .globl realmode_swtch 260realmode_swtch: .word 0, 0 # default_switch, SETUPSEG 261start_sys_seg: .word SYSSEG # obsolete and meaningless, but just 262 # in case something decided to "use" it 263 .word kernel_version-512 # pointing to kernel version string 264 # above section of header is compatible 265 # with loadlin-1.5 (header v1.5). Don't 266 # change it. 267 268type_of_loader: .byte 0 # 0 means ancient bootloader, newer 269 # bootloaders know to change this. 270 # See Documentation/arch/x86/boot.rst for 271 # assigned ids 272 273# flags, unused bits must be zero (RFU) bit within loadflags 274loadflags: 275 .byte LOADED_HIGH # The kernel is to be loaded high 276 277setup_move_size: .word 0x8000 # size to move, when setup is not 278 # loaded at 0x90000. We will move setup 279 # to 0x90000 then just before jumping 280 # into the kernel. However, only the 281 # loader knows how much data behind 282 # us also needs to be loaded. 283 284code32_start: # here loaders can put a different 285 # start address for 32-bit code. 286 .long 0x100000 # 0x100000 = default for big kernel 287 288ramdisk_image: .long 0 # address of loaded ramdisk image 289 # Here the loader puts the 32-bit 290 # address where it loaded the image. 291 # This only will be read by the kernel. 292 293ramdisk_size: .long 0 # its size in bytes 294 295bootsect_kludge: 296 .long 0 # obsolete 297 298heap_end_ptr: .word _end+STACK_SIZE-512 299 # (Header version 0x0201 or later) 300 # space from here (exclusive) down to 301 # end of setup code can be used by setup 302 # for local heap purposes. 303 304ext_loader_ver: 305 .byte 0 # Extended boot loader version 306ext_loader_type: 307 .byte 0 # Extended boot loader type 308 309cmd_line_ptr: .long 0 # (Header version 0x0202 or later) 310 # If nonzero, a 32-bit pointer 311 # to the kernel command line. 312 # The command line should be 313 # located between the start of 314 # setup and the end of low 315 # memory (0xa0000), or it may 316 # get overwritten before it 317 # gets read. If this field is 318 # used, there is no longer 319 # anything magical about the 320 # 0x90000 segment; the setup 321 # can be located anywhere in 322 # low memory 0x10000 or higher. 323 324initrd_addr_max: .long 0x7fffffff 325 # (Header version 0x0203 or later) 326 # The highest safe address for 327 # the contents of an initrd 328 # The current kernel allows up to 4 GB, 329 # but leave it at 2 GB to avoid 330 # possible bootloader bugs. 331 332kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment 333 #required for protected mode 334 #kernel 335#ifdef CONFIG_RELOCATABLE 336relocatable_kernel: .byte 1 337#else 338relocatable_kernel: .byte 0 339#endif 340min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment 341 342xloadflags: 343#ifdef CONFIG_X86_64 344# define XLF0 XLF_KERNEL_64 /* 64-bit kernel */ 345#else 346# define XLF0 0 347#endif 348 349#if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64) 350 /* kernel/boot_param/ramdisk could be loaded above 4g */ 351# define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G 352#else 353# define XLF1 0 354#endif 355 356#ifdef CONFIG_EFI_HANDOVER_PROTOCOL 357# ifdef CONFIG_EFI_MIXED 358# define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64) 359# else 360# ifdef CONFIG_X86_64 361# define XLF23 XLF_EFI_HANDOVER_64 /* 64-bit EFI handover ok */ 362# else 363# define XLF23 XLF_EFI_HANDOVER_32 /* 32-bit EFI handover ok */ 364# endif 365# endif 366#else 367# define XLF23 0 368#endif 369 370#if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE) 371# define XLF4 XLF_EFI_KEXEC 372#else 373# define XLF4 0 374#endif 375 376#ifdef CONFIG_X86_64 377#define XLF56 (XLF_5LEVEL|XLF_5LEVEL_ENABLED) 378#else 379#define XLF56 0 380#endif 381 382 .word XLF0 | XLF1 | XLF23 | XLF4 | XLF56 383 384cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, 385 #added with boot protocol 386 #version 2.06 387 388hardware_subarch: .long 0 # subarchitecture, added with 2.07 389 # default to 0 for normal x86 PC 390 391hardware_subarch_data: .quad 0 392 393payload_offset: .long ZO_input_data 394payload_length: .long ZO_z_input_len 395 396setup_data: .quad 0 # 64-bit physical pointer to 397 # single linked list of 398 # struct setup_data 399 400pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr 401 402# 403# Getting to provably safe in-place decompression is hard. Worst case 404# behaviours need to be analyzed. Here let's take the decompression of 405# a gzip-compressed kernel as example, to illustrate it: 406# 407# The file layout of gzip compressed kernel is: 408# 409# magic[2] 410# method[1] 411# flags[1] 412# timestamp[4] 413# extraflags[1] 414# os[1] 415# compressed data blocks[N] 416# crc[4] orig_len[4] 417# 418# ... resulting in +18 bytes overhead of uncompressed data. 419# 420# (For more information, please refer to RFC 1951 and RFC 1952.) 421# 422# Files divided into blocks 423# 1 bit (last block flag) 424# 2 bits (block type) 425# 426# 1 block occurs every 32K -1 bytes or when there 50% compression 427# has been achieved. The smallest block type encoding is always used. 428# 429# stored: 430# 32 bits length in bytes. 431# 432# fixed: 433# magic fixed tree. 434# symbols. 435# 436# dynamic: 437# dynamic tree encoding. 438# symbols. 439# 440# 441# The buffer for decompression in place is the length of the uncompressed 442# data, plus a small amount extra to keep the algorithm safe. The 443# compressed data is placed at the end of the buffer. The output pointer 444# is placed at the start of the buffer and the input pointer is placed 445# where the compressed data starts. Problems will occur when the output 446# pointer overruns the input pointer. 447# 448# The output pointer can only overrun the input pointer if the input 449# pointer is moving faster than the output pointer. A condition only 450# triggered by data whose compressed form is larger than the uncompressed 451# form. 452# 453# The worst case at the block level is a growth of the compressed data 454# of 5 bytes per 32767 bytes. 455# 456# The worst case internal to a compressed block is very hard to figure. 457# The worst case can at least be bounded by having one bit that represents 458# 32764 bytes and then all of the rest of the bytes representing the very 459# very last byte. 460# 461# All of which is enough to compute an amount of extra data that is required 462# to be safe. To avoid problems at the block level allocating 5 extra bytes 463# per 32767 bytes of data is sufficient. To avoid problems internal to a 464# block adding an extra 32767 bytes (the worst case uncompressed block size) 465# is sufficient, to ensure that in the worst case the decompressed data for 466# block will stop the byte before the compressed data for a block begins. 467# To avoid problems with the compressed data's meta information an extra 18 468# bytes are needed. Leading to the formula: 469# 470# extra_bytes = (uncompressed_size >> 12) + 32768 + 18 471# 472# Adding 8 bytes per 32K is a bit excessive but much easier to calculate. 473# Adding 32768 instead of 32767 just makes for round numbers. 474# 475# Above analysis is for decompressing gzip compressed kernel only. Up to 476# now 6 different decompressor are supported all together. And among them 477# xz stores data in chunks and has maximum chunk of 64K. Hence safety 478# margin should be updated to cover all decompressors so that we don't 479# need to deal with each of them separately. Please check 480# the description in lib/decompressor_xxx.c for specific information. 481# 482# extra_bytes = (uncompressed_size >> 12) + 65536 + 128 483# 484# LZ4 is even worse: data that cannot be further compressed grows by 0.4%, 485# or one byte per 256 bytes. OTOH, we can safely get rid of the +128 as 486# the size-dependent part now grows so fast. 487# 488# extra_bytes = (uncompressed_size >> 8) + 65536 489# 490# ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22 491# byte fixed overhead but has a maximum block size of 128K, so it needs a 492# larger margin. 493# 494# extra_bytes = (uncompressed_size >> 8) + 131072 495 496#define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072) 497#if ZO_z_output_len > ZO_z_input_len 498# define ZO_z_extract_offset (ZO_z_output_len + ZO_z_extra_bytes - \ 499 ZO_z_input_len) 500#else 501# define ZO_z_extract_offset ZO_z_extra_bytes 502#endif 503 504/* 505 * The extract_offset has to be bigger than ZO head section. Otherwise when 506 * the head code is running to move ZO to the end of the buffer, it will 507 * overwrite the head code itself. 508 */ 509#if (ZO__ehead - ZO_startup_32) > ZO_z_extract_offset 510# define ZO_z_min_extract_offset ((ZO__ehead - ZO_startup_32 + 4095) & ~4095) 511#else 512# define ZO_z_min_extract_offset ((ZO_z_extract_offset + 4095) & ~4095) 513#endif 514 515#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_min_extract_offset) 516 517#define VO_INIT_SIZE (VO__end - VO__text) 518#if ZO_INIT_SIZE > VO_INIT_SIZE 519# define INIT_SIZE ZO_INIT_SIZE 520#else 521# define INIT_SIZE VO_INIT_SIZE 522#endif 523 524 .macro __handover_offset 525#ifndef CONFIG_EFI_HANDOVER_PROTOCOL 526 .long 0 527#elif !defined(CONFIG_X86_64) 528 .long ZO_efi32_stub_entry 529#else 530 /* Yes, this is really how we defined it :( */ 531 .long ZO_efi64_stub_entry - 0x200 532#ifdef CONFIG_EFI_MIXED 533 .if ZO_efi32_stub_entry != ZO_efi64_stub_entry - 0x200 534 .error "32-bit and 64-bit EFI entry points do not match" 535 .endif 536#endif 537#endif 538 .endm 539 540init_size: .long INIT_SIZE # kernel initialization size 541handover_offset: __handover_offset 542kernel_info_offset: .long ZO_kernel_info 543 544# End of setup header ##################################################### 545 546 .section ".entrytext", "ax" 547start_of_setup: 548# Force %es = %ds 549 movw %ds, %ax 550 movw %ax, %es 551 cld 552 553# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds, 554# which happened to work by accident for the old code. Recalculate the stack 555# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the 556# stack behind its own code, so we can't blindly put it directly past the heap. 557 558 movw %ss, %dx 559 cmpw %ax, %dx # %ds == %ss? 560 movw %sp, %dx 561 je 2f # -> assume %sp is reasonably set 562 563 # Invalid %ss, make up a new stack 564 movw $_end, %dx 565 testb $CAN_USE_HEAP, loadflags 566 jz 1f 567 movw heap_end_ptr, %dx 5681: addw $STACK_SIZE, %dx 569 jnc 2f 570 xorw %dx, %dx # Prevent wraparound 571 5722: # Now %dx should point to the end of our stack space 573 andw $~3, %dx # dword align (might as well...) 574 jnz 3f 575 movw $0xfffc, %dx # Make sure we're not zero 5763: movw %ax, %ss 577 movzwl %dx, %esp # Clear upper half of %esp 578 sti # Now we should have a working stack 579 580# We will have entered with %cs = %ds+0x20, normalize %cs so 581# it is on par with the other segments. 582 pushw %ds 583 pushw $6f 584 lretw 5856: 586 587# Check signature at end of setup 588 cmpl $0x5a5aaa55, setup_sig 589 jne setup_bad 590 591# Zero the bss 592 movw $__bss_start, %di 593 movw $_end+3, %cx 594 xorl %eax, %eax 595 subw %di, %cx 596 shrw $2, %cx 597 rep stosl 598 599# Jump to C code (should not return) 600 calll main 601 602# Setup corrupt somehow... 603setup_bad: 604 movl $setup_corrupt, %eax 605 calll puts 606 # Fall through... 607 608 .globl die 609 .type die, @function 610die: 611 hlt 612 jmp die 613 614 .size die, .-die 615 616 .section ".initdata", "a" 617setup_corrupt: 618 .byte 7 619 .string "No setup signature found...\n" 620