1/* 2 * header.S 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 * 6 * Based on bootsect.S and setup.S 7 * modified by more people than can be counted 8 * 9 * Rewritten as a common file by H. Peter Anvin (Apr 2007) 10 * 11 * BIG FAT NOTE: We're in real mode using 64k segments. Therefore segment 12 * addresses must be multiplied by 16 to obtain their respective linear 13 * addresses. To avoid confusion, linear addresses are written using leading 14 * hex while segment addresses are written as segment:offset. 15 * 16 */ 17 18#include <asm/segment.h> 19#include <generated/utsrelease.h> 20#include <asm/boot.h> 21#include <asm/e820.h> 22#include <asm/page_types.h> 23#include <asm/setup.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 RAMDISK 36#define RAMDISK 0 37#endif 38 39#ifndef ROOT_RDONLY 40#define ROOT_RDONLY 1 41#endif 42 43 .code16 44 .section ".bstext", "ax" 45 46 .global bootsect_start 47bootsect_start: 48#ifdef CONFIG_EFI_STUB 49 # "MZ", MS-DOS header 50 .byte 0x4d 51 .byte 0x5a 52#endif 53 54 # Normalize the start address 55 ljmp $BOOTSEG, $start2 56 57start2: 58 movw %cs, %ax 59 movw %ax, %ds 60 movw %ax, %es 61 movw %ax, %ss 62 xorw %sp, %sp 63 sti 64 cld 65 66 movw $bugger_off_msg, %si 67 68msg_loop: 69 lodsb 70 andb %al, %al 71 jz bs_die 72 movb $0xe, %ah 73 movw $7, %bx 74 int $0x10 75 jmp msg_loop 76 77bs_die: 78 # Allow the user to press a key, then reboot 79 xorw %ax, %ax 80 int $0x16 81 int $0x19 82 83 # int 0x19 should never return. In case it does anyway, 84 # invoke the BIOS reset code... 85 ljmp $0xf000,$0xfff0 86 87#ifdef CONFIG_EFI_STUB 88 .org 0x3c 89 # 90 # Offset to the PE header. 91 # 92 .long pe_header 93#endif /* CONFIG_EFI_STUB */ 94 95 .section ".bsdata", "a" 96bugger_off_msg: 97 .ascii "Direct booting from floppy is no longer supported.\r\n" 98 .ascii "Please use a boot loader program instead.\r\n" 99 .ascii "\n" 100 .ascii "Remove disk and press any key to reboot . . .\r\n" 101 .byte 0 102 103#ifdef CONFIG_EFI_STUB 104pe_header: 105 .ascii "PE" 106 .word 0 107 108coff_header: 109#ifdef CONFIG_X86_32 110 .word 0x14c # i386 111#else 112 .word 0x8664 # x86-64 113#endif 114 .word 2 # nr_sections 115 .long 0 # TimeDateStamp 116 .long 0 # PointerToSymbolTable 117 .long 1 # NumberOfSymbols 118 .word section_table - optional_header # SizeOfOptionalHeader 119#ifdef CONFIG_X86_32 120 .word 0x306 # Characteristics. 121 # IMAGE_FILE_32BIT_MACHINE | 122 # IMAGE_FILE_DEBUG_STRIPPED | 123 # IMAGE_FILE_EXECUTABLE_IMAGE | 124 # IMAGE_FILE_LINE_NUMS_STRIPPED 125#else 126 .word 0x206 # Characteristics 127 # IMAGE_FILE_DEBUG_STRIPPED | 128 # IMAGE_FILE_EXECUTABLE_IMAGE | 129 # IMAGE_FILE_LINE_NUMS_STRIPPED 130#endif 131 132optional_header: 133#ifdef CONFIG_X86_32 134 .word 0x10b # PE32 format 135#else 136 .word 0x20b # PE32+ format 137#endif 138 .byte 0x02 # MajorLinkerVersion 139 .byte 0x14 # MinorLinkerVersion 140 141 # Filled in by build.c 142 .long 0 # SizeOfCode 143 144 .long 0 # SizeOfInitializedData 145 .long 0 # SizeOfUninitializedData 146 147 # Filled in by build.c 148 .long 0x0000 # AddressOfEntryPoint 149 150 .long 0x0000 # BaseOfCode 151#ifdef CONFIG_X86_32 152 .long 0 # data 153#endif 154 155extra_header_fields: 156#ifdef CONFIG_X86_32 157 .long 0 # ImageBase 158#else 159 .quad 0 # ImageBase 160#endif 161 .long 0x1000 # SectionAlignment 162 .long 0x200 # FileAlignment 163 .word 0 # MajorOperatingSystemVersion 164 .word 0 # MinorOperatingSystemVersion 165 .word 0 # MajorImageVersion 166 .word 0 # MinorImageVersion 167 .word 0 # MajorSubsystemVersion 168 .word 0 # MinorSubsystemVersion 169 .long 0 # Win32VersionValue 170 171 # 172 # The size of the bzImage is written in tools/build.c 173 # 174 .long 0 # SizeOfImage 175 176 .long 0x200 # SizeOfHeaders 177 .long 0 # CheckSum 178 .word 0xa # Subsystem (EFI application) 179 .word 0 # DllCharacteristics 180#ifdef CONFIG_X86_32 181 .long 0 # SizeOfStackReserve 182 .long 0 # SizeOfStackCommit 183 .long 0 # SizeOfHeapReserve 184 .long 0 # SizeOfHeapCommit 185#else 186 .quad 0 # SizeOfStackReserve 187 .quad 0 # SizeOfStackCommit 188 .quad 0 # SizeOfHeapReserve 189 .quad 0 # SizeOfHeapCommit 190#endif 191 .long 0 # LoaderFlags 192 .long 0x1 # NumberOfRvaAndSizes 193 194 .quad 0 # ExportTable 195 .quad 0 # ImportTable 196 .quad 0 # ResourceTable 197 .quad 0 # ExceptionTable 198 .quad 0 # CertificationTable 199 .quad 0 # BaseRelocationTable 200 201 # Section table 202section_table: 203 .ascii ".text" 204 .byte 0 205 .byte 0 206 .byte 0 207 .long 0 208 .long 0x0 # startup_{32,64} 209 .long 0 # Size of initialized data 210 # on disk 211 .long 0x0 # startup_{32,64} 212 .long 0 # PointerToRelocations 213 .long 0 # PointerToLineNumbers 214 .word 0 # NumberOfRelocations 215 .word 0 # NumberOfLineNumbers 216 .long 0x60500020 # Characteristics (section flags) 217 218 # 219 # The EFI application loader requires a relocation section 220 # because EFI applications are relocatable and not having 221 # this section seems to confuse it. But since we don't need 222 # the loader to fixup any relocs for us just fill it with a 223 # single dummy reloc. 224 # 225 .ascii ".reloc" 226 .byte 0 227 .byte 0 228 .long reloc_end - reloc_start 229 .long reloc_start 230 .long reloc_end - reloc_start # SizeOfRawData 231 .long reloc_start # PointerToRawData 232 .long 0 # PointerToRelocations 233 .long 0 # PointerToLineNumbers 234 .word 0 # NumberOfRelocations 235 .word 0 # NumberOfLineNumbers 236 .long 0x42100040 # Characteristics (section flags) 237#endif /* CONFIG_EFI_STUB */ 238 239 # Kernel attributes; used by setup. This is part 1 of the 240 # header, from the old boot sector. 241 242 .section ".header", "a" 243 .globl hdr 244hdr: 245setup_sects: .byte 0 /* Filled in by build.c */ 246root_flags: .word ROOT_RDONLY 247syssize: .long 0 /* Filled in by build.c */ 248ram_size: .word 0 /* Obsolete */ 249vid_mode: .word SVGA_MODE 250root_dev: .word 0 /* Filled in by build.c */ 251boot_flag: .word 0xAA55 252 253 # offset 512, entry point 254 255 .globl _start 256_start: 257 # Explicitly enter this as bytes, or the assembler 258 # tries to generate a 3-byte jump here, which causes 259 # everything else to push off to the wrong offset. 260 .byte 0xeb # short (2-byte) jump 261 .byte start_of_setup-1f 2621: 263 264 # Part 2 of the header, from the old setup.S 265 266 .ascii "HdrS" # header signature 267 .word 0x020a # header version number (>= 0x0105) 268 # or else old loadlin-1.5 will fail) 269 .globl realmode_swtch 270realmode_swtch: .word 0, 0 # default_switch, SETUPSEG 271start_sys_seg: .word SYSSEG # obsolete and meaningless, but just 272 # in case something decided to "use" it 273 .word kernel_version-512 # pointing to kernel version string 274 # above section of header is compatible 275 # with loadlin-1.5 (header v1.5). Don't 276 # change it. 277 278type_of_loader: .byte 0 # 0 means ancient bootloader, newer 279 # bootloaders know to change this. 280 # See Documentation/x86/boot.txt for 281 # assigned ids 282 283# flags, unused bits must be zero (RFU) bit within loadflags 284loadflags: 285LOADED_HIGH = 1 # If set, the kernel is loaded high 286CAN_USE_HEAP = 0x80 # If set, the loader also has set 287 # heap_end_ptr to tell how much 288 # space behind setup.S can be used for 289 # heap purposes. 290 # Only the loader knows what is free 291 .byte LOADED_HIGH 292 293setup_move_size: .word 0x8000 # size to move, when setup is not 294 # loaded at 0x90000. We will move setup 295 # to 0x90000 then just before jumping 296 # into the kernel. However, only the 297 # loader knows how much data behind 298 # us also needs to be loaded. 299 300code32_start: # here loaders can put a different 301 # start address for 32-bit code. 302 .long 0x100000 # 0x100000 = default for big kernel 303 304ramdisk_image: .long 0 # address of loaded ramdisk image 305 # Here the loader puts the 32-bit 306 # address where it loaded the image. 307 # This only will be read by the kernel. 308 309ramdisk_size: .long 0 # its size in bytes 310 311bootsect_kludge: 312 .long 0 # obsolete 313 314heap_end_ptr: .word _end+STACK_SIZE-512 315 # (Header version 0x0201 or later) 316 # space from here (exclusive) down to 317 # end of setup code can be used by setup 318 # for local heap purposes. 319 320ext_loader_ver: 321 .byte 0 # Extended boot loader version 322ext_loader_type: 323 .byte 0 # Extended boot loader type 324 325cmd_line_ptr: .long 0 # (Header version 0x0202 or later) 326 # If nonzero, a 32-bit pointer 327 # to the kernel command line. 328 # The command line should be 329 # located between the start of 330 # setup and the end of low 331 # memory (0xa0000), or it may 332 # get overwritten before it 333 # gets read. If this field is 334 # used, there is no longer 335 # anything magical about the 336 # 0x90000 segment; the setup 337 # can be located anywhere in 338 # low memory 0x10000 or higher. 339 340ramdisk_max: .long 0x7fffffff 341 # (Header version 0x0203 or later) 342 # The highest safe address for 343 # the contents of an initrd 344 # The current kernel allows up to 4 GB, 345 # but leave it at 2 GB to avoid 346 # possible bootloader bugs. 347 348kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment 349 #required for protected mode 350 #kernel 351#ifdef CONFIG_RELOCATABLE 352relocatable_kernel: .byte 1 353#else 354relocatable_kernel: .byte 0 355#endif 356min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment 357pad3: .word 0 358 359cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, 360 #added with boot protocol 361 #version 2.06 362 363hardware_subarch: .long 0 # subarchitecture, added with 2.07 364 # default to 0 for normal x86 PC 365 366hardware_subarch_data: .quad 0 367 368payload_offset: .long ZO_input_data 369payload_length: .long ZO_z_input_len 370 371setup_data: .quad 0 # 64-bit physical pointer to 372 # single linked list of 373 # struct setup_data 374 375pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr 376 377#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset) 378#define VO_INIT_SIZE (VO__end - VO__text) 379#if ZO_INIT_SIZE > VO_INIT_SIZE 380#define INIT_SIZE ZO_INIT_SIZE 381#else 382#define INIT_SIZE VO_INIT_SIZE 383#endif 384init_size: .long INIT_SIZE # kernel initialization size 385 386# End of setup header ##################################################### 387 388 .section ".entrytext", "ax" 389start_of_setup: 390#ifdef SAFE_RESET_DISK_CONTROLLER 391# Reset the disk controller. 392 movw $0x0000, %ax # Reset disk controller 393 movb $0x80, %dl # All disks 394 int $0x13 395#endif 396 397# Force %es = %ds 398 movw %ds, %ax 399 movw %ax, %es 400 cld 401 402# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds, 403# which happened to work by accident for the old code. Recalculate the stack 404# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the 405# stack behind its own code, so we can't blindly put it directly past the heap. 406 407 movw %ss, %dx 408 cmpw %ax, %dx # %ds == %ss? 409 movw %sp, %dx 410 je 2f # -> assume %sp is reasonably set 411 412 # Invalid %ss, make up a new stack 413 movw $_end, %dx 414 testb $CAN_USE_HEAP, loadflags 415 jz 1f 416 movw heap_end_ptr, %dx 4171: addw $STACK_SIZE, %dx 418 jnc 2f 419 xorw %dx, %dx # Prevent wraparound 420 4212: # Now %dx should point to the end of our stack space 422 andw $~3, %dx # dword align (might as well...) 423 jnz 3f 424 movw $0xfffc, %dx # Make sure we're not zero 4253: movw %ax, %ss 426 movzwl %dx, %esp # Clear upper half of %esp 427 sti # Now we should have a working stack 428 429# We will have entered with %cs = %ds+0x20, normalize %cs so 430# it is on par with the other segments. 431 pushw %ds 432 pushw $6f 433 lretw 4346: 435 436# Check signature at end of setup 437 cmpl $0x5a5aaa55, setup_sig 438 jne setup_bad 439 440# Zero the bss 441 movw $__bss_start, %di 442 movw $_end+3, %cx 443 xorl %eax, %eax 444 subw %di, %cx 445 shrw $2, %cx 446 rep; stosl 447 448# Jump to C code (should not return) 449 calll main 450 451# Setup corrupt somehow... 452setup_bad: 453 movl $setup_corrupt, %eax 454 calll puts 455 # Fall through... 456 457 .globl die 458 .type die, @function 459die: 460 hlt 461 jmp die 462 463 .size die, .-die 464 465 .section ".initdata", "a" 466setup_corrupt: 467 .byte 7 468 .string "No setup signature found...\n" 469 470 .data 471dummy: .long 0 472 473 .section .reloc 474reloc_start: 475 .long dummy - reloc_start 476 .long 10 477 .word 0 478reloc_end: 479