arch/x86/boot/header.S

   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 <asm/bootparam.h>
  25 #include "boot.h"
  26 #include "voffset.h"
  27 #include "zoffset.h"
  28
  29 BOOTSEG         = 0x07C0                /* original address of boot-sector */
  30 SYSSEG          = 0x1000                /* historical load address >> 4 */
  31
  32 #ifndef SVGA_MODE
  33 #define SVGA_MODE ASK_VGA
  34 #endif
  35
  36 #ifndef ROOT_RDONLY
  37 #define ROOT_RDONLY 1
  38 #endif
  39
  40         .code16
  41         .section ".bstext", "ax"
  42
  43         .global bootsect_start
  44 bootsect_start:
  45 #ifdef CONFIG_EFI_STUB
  46         # "MZ", MS-DOS header
  47         .byte 0x4d
  48         .byte 0x5a
  49 #endif
  50
  51         # Normalize the start address
  52         ljmp    $BOOTSEG, $start2
  53
  54 start2:
  55         movw    %cs, %ax
  56         movw    %ax, %ds
  57         movw    %ax, %es
  58         movw    %ax, %ss
  59         xorw    %sp, %sp
  60         sti
  61         cld
  62
  63         movw    $bugger_off_msg, %si
  64
  65 msg_loop:
  66         lodsb
  67         andb    %al, %al
  68         jz      bs_die
  69         movb    $0xe, %ah
  70         movw    $7, %bx
  71         int     $0x10
  72         jmp     msg_loop
  73
  74 bs_die:
  75         # Allow the user to press a key, then reboot
  76         xorw    %ax, %ax
  77         int     $0x16
  78         int     $0x19
  79
  80         # int 0x19 should never return.  In case it does anyway,
  81         # invoke the BIOS reset code...
  82         ljmp    $0xf000,$0xfff0
  83
  84 #ifdef CONFIG_EFI_STUB
  85         .org    0x3c
  86         #
  87         # Offset to the PE header.
  88         #
  89         .long   pe_header
  90 #endif /* CONFIG_EFI_STUB */
  91
  92         .section ".bsdata", "a"
  93 bugger_off_msg:
  94         .ascii  "Use a boot loader.\r\n"
  95         .ascii  "\n"
  96         .ascii  "Remove disk and press any key to reboot...\r\n"
  97         .byte   0
  98
  99 #ifdef CONFIG_EFI_STUB
 100 pe_header:
 101         .ascii  "PE"
 102         .word   0
 103
 104 coff_header:
 105 #ifdef CONFIG_X86_32
 106         .word   0x14c                           # i386
 107 #else
 108         .word   0x8664                          # x86-64
 109 #endif
 110         .word   4                               # nr_sections
 111         .long   0                               # TimeDateStamp
 112         .long   0                               # PointerToSymbolTable
 113         .long   1                               # NumberOfSymbols
 114         .word   section_table - optional_header # SizeOfOptionalHeader
 115 #ifdef CONFIG_X86_32
 116         .word   0x306                           # Characteristics.
 117                                                 # IMAGE_FILE_32BIT_MACHINE |
 118                                                 # IMAGE_FILE_DEBUG_STRIPPED |
 119                                                 # IMAGE_FILE_EXECUTABLE_IMAGE |
 120                                                 # IMAGE_FILE_LINE_NUMS_STRIPPED
 121 #else
 122         .word   0x206                           # Characteristics
 123                                                 # IMAGE_FILE_DEBUG_STRIPPED |
 124                                                 # IMAGE_FILE_EXECUTABLE_IMAGE |
 125                                                 # IMAGE_FILE_LINE_NUMS_STRIPPED
 126 #endif
 127
 128 optional_header:
 129 #ifdef CONFIG_X86_32
 130         .word   0x10b                           # PE32 format
 131 #else
 132         .word   0x20b                           # PE32+ format
 133 #endif
 134         .byte   0x02                            # MajorLinkerVersion
 135         .byte   0x14                            # MinorLinkerVersion
 136
 137         # Filled in by build.c
 138         .long   0                               # SizeOfCode
 139
 140         .long   0                               # SizeOfInitializedData
 141         .long   0                               # SizeOfUninitializedData
 142
 143         # Filled in by build.c
 144         .long   0x0000                          # AddressOfEntryPoint
 145
 146         .long   0x0200                          # BaseOfCode
 147 #ifdef CONFIG_X86_32
 148         .long   0                               # data
 149 #endif
 150
 151 extra_header_fields:
 152 #ifdef CONFIG_X86_32
 153         .long   0                               # ImageBase
 154 #else
 155         .quad   0                               # ImageBase
 156 #endif
 157         .long   0x20                            # SectionAlignment
 158         .long   0x20                            # FileAlignment
 159         .word   0                               # MajorOperatingSystemVersion
 160         .word   0                               # MinorOperatingSystemVersion
 161         .word   0                               # MajorImageVersion
 162         .word   0                               # MinorImageVersion
 163         .word   0                               # MajorSubsystemVersion
 164         .word   0                               # MinorSubsystemVersion
 165         .long   0                               # Win32VersionValue
 166
 167         #
 168         # The size of the bzImage is written in tools/build.c
 169         #
 170         .long   0                               # SizeOfImage
 171
 172         .long   0x200                           # SizeOfHeaders
 173         .long   0                               # CheckSum
 174         .word   0xa                             # Subsystem (EFI application)
 175         .word   0                               # DllCharacteristics
 176 #ifdef CONFIG_X86_32
 177         .long   0                               # SizeOfStackReserve
 178         .long   0                               # SizeOfStackCommit
 179         .long   0                               # SizeOfHeapReserve
 180         .long   0                               # SizeOfHeapCommit
 181 #else
 182         .quad   0                               # SizeOfStackReserve
 183         .quad   0                               # SizeOfStackCommit
 184         .quad   0                               # SizeOfHeapReserve
 185         .quad   0                               # SizeOfHeapCommit
 186 #endif
 187         .long   0                               # LoaderFlags
 188         .long   0x6                             # NumberOfRvaAndSizes
 189
 190         .quad   0                               # ExportTable
 191         .quad   0                               # ImportTable
 192         .quad   0                               # ResourceTable
 193         .quad   0                               # ExceptionTable
 194         .quad   0                               # CertificationTable
 195         .quad   0                               # BaseRelocationTable
 196
 197         # Section table
 198 section_table:
 199         #
 200         # The offset & size fields are filled in by build.c.
 201         #
 202         .ascii  ".setup"
 203         .byte   0
 204         .byte   0
 205         .long   0
 206         .long   0x0                             # startup_{32,64}
 207         .long   0                               # Size of initialized data
 208                                                 # on disk
 209         .long   0x0                             # startup_{32,64}
 210         .long   0                               # PointerToRelocations
 211         .long   0                               # PointerToLineNumbers
 212         .word   0                               # NumberOfRelocations
 213         .word   0                               # NumberOfLineNumbers
 214         .long   0x60500020                      # Characteristics (section flags)
 215
 216         #
 217         # The EFI application loader requires a relocation section
 218         # because EFI applications must be relocatable. The .reloc
 219         # offset & size fields are filled in by build.c.
 220         #
 221         .ascii  ".reloc"
 222         .byte   0
 223         .byte   0
 224         .long   0
 225         .long   0
 226         .long   0                               # SizeOfRawData
 227         .long   0                               # PointerToRawData
 228         .long   0                               # PointerToRelocations
 229         .long   0                               # PointerToLineNumbers
 230         .word   0                               # NumberOfRelocations
 231         .word   0                               # NumberOfLineNumbers
 232         .long   0x42100040                      # Characteristics (section flags)
 233
 234         #
 235         # The offset & size fields are filled in by build.c.
 236         #
 237         .ascii  ".text"
 238         .byte   0
 239         .byte   0
 240         .byte   0
 241         .long   0
 242         .long   0x0                             # startup_{32,64}
 243         .long   0                               # Size of initialized data
 244                                                 # on disk
 245         .long   0x0                             # startup_{32,64}
 246         .long   0                               # PointerToRelocations
 247         .long   0                               # PointerToLineNumbers
 248         .word   0                               # NumberOfRelocations
 249         .word   0                               # NumberOfLineNumbers
 250         .long   0x60500020                      # Characteristics (section flags)
 251
 252         #
 253         # The offset & size fields are filled in by build.c.
 254         #
 255         .ascii  ".bss"
 256         .byte   0
 257         .byte   0
 258         .byte   0
 259         .byte   0
 260         .long   0
 261         .long   0x0
 262         .long   0                               # Size of initialized data
 263                                                 # on disk
 264         .long   0x0
 265         .long   0                               # PointerToRelocations
 266         .long   0                               # PointerToLineNumbers
 267         .word   0                               # NumberOfRelocations
 268         .word   0                               # NumberOfLineNumbers
 269         .long   0xc8000080                      # Characteristics (section flags)
 270
 271 #endif /* CONFIG_EFI_STUB */
 272
 273         # Kernel attributes; used by setup.  This is part 1 of the
 274         # header, from the old boot sector.
 275
 276         .section ".header", "a"
 277         .globl  sentinel
 278 sentinel:       .byte 0xff, 0xff        /* Used to detect broken loaders */
 279
 280         .globl  hdr
 281 hdr:
 282 setup_sects:    .byte 0                 /* Filled in by build.c */
 283 root_flags:     .word ROOT_RDONLY
 284 syssize:        .long 0                 /* Filled in by build.c */
 285 ram_size:       .word 0                 /* Obsolete */
 286 vid_mode:       .word SVGA_MODE
 287 root_dev:       .word 0                 /* Filled in by build.c */
 288 boot_flag:      .word 0xAA55
 289
 290         # offset 512, entry point
 291
 292         .globl  _start
 293 _start:
 294                 # Explicitly enter this as bytes, or the assembler
 295                 # tries to generate a 3-byte jump here, which causes
 296                 # everything else to push off to the wrong offset.
 297                 .byte   0xeb            # short (2-byte) jump
 298                 .byte   start_of_setup-1f
 299 1:
 300
 301         # Part 2 of the header, from the old setup.S
 302
 303                 .ascii  "HdrS"          # header signature
 304                 .word   0x020d          # header version number (>= 0x0105)
 305                                         # or else old loadlin-1.5 will fail)
 306                 .globl realmode_swtch
 307 realmode_swtch: .word   0, 0            # default_switch, SETUPSEG
 308 start_sys_seg:  .word   SYSSEG          # obsolete and meaningless, but just
 309                                         # in case something decided to "use" it
 310                 .word   kernel_version-512 # pointing to kernel version string
 311                                         # above section of header is compatible
 312                                         # with loadlin-1.5 (header v1.5). Don't
 313                                         # change it.
 314
 315 type_of_loader: .byte   0               # 0 means ancient bootloader, newer
 316                                         # bootloaders know to change this.
 317                                         # See Documentation/x86/boot.txt for
 318                                         # assigned ids
 319
 320 # flags, unused bits must be zero (RFU) bit within loadflags
 321 loadflags:
 322                 .byte   LOADED_HIGH     # The kernel is to be loaded high
 323
 324 setup_move_size: .word  0x8000          # size to move, when setup is not
 325                                         # loaded at 0x90000. We will move setup
 326                                         # to 0x90000 then just before jumping
 327                                         # into the kernel. However, only the
 328                                         # loader knows how much data behind
 329                                         # us also needs to be loaded.
 330
 331 code32_start:                           # here loaders can put a different
 332                                         # start address for 32-bit code.
 333                 .long   0x100000        # 0x100000 = default for big kernel
 334
 335 ramdisk_image:  .long   0               # address of loaded ramdisk image
 336                                         # Here the loader puts the 32-bit
 337                                         # address where it loaded the image.
 338                                         # This only will be read by the kernel.
 339
 340 ramdisk_size:   .long   0               # its size in bytes
 341
 342 bootsect_kludge:
 343                 .long   0               # obsolete
 344
 345 heap_end_ptr:   .word   _end+STACK_SIZE-512
 346                                         # (Header version 0x0201 or later)
 347                                         # space from here (exclusive) down to
 348                                         # end of setup code can be used by setup
 349                                         # for local heap purposes.
 350
 351 ext_loader_ver:
 352                 .byte   0               # Extended boot loader version
 353 ext_loader_type:
 354                 .byte   0               # Extended boot loader type
 355
 356 cmd_line_ptr:   .long   0               # (Header version 0x0202 or later)
 357                                         # If nonzero, a 32-bit pointer
 358                                         # to the kernel command line.
 359                                         # The command line should be
 360                                         # located between the start of
 361                                         # setup and the end of low
 362                                         # memory (0xa0000), or it may
 363                                         # get overwritten before it
 364                                         # gets read.  If this field is
 365                                         # used, there is no longer
 366                                         # anything magical about the
 367                                         # 0x90000 segment; the setup
 368                                         # can be located anywhere in
 369                                         # low memory 0x10000 or higher.
 370
 371 initrd_addr_max: .long 0x7fffffff
 372                                         # (Header version 0x0203 or later)
 373                                         # The highest safe address for
 374                                         # the contents of an initrd
 375                                         # The current kernel allows up to 4 GB,
 376                                         # but leave it at 2 GB to avoid
 377                                         # possible bootloader bugs.
 378
 379 kernel_alignment:  .long CONFIG_PHYSICAL_ALIGN  #physical addr alignment
 380                                                 #required for protected mode
 381                                                 #kernel
 382 #ifdef CONFIG_RELOCATABLE
 383 relocatable_kernel:    .byte 1
 384 #else
 385 relocatable_kernel:    .byte 0
 386 #endif
 387 min_alignment:          .byte MIN_KERNEL_ALIGN_LG2      # minimum alignment
 388
 389 xloadflags:
 390 #ifdef CONFIG_X86_64
 391 # define XLF0 XLF_KERNEL_64                     /* 64-bit kernel */
 392 #else
 393 # define XLF0 0
 394 #endif
 395
 396 #if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64)
 397    /* kernel/boot_param/ramdisk could be loaded above 4g */
 398 # define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G
 399 #else
 400 # define XLF1 0
 401 #endif
 402
 403 #ifdef CONFIG_EFI_STUB
 404 # ifdef CONFIG_EFI_MIXED
 405 #  define XLF23 (XLF_EFI_HANDOVER_32|XLF_EFI_HANDOVER_64)
 406 # else
 407 #  ifdef CONFIG_X86_64
 408 #   define XLF23 XLF_EFI_HANDOVER_64            /* 64-bit EFI handover ok */
 409 #  else
 410 #   define XLF23 XLF_EFI_HANDOVER_32            /* 32-bit EFI handover ok */
 411 #  endif
 412 # endif
 413 #else
 414 # define XLF23 0
 415 #endif
 416
 417 #if defined(CONFIG_X86_64) && defined(CONFIG_EFI) && defined(CONFIG_KEXEC_CORE)
 418 # define XLF4 XLF_EFI_KEXEC
 419 #else
 420 # define XLF4 0
 421 #endif
 422
 423                         .word XLF0 | XLF1 | XLF23 | XLF4
 424
 425 cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
 426                                                 #added with boot protocol
 427                                                 #version 2.06
 428
 429 hardware_subarch:       .long 0                 # subarchitecture, added with 2.07
 430                                                 # default to 0 for normal x86 PC
 431
 432 hardware_subarch_data:  .quad 0
 433
 434 payload_offset:         .long ZO_input_data
 435 payload_length:         .long ZO_z_input_len
 436
 437 setup_data:             .quad 0                 # 64-bit physical pointer to
 438                                                 # single linked list of
 439                                                 # struct setup_data
 440
 441 pref_address:           .quad LOAD_PHYSICAL_ADDR        # preferred load addr
 442
 443 #define ZO_INIT_SIZE    (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
 444 #define VO_INIT_SIZE    (VO__end - VO__text)
 445 #if ZO_INIT_SIZE > VO_INIT_SIZE
 446 #define INIT_SIZE ZO_INIT_SIZE
 447 #else
 448 #define INIT_SIZE VO_INIT_SIZE
 449 #endif
 450 init_size:              .long INIT_SIZE         # kernel initialization size
 451 handover_offset:        .long 0                 # Filled in by build.c
 452
 453 # End of setup header #####################################################
 454
 455         .section ".entrytext", "ax"
 456 start_of_setup:
 457 # Force %es = %ds
 458         movw    %ds, %ax
 459         movw    %ax, %es
 460         cld
 461
 462 # Apparently some ancient versions of LILO invoked the kernel with %ss != %ds,
 463 # which happened to work by accident for the old code.  Recalculate the stack
 464 # pointer if %ss is invalid.  Otherwise leave it alone, LOADLIN sets up the
 465 # stack behind its own code, so we can't blindly put it directly past the heap.
 466
 467         movw    %ss, %dx
 468         cmpw    %ax, %dx        # %ds == %ss?
 469         movw    %sp, %dx
 470         je      2f              # -> assume %sp is reasonably set
 471
 472         # Invalid %ss, make up a new stack
 473         movw    $_end, %dx
 474         testb   $CAN_USE_HEAP, loadflags
 475         jz      1f
 476         movw    heap_end_ptr, %dx
 477 1:      addw    $STACK_SIZE, %dx
 478         jnc     2f
 479         xorw    %dx, %dx        # Prevent wraparound
 480
 481 2:      # Now %dx should point to the end of our stack space
 482         andw    $~3, %dx        # dword align (might as well...)
 483         jnz     3f
 484         movw    $0xfffc, %dx    # Make sure we're not zero
 485 3:      movw    %ax, %ss
 486         movzwl  %dx, %esp       # Clear upper half of %esp
 487         sti                     # Now we should have a working stack
 488
 489 # We will have entered with %cs = %ds+0x20, normalize %cs so
 490 # it is on par with the other segments.
 491         pushw   %ds
 492         pushw   $6f
 493         lretw
 494 6:
 495
 496 # Check signature at end of setup
 497         cmpl    $0x5a5aaa55, setup_sig
 498         jne     setup_bad
 499
 500 # Zero the bss
 501         movw    $__bss_start, %di
 502         movw    $_end+3, %cx
 503         xorl    %eax, %eax
 504         subw    %di, %cx
 505         shrw    $2, %cx
 506         rep; stosl
 507
 508 # Jump to C code (should not return)
 509         calll   main
 510
 511 # Setup corrupt somehow...
 512 setup_bad:
 513         movl    $setup_corrupt, %eax
 514         calll   puts
 515         # Fall through...
 516
 517         .globl  die
 518         .type   die, @function
 519 die:
 520         hlt
 521         jmp     die
 522
 523         .size   die, .-die
 524
 525         .section ".initdata", "a"
 526 setup_corrupt:
 527         .byte   7
 528         .string "No setup signature found...\n"