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 floppy boot is not supported. " 98 .ascii "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 3 # 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 0x0200 # 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 0x20 # SectionAlignment 162 .long 0x20 # 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 0x6 # 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 # 204 # The offset & size fields are filled in by build.c. 205 # 206 .ascii ".setup" 207 .byte 0 208 .byte 0 209 .long 0 210 .long 0x0 # startup_{32,64} 211 .long 0 # Size of initialized data 212 # on disk 213 .long 0x0 # startup_{32,64} 214 .long 0 # PointerToRelocations 215 .long 0 # PointerToLineNumbers 216 .word 0 # NumberOfRelocations 217 .word 0 # NumberOfLineNumbers 218 .long 0x60500020 # Characteristics (section flags) 219 220 # 221 # The EFI application loader requires a relocation section 222 # because EFI applications must be relocatable. The .reloc 223 # offset & size fields are filled in by build.c. 224 # 225 .ascii ".reloc" 226 .byte 0 227 .byte 0 228 .long 0 229 .long 0 230 .long 0 # SizeOfRawData 231 .long 0 # PointerToRawData 232 .long 0 # PointerToRelocations 233 .long 0 # PointerToLineNumbers 234 .word 0 # NumberOfRelocations 235 .word 0 # NumberOfLineNumbers 236 .long 0x42100040 # Characteristics (section flags) 237 238 # 239 # The offset & size fields are filled in by build.c. 240 # 241 .ascii ".text" 242 .byte 0 243 .byte 0 244 .byte 0 245 .long 0 246 .long 0x0 # startup_{32,64} 247 .long 0 # Size of initialized data 248 # on disk 249 .long 0x0 # startup_{32,64} 250 .long 0 # PointerToRelocations 251 .long 0 # PointerToLineNumbers 252 .word 0 # NumberOfRelocations 253 .word 0 # NumberOfLineNumbers 254 .long 0x60500020 # Characteristics (section flags) 255 256#endif /* CONFIG_EFI_STUB */ 257 258 # Kernel attributes; used by setup. This is part 1 of the 259 # header, from the old boot sector. 260 261 .section ".header", "a" 262 .globl hdr 263hdr: 264setup_sects: .byte 0 /* Filled in by build.c */ 265root_flags: .word ROOT_RDONLY 266syssize: .long 0 /* Filled in by build.c */ 267ram_size: .word 0 /* Obsolete */ 268vid_mode: .word SVGA_MODE 269root_dev: .word 0 /* Filled in by build.c */ 270boot_flag: .word 0xAA55 271 272 # offset 512, entry point 273 274 .globl _start 275_start: 276 # Explicitly enter this as bytes, or the assembler 277 # tries to generate a 3-byte jump here, which causes 278 # everything else to push off to the wrong offset. 279 .byte 0xeb # short (2-byte) jump 280 .byte start_of_setup-1f 2811: 282 283 # Part 2 of the header, from the old setup.S 284 285 .ascii "HdrS" # header signature 286 .word 0x020b # header version number (>= 0x0105) 287 # or else old loadlin-1.5 will fail) 288 .globl realmode_swtch 289realmode_swtch: .word 0, 0 # default_switch, SETUPSEG 290start_sys_seg: .word SYSSEG # obsolete and meaningless, but just 291 # in case something decided to "use" it 292 .word kernel_version-512 # pointing to kernel version string 293 # above section of header is compatible 294 # with loadlin-1.5 (header v1.5). Don't 295 # change it. 296 297type_of_loader: .byte 0 # 0 means ancient bootloader, newer 298 # bootloaders know to change this. 299 # See Documentation/x86/boot.txt for 300 # assigned ids 301 302# flags, unused bits must be zero (RFU) bit within loadflags 303loadflags: 304LOADED_HIGH = 1 # If set, the kernel is loaded high 305CAN_USE_HEAP = 0x80 # If set, the loader also has set 306 # heap_end_ptr to tell how much 307 # space behind setup.S can be used for 308 # heap purposes. 309 # Only the loader knows what is free 310 .byte LOADED_HIGH 311 312setup_move_size: .word 0x8000 # size to move, when setup is not 313 # loaded at 0x90000. We will move setup 314 # to 0x90000 then just before jumping 315 # into the kernel. However, only the 316 # loader knows how much data behind 317 # us also needs to be loaded. 318 319code32_start: # here loaders can put a different 320 # start address for 32-bit code. 321 .long 0x100000 # 0x100000 = default for big kernel 322 323ramdisk_image: .long 0 # address of loaded ramdisk image 324 # Here the loader puts the 32-bit 325 # address where it loaded the image. 326 # This only will be read by the kernel. 327 328ramdisk_size: .long 0 # its size in bytes 329 330bootsect_kludge: 331 .long 0 # obsolete 332 333heap_end_ptr: .word _end+STACK_SIZE-512 334 # (Header version 0x0201 or later) 335 # space from here (exclusive) down to 336 # end of setup code can be used by setup 337 # for local heap purposes. 338 339ext_loader_ver: 340 .byte 0 # Extended boot loader version 341ext_loader_type: 342 .byte 0 # Extended boot loader type 343 344cmd_line_ptr: .long 0 # (Header version 0x0202 or later) 345 # If nonzero, a 32-bit pointer 346 # to the kernel command line. 347 # The command line should be 348 # located between the start of 349 # setup and the end of low 350 # memory (0xa0000), or it may 351 # get overwritten before it 352 # gets read. If this field is 353 # used, there is no longer 354 # anything magical about the 355 # 0x90000 segment; the setup 356 # can be located anywhere in 357 # low memory 0x10000 or higher. 358 359ramdisk_max: .long 0x7fffffff 360 # (Header version 0x0203 or later) 361 # The highest safe address for 362 # the contents of an initrd 363 # The current kernel allows up to 4 GB, 364 # but leave it at 2 GB to avoid 365 # possible bootloader bugs. 366 367kernel_alignment: .long CONFIG_PHYSICAL_ALIGN #physical addr alignment 368 #required for protected mode 369 #kernel 370#ifdef CONFIG_RELOCATABLE 371relocatable_kernel: .byte 1 372#else 373relocatable_kernel: .byte 0 374#endif 375min_alignment: .byte MIN_KERNEL_ALIGN_LG2 # minimum alignment 376pad3: .word 0 377 378cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, 379 #added with boot protocol 380 #version 2.06 381 382hardware_subarch: .long 0 # subarchitecture, added with 2.07 383 # default to 0 for normal x86 PC 384 385hardware_subarch_data: .quad 0 386 387payload_offset: .long ZO_input_data 388payload_length: .long ZO_z_input_len 389 390setup_data: .quad 0 # 64-bit physical pointer to 391 # single linked list of 392 # struct setup_data 393 394pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr 395 396#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset) 397#define VO_INIT_SIZE (VO__end - VO__text) 398#if ZO_INIT_SIZE > VO_INIT_SIZE 399#define INIT_SIZE ZO_INIT_SIZE 400#else 401#define INIT_SIZE VO_INIT_SIZE 402#endif 403init_size: .long INIT_SIZE # kernel initialization size 404handover_offset: .long 0x30 # offset to the handover 405 # protocol entry point 406 407# End of setup header ##################################################### 408 409 .section ".entrytext", "ax" 410start_of_setup: 411# Force %es = %ds 412 movw %ds, %ax 413 movw %ax, %es 414 cld 415 416# Apparently some ancient versions of LILO invoked the kernel with %ss != %ds, 417# which happened to work by accident for the old code. Recalculate the stack 418# pointer if %ss is invalid. Otherwise leave it alone, LOADLIN sets up the 419# stack behind its own code, so we can't blindly put it directly past the heap. 420 421 movw %ss, %dx 422 cmpw %ax, %dx # %ds == %ss? 423 movw %sp, %dx 424 je 2f # -> assume %sp is reasonably set 425 426 # Invalid %ss, make up a new stack 427 movw $_end, %dx 428 testb $CAN_USE_HEAP, loadflags 429 jz 1f 430 movw heap_end_ptr, %dx 4311: addw $STACK_SIZE, %dx 432 jnc 2f 433 xorw %dx, %dx # Prevent wraparound 434 4352: # Now %dx should point to the end of our stack space 436 andw $~3, %dx # dword align (might as well...) 437 jnz 3f 438 movw $0xfffc, %dx # Make sure we're not zero 4393: movw %ax, %ss 440 movzwl %dx, %esp # Clear upper half of %esp 441 sti # Now we should have a working stack 442 443# We will have entered with %cs = %ds+0x20, normalize %cs so 444# it is on par with the other segments. 445 pushw %ds 446 pushw $6f 447 lretw 4486: 449 450# Check signature at end of setup 451 cmpl $0x5a5aaa55, setup_sig 452 jne setup_bad 453 454# Zero the bss 455 movw $__bss_start, %di 456 movw $_end+3, %cx 457 xorl %eax, %eax 458 subw %di, %cx 459 shrw $2, %cx 460 rep; stosl 461 462# Jump to C code (should not return) 463 calll main 464 465# Setup corrupt somehow... 466setup_bad: 467 movl $setup_corrupt, %eax 468 calll puts 469 # Fall through... 470 471 .globl die 472 .type die, @function 473die: 474 hlt 475 jmp die 476 477 .size die, .-die 478 479 .section ".initdata", "a" 480setup_corrupt: 481 .byte 7 482 .string "No setup signature found...\n" 483 484 .data 485dummy: .long 0 486