1/* 2 * linux/boot/head.S 3 * 4 * Copyright (C) 1991, 1992, 1993 Linus Torvalds 5 */ 6 7/* 8 * head.S contains the 32-bit startup code. 9 * 10 * NOTE!!! Startup happens at absolute address 0x00001000, which is also where 11 * the page directory will exist. The startup code will be overwritten by 12 * the page directory. [According to comments etc elsewhere on a compressed 13 * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC] 14 * 15 * Page 0 is deliberately kept safe, since System Management Mode code in 16 * laptops may need to access the BIOS data stored there. This is also 17 * useful for future device drivers that either access the BIOS via VM86 18 * mode. 19 */ 20 21/* 22 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 23 */ 24 .code32 25 .text 26 27#include <linux/init.h> 28#include <linux/linkage.h> 29#include <asm/segment.h> 30#include <asm/boot.h> 31#include <asm/msr.h> 32#include <asm/processor-flags.h> 33#include <asm/asm-offsets.h> 34#include <asm/bootparam.h> 35 36/* 37 * Locally defined symbols should be marked hidden: 38 */ 39 .hidden _bss 40 .hidden _ebss 41 .hidden _got 42 .hidden _egot 43 44 __HEAD 45 .code32 46ENTRY(startup_32) 47 /* 48 * 32bit entry is 0 and it is ABI so immutable! 49 * If we come here directly from a bootloader, 50 * kernel(text+data+bss+brk) ramdisk, zero_page, command line 51 * all need to be under the 4G limit. 52 */ 53 cld 54 /* 55 * Test KEEP_SEGMENTS flag to see if the bootloader is asking 56 * us to not reload segments 57 */ 58 testb $KEEP_SEGMENTS, BP_loadflags(%esi) 59 jnz 1f 60 61 cli 62 movl $(__BOOT_DS), %eax 63 movl %eax, %ds 64 movl %eax, %es 65 movl %eax, %ss 661: 67 68/* 69 * Calculate the delta between where we were compiled to run 70 * at and where we were actually loaded at. This can only be done 71 * with a short local call on x86. Nothing else will tell us what 72 * address we are running at. The reserved chunk of the real-mode 73 * data at 0x1e4 (defined as a scratch field) are used as the stack 74 * for this calculation. Only 4 bytes are needed. 75 */ 76 leal (BP_scratch+4)(%esi), %esp 77 call 1f 781: popl %ebp 79 subl $1b, %ebp 80 81/* setup a stack and make sure cpu supports long mode. */ 82 movl $boot_stack_end, %eax 83 addl %ebp, %eax 84 movl %eax, %esp 85 86 call verify_cpu 87 testl %eax, %eax 88 jnz no_longmode 89 90/* 91 * Compute the delta between where we were compiled to run at 92 * and where the code will actually run at. 93 * 94 * %ebp contains the address we are loaded at by the boot loader and %ebx 95 * contains the address where we should move the kernel image temporarily 96 * for safe in-place decompression. 97 */ 98 99#ifdef CONFIG_RELOCATABLE 100 movl %ebp, %ebx 101 movl BP_kernel_alignment(%esi), %eax 102 decl %eax 103 addl %eax, %ebx 104 notl %eax 105 andl %eax, %ebx 106 cmpl $LOAD_PHYSICAL_ADDR, %ebx 107 jge 1f 108#endif 109 movl $LOAD_PHYSICAL_ADDR, %ebx 1101: 111 112 /* Target address to relocate to for decompression */ 113 movl BP_init_size(%esi), %eax 114 subl $_end, %eax 115 addl %eax, %ebx 116 117/* 118 * Prepare for entering 64 bit mode 119 */ 120 121 /* Load new GDT with the 64bit segments using 32bit descriptor */ 122 leal gdt(%ebp), %eax 123 movl %eax, gdt+2(%ebp) 124 lgdt gdt(%ebp) 125 126 /* Enable PAE mode */ 127 movl %cr4, %eax 128 orl $X86_CR4_PAE, %eax 129 movl %eax, %cr4 130 131 /* 132 * Build early 4G boot pagetable 133 */ 134 /* Initialize Page tables to 0 */ 135 leal pgtable(%ebx), %edi 136 xorl %eax, %eax 137 movl $(BOOT_INIT_PGT_SIZE/4), %ecx 138 rep stosl 139 140 /* Build Level 4 */ 141 leal pgtable + 0(%ebx), %edi 142 leal 0x1007 (%edi), %eax 143 movl %eax, 0(%edi) 144 145 /* Build Level 3 */ 146 leal pgtable + 0x1000(%ebx), %edi 147 leal 0x1007(%edi), %eax 148 movl $4, %ecx 1491: movl %eax, 0x00(%edi) 150 addl $0x00001000, %eax 151 addl $8, %edi 152 decl %ecx 153 jnz 1b 154 155 /* Build Level 2 */ 156 leal pgtable + 0x2000(%ebx), %edi 157 movl $0x00000183, %eax 158 movl $2048, %ecx 1591: movl %eax, 0(%edi) 160 addl $0x00200000, %eax 161 addl $8, %edi 162 decl %ecx 163 jnz 1b 164 165 /* Enable the boot page tables */ 166 leal pgtable(%ebx), %eax 167 movl %eax, %cr3 168 169 /* Enable Long mode in EFER (Extended Feature Enable Register) */ 170 movl $MSR_EFER, %ecx 171 rdmsr 172 btsl $_EFER_LME, %eax 173 wrmsr 174 175 /* After gdt is loaded */ 176 xorl %eax, %eax 177 lldt %ax 178 movl $__BOOT_TSS, %eax 179 ltr %ax 180 181 /* 182 * Setup for the jump to 64bit mode 183 * 184 * When the jump is performend we will be in long mode but 185 * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1 186 * (and in turn EFER.LMA = 1). To jump into 64bit mode we use 187 * the new gdt/idt that has __KERNEL_CS with CS.L = 1. 188 * We place all of the values on our mini stack so lret can 189 * used to perform that far jump. 190 */ 191 pushl $__KERNEL_CS 192 leal startup_64(%ebp), %eax 193#ifdef CONFIG_EFI_MIXED 194 movl efi32_config(%ebp), %ebx 195 cmp $0, %ebx 196 jz 1f 197 leal handover_entry(%ebp), %eax 1981: 199#endif 200 pushl %eax 201 202 /* Enter paged protected Mode, activating Long Mode */ 203 movl $(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */ 204 movl %eax, %cr0 205 206 /* Jump from 32bit compatibility mode into 64bit mode. */ 207 lret 208ENDPROC(startup_32) 209 210#ifdef CONFIG_EFI_MIXED 211 .org 0x190 212ENTRY(efi32_stub_entry) 213 add $0x4, %esp /* Discard return address */ 214 popl %ecx 215 popl %edx 216 popl %esi 217 218 leal (BP_scratch+4)(%esi), %esp 219 call 1f 2201: pop %ebp 221 subl $1b, %ebp 222 223 movl %ecx, efi32_config(%ebp) 224 movl %edx, efi32_config+8(%ebp) 225 sgdtl efi32_boot_gdt(%ebp) 226 227 leal efi32_config(%ebp), %eax 228 movl %eax, efi_config(%ebp) 229 230 jmp startup_32 231ENDPROC(efi32_stub_entry) 232#endif 233 234 .code64 235 .org 0x200 236ENTRY(startup_64) 237 /* 238 * 64bit entry is 0x200 and it is ABI so immutable! 239 * We come here either from startup_32 or directly from a 240 * 64bit bootloader. 241 * If we come here from a bootloader, kernel(text+data+bss+brk), 242 * ramdisk, zero_page, command line could be above 4G. 243 * We depend on an identity mapped page table being provided 244 * that maps our entire kernel(text+data+bss+brk), zero page 245 * and command line. 246 */ 247#ifdef CONFIG_EFI_STUB 248 /* 249 * The entry point for the PE/COFF executable is efi_pe_entry, so 250 * only legacy boot loaders will execute this jmp. 251 */ 252 jmp preferred_addr 253 254ENTRY(efi_pe_entry) 255 movq %rcx, efi64_config(%rip) /* Handle */ 256 movq %rdx, efi64_config+8(%rip) /* EFI System table pointer */ 257 258 leaq efi64_config(%rip), %rax 259 movq %rax, efi_config(%rip) 260 261 call 1f 2621: popq %rbp 263 subq $1b, %rbp 264 265 /* 266 * Relocate efi_config->call(). 267 */ 268 addq %rbp, efi64_config+32(%rip) 269 270 movq %rax, %rdi 271 call make_boot_params 272 cmpq $0,%rax 273 je fail 274 mov %rax, %rsi 275 leaq startup_32(%rip), %rax 276 movl %eax, BP_code32_start(%rsi) 277 jmp 2f /* Skip the relocation */ 278 279handover_entry: 280 call 1f 2811: popq %rbp 282 subq $1b, %rbp 283 284 /* 285 * Relocate efi_config->call(). 286 */ 287 movq efi_config(%rip), %rax 288 addq %rbp, 32(%rax) 2892: 290 movq efi_config(%rip), %rdi 291 call efi_main 292 movq %rax,%rsi 293 cmpq $0,%rax 294 jne 2f 295fail: 296 /* EFI init failed, so hang. */ 297 hlt 298 jmp fail 2992: 300 movl BP_code32_start(%esi), %eax 301 leaq preferred_addr(%rax), %rax 302 jmp *%rax 303 304preferred_addr: 305#endif 306 307 /* Setup data segments. */ 308 xorl %eax, %eax 309 movl %eax, %ds 310 movl %eax, %es 311 movl %eax, %ss 312 movl %eax, %fs 313 movl %eax, %gs 314 315 /* 316 * Compute the decompressed kernel start address. It is where 317 * we were loaded at aligned to a 2M boundary. %rbp contains the 318 * decompressed kernel start address. 319 * 320 * If it is a relocatable kernel then decompress and run the kernel 321 * from load address aligned to 2MB addr, otherwise decompress and 322 * run the kernel from LOAD_PHYSICAL_ADDR 323 * 324 * We cannot rely on the calculation done in 32-bit mode, since we 325 * may have been invoked via the 64-bit entry point. 326 */ 327 328 /* Start with the delta to where the kernel will run at. */ 329#ifdef CONFIG_RELOCATABLE 330 leaq startup_32(%rip) /* - $startup_32 */, %rbp 331 movl BP_kernel_alignment(%rsi), %eax 332 decl %eax 333 addq %rax, %rbp 334 notq %rax 335 andq %rax, %rbp 336 cmpq $LOAD_PHYSICAL_ADDR, %rbp 337 jge 1f 338#endif 339 movq $LOAD_PHYSICAL_ADDR, %rbp 3401: 341 342 /* Target address to relocate to for decompression */ 343 movl BP_init_size(%rsi), %ebx 344 subl $_end, %ebx 345 addq %rbp, %rbx 346 347 /* Set up the stack */ 348 leaq boot_stack_end(%rbx), %rsp 349 350 /* Zero EFLAGS */ 351 pushq $0 352 popfq 353 354/* 355 * Copy the compressed kernel to the end of our buffer 356 * where decompression in place becomes safe. 357 */ 358 pushq %rsi 359 leaq (_bss-8)(%rip), %rsi 360 leaq (_bss-8)(%rbx), %rdi 361 movq $_bss /* - $startup_32 */, %rcx 362 shrq $3, %rcx 363 std 364 rep movsq 365 cld 366 popq %rsi 367 368/* 369 * Jump to the relocated address. 370 */ 371 leaq relocated(%rbx), %rax 372 jmp *%rax 373 374#ifdef CONFIG_EFI_STUB 375 .org 0x390 376ENTRY(efi64_stub_entry) 377 movq %rdi, efi64_config(%rip) /* Handle */ 378 movq %rsi, efi64_config+8(%rip) /* EFI System table pointer */ 379 380 leaq efi64_config(%rip), %rax 381 movq %rax, efi_config(%rip) 382 383 movq %rdx, %rsi 384 jmp handover_entry 385ENDPROC(efi64_stub_entry) 386#endif 387 388 .text 389relocated: 390 391/* 392 * Clear BSS (stack is currently empty) 393 */ 394 xorl %eax, %eax 395 leaq _bss(%rip), %rdi 396 leaq _ebss(%rip), %rcx 397 subq %rdi, %rcx 398 shrq $3, %rcx 399 rep stosq 400 401/* 402 * Adjust our own GOT 403 */ 404 leaq _got(%rip), %rdx 405 leaq _egot(%rip), %rcx 4061: 407 cmpq %rcx, %rdx 408 jae 2f 409 addq %rbx, (%rdx) 410 addq $8, %rdx 411 jmp 1b 4122: 413 414/* 415 * Do the extraction, and jump to the new kernel.. 416 */ 417 pushq %rsi /* Save the real mode argument */ 418 movq %rsi, %rdi /* real mode address */ 419 leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ 420 leaq input_data(%rip), %rdx /* input_data */ 421 movl $z_input_len, %ecx /* input_len */ 422 movq %rbp, %r8 /* output target address */ 423 movq $z_output_len, %r9 /* decompressed length, end of relocs */ 424 call extract_kernel /* returns kernel location in %rax */ 425 popq %rsi 426 427/* 428 * Jump to the decompressed kernel. 429 */ 430 jmp *%rax 431 432 .code32 433no_longmode: 434 /* This isn't an x86-64 CPU so hang */ 4351: 436 hlt 437 jmp 1b 438 439#include "../../kernel/verify_cpu.S" 440 441 .data 442gdt: 443 .word gdt_end - gdt 444 .long gdt 445 .word 0 446 .quad 0x0000000000000000 /* NULL descriptor */ 447 .quad 0x00af9a000000ffff /* __KERNEL_CS */ 448 .quad 0x00cf92000000ffff /* __KERNEL_DS */ 449 .quad 0x0080890000000000 /* TS descriptor */ 450 .quad 0x0000000000000000 /* TS continued */ 451gdt_end: 452 453#ifdef CONFIG_EFI_STUB 454efi_config: 455 .quad 0 456 457#ifdef CONFIG_EFI_MIXED 458 .global efi32_config 459efi32_config: 460 .fill 4,8,0 461 .quad efi64_thunk 462 .byte 0 463#endif 464 465 .global efi64_config 466efi64_config: 467 .fill 4,8,0 468 .quad efi_call 469 .byte 1 470#endif /* CONFIG_EFI_STUB */ 471 472/* 473 * Stack and heap for uncompression 474 */ 475 .bss 476 .balign 4 477boot_heap: 478 .fill BOOT_HEAP_SIZE, 1, 0 479boot_stack: 480 .fill BOOT_STACK_SIZE, 1, 0 481boot_stack_end: 482 483/* 484 * Space for page tables (not in .bss so not zeroed) 485 */ 486 .section ".pgtable","a",@nobits 487 .balign 4096 488pgtable: 489 .fill BOOT_PGT_SIZE, 1, 0 490