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 35 __HEAD 36 .code32 37ENTRY(startup_32) 38 /* 39 * 32bit entry is 0 and it is ABI so immutable! 40 * If we come here directly from a bootloader, 41 * kernel(text+data+bss+brk) ramdisk, zero_page, command line 42 * all need to be under the 4G limit. 43 */ 44 cld 45 /* 46 * Test KEEP_SEGMENTS flag to see if the bootloader is asking 47 * us to not reload segments 48 */ 49 testb $(1<<6), BP_loadflags(%esi) 50 jnz 1f 51 52 cli 53 movl $(__BOOT_DS), %eax 54 movl %eax, %ds 55 movl %eax, %es 56 movl %eax, %ss 571: 58 59/* 60 * Calculate the delta between where we were compiled to run 61 * at and where we were actually loaded at. This can only be done 62 * with a short local call on x86. Nothing else will tell us what 63 * address we are running at. The reserved chunk of the real-mode 64 * data at 0x1e4 (defined as a scratch field) are used as the stack 65 * for this calculation. Only 4 bytes are needed. 66 */ 67 leal (BP_scratch+4)(%esi), %esp 68 call 1f 691: popl %ebp 70 subl $1b, %ebp 71 72/* setup a stack and make sure cpu supports long mode. */ 73 movl $boot_stack_end, %eax 74 addl %ebp, %eax 75 movl %eax, %esp 76 77 call verify_cpu 78 testl %eax, %eax 79 jnz no_longmode 80 81/* 82 * Compute the delta between where we were compiled to run at 83 * and where the code will actually run at. 84 * 85 * %ebp contains the address we are loaded at by the boot loader and %ebx 86 * contains the address where we should move the kernel image temporarily 87 * for safe in-place decompression. 88 */ 89 90#ifdef CONFIG_RELOCATABLE 91 movl %ebp, %ebx 92 movl BP_kernel_alignment(%esi), %eax 93 decl %eax 94 addl %eax, %ebx 95 notl %eax 96 andl %eax, %ebx 97 cmpl $LOAD_PHYSICAL_ADDR, %ebx 98 jge 1f 99#endif 100 movl $LOAD_PHYSICAL_ADDR, %ebx 1011: 102 103 /* Target address to relocate to for decompression */ 104 addl $z_extract_offset, %ebx 105 106/* 107 * Prepare for entering 64 bit mode 108 */ 109 110 /* Load new GDT with the 64bit segments using 32bit descriptor */ 111 leal gdt(%ebp), %eax 112 movl %eax, gdt+2(%ebp) 113 lgdt gdt(%ebp) 114 115 /* Enable PAE mode */ 116 movl %cr4, %eax 117 orl $X86_CR4_PAE, %eax 118 movl %eax, %cr4 119 120 /* 121 * Build early 4G boot pagetable 122 */ 123 /* Initialize Page tables to 0 */ 124 leal pgtable(%ebx), %edi 125 xorl %eax, %eax 126 movl $((4096*6)/4), %ecx 127 rep stosl 128 129 /* Build Level 4 */ 130 leal pgtable + 0(%ebx), %edi 131 leal 0x1007 (%edi), %eax 132 movl %eax, 0(%edi) 133 134 /* Build Level 3 */ 135 leal pgtable + 0x1000(%ebx), %edi 136 leal 0x1007(%edi), %eax 137 movl $4, %ecx 1381: movl %eax, 0x00(%edi) 139 addl $0x00001000, %eax 140 addl $8, %edi 141 decl %ecx 142 jnz 1b 143 144 /* Build Level 2 */ 145 leal pgtable + 0x2000(%ebx), %edi 146 movl $0x00000183, %eax 147 movl $2048, %ecx 1481: movl %eax, 0(%edi) 149 addl $0x00200000, %eax 150 addl $8, %edi 151 decl %ecx 152 jnz 1b 153 154 /* Enable the boot page tables */ 155 leal pgtable(%ebx), %eax 156 movl %eax, %cr3 157 158 /* Enable Long mode in EFER (Extended Feature Enable Register) */ 159 movl $MSR_EFER, %ecx 160 rdmsr 161 btsl $_EFER_LME, %eax 162 wrmsr 163 164 /* After gdt is loaded */ 165 xorl %eax, %eax 166 lldt %ax 167 movl $0x20, %eax 168 ltr %ax 169 170 /* 171 * Setup for the jump to 64bit mode 172 * 173 * When the jump is performend we will be in long mode but 174 * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1 175 * (and in turn EFER.LMA = 1). To jump into 64bit mode we use 176 * the new gdt/idt that has __KERNEL_CS with CS.L = 1. 177 * We place all of the values on our mini stack so lret can 178 * used to perform that far jump. 179 */ 180 pushl $__KERNEL_CS 181 leal startup_64(%ebp), %eax 182#ifdef CONFIG_EFI_MIXED 183 movl efi32_config(%ebp), %ebx 184 cmp $0, %ebx 185 jz 1f 186 leal handover_entry(%ebp), %eax 1871: 188#endif 189 pushl %eax 190 191 /* Enter paged protected Mode, activating Long Mode */ 192 movl $(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */ 193 movl %eax, %cr0 194 195 /* Jump from 32bit compatibility mode into 64bit mode. */ 196 lret 197ENDPROC(startup_32) 198 199#ifdef CONFIG_EFI_MIXED 200 .org 0x190 201ENTRY(efi32_stub_entry) 202 add $0x4, %esp /* Discard return address */ 203 popl %ecx 204 popl %edx 205 popl %esi 206 207 leal (BP_scratch+4)(%esi), %esp 208 call 1f 2091: pop %ebp 210 subl $1b, %ebp 211 212 movl %ecx, efi32_config(%ebp) 213 movl %edx, efi32_config+8(%ebp) 214 sgdtl efi32_boot_gdt(%ebp) 215 216 leal efi32_config(%ebp), %eax 217 movl %eax, efi_config(%ebp) 218 219 jmp startup_32 220ENDPROC(efi32_stub_entry) 221#endif 222 223 .code64 224 .org 0x200 225ENTRY(startup_64) 226 /* 227 * 64bit entry is 0x200 and it is ABI so immutable! 228 * We come here either from startup_32 or directly from a 229 * 64bit bootloader. 230 * If we come here from a bootloader, kernel(text+data+bss+brk), 231 * ramdisk, zero_page, command line could be above 4G. 232 * We depend on an identity mapped page table being provided 233 * that maps our entire kernel(text+data+bss+brk), zero page 234 * and command line. 235 */ 236#ifdef CONFIG_EFI_STUB 237 /* 238 * The entry point for the PE/COFF executable is efi_pe_entry, so 239 * only legacy boot loaders will execute this jmp. 240 */ 241 jmp preferred_addr 242 243ENTRY(efi_pe_entry) 244 movq %rcx, efi64_config(%rip) /* Handle */ 245 movq %rdx, efi64_config+8(%rip) /* EFI System table pointer */ 246 247 leaq efi64_config(%rip), %rax 248 movq %rax, efi_config(%rip) 249 250 call 1f 2511: popq %rbp 252 subq $1b, %rbp 253 254 /* 255 * Relocate efi_config->call(). 256 */ 257 addq %rbp, efi64_config+88(%rip) 258 259 movq %rax, %rdi 260 call make_boot_params 261 cmpq $0,%rax 262 je fail 263 mov %rax, %rsi 264 leaq startup_32(%rip), %rax 265 movl %eax, BP_code32_start(%rsi) 266 jmp 2f /* Skip the relocation */ 267 268handover_entry: 269 call 1f 2701: popq %rbp 271 subq $1b, %rbp 272 273 /* 274 * Relocate efi_config->call(). 275 */ 276 movq efi_config(%rip), %rax 277 addq %rbp, 88(%rax) 2782: 279 movq efi_config(%rip), %rdi 280 call efi_main 281 movq %rax,%rsi 282 cmpq $0,%rax 283 jne 2f 284fail: 285 /* EFI init failed, so hang. */ 286 hlt 287 jmp fail 2882: 289 movl BP_code32_start(%esi), %eax 290 leaq preferred_addr(%rax), %rax 291 jmp *%rax 292 293preferred_addr: 294#endif 295 296 /* Setup data segments. */ 297 xorl %eax, %eax 298 movl %eax, %ds 299 movl %eax, %es 300 movl %eax, %ss 301 movl %eax, %fs 302 movl %eax, %gs 303 304 /* 305 * Compute the decompressed kernel start address. It is where 306 * we were loaded at aligned to a 2M boundary. %rbp contains the 307 * decompressed kernel start address. 308 * 309 * If it is a relocatable kernel then decompress and run the kernel 310 * from load address aligned to 2MB addr, otherwise decompress and 311 * run the kernel from LOAD_PHYSICAL_ADDR 312 * 313 * We cannot rely on the calculation done in 32-bit mode, since we 314 * may have been invoked via the 64-bit entry point. 315 */ 316 317 /* Start with the delta to where the kernel will run at. */ 318#ifdef CONFIG_RELOCATABLE 319 leaq startup_32(%rip) /* - $startup_32 */, %rbp 320 movl BP_kernel_alignment(%rsi), %eax 321 decl %eax 322 addq %rax, %rbp 323 notq %rax 324 andq %rax, %rbp 325 cmpq $LOAD_PHYSICAL_ADDR, %rbp 326 jge 1f 327#endif 328 movq $LOAD_PHYSICAL_ADDR, %rbp 3291: 330 331 /* Target address to relocate to for decompression */ 332 leaq z_extract_offset(%rbp), %rbx 333 334 /* Set up the stack */ 335 leaq boot_stack_end(%rbx), %rsp 336 337 /* Zero EFLAGS */ 338 pushq $0 339 popfq 340 341/* 342 * Copy the compressed kernel to the end of our buffer 343 * where decompression in place becomes safe. 344 */ 345 pushq %rsi 346 leaq (_bss-8)(%rip), %rsi 347 leaq (_bss-8)(%rbx), %rdi 348 movq $_bss /* - $startup_32 */, %rcx 349 shrq $3, %rcx 350 std 351 rep movsq 352 cld 353 popq %rsi 354 355/* 356 * Jump to the relocated address. 357 */ 358 leaq relocated(%rbx), %rax 359 jmp *%rax 360 361#ifdef CONFIG_EFI_STUB 362 .org 0x390 363ENTRY(efi64_stub_entry) 364 movq %rdi, efi64_config(%rip) /* Handle */ 365 movq %rsi, efi64_config+8(%rip) /* EFI System table pointer */ 366 367 leaq efi64_config(%rip), %rax 368 movq %rax, efi_config(%rip) 369 370 movq %rdx, %rsi 371 jmp handover_entry 372ENDPROC(efi64_stub_entry) 373#endif 374 375 .text 376relocated: 377 378/* 379 * Clear BSS (stack is currently empty) 380 */ 381 xorl %eax, %eax 382 leaq _bss(%rip), %rdi 383 leaq _ebss(%rip), %rcx 384 subq %rdi, %rcx 385 shrq $3, %rcx 386 rep stosq 387 388/* 389 * Adjust our own GOT 390 */ 391 leaq _got(%rip), %rdx 392 leaq _egot(%rip), %rcx 3931: 394 cmpq %rcx, %rdx 395 jae 2f 396 addq %rbx, (%rdx) 397 addq $8, %rdx 398 jmp 1b 3992: 400 401/* 402 * Do the decompression, and jump to the new kernel.. 403 */ 404 pushq %rsi /* Save the real mode argument */ 405 movq $z_run_size, %r9 /* size of kernel with .bss and .brk */ 406 pushq %r9 407 movq %rsi, %rdi /* real mode address */ 408 leaq boot_heap(%rip), %rsi /* malloc area for uncompression */ 409 leaq input_data(%rip), %rdx /* input_data */ 410 movl $z_input_len, %ecx /* input_len */ 411 movq %rbp, %r8 /* output target address */ 412 movq $z_output_len, %r9 /* decompressed length, end of relocs */ 413 call decompress_kernel /* returns kernel location in %rax */ 414 popq %r9 415 popq %rsi 416 417/* 418 * Jump to the decompressed kernel. 419 */ 420 jmp *%rax 421 422 .code32 423no_longmode: 424 /* This isn't an x86-64 CPU so hang */ 4251: 426 hlt 427 jmp 1b 428 429#include "../../kernel/verify_cpu.S" 430 431 .data 432gdt: 433 .word gdt_end - gdt 434 .long gdt 435 .word 0 436 .quad 0x0000000000000000 /* NULL descriptor */ 437 .quad 0x00af9a000000ffff /* __KERNEL_CS */ 438 .quad 0x00cf92000000ffff /* __KERNEL_DS */ 439 .quad 0x0080890000000000 /* TS descriptor */ 440 .quad 0x0000000000000000 /* TS continued */ 441gdt_end: 442 443#ifdef CONFIG_EFI_STUB 444efi_config: 445 .quad 0 446 447#ifdef CONFIG_EFI_MIXED 448 .global efi32_config 449efi32_config: 450 .fill 11,8,0 451 .quad efi64_thunk 452 .byte 0 453#endif 454 455 .global efi64_config 456efi64_config: 457 .fill 11,8,0 458 .quad efi_call 459 .byte 1 460#endif /* CONFIG_EFI_STUB */ 461 462/* 463 * Stack and heap for uncompression 464 */ 465 .bss 466 .balign 4 467boot_heap: 468 .fill BOOT_HEAP_SIZE, 1, 0 469boot_stack: 470 .fill BOOT_STACK_SIZE, 1, 0 471boot_stack_end: 472 473/* 474 * Space for page tables (not in .bss so not zeroed) 475 */ 476 .section ".pgtable","a",@nobits 477 .balign 4096 478pgtable: 479 .fill 6*4096, 1, 0 480