1/* 2 * linux/arch/x86_64/kernel/head.S -- start in 32bit and switch to 64bit 3 * 4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE 5 * Copyright (C) 2000 Pavel Machek <pavel@suse.cz> 6 * Copyright (C) 2000 Karsten Keil <kkeil@suse.de> 7 * Copyright (C) 2001,2002 Andi Kleen <ak@suse.de> 8 * Copyright (C) 2005 Eric Biederman <ebiederm@xmission.com> 9 */ 10 11 12#include <linux/linkage.h> 13#include <linux/threads.h> 14#include <linux/init.h> 15#include <asm/segment.h> 16#include <asm/pgtable.h> 17#include <asm/page.h> 18#include <asm/msr.h> 19#include <asm/cache.h> 20#include <asm/processor-flags.h> 21#include <asm/percpu.h> 22#include <asm/nops.h> 23 24#ifdef CONFIG_PARAVIRT 25#include <asm/asm-offsets.h> 26#include <asm/paravirt.h> 27#define GET_CR2_INTO(reg) GET_CR2_INTO_RAX ; movq %rax, reg 28#else 29#define GET_CR2_INTO(reg) movq %cr2, reg 30#define INTERRUPT_RETURN iretq 31#endif 32 33/* we are not able to switch in one step to the final KERNEL ADDRESS SPACE 34 * because we need identity-mapped pages. 35 * 36 */ 37 38#define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1)) 39 40L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET) 41L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET) 42L4_START_KERNEL = pgd_index(__START_KERNEL_map) 43L3_START_KERNEL = pud_index(__START_KERNEL_map) 44 45 .text 46 __HEAD 47 .code64 48 .globl startup_64 49startup_64: 50 51 /* 52 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1, 53 * and someone has loaded an identity mapped page table 54 * for us. These identity mapped page tables map all of the 55 * kernel pages and possibly all of memory. 56 * 57 * %esi holds a physical pointer to real_mode_data. 58 * 59 * We come here either directly from a 64bit bootloader, or from 60 * arch/x86_64/boot/compressed/head.S. 61 * 62 * We only come here initially at boot nothing else comes here. 63 * 64 * Since we may be loaded at an address different from what we were 65 * compiled to run at we first fixup the physical addresses in our page 66 * tables and then reload them. 67 */ 68 69 /* Compute the delta between the address I am compiled to run at and the 70 * address I am actually running at. 71 */ 72 leaq _text(%rip), %rbp 73 subq $_text - __START_KERNEL_map, %rbp 74 75 /* Is the address not 2M aligned? */ 76 movq %rbp, %rax 77 andl $~PMD_PAGE_MASK, %eax 78 testl %eax, %eax 79 jnz bad_address 80 81 /* Is the address too large? */ 82 leaq _text(%rip), %rdx 83 movq $PGDIR_SIZE, %rax 84 cmpq %rax, %rdx 85 jae bad_address 86 87 /* Fixup the physical addresses in the page table 88 */ 89 addq %rbp, init_level4_pgt + 0(%rip) 90 addq %rbp, init_level4_pgt + (L4_PAGE_OFFSET*8)(%rip) 91 addq %rbp, init_level4_pgt + (L4_START_KERNEL*8)(%rip) 92 93 addq %rbp, level3_ident_pgt + 0(%rip) 94 95 addq %rbp, level3_kernel_pgt + (510*8)(%rip) 96 addq %rbp, level3_kernel_pgt + (511*8)(%rip) 97 98 addq %rbp, level2_fixmap_pgt + (506*8)(%rip) 99 100 /* Add an Identity mapping if I am above 1G */ 101 leaq _text(%rip), %rdi 102 andq $PMD_PAGE_MASK, %rdi 103 104 movq %rdi, %rax 105 shrq $PUD_SHIFT, %rax 106 andq $(PTRS_PER_PUD - 1), %rax 107 jz ident_complete 108 109 leaq (level2_spare_pgt - __START_KERNEL_map + _KERNPG_TABLE)(%rbp), %rdx 110 leaq level3_ident_pgt(%rip), %rbx 111 movq %rdx, 0(%rbx, %rax, 8) 112 113 movq %rdi, %rax 114 shrq $PMD_SHIFT, %rax 115 andq $(PTRS_PER_PMD - 1), %rax 116 leaq __PAGE_KERNEL_IDENT_LARGE_EXEC(%rdi), %rdx 117 leaq level2_spare_pgt(%rip), %rbx 118 movq %rdx, 0(%rbx, %rax, 8) 119ident_complete: 120 121 /* 122 * Fixup the kernel text+data virtual addresses. Note that 123 * we might write invalid pmds, when the kernel is relocated 124 * cleanup_highmap() fixes this up along with the mappings 125 * beyond _end. 126 */ 127 128 leaq level2_kernel_pgt(%rip), %rdi 129 leaq 4096(%rdi), %r8 130 /* See if it is a valid page table entry */ 1311: testq $1, 0(%rdi) 132 jz 2f 133 addq %rbp, 0(%rdi) 134 /* Go to the next page */ 1352: addq $8, %rdi 136 cmp %r8, %rdi 137 jne 1b 138 139 /* Fixup phys_base */ 140 addq %rbp, phys_base(%rip) 141 142 /* Due to ENTRY(), sometimes the empty space gets filled with 143 * zeros. Better take a jmp than relying on empty space being 144 * filled with 0x90 (nop) 145 */ 146 jmp secondary_startup_64 147ENTRY(secondary_startup_64) 148 /* 149 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1, 150 * and someone has loaded a mapped page table. 151 * 152 * %esi holds a physical pointer to real_mode_data. 153 * 154 * We come here either from startup_64 (using physical addresses) 155 * or from trampoline.S (using virtual addresses). 156 * 157 * Using virtual addresses from trampoline.S removes the need 158 * to have any identity mapped pages in the kernel page table 159 * after the boot processor executes this code. 160 */ 161 162 /* Enable PAE mode and PGE */ 163 movl $(X86_CR4_PAE | X86_CR4_PGE), %eax 164 movq %rax, %cr4 165 166 /* Setup early boot stage 4 level pagetables. */ 167 movq $(init_level4_pgt - __START_KERNEL_map), %rax 168 addq phys_base(%rip), %rax 169 movq %rax, %cr3 170 171 /* Ensure I am executing from virtual addresses */ 172 movq $1f, %rax 173 jmp *%rax 1741: 175 176 /* Check if nx is implemented */ 177 movl $0x80000001, %eax 178 cpuid 179 movl %edx,%edi 180 181 /* Setup EFER (Extended Feature Enable Register) */ 182 movl $MSR_EFER, %ecx 183 rdmsr 184 btsl $_EFER_SCE, %eax /* Enable System Call */ 185 btl $20,%edi /* No Execute supported? */ 186 jnc 1f 187 btsl $_EFER_NX, %eax 1881: wrmsr /* Make changes effective */ 189 190 /* Setup cr0 */ 191#define CR0_STATE (X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \ 192 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \ 193 X86_CR0_PG) 194 movl $CR0_STATE, %eax 195 /* Make changes effective */ 196 movq %rax, %cr0 197 198 /* Setup a boot time stack */ 199 movq stack_start(%rip),%rsp 200 201 /* zero EFLAGS after setting rsp */ 202 pushq $0 203 popfq 204 205 /* 206 * We must switch to a new descriptor in kernel space for the GDT 207 * because soon the kernel won't have access anymore to the userspace 208 * addresses where we're currently running on. We have to do that here 209 * because in 32bit we couldn't load a 64bit linear address. 210 */ 211 lgdt early_gdt_descr(%rip) 212 213 /* set up data segments */ 214 xorl %eax,%eax 215 movl %eax,%ds 216 movl %eax,%ss 217 movl %eax,%es 218 219 /* 220 * We don't really need to load %fs or %gs, but load them anyway 221 * to kill any stale realmode selectors. This allows execution 222 * under VT hardware. 223 */ 224 movl %eax,%fs 225 movl %eax,%gs 226 227 /* Set up %gs. 228 * 229 * The base of %gs always points to the bottom of the irqstack 230 * union. If the stack protector canary is enabled, it is 231 * located at %gs:40. Note that, on SMP, the boot cpu uses 232 * init data section till per cpu areas are set up. 233 */ 234 movl $MSR_GS_BASE,%ecx 235 movl initial_gs(%rip),%eax 236 movl initial_gs+4(%rip),%edx 237 wrmsr 238 239 /* esi is pointer to real mode structure with interesting info. 240 pass it to C */ 241 movl %esi, %edi 242 243 /* Finally jump to run C code and to be on real kernel address 244 * Since we are running on identity-mapped space we have to jump 245 * to the full 64bit address, this is only possible as indirect 246 * jump. In addition we need to ensure %cs is set so we make this 247 * a far return. 248 */ 249 movq initial_code(%rip),%rax 250 pushq $0 # fake return address to stop unwinder 251 pushq $__KERNEL_CS # set correct cs 252 pushq %rax # target address in negative space 253 lretq 254 255#ifdef CONFIG_HOTPLUG_CPU 256/* 257 * Boot CPU0 entry point. It's called from play_dead(). Everything has been set 258 * up already except stack. We just set up stack here. Then call 259 * start_secondary(). 260 */ 261ENTRY(start_cpu0) 262 movq stack_start(%rip),%rsp 263 movq initial_code(%rip),%rax 264 pushq $0 # fake return address to stop unwinder 265 pushq $__KERNEL_CS # set correct cs 266 pushq %rax # target address in negative space 267 lretq 268ENDPROC(start_cpu0) 269#endif 270 271 /* SMP bootup changes these two */ 272 __REFDATA 273 .align 8 274 ENTRY(initial_code) 275 .quad x86_64_start_kernel 276 ENTRY(initial_gs) 277 .quad INIT_PER_CPU_VAR(irq_stack_union) 278 279 ENTRY(stack_start) 280 .quad init_thread_union+THREAD_SIZE-8 281 .word 0 282 __FINITDATA 283 284bad_address: 285 jmp bad_address 286 287 .section ".init.text","ax" 288 .globl early_idt_handlers 289early_idt_handlers: 290 # 104(%rsp) %rflags 291 # 96(%rsp) %cs 292 # 88(%rsp) %rip 293 # 80(%rsp) error code 294 i = 0 295 .rept NUM_EXCEPTION_VECTORS 296 .if (EXCEPTION_ERRCODE_MASK >> i) & 1 297 ASM_NOP2 298 .else 299 pushq $0 # Dummy error code, to make stack frame uniform 300 .endif 301 pushq $i # 72(%rsp) Vector number 302 jmp early_idt_handler 303 i = i + 1 304 .endr 305 306ENTRY(early_idt_handler) 307 cld 308 309 cmpl $2,early_recursion_flag(%rip) 310 jz 1f 311 incl early_recursion_flag(%rip) 312 313 pushq %rax # 64(%rsp) 314 pushq %rcx # 56(%rsp) 315 pushq %rdx # 48(%rsp) 316 pushq %rsi # 40(%rsp) 317 pushq %rdi # 32(%rsp) 318 pushq %r8 # 24(%rsp) 319 pushq %r9 # 16(%rsp) 320 pushq %r10 # 8(%rsp) 321 pushq %r11 # 0(%rsp) 322 323 cmpl $__KERNEL_CS,96(%rsp) 324 jne 10f 325 326 leaq 88(%rsp),%rdi # Pointer to %rip 327 call early_fixup_exception 328 andl %eax,%eax 329 jnz 20f # Found an exception entry 330 33110: 332#ifdef CONFIG_EARLY_PRINTK 333 GET_CR2_INTO(%r9) # can clobber any volatile register if pv 334 movl 80(%rsp),%r8d # error code 335 movl 72(%rsp),%esi # vector number 336 movl 96(%rsp),%edx # %cs 337 movq 88(%rsp),%rcx # %rip 338 xorl %eax,%eax 339 leaq early_idt_msg(%rip),%rdi 340 call early_printk 341 cmpl $2,early_recursion_flag(%rip) 342 jz 1f 343 call dump_stack 344#ifdef CONFIG_KALLSYMS 345 leaq early_idt_ripmsg(%rip),%rdi 346 movq 40(%rsp),%rsi # %rip again 347 call __print_symbol 348#endif 349#endif /* EARLY_PRINTK */ 3501: hlt 351 jmp 1b 352 35320: # Exception table entry found 354 popq %r11 355 popq %r10 356 popq %r9 357 popq %r8 358 popq %rdi 359 popq %rsi 360 popq %rdx 361 popq %rcx 362 popq %rax 363 addq $16,%rsp # drop vector number and error code 364 decl early_recursion_flag(%rip) 365 INTERRUPT_RETURN 366 367 .balign 4 368early_recursion_flag: 369 .long 0 370 371#ifdef CONFIG_EARLY_PRINTK 372early_idt_msg: 373 .asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n" 374early_idt_ripmsg: 375 .asciz "RIP %s\n" 376#endif /* CONFIG_EARLY_PRINTK */ 377 .previous 378 379#define NEXT_PAGE(name) \ 380 .balign PAGE_SIZE; \ 381ENTRY(name) 382 383/* Automate the creation of 1 to 1 mapping pmd entries */ 384#define PMDS(START, PERM, COUNT) \ 385 i = 0 ; \ 386 .rept (COUNT) ; \ 387 .quad (START) + (i << PMD_SHIFT) + (PERM) ; \ 388 i = i + 1 ; \ 389 .endr 390 391 .data 392 /* 393 * This default setting generates an ident mapping at address 0x100000 394 * and a mapping for the kernel that precisely maps virtual address 395 * 0xffffffff80000000 to physical address 0x000000. (always using 396 * 2Mbyte large pages provided by PAE mode) 397 */ 398NEXT_PAGE(init_level4_pgt) 399 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE 400 .org init_level4_pgt + L4_PAGE_OFFSET*8, 0 401 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE 402 .org init_level4_pgt + L4_START_KERNEL*8, 0 403 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */ 404 .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE 405 406NEXT_PAGE(level3_ident_pgt) 407 .quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE 408 .fill 511,8,0 409 410NEXT_PAGE(level3_kernel_pgt) 411 .fill L3_START_KERNEL,8,0 412 /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */ 413 .quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE 414 .quad level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE 415 416NEXT_PAGE(level2_fixmap_pgt) 417 .fill 506,8,0 418 .quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE 419 /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */ 420 .fill 5,8,0 421 422NEXT_PAGE(level1_fixmap_pgt) 423 .fill 512,8,0 424 425NEXT_PAGE(level2_ident_pgt) 426 /* Since I easily can, map the first 1G. 427 * Don't set NX because code runs from these pages. 428 */ 429 PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD) 430 431NEXT_PAGE(level2_kernel_pgt) 432 /* 433 * 512 MB kernel mapping. We spend a full page on this pagetable 434 * anyway. 435 * 436 * The kernel code+data+bss must not be bigger than that. 437 * 438 * (NOTE: at +512MB starts the module area, see MODULES_VADDR. 439 * If you want to increase this then increase MODULES_VADDR 440 * too.) 441 */ 442 PMDS(0, __PAGE_KERNEL_LARGE_EXEC, 443 KERNEL_IMAGE_SIZE/PMD_SIZE) 444 445NEXT_PAGE(level2_spare_pgt) 446 .fill 512, 8, 0 447 448#undef PMDS 449#undef NEXT_PAGE 450 451 .data 452 .align 16 453 .globl early_gdt_descr 454early_gdt_descr: 455 .word GDT_ENTRIES*8-1 456early_gdt_descr_base: 457 .quad INIT_PER_CPU_VAR(gdt_page) 458 459ENTRY(phys_base) 460 /* This must match the first entry in level2_kernel_pgt */ 461 .quad 0x0000000000000000 462 463#include "../../x86/xen/xen-head.S" 464 465 .section .bss, "aw", @nobits 466 .align L1_CACHE_BYTES 467ENTRY(idt_table) 468 .skip IDT_ENTRIES * 16 469 470 .align L1_CACHE_BYTES 471ENTRY(nmi_idt_table) 472 .skip IDT_ENTRIES * 16 473 474 __PAGE_ALIGNED_BSS 475 .align PAGE_SIZE 476ENTRY(empty_zero_page) 477 .skip PAGE_SIZE 478