arch/x86/kernel/head_64.S

   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
  40 L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET)
  41 L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET)
  42 L4_START_KERNEL = pgd_index(__START_KERNEL_map)
  43 L3_START_KERNEL = pud_index(__START_KERNEL_map)
  44
  45         .text
  46         __HEAD
  47         .code64
  48         .globl startup_64
  49 startup_64:
  50         /*
  51          * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
  52          * and someone has loaded an identity mapped page table
  53          * for us.  These identity mapped page tables map all of the
  54          * kernel pages and possibly all of memory.
  55          *
  56          * %rsi holds a physical pointer to real_mode_data.
  57          *
  58          * We come here either directly from a 64bit bootloader, or from
  59          * arch/x86_64/boot/compressed/head.S.
  60          *
  61          * We only come here initially at boot nothing else comes here.
  62          *
  63          * Since we may be loaded at an address different from what we were
  64          * compiled to run at we first fixup the physical addresses in our page
  65          * tables and then reload them.
  66          */
  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         /*
  82          * Is the address too large?
  83          */
  84         leaq    _text(%rip), %rax
  85         shrq    $MAX_PHYSMEM_BITS, %rax
  86         jnz     bad_address
  87
  88         /*
  89          * Fixup the physical addresses in the page table
  90          */
  91         addq    %rbp, early_level4_pgt + (L4_START_KERNEL*8)(%rip)
  92
  93         addq    %rbp, level3_kernel_pgt + (510*8)(%rip)
  94         addq    %rbp, level3_kernel_pgt + (511*8)(%rip)
  95
  96         addq    %rbp, level2_fixmap_pgt + (506*8)(%rip)
  97
  98         /*
  99          * Set up the identity mapping for the switchover.  These
 100          * entries should *NOT* have the global bit set!  This also
 101          * creates a bunch of nonsense entries but that is fine --
 102          * it avoids problems around wraparound.
 103          */
 104         leaq    _text(%rip), %rdi
 105         leaq    early_level4_pgt(%rip), %rbx
 106
 107         movq    %rdi, %rax
 108         shrq    $PGDIR_SHIFT, %rax
 109
 110         leaq    (4096 + _KERNPG_TABLE)(%rbx), %rdx
 111         movq    %rdx, 0(%rbx,%rax,8)
 112         movq    %rdx, 8(%rbx,%rax,8)
 113
 114         addq    $4096, %rdx
 115         movq    %rdi, %rax
 116         shrq    $PUD_SHIFT, %rax
 117         andl    $(PTRS_PER_PUD-1), %eax
 118         movq    %rdx, 4096(%rbx,%rax,8)
 119         incl    %eax
 120         andl    $(PTRS_PER_PUD-1), %eax
 121         movq    %rdx, 4096(%rbx,%rax,8)
 122
 123         addq    $8192, %rbx
 124         movq    %rdi, %rax
 125         shrq    $PMD_SHIFT, %rdi
 126         addq    $(__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL), %rax
 127         leaq    (_end - 1)(%rip), %rcx
 128         shrq    $PMD_SHIFT, %rcx
 129         subq    %rdi, %rcx
 130         incl    %ecx
 131
 132 1:
 133         andq    $(PTRS_PER_PMD - 1), %rdi
 134         movq    %rax, (%rbx,%rdi,8)
 135         incq    %rdi
 136         addq    $PMD_SIZE, %rax
 137         decl    %ecx
 138         jnz     1b
 139
 140         /*
 141          * Fixup the kernel text+data virtual addresses. Note that
 142          * we might write invalid pmds, when the kernel is relocated
 143          * cleanup_highmap() fixes this up along with the mappings
 144          * beyond _end.
 145          */
 146         leaq    level2_kernel_pgt(%rip), %rdi
 147         leaq    4096(%rdi), %r8
 148         /* See if it is a valid page table entry */
 149 1:      testq   $1, 0(%rdi)
 150         jz      2f
 151         addq    %rbp, 0(%rdi)
 152         /* Go to the next page */
 153 2:      addq    $8, %rdi
 154         cmp     %r8, %rdi
 155         jne     1b
 156
 157         /* Fixup phys_base */
 158         addq    %rbp, phys_base(%rip)
 159
 160         movq    $(early_level4_pgt - __START_KERNEL_map), %rax
 161         jmp 1f
 162 ENTRY(secondary_startup_64)
 163         /*
 164          * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
 165          * and someone has loaded a mapped page table.
 166          *
 167          * %rsi holds a physical pointer to real_mode_data.
 168          *
 169          * We come here either from startup_64 (using physical addresses)
 170          * or from trampoline.S (using virtual addresses).
 171          *
 172          * Using virtual addresses from trampoline.S removes the need
 173          * to have any identity mapped pages in the kernel page table
 174          * after the boot processor executes this code.
 175          */
 176
 177         movq    $(init_level4_pgt - __START_KERNEL_map), %rax
 178 1:
 179
 180         /* Enable PAE mode and PGE */
 181         movl    $(X86_CR4_PAE | X86_CR4_PGE), %ecx
 182         movq    %rcx, %cr4
 183
 184         /* Setup early boot stage 4 level pagetables. */
 185         addq    phys_base(%rip), %rax
 186         movq    %rax, %cr3
 187
 188         /* Ensure I am executing from virtual addresses */
 189         movq    $1f, %rax
 190         jmp     *%rax
 191 1:
 192
 193         /* Check if nx is implemented */
 194         movl    $0x80000001, %eax
 195         cpuid
 196         movl    %edx,%edi
 197
 198         /* Setup EFER (Extended Feature Enable Register) */
 199         movl    $MSR_EFER, %ecx
 200         rdmsr
 201         btsl    $_EFER_SCE, %eax        /* Enable System Call */
 202         btl     $20,%edi                /* No Execute supported? */
 203         jnc     1f
 204         btsl    $_EFER_NX, %eax
 205         btsq    $_PAGE_BIT_NX,early_pmd_flags(%rip)
 206 1:      wrmsr                           /* Make changes effective */
 207
 208         /* Setup cr0 */
 209 #define CR0_STATE       (X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
 210                          X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
 211                          X86_CR0_PG)
 212         movl    $CR0_STATE, %eax
 213         /* Make changes effective */
 214         movq    %rax, %cr0
 215
 216         /* Setup a boot time stack */
 217         movq stack_start(%rip), %rsp
 218
 219         /* zero EFLAGS after setting rsp */
 220         pushq $0
 221         popfq
 222
 223         /*
 224          * We must switch to a new descriptor in kernel space for the GDT
 225          * because soon the kernel won't have access anymore to the userspace
 226          * addresses where we're currently running on. We have to do that here
 227          * because in 32bit we couldn't load a 64bit linear address.
 228          */
 229         lgdt    early_gdt_descr(%rip)
 230
 231         /* set up data segments */
 232         xorl %eax,%eax
 233         movl %eax,%ds
 234         movl %eax,%ss
 235         movl %eax,%es
 236
 237         /*
 238          * We don't really need to load %fs or %gs, but load them anyway
 239          * to kill any stale realmode selectors.  This allows execution
 240          * under VT hardware.
 241          */
 242         movl %eax,%fs
 243         movl %eax,%gs
 244
 245         /* Set up %gs.
 246          *
 247          * The base of %gs always points to the bottom of the irqstack
 248          * union.  If the stack protector canary is enabled, it is
 249          * located at %gs:40.  Note that, on SMP, the boot cpu uses
 250          * init data section till per cpu areas are set up.
 251          */
 252         movl    $MSR_GS_BASE,%ecx
 253         movl    initial_gs(%rip),%eax
 254         movl    initial_gs+4(%rip),%edx
 255         wrmsr
 256
 257         /* rsi is pointer to real mode structure with interesting info.
 258            pass it to C */
 259         movq    %rsi, %rdi
 260
 261         /* Finally jump to run C code and to be on real kernel address
 262          * Since we are running on identity-mapped space we have to jump
 263          * to the full 64bit address, this is only possible as indirect
 264          * jump.  In addition we need to ensure %cs is set so we make this
 265          * a far return.
 266          *
 267          * Note: do not change to far jump indirect with 64bit offset.
 268          *
 269          * AMD does not support far jump indirect with 64bit offset.
 270          * AMD64 Architecture Programmer's Manual, Volume 3: states only
 271          *      JMP FAR mem16:16 FF /5 Far jump indirect,
 272          *              with the target specified by a far pointer in memory.
 273          *      JMP FAR mem16:32 FF /5 Far jump indirect,
 274          *              with the target specified by a far pointer in memory.
 275          *
 276          * Intel64 does support 64bit offset.
 277          * Software Developer Manual Vol 2: states:
 278          *      FF /5 JMP m16:16 Jump far, absolute indirect,
 279          *              address given in m16:16
 280          *      FF /5 JMP m16:32 Jump far, absolute indirect,
 281          *              address given in m16:32.
 282          *      REX.W + FF /5 JMP m16:64 Jump far, absolute indirect,
 283          *              address given in m16:64.
 284          */
 285         movq    initial_code(%rip),%rax
 286         pushq   $0              # fake return address to stop unwinder
 287         pushq   $__KERNEL_CS    # set correct cs
 288         pushq   %rax            # target address in negative space
 289         lretq
 290
 291 #ifdef CONFIG_HOTPLUG_CPU
 292 /*
 293  * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
 294  * up already except stack. We just set up stack here. Then call
 295  * start_secondary().
 296  */
 297 ENTRY(start_cpu0)
 298         movq stack_start(%rip),%rsp
 299         movq    initial_code(%rip),%rax
 300         pushq   $0              # fake return address to stop unwinder
 301         pushq   $__KERNEL_CS    # set correct cs
 302         pushq   %rax            # target address in negative space
 303         lretq
 304 ENDPROC(start_cpu0)
 305 #endif
 306
 307         /* SMP bootup changes these two */
 308         __REFDATA
 309         .balign 8
 310         GLOBAL(initial_code)
 311         .quad   x86_64_start_kernel
 312         GLOBAL(initial_gs)
 313         .quad   INIT_PER_CPU_VAR(irq_stack_union)
 314
 315         GLOBAL(stack_start)
 316         .quad  init_thread_union+THREAD_SIZE-8
 317         .word  0
 318         __FINITDATA
 319
 320 bad_address:
 321         jmp bad_address
 322
 323         __INIT
 324         .globl early_idt_handlers
 325 early_idt_handlers:
 326         # 104(%rsp) %rflags
 327         #  96(%rsp) %cs
 328         #  88(%rsp) %rip
 329         #  80(%rsp) error code
 330         i = 0
 331         .rept NUM_EXCEPTION_VECTORS
 332         .if (EXCEPTION_ERRCODE_MASK >> i) & 1
 333         ASM_NOP2
 334         .else
 335         pushq $0                # Dummy error code, to make stack frame uniform
 336         .endif
 337         pushq $i                # 72(%rsp) Vector number
 338         jmp early_idt_handler
 339         i = i + 1
 340         .endr
 341
 342 /* This is global to keep gas from relaxing the jumps */
 343 ENTRY(early_idt_handler)
 344         cld
 345
 346         cmpl $2,(%rsp)          # X86_TRAP_NMI
 347         je is_nmi               # Ignore NMI
 348
 349         cmpl $2,early_recursion_flag(%rip)
 350         jz  1f
 351         incl early_recursion_flag(%rip)
 352
 353         pushq %rax              # 64(%rsp)
 354         pushq %rcx              # 56(%rsp)
 355         pushq %rdx              # 48(%rsp)
 356         pushq %rsi              # 40(%rsp)
 357         pushq %rdi              # 32(%rsp)
 358         pushq %r8               # 24(%rsp)
 359         pushq %r9               # 16(%rsp)
 360         pushq %r10              #  8(%rsp)
 361         pushq %r11              #  0(%rsp)
 362
 363         cmpl $__KERNEL_CS,96(%rsp)
 364         jne 11f
 365
 366         cmpl $14,72(%rsp)       # Page fault?
 367         jnz 10f
 368         GET_CR2_INTO(%rdi)      # can clobber any volatile register if pv
 369         call early_make_pgtable
 370         andl %eax,%eax
 371         jz 20f                  # All good
 372
 373 10:
 374         leaq 88(%rsp),%rdi      # Pointer to %rip
 375         call early_fixup_exception
 376         andl %eax,%eax
 377         jnz 20f                 # Found an exception entry
 378
 379 11:
 380 #ifdef CONFIG_EARLY_PRINTK
 381         GET_CR2_INTO(%r9)       # can clobber any volatile register if pv
 382         movl 80(%rsp),%r8d      # error code
 383         movl 72(%rsp),%esi      # vector number
 384         movl 96(%rsp),%edx      # %cs
 385         movq 88(%rsp),%rcx      # %rip
 386         xorl %eax,%eax
 387         leaq early_idt_msg(%rip),%rdi
 388         call early_printk
 389         cmpl $2,early_recursion_flag(%rip)
 390         jz  1f
 391         call dump_stack
 392 #ifdef CONFIG_KALLSYMS
 393         leaq early_idt_ripmsg(%rip),%rdi
 394         movq 40(%rsp),%rsi      # %rip again
 395         call __print_symbol
 396 #endif
 397 #endif /* EARLY_PRINTK */
 398 1:      hlt
 399         jmp 1b
 400
 401 20:     # Exception table entry found or page table generated
 402         popq %r11
 403         popq %r10
 404         popq %r9
 405         popq %r8
 406         popq %rdi
 407         popq %rsi
 408         popq %rdx
 409         popq %rcx
 410         popq %rax
 411         decl early_recursion_flag(%rip)
 412 is_nmi:
 413         addq $16,%rsp           # drop vector number and error code
 414         INTERRUPT_RETURN
 415 ENDPROC(early_idt_handler)
 416
 417         __INITDATA
 418
 419         .balign 4
 420 early_recursion_flag:
 421         .long 0
 422
 423 #ifdef CONFIG_EARLY_PRINTK
 424 early_idt_msg:
 425         .asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n"
 426 early_idt_ripmsg:
 427         .asciz "RIP %s\n"
 428 #endif /* CONFIG_EARLY_PRINTK */
 429
 430 #define NEXT_PAGE(name) \
 431         .balign PAGE_SIZE; \
 432 GLOBAL(name)
 433
 434 /* Automate the creation of 1 to 1 mapping pmd entries */
 435 #define PMDS(START, PERM, COUNT)                        \
 436         i = 0 ;                                         \
 437         .rept (COUNT) ;                                 \
 438         .quad   (START) + (i << PMD_SHIFT) + (PERM) ;   \
 439         i = i + 1 ;                                     \
 440         .endr
 441
 442         __INITDATA
 443 NEXT_PAGE(early_level4_pgt)
 444         .fill   511,8,0
 445         .quad   level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
 446
 447 NEXT_PAGE(early_dynamic_pgts)
 448         .fill   512*EARLY_DYNAMIC_PAGE_TABLES,8,0
 449
 450         .data
 451
 452 #ifndef CONFIG_XEN
 453 NEXT_PAGE(init_level4_pgt)
 454         .fill   512,8,0
 455 #else
 456 NEXT_PAGE(init_level4_pgt)
 457         .quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
 458         .org    init_level4_pgt + L4_PAGE_OFFSET*8, 0
 459         .quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
 460         .org    init_level4_pgt + L4_START_KERNEL*8, 0
 461         /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
 462         .quad   level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
 463
 464 NEXT_PAGE(level3_ident_pgt)
 465         .quad   level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
 466         .fill   511, 8, 0
 467 NEXT_PAGE(level2_ident_pgt)
 468         /* Since I easily can, map the first 1G.
 469          * Don't set NX because code runs from these pages.
 470          */
 471         PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
 472 #endif
 473
 474 NEXT_PAGE(level3_kernel_pgt)
 475         .fill   L3_START_KERNEL,8,0
 476         /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
 477         .quad   level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
 478         .quad   level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
 479
 480 NEXT_PAGE(level2_kernel_pgt)
 481         /*
 482          * 512 MB kernel mapping. We spend a full page on this pagetable
 483          * anyway.
 484          *
 485          * The kernel code+data+bss must not be bigger than that.
 486          *
 487          * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
 488          *  If you want to increase this then increase MODULES_VADDR
 489          *  too.)
 490          */
 491         PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
 492                 KERNEL_IMAGE_SIZE/PMD_SIZE)
 493
 494 NEXT_PAGE(level2_fixmap_pgt)
 495         .fill   506,8,0
 496         .quad   level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
 497         /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
 498         .fill   5,8,0
 499
 500 NEXT_PAGE(level1_fixmap_pgt)
 501         .fill   512,8,0
 502
 503 #undef PMDS
 504
 505         .data
 506         .align 16
 507         .globl early_gdt_descr
 508 early_gdt_descr:
 509         .word   GDT_ENTRIES*8-1
 510 early_gdt_descr_base:
 511         .quad   INIT_PER_CPU_VAR(gdt_page)
 512
 513 ENTRY(phys_base)
 514         /* This must match the first entry in level2_kernel_pgt */
 515         .quad   0x0000000000000000
 516
 517 #include "../../x86/xen/xen-head.S"
 518
 519         __PAGE_ALIGNED_BSS
 520 NEXT_PAGE(empty_zero_page)
 521         .skip PAGE_SIZE