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/desc.h>
  16 #include <asm/segment.h>
  17 #include <asm/pgtable.h>
  18 #include <asm/page.h>
  19 #include <asm/msr.h>
  20 #include <asm/cache.h>
  21 #include <asm/processor-flags.h>
  22
  23 #ifdef CONFIG_PARAVIRT
  24 #include <asm/asm-offsets.h>
  25 #include <asm/paravirt.h>
  26 #else
  27 #define GET_CR2_INTO_RCX movq %cr2, %rcx
  28 #endif
  29
  30 /* we are not able to switch in one step to the final KERNEL ADRESS SPACE
  31  * because we need identity-mapped pages.
  32  *
  33  */
  34
  35 #define pud_index(x)    (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
  36
  37 L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET)
  38 L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET)
  39 L4_START_KERNEL = pgd_index(__START_KERNEL_map)
  40 L3_START_KERNEL = pud_index(__START_KERNEL_map)
  41
  42         .text
  43         .section .text.head
  44         .code64
  45         .globl startup_64
  46 startup_64:
  47
  48         /*
  49          * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
  50          * and someone has loaded an identity mapped page table
  51          * for us.  These identity mapped page tables map all of the
  52          * kernel pages and possibly all of memory.
  53          *
  54          * %esi holds a physical pointer to real_mode_data.
  55          *
  56          * We come here either directly from a 64bit bootloader, or from
  57          * arch/x86_64/boot/compressed/head.S.
  58          *
  59          * We only come here initially at boot nothing else comes here.
  60          *
  61          * Since we may be loaded at an address different from what we were
  62          * compiled to run at we first fixup the physical addresses in our page
  63          * tables and then reload them.
  64          */
  65
  66         /* Compute the delta between the address I am compiled to run at and the
  67          * address I am actually running at.
  68          */
  69         leaq    _text(%rip), %rbp
  70         subq    $_text - __START_KERNEL_map, %rbp
  71
  72         /* Is the address not 2M aligned? */
  73         movq    %rbp, %rax
  74         andl    $~PMD_PAGE_MASK, %eax
  75         testl   %eax, %eax
  76         jnz     bad_address
  77
  78         /* Is the address too large? */
  79         leaq    _text(%rip), %rdx
  80         movq    $PGDIR_SIZE, %rax
  81         cmpq    %rax, %rdx
  82         jae     bad_address
  83
  84         /* Fixup the physical addresses in the page table
  85          */
  86         addq    %rbp, init_level4_pgt + 0(%rip)
  87         addq    %rbp, init_level4_pgt + (L4_PAGE_OFFSET*8)(%rip)
  88         addq    %rbp, init_level4_pgt + (L4_START_KERNEL*8)(%rip)
  89
  90         addq    %rbp, level3_ident_pgt + 0(%rip)
  91
  92         addq    %rbp, level3_kernel_pgt + (510*8)(%rip)
  93         addq    %rbp, level3_kernel_pgt + (511*8)(%rip)
  94
  95         addq    %rbp, level2_fixmap_pgt + (506*8)(%rip)
  96
  97         /* Add an Identity mapping if I am above 1G */
  98         leaq    _text(%rip), %rdi
  99         andq    $PMD_PAGE_MASK, %rdi
 100
 101         movq    %rdi, %rax
 102         shrq    $PUD_SHIFT, %rax
 103         andq    $(PTRS_PER_PUD - 1), %rax
 104         jz      ident_complete
 105
 106         leaq    (level2_spare_pgt - __START_KERNEL_map + _KERNPG_TABLE)(%rbp), %rdx
 107         leaq    level3_ident_pgt(%rip), %rbx
 108         movq    %rdx, 0(%rbx, %rax, 8)
 109
 110         movq    %rdi, %rax
 111         shrq    $PMD_SHIFT, %rax
 112         andq    $(PTRS_PER_PMD - 1), %rax
 113         leaq    __PAGE_KERNEL_LARGE_EXEC(%rdi), %rdx
 114         leaq    level2_spare_pgt(%rip), %rbx
 115         movq    %rdx, 0(%rbx, %rax, 8)
 116 ident_complete:
 117
 118         /*
 119          * Fixup the kernel text+data virtual addresses. Note that
 120          * we might write invalid pmds, when the kernel is relocated
 121          * cleanup_highmap() fixes this up along with the mappings
 122          * beyond _end.
 123          */
 124
 125         leaq    level2_kernel_pgt(%rip), %rdi
 126         leaq    4096(%rdi), %r8
 127         /* See if it is a valid page table entry */
 128 1:      testq   $1, 0(%rdi)
 129         jz      2f
 130         addq    %rbp, 0(%rdi)
 131         /* Go to the next page */
 132 2:      addq    $8, %rdi
 133         cmp     %r8, %rdi
 134         jne     1b
 135
 136         /* Fixup phys_base */
 137         addq    %rbp, phys_base(%rip)
 138
 139 #ifdef CONFIG_X86_TRAMPOLINE
 140         addq    %rbp, trampoline_level4_pgt + 0(%rip)
 141         addq    %rbp, trampoline_level4_pgt + (511*8)(%rip)
 142 #endif
 143
 144         /* Due to ENTRY(), sometimes the empty space gets filled with
 145          * zeros. Better take a jmp than relying on empty space being
 146          * filled with 0x90 (nop)
 147          */
 148         jmp secondary_startup_64
 149 ENTRY(secondary_startup_64)
 150         /*
 151          * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
 152          * and someone has loaded a mapped page table.
 153          *
 154          * %esi holds a physical pointer to real_mode_data.
 155          *
 156          * We come here either from startup_64 (using physical addresses)
 157          * or from trampoline.S (using virtual addresses).
 158          *
 159          * Using virtual addresses from trampoline.S removes the need
 160          * to have any identity mapped pages in the kernel page table
 161          * after the boot processor executes this code.
 162          */
 163
 164         /* Enable PAE mode and PGE */
 165         movl    $(X86_CR4_PAE | X86_CR4_PGE), %eax
 166         movq    %rax, %cr4
 167
 168         /* Setup early boot stage 4 level pagetables. */
 169         movq    $(init_level4_pgt - __START_KERNEL_map), %rax
 170         addq    phys_base(%rip), %rax
 171         movq    %rax, %cr3
 172
 173         /* Ensure I am executing from virtual addresses */
 174         movq    $1f, %rax
 175         jmp     *%rax
 176 1:
 177
 178         /* Check if nx is implemented */
 179         movl    $0x80000001, %eax
 180         cpuid
 181         movl    %edx,%edi
 182
 183         /* Setup EFER (Extended Feature Enable Register) */
 184         movl    $MSR_EFER, %ecx
 185         rdmsr
 186         btsl    $_EFER_SCE, %eax        /* Enable System Call */
 187         btl     $20,%edi                /* No Execute supported? */
 188         jnc     1f
 189         btsl    $_EFER_NX, %eax
 190 1:      wrmsr                           /* Make changes effective */
 191
 192         /* Setup cr0 */
 193 #define CR0_STATE       (X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
 194                          X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
 195                          X86_CR0_PG)
 196         movl    $CR0_STATE, %eax
 197         /* Make changes effective */
 198         movq    %rax, %cr0
 199
 200         /* Setup a boot time stack */
 201         movq stack_start(%rip),%rsp
 202
 203         /* zero EFLAGS after setting rsp */
 204         pushq $0
 205         popfq
 206
 207         /*
 208          * We must switch to a new descriptor in kernel space for the GDT
 209          * because soon the kernel won't have access anymore to the userspace
 210          * addresses where we're currently running on. We have to do that here
 211          * because in 32bit we couldn't load a 64bit linear address.
 212          */
 213         lgdt    early_gdt_descr(%rip)
 214
 215         /* set up data segments. actually 0 would do too */
 216         movl $__KERNEL_DS,%eax
 217         movl %eax,%ds
 218         movl %eax,%ss
 219         movl %eax,%es
 220
 221         /*
 222          * We don't really need to load %fs or %gs, but load them anyway
 223          * to kill any stale realmode selectors.  This allows execution
 224          * under VT hardware.
 225          */
 226         movl %eax,%fs
 227         movl %eax,%gs
 228
 229         /*
 230          * Setup up a dummy PDA. this is just for some early bootup code
 231          * that does in_interrupt()
 232          */
 233         movl    $MSR_GS_BASE,%ecx
 234         movq    $empty_zero_page,%rax
 235         movq    %rax,%rdx
 236         shrq    $32,%rdx
 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         /* SMP bootup changes these two */
 256         __REFDATA
 257         .align  8
 258         ENTRY(initial_code)
 259         .quad   x86_64_start_kernel
 260         __FINITDATA
 261
 262         ENTRY(stack_start)
 263         .quad  init_thread_union+THREAD_SIZE-8
 264         .word  0
 265
 266 bad_address:
 267         jmp bad_address
 268
 269         .section ".init.text","ax"
 270 #ifdef CONFIG_EARLY_PRINTK
 271         .globl early_idt_handlers
 272 early_idt_handlers:
 273         i = 0
 274         .rept NUM_EXCEPTION_VECTORS
 275         movl $i, %esi
 276         jmp early_idt_handler
 277         i = i + 1
 278         .endr
 279 #endif
 280
 281 ENTRY(early_idt_handler)
 282 #ifdef CONFIG_EARLY_PRINTK
 283         cmpl $2,early_recursion_flag(%rip)
 284         jz  1f
 285         incl early_recursion_flag(%rip)
 286         GET_CR2_INTO_RCX
 287         movq %rcx,%r9
 288         xorl %r8d,%r8d          # zero for error code
 289         movl %esi,%ecx          # get vector number
 290         # Test %ecx against mask of vectors that push error code.
 291         cmpl $31,%ecx
 292         ja 0f
 293         movl $1,%eax
 294         salq %cl,%rax
 295         testl $0x27d00,%eax
 296         je 0f
 297         popq %r8                # get error code
 298 0:      movq 0(%rsp),%rcx       # get ip
 299         movq 8(%rsp),%rdx       # get cs
 300         xorl %eax,%eax
 301         leaq early_idt_msg(%rip),%rdi
 302         call early_printk
 303         cmpl $2,early_recursion_flag(%rip)
 304         jz  1f
 305         call dump_stack
 306 #ifdef CONFIG_KALLSYMS
 307         leaq early_idt_ripmsg(%rip),%rdi
 308         movq 8(%rsp),%rsi       # get rip again
 309         call __print_symbol
 310 #endif
 311 #endif /* EARLY_PRINTK */
 312 1:      hlt
 313         jmp 1b
 314
 315 #ifdef CONFIG_EARLY_PRINTK
 316 early_recursion_flag:
 317         .long 0
 318
 319 early_idt_msg:
 320         .asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n"
 321 early_idt_ripmsg:
 322         .asciz "RIP %s\n"
 323 #endif /* CONFIG_EARLY_PRINTK */
 324         .previous
 325
 326 .balign PAGE_SIZE
 327
 328 #define NEXT_PAGE(name) \
 329         .balign PAGE_SIZE; \
 330 ENTRY(name)
 331
 332 /* Automate the creation of 1 to 1 mapping pmd entries */
 333 #define PMDS(START, PERM, COUNT)                        \
 334         i = 0 ;                                         \
 335         .rept (COUNT) ;                                 \
 336         .quad   (START) + (i << PMD_SHIFT) + (PERM) ;   \
 337         i = i + 1 ;                                     \
 338         .endr
 339
 340         /*
 341          * This default setting generates an ident mapping at address 0x100000
 342          * and a mapping for the kernel that precisely maps virtual address
 343          * 0xffffffff80000000 to physical address 0x000000. (always using
 344          * 2Mbyte large pages provided by PAE mode)
 345          */
 346 NEXT_PAGE(init_level4_pgt)
 347         .quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
 348         .org    init_level4_pgt + L4_PAGE_OFFSET*8, 0
 349         .quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
 350         .org    init_level4_pgt + L4_START_KERNEL*8, 0
 351         /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
 352         .quad   level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
 353
 354 NEXT_PAGE(level3_ident_pgt)
 355         .quad   level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
 356         .fill   511,8,0
 357
 358 NEXT_PAGE(level3_kernel_pgt)
 359         .fill   L3_START_KERNEL,8,0
 360         /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
 361         .quad   level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
 362         .quad   level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
 363
 364 NEXT_PAGE(level2_fixmap_pgt)
 365         .fill   506,8,0
 366         .quad   level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
 367         /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
 368         .fill   5,8,0
 369
 370 NEXT_PAGE(level1_fixmap_pgt)
 371         .fill   512,8,0
 372
 373 NEXT_PAGE(level2_ident_pgt)
 374         /* Since I easily can, map the first 1G.
 375          * Don't set NX because code runs from these pages.
 376          */
 377         PMDS(0, __PAGE_KERNEL_LARGE_EXEC, PTRS_PER_PMD)
 378
 379 NEXT_PAGE(level2_kernel_pgt)
 380         /*
 381          * 512 MB kernel mapping. We spend a full page on this pagetable
 382          * anyway.
 383          *
 384          * The kernel code+data+bss must not be bigger than that.
 385          *
 386          * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
 387          *  If you want to increase this then increase MODULES_VADDR
 388          *  too.)
 389          */
 390         PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
 391                 KERNEL_IMAGE_SIZE/PMD_SIZE)
 392
 393 NEXT_PAGE(level2_spare_pgt)
 394         .fill   512, 8, 0
 395
 396 #undef PMDS
 397 #undef NEXT_PAGE
 398
 399         .data
 400         .align 16
 401         .globl early_gdt_descr
 402 early_gdt_descr:
 403         .word   GDT_ENTRIES*8-1
 404         .quad   per_cpu__gdt_page
 405
 406 ENTRY(phys_base)
 407         /* This must match the first entry in level2_kernel_pgt */
 408         .quad   0x0000000000000000
 409
 410
 411         .section .bss, "aw", @nobits
 412         .align L1_CACHE_BYTES
 413 ENTRY(idt_table)
 414         .skip 256 * 16
 415
 416         .section .bss.page_aligned, "aw", @nobits
 417         .align PAGE_SIZE
 418 ENTRY(empty_zero_page)
 419         .skip PAGE_SIZE