arch/x86/kernel/head_32.S

   1 /*
   2  *
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *
   5  *  Enhanced CPU detection and feature setting code by Mike Jagdis
   6  *  and Martin Mares, November 1997.
   7  */
   8
   9 .text
  10 #include <linux/threads.h>
  11 #include <linux/init.h>
  12 #include <linux/linkage.h>
  13 #include <asm/segment.h>
  14 #include <asm/page_types.h>
  15 #include <asm/pgtable_types.h>
  16 #include <asm/cache.h>
  17 #include <asm/thread_info.h>
  18 #include <asm/asm-offsets.h>
  19 #include <asm/setup.h>
  20 #include <asm/processor-flags.h>
  21 #include <asm/msr-index.h>
  22 #include <asm/cpufeature.h>
  23 #include <asm/percpu.h>
  24 #include <asm/nops.h>
  25 #include <asm/bootparam.h>
  26
  27 /* Physical address */
  28 #define pa(X) ((X) - __PAGE_OFFSET)
  29
  30 /*
  31  * References to members of the new_cpu_data structure.
  32  */
  33
  34 #define X86             new_cpu_data+CPUINFO_x86
  35 #define X86_VENDOR      new_cpu_data+CPUINFO_x86_vendor
  36 #define X86_MODEL       new_cpu_data+CPUINFO_x86_model
  37 #define X86_MASK        new_cpu_data+CPUINFO_x86_mask
  38 #define X86_HARD_MATH   new_cpu_data+CPUINFO_hard_math
  39 #define X86_CPUID       new_cpu_data+CPUINFO_cpuid_level
  40 #define X86_CAPABILITY  new_cpu_data+CPUINFO_x86_capability
  41 #define X86_VENDOR_ID   new_cpu_data+CPUINFO_x86_vendor_id
  42
  43 /*
  44  * This is how much memory in addition to the memory covered up to
  45  * and including _end we need mapped initially.
  46  * We need:
  47  *     (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
  48  *     (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
  49  *
  50  * Modulo rounding, each megabyte assigned here requires a kilobyte of
  51  * memory, which is currently unreclaimed.
  52  *
  53  * This should be a multiple of a page.
  54  *
  55  * KERNEL_IMAGE_SIZE should be greater than pa(_end)
  56  * and small than max_low_pfn, otherwise will waste some page table entries
  57  */
  58
  59 #if PTRS_PER_PMD > 1
  60 #define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
  61 #else
  62 #define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
  63 #endif
  64
  65 /* Number of possible pages in the lowmem region */
  66 LOWMEM_PAGES = (((1<<32) - __PAGE_OFFSET) >> PAGE_SHIFT)
  67
  68 /* Enough space to fit pagetables for the low memory linear map */
  69 MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
  70
  71 /*
  72  * Worst-case size of the kernel mapping we need to make:
  73  * a relocatable kernel can live anywhere in lowmem, so we need to be able
  74  * to map all of lowmem.
  75  */
  76 KERNEL_PAGES = LOWMEM_PAGES
  77
  78 INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
  79 RESERVE_BRK(pagetables, INIT_MAP_SIZE)
  80
  81 /*
  82  * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
  83  * %esi points to the real-mode code as a 32-bit pointer.
  84  * CS and DS must be 4 GB flat segments, but we don't depend on
  85  * any particular GDT layout, because we load our own as soon as we
  86  * can.
  87  */
  88 __HEAD
  89 ENTRY(startup_32)
  90         movl pa(stack_start),%ecx
  91
  92         /* test KEEP_SEGMENTS flag to see if the bootloader is asking
  93                 us to not reload segments */
  94         testb $KEEP_SEGMENTS, BP_loadflags(%esi)
  95         jnz 2f
  96
  97 /*
  98  * Set segments to known values.
  99  */
 100         lgdt pa(boot_gdt_descr)
 101         movl $(__BOOT_DS),%eax
 102         movl %eax,%ds
 103         movl %eax,%es
 104         movl %eax,%fs
 105         movl %eax,%gs
 106         movl %eax,%ss
 107 2:
 108         leal -__PAGE_OFFSET(%ecx),%esp
 109
 110 /*
 111  * Clear BSS first so that there are no surprises...
 112  */
 113         cld
 114         xorl %eax,%eax
 115         movl $pa(__bss_start),%edi
 116         movl $pa(__bss_stop),%ecx
 117         subl %edi,%ecx
 118         shrl $2,%ecx
 119         rep ; stosl
 120 /*
 121  * Copy bootup parameters out of the way.
 122  * Note: %esi still has the pointer to the real-mode data.
 123  * With the kexec as boot loader, parameter segment might be loaded beyond
 124  * kernel image and might not even be addressable by early boot page tables.
 125  * (kexec on panic case). Hence copy out the parameters before initializing
 126  * page tables.
 127  */
 128         movl $pa(boot_params),%edi
 129         movl $(PARAM_SIZE/4),%ecx
 130         cld
 131         rep
 132         movsl
 133         movl pa(boot_params) + NEW_CL_POINTER,%esi
 134         andl %esi,%esi
 135         jz 1f                   # No command line
 136         movl $pa(boot_command_line),%edi
 137         movl $(COMMAND_LINE_SIZE/4),%ecx
 138         rep
 139         movsl
 140 1:
 141
 142 #ifdef CONFIG_OLPC
 143         /* save OFW's pgdir table for later use when calling into OFW */
 144         movl %cr3, %eax
 145         movl %eax, pa(olpc_ofw_pgd)
 146 #endif
 147
 148 #ifdef CONFIG_MICROCODE_EARLY
 149         /* Early load ucode on BSP. */
 150         call load_ucode_bsp
 151 #endif
 152
 153 /*
 154  * Initialize page tables.  This creates a PDE and a set of page
 155  * tables, which are located immediately beyond __brk_base.  The variable
 156  * _brk_end is set up to point to the first "safe" location.
 157  * Mappings are created both at virtual address 0 (identity mapping)
 158  * and PAGE_OFFSET for up to _end.
 159  */
 160 #ifdef CONFIG_X86_PAE
 161
 162         /*
 163          * In PAE mode initial_page_table is statically defined to contain
 164          * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
 165          * entries). The identity mapping is handled by pointing two PGD entries
 166          * to the first kernel PMD.
 167          *
 168          * Note the upper half of each PMD or PTE are always zero at this stage.
 169          */
 170
 171 #define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
 172
 173         xorl %ebx,%ebx                          /* %ebx is kept at zero */
 174
 175         movl $pa(__brk_base), %edi
 176         movl $pa(initial_pg_pmd), %edx
 177         movl $PTE_IDENT_ATTR, %eax
 178 10:
 179         leal PDE_IDENT_ATTR(%edi),%ecx          /* Create PMD entry */
 180         movl %ecx,(%edx)                        /* Store PMD entry */
 181                                                 /* Upper half already zero */
 182         addl $8,%edx
 183         movl $512,%ecx
 184 11:
 185         stosl
 186         xchgl %eax,%ebx
 187         stosl
 188         xchgl %eax,%ebx
 189         addl $0x1000,%eax
 190         loop 11b
 191
 192         /*
 193          * End condition: we must map up to the end + MAPPING_BEYOND_END.
 194          */
 195         movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
 196         cmpl %ebp,%eax
 197         jb 10b
 198 1:
 199         addl $__PAGE_OFFSET, %edi
 200         movl %edi, pa(_brk_end)
 201         shrl $12, %eax
 202         movl %eax, pa(max_pfn_mapped)
 203
 204         /* Do early initialization of the fixmap area */
 205         movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
 206         movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
 207 #else   /* Not PAE */
 208
 209 page_pde_offset = (__PAGE_OFFSET >> 20);
 210
 211         movl $pa(__brk_base), %edi
 212         movl $pa(initial_page_table), %edx
 213         movl $PTE_IDENT_ATTR, %eax
 214 10:
 215         leal PDE_IDENT_ATTR(%edi),%ecx          /* Create PDE entry */
 216         movl %ecx,(%edx)                        /* Store identity PDE entry */
 217         movl %ecx,page_pde_offset(%edx)         /* Store kernel PDE entry */
 218         addl $4,%edx
 219         movl $1024, %ecx
 220 11:
 221         stosl
 222         addl $0x1000,%eax
 223         loop 11b
 224         /*
 225          * End condition: we must map up to the end + MAPPING_BEYOND_END.
 226          */
 227         movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
 228         cmpl %ebp,%eax
 229         jb 10b
 230         addl $__PAGE_OFFSET, %edi
 231         movl %edi, pa(_brk_end)
 232         shrl $12, %eax
 233         movl %eax, pa(max_pfn_mapped)
 234
 235         /* Do early initialization of the fixmap area */
 236         movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
 237         movl %eax,pa(initial_page_table+0xffc)
 238 #endif
 239
 240 #ifdef CONFIG_PARAVIRT
 241         /* This is can only trip for a broken bootloader... */
 242         cmpw $0x207, pa(boot_params + BP_version)
 243         jb default_entry
 244
 245         /* Paravirt-compatible boot parameters.  Look to see what architecture
 246                 we're booting under. */
 247         movl pa(boot_params + BP_hardware_subarch), %eax
 248         cmpl $num_subarch_entries, %eax
 249         jae bad_subarch
 250
 251         movl pa(subarch_entries)(,%eax,4), %eax
 252         subl $__PAGE_OFFSET, %eax
 253         jmp *%eax
 254
 255 bad_subarch:
 256 WEAK(lguest_entry)
 257 WEAK(xen_entry)
 258         /* Unknown implementation; there's really
 259            nothing we can do at this point. */
 260         ud2a
 261
 262         __INITDATA
 263
 264 subarch_entries:
 265         .long default_entry             /* normal x86/PC */
 266         .long lguest_entry              /* lguest hypervisor */
 267         .long xen_entry                 /* Xen hypervisor */
 268         .long default_entry             /* Moorestown MID */
 269 num_subarch_entries = (. - subarch_entries) / 4
 270 .previous
 271 #else
 272         jmp default_entry
 273 #endif /* CONFIG_PARAVIRT */
 274
 275 #ifdef CONFIG_HOTPLUG_CPU
 276 /*
 277  * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
 278  * up already except stack. We just set up stack here. Then call
 279  * start_secondary().
 280  */
 281 ENTRY(start_cpu0)
 282         movl stack_start, %ecx
 283         movl %ecx, %esp
 284         jmp  *(initial_code)
 285 ENDPROC(start_cpu0)
 286 #endif
 287
 288 /*
 289  * Non-boot CPU entry point; entered from trampoline.S
 290  * We can't lgdt here, because lgdt itself uses a data segment, but
 291  * we know the trampoline has already loaded the boot_gdt for us.
 292  *
 293  * If cpu hotplug is not supported then this code can go in init section
 294  * which will be freed later
 295  */
 296 ENTRY(startup_32_smp)
 297         cld
 298         movl $(__BOOT_DS),%eax
 299         movl %eax,%ds
 300         movl %eax,%es
 301         movl %eax,%fs
 302         movl %eax,%gs
 303         movl pa(stack_start),%ecx
 304         movl %eax,%ss
 305         leal -__PAGE_OFFSET(%ecx),%esp
 306
 307 #ifdef CONFIG_MICROCODE_EARLY
 308         /* Early load ucode on AP. */
 309         call load_ucode_ap
 310 #endif
 311
 312
 313 default_entry:
 314 #define CR0_STATE       (X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
 315                          X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
 316                          X86_CR0_PG)
 317         movl $(CR0_STATE & ~X86_CR0_PG),%eax
 318         movl %eax,%cr0
 319
 320 /*
 321  * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
 322  * bits like NT set. This would confuse the debugger if this code is traced. So
 323  * initialize them properly now before switching to protected mode. That means
 324  * DF in particular (even though we have cleared it earlier after copying the
 325  * command line) because GCC expects it.
 326  */
 327         pushl $0
 328         popfl
 329
 330 /*
 331  * New page tables may be in 4Mbyte page mode and may be using the global pages.
 332  *
 333  * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
 334  * if and only if CPUID exists and has flags other than the FPU flag set.
 335  */
 336         movl $-1,pa(X86_CPUID)          # preset CPUID level
 337         movl $X86_EFLAGS_ID,%ecx
 338         pushl %ecx
 339         popfl                           # set EFLAGS=ID
 340         pushfl
 341         popl %eax                       # get EFLAGS
 342         testl $X86_EFLAGS_ID,%eax       # did EFLAGS.ID remained set?
 343         jz enable_paging                # hw disallowed setting of ID bit
 344                                         # which means no CPUID and no CR4
 345
 346         xorl %eax,%eax
 347         cpuid
 348         movl %eax,pa(X86_CPUID)         # save largest std CPUID function
 349
 350         movl $1,%eax
 351         cpuid
 352         andl $~1,%edx                   # Ignore CPUID.FPU
 353         jz enable_paging                # No flags or only CPUID.FPU = no CR4
 354
 355         movl pa(mmu_cr4_features),%eax
 356         movl %eax,%cr4
 357
 358         testb $X86_CR4_PAE, %al         # check if PAE is enabled
 359         jz enable_paging
 360
 361         /* Check if extended functions are implemented */
 362         movl $0x80000000, %eax
 363         cpuid
 364         /* Value must be in the range 0x80000001 to 0x8000ffff */
 365         subl $0x80000001, %eax
 366         cmpl $(0x8000ffff-0x80000001), %eax
 367         ja enable_paging
 368
 369         /* Clear bogus XD_DISABLE bits */
 370         call verify_cpu
 371
 372         mov $0x80000001, %eax
 373         cpuid
 374         /* Execute Disable bit supported? */
 375         btl $(X86_FEATURE_NX & 31), %edx
 376         jnc enable_paging
 377
 378         /* Setup EFER (Extended Feature Enable Register) */
 379         movl $MSR_EFER, %ecx
 380         rdmsr
 381
 382         btsl $_EFER_NX, %eax
 383         /* Make changes effective */
 384         wrmsr
 385
 386 enable_paging:
 387
 388 /*
 389  * Enable paging
 390  */
 391         movl $pa(initial_page_table), %eax
 392         movl %eax,%cr3          /* set the page table pointer.. */
 393         movl $CR0_STATE,%eax
 394         movl %eax,%cr0          /* ..and set paging (PG) bit */
 395         ljmp $__BOOT_CS,$1f     /* Clear prefetch and normalize %eip */
 396 1:
 397         /* Shift the stack pointer to a virtual address */
 398         addl $__PAGE_OFFSET, %esp
 399
 400 /*
 401  * start system 32-bit setup. We need to re-do some of the things done
 402  * in 16-bit mode for the "real" operations.
 403  */
 404         movl setup_once_ref,%eax
 405         andl %eax,%eax
 406         jz 1f                           # Did we do this already?
 407         call *%eax
 408 1:
 409
 410 /*
 411  * Check if it is 486
 412  */
 413         movb $4,X86                     # at least 486
 414         cmpl $-1,X86_CPUID
 415         je is486
 416
 417         /* get vendor info */
 418         xorl %eax,%eax                  # call CPUID with 0 -> return vendor ID
 419         cpuid
 420         movl %eax,X86_CPUID             # save CPUID level
 421         movl %ebx,X86_VENDOR_ID         # lo 4 chars
 422         movl %edx,X86_VENDOR_ID+4       # next 4 chars
 423         movl %ecx,X86_VENDOR_ID+8       # last 4 chars
 424
 425         orl %eax,%eax                   # do we have processor info as well?
 426         je is486
 427
 428         movl $1,%eax            # Use the CPUID instruction to get CPU type
 429         cpuid
 430         movb %al,%cl            # save reg for future use
 431         andb $0x0f,%ah          # mask processor family
 432         movb %ah,X86
 433         andb $0xf0,%al          # mask model
 434         shrb $4,%al
 435         movb %al,X86_MODEL
 436         andb $0x0f,%cl          # mask mask revision
 437         movb %cl,X86_MASK
 438         movl %edx,X86_CAPABILITY
 439
 440 is486:
 441         movl $0x50022,%ecx      # set AM, WP, NE and MP
 442         movl %cr0,%eax
 443         andl $0x80000011,%eax   # Save PG,PE,ET
 444         orl %ecx,%eax
 445         movl %eax,%cr0
 446
 447         lgdt early_gdt_descr
 448         lidt idt_descr
 449         ljmp $(__KERNEL_CS),$1f
 450 1:      movl $(__KERNEL_DS),%eax        # reload all the segment registers
 451         movl %eax,%ss                   # after changing gdt.
 452
 453         movl $(__USER_DS),%eax          # DS/ES contains default USER segment
 454         movl %eax,%ds
 455         movl %eax,%es
 456
 457         movl $(__KERNEL_PERCPU), %eax
 458         movl %eax,%fs                   # set this cpu's percpu
 459
 460         movl $(__KERNEL_STACK_CANARY),%eax
 461         movl %eax,%gs
 462
 463         xorl %eax,%eax                  # Clear LDT
 464         lldt %ax
 465
 466         pushl $0                # fake return address for unwinder
 467         jmp *(initial_code)
 468
 469 #include "verify_cpu.S"
 470
 471 /*
 472  *  setup_once
 473  *
 474  *  The setup work we only want to run on the BSP.
 475  *
 476  *  Warning: %esi is live across this function.
 477  */
 478 __INIT
 479 setup_once:
 480         /*
 481          * Set up a idt with 256 entries pointing to ignore_int,
 482          * interrupt gates. It doesn't actually load idt - that needs
 483          * to be done on each CPU. Interrupts are enabled elsewhere,
 484          * when we can be relatively sure everything is ok.
 485          */
 486
 487         movl $idt_table,%edi
 488         movl $early_idt_handlers,%eax
 489         movl $NUM_EXCEPTION_VECTORS,%ecx
 490 1:
 491         movl %eax,(%edi)
 492         movl %eax,4(%edi)
 493         /* interrupt gate, dpl=0, present */
 494         movl $(0x8E000000 + __KERNEL_CS),2(%edi)
 495         addl $9,%eax
 496         addl $8,%edi
 497         loop 1b
 498
 499         movl $256 - NUM_EXCEPTION_VECTORS,%ecx
 500         movl $ignore_int,%edx
 501         movl $(__KERNEL_CS << 16),%eax
 502         movw %dx,%ax            /* selector = 0x0010 = cs */
 503         movw $0x8E00,%dx        /* interrupt gate - dpl=0, present */
 504 2:
 505         movl %eax,(%edi)
 506         movl %edx,4(%edi)
 507         addl $8,%edi
 508         loop 2b
 509
 510 #ifdef CONFIG_CC_STACKPROTECTOR
 511         /*
 512          * Configure the stack canary. The linker can't handle this by
 513          * relocation.  Manually set base address in stack canary
 514          * segment descriptor.
 515          */
 516         movl $gdt_page,%eax
 517         movl $stack_canary,%ecx
 518         movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
 519         shrl $16, %ecx
 520         movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
 521         movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
 522 #endif
 523
 524         andl $0,setup_once_ref  /* Once is enough, thanks */
 525         ret
 526
 527 ENTRY(early_idt_handlers)
 528         # 36(%esp) %eflags
 529         # 32(%esp) %cs
 530         # 28(%esp) %eip
 531         # 24(%rsp) error code
 532         i = 0
 533         .rept NUM_EXCEPTION_VECTORS
 534         .if (EXCEPTION_ERRCODE_MASK >> i) & 1
 535         ASM_NOP2
 536         .else
 537         pushl $0                # Dummy error code, to make stack frame uniform
 538         .endif
 539         pushl $i                # 20(%esp) Vector number
 540         jmp early_idt_handler
 541         i = i + 1
 542         .endr
 543 ENDPROC(early_idt_handlers)
 544
 545         /* This is global to keep gas from relaxing the jumps */
 546 ENTRY(early_idt_handler)
 547         cld
 548
 549         cmpl $2,(%esp)          # X86_TRAP_NMI
 550         je is_nmi               # Ignore NMI
 551
 552         cmpl $2,%ss:early_recursion_flag
 553         je hlt_loop
 554         incl %ss:early_recursion_flag
 555
 556         push %eax               # 16(%esp)
 557         push %ecx               # 12(%esp)
 558         push %edx               #  8(%esp)
 559         push %ds                #  4(%esp)
 560         push %es                #  0(%esp)
 561         movl $(__KERNEL_DS),%eax
 562         movl %eax,%ds
 563         movl %eax,%es
 564
 565         cmpl $(__KERNEL_CS),32(%esp)
 566         jne 10f
 567
 568         leal 28(%esp),%eax      # Pointer to %eip
 569         call early_fixup_exception
 570         andl %eax,%eax
 571         jnz ex_entry            /* found an exception entry */
 572
 573 10:
 574 #ifdef CONFIG_PRINTK
 575         xorl %eax,%eax
 576         movw %ax,2(%esp)        /* clean up the segment values on some cpus */
 577         movw %ax,6(%esp)
 578         movw %ax,34(%esp)
 579         leal  40(%esp),%eax
 580         pushl %eax              /* %esp before the exception */
 581         pushl %ebx
 582         pushl %ebp
 583         pushl %esi
 584         pushl %edi
 585         movl %cr2,%eax
 586         pushl %eax
 587         pushl (20+6*4)(%esp)    /* trapno */
 588         pushl $fault_msg
 589         call printk
 590 #endif
 591         call dump_stack
 592 hlt_loop:
 593         hlt
 594         jmp hlt_loop
 595
 596 ex_entry:
 597         pop %es
 598         pop %ds
 599         pop %edx
 600         pop %ecx
 601         pop %eax
 602         decl %ss:early_recursion_flag
 603 is_nmi:
 604         addl $8,%esp            /* drop vector number and error code */
 605         iret
 606 ENDPROC(early_idt_handler)
 607
 608 /* This is the default interrupt "handler" :-) */
 609         ALIGN
 610 ignore_int:
 611         cld
 612 #ifdef CONFIG_PRINTK
 613         pushl %eax
 614         pushl %ecx
 615         pushl %edx
 616         pushl %es
 617         pushl %ds
 618         movl $(__KERNEL_DS),%eax
 619         movl %eax,%ds
 620         movl %eax,%es
 621         cmpl $2,early_recursion_flag
 622         je hlt_loop
 623         incl early_recursion_flag
 624         pushl 16(%esp)
 625         pushl 24(%esp)
 626         pushl 32(%esp)
 627         pushl 40(%esp)
 628         pushl $int_msg
 629         call printk
 630
 631         call dump_stack
 632
 633         addl $(5*4),%esp
 634         popl %ds
 635         popl %es
 636         popl %edx
 637         popl %ecx
 638         popl %eax
 639 #endif
 640         iret
 641 ENDPROC(ignore_int)
 642 __INITDATA
 643         .align 4
 644 early_recursion_flag:
 645         .long 0
 646
 647 __REFDATA
 648         .align 4
 649 ENTRY(initial_code)
 650         .long i386_start_kernel
 651 ENTRY(setup_once_ref)
 652         .long setup_once
 653
 654 /*
 655  * BSS section
 656  */
 657 __PAGE_ALIGNED_BSS
 658         .align PAGE_SIZE
 659 #ifdef CONFIG_X86_PAE
 660 initial_pg_pmd:
 661         .fill 1024*KPMDS,4,0
 662 #else
 663 ENTRY(initial_page_table)
 664         .fill 1024,4,0
 665 #endif
 666 initial_pg_fixmap:
 667         .fill 1024,4,0
 668 ENTRY(empty_zero_page)
 669         .fill 4096,1,0
 670 ENTRY(swapper_pg_dir)
 671         .fill 1024,4,0
 672
 673 /*
 674  * This starts the data section.
 675  */
 676 #ifdef CONFIG_X86_PAE
 677 __PAGE_ALIGNED_DATA
 678         /* Page-aligned for the benefit of paravirt? */
 679         .align PAGE_SIZE
 680 ENTRY(initial_page_table)
 681         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0     /* low identity map */
 682 # if KPMDS == 3
 683         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
 684         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
 685         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
 686 # elif KPMDS == 2
 687         .long   0,0
 688         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
 689         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
 690 # elif KPMDS == 1
 691         .long   0,0
 692         .long   0,0
 693         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
 694 # else
 695 #  error "Kernel PMDs should be 1, 2 or 3"
 696 # endif
 697         .align PAGE_SIZE                /* needs to be page-sized too */
 698 #endif
 699
 700 .data
 701 .balign 4
 702 ENTRY(stack_start)
 703         .long init_thread_union+THREAD_SIZE
 704
 705 __INITRODATA
 706 int_msg:
 707         .asciz "Unknown interrupt or fault at: %p %p %p\n"
 708
 709 fault_msg:
 710 /* fault info: */
 711         .ascii "BUG: Int %d: CR2 %p\n"
 712 /* regs pushed in early_idt_handler: */
 713         .ascii "     EDI %p  ESI %p  EBP %p  EBX %p\n"
 714         .ascii "     ESP %p   ES %p   DS %p\n"
 715         .ascii "     EDX %p  ECX %p  EAX %p\n"
 716 /* fault frame: */
 717         .ascii "     vec %p  err %p  EIP %p   CS %p  flg %p\n"
 718         .ascii "Stack: %p %p %p %p %p %p %p %p\n"
 719         .ascii "       %p %p %p %p %p %p %p %p\n"
 720         .asciz "       %p %p %p %p %p %p %p %p\n"
 721
 722 #include "../../x86/xen/xen-head.S"
 723
 724 /*
 725  * The IDT and GDT 'descriptors' are a strange 48-bit object
 726  * only used by the lidt and lgdt instructions. They are not
 727  * like usual segment descriptors - they consist of a 16-bit
 728  * segment size, and 32-bit linear address value:
 729  */
 730
 731         .data
 732 .globl boot_gdt_descr
 733 .globl idt_descr
 734
 735         ALIGN
 736 # early boot GDT descriptor (must use 1:1 address mapping)
 737         .word 0                         # 32 bit align gdt_desc.address
 738 boot_gdt_descr:
 739         .word __BOOT_DS+7
 740         .long boot_gdt - __PAGE_OFFSET
 741
 742         .word 0                         # 32-bit align idt_desc.address
 743 idt_descr:
 744         .word IDT_ENTRIES*8-1           # idt contains 256 entries
 745         .long idt_table
 746
 747 # boot GDT descriptor (later on used by CPU#0):
 748         .word 0                         # 32 bit align gdt_desc.address
 749 ENTRY(early_gdt_descr)
 750         .word GDT_ENTRIES*8-1
 751         .long gdt_page                  /* Overwritten for secondary CPUs */
 752
 753 /*
 754  * The boot_gdt must mirror the equivalent in setup.S and is
 755  * used only for booting.
 756  */
 757         .align L1_CACHE_BYTES
 758 ENTRY(boot_gdt)
 759         .fill GDT_ENTRY_BOOT_CS,8,0
 760         .quad 0x00cf9a000000ffff        /* kernel 4GB code at 0x00000000 */
 761         .quad 0x00cf92000000ffff        /* kernel 4GB data at 0x00000000 */