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/desc.h>
  17 #include <asm/cache.h>
  18 #include <asm/thread_info.h>
  19 #include <asm/asm-offsets.h>
  20 #include <asm/setup.h>
  21 #include <asm/processor-flags.h>
  22 #include <asm/percpu.h>
  23
  24 /* Physical address */
  25 #define pa(X) ((X) - __PAGE_OFFSET)
  26
  27 /*
  28  * References to members of the new_cpu_data structure.
  29  */
  30
  31 #define X86             new_cpu_data+CPUINFO_x86
  32 #define X86_VENDOR      new_cpu_data+CPUINFO_x86_vendor
  33 #define X86_MODEL       new_cpu_data+CPUINFO_x86_model
  34 #define X86_MASK        new_cpu_data+CPUINFO_x86_mask
  35 #define X86_HARD_MATH   new_cpu_data+CPUINFO_hard_math
  36 #define X86_CPUID       new_cpu_data+CPUINFO_cpuid_level
  37 #define X86_CAPABILITY  new_cpu_data+CPUINFO_x86_capability
  38 #define X86_VENDOR_ID   new_cpu_data+CPUINFO_x86_vendor_id
  39
  40 /*
  41  * This is how much memory *in addition to the memory covered up to
  42  * and including _end* we need mapped initially.
  43  * We need:
  44  *  - one bit for each possible page, but only in low memory, which means
  45  *     2^32/4096/8 = 128K worst case (4G/4G split.)
  46  *  - enough space to map all low memory, which means
  47  *     (2^32/4096) / 1024 pages (worst case, non PAE)
  48  *     (2^32/4096) / 512 + 4 pages (worst case for PAE)
  49  *  - a few pages for allocator use before the kernel pagetable has
  50  *     been set up
  51  *
  52  * Modulo rounding, each megabyte assigned here requires a kilobyte of
  53  * memory, which is currently unreclaimed.
  54  *
  55  * This should be a multiple of a page.
  56  */
  57 LOW_PAGES = 1<<(32-PAGE_SHIFT_asm)
  58
  59 /*
  60  * To preserve the DMA pool in PAGEALLOC kernels, we'll allocate
  61  * pagetables from above the 16MB DMA limit, so we'll have to set
  62  * up pagetables 16MB more (worst-case):
  63  */
  64 #ifdef CONFIG_DEBUG_PAGEALLOC
  65 LOW_PAGES = LOW_PAGES + 0x1000000
  66 #endif
  67
  68 #if PTRS_PER_PMD > 1
  69 PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD
  70 #else
  71 PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD)
  72 #endif
  73 BOOTBITMAP_SIZE = LOW_PAGES / 8
  74 ALLOCATOR_SLOP = 4
  75
  76 INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_SIZE_asm
  77
  78 /*
  79  * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
  80  * %esi points to the real-mode code as a 32-bit pointer.
  81  * CS and DS must be 4 GB flat segments, but we don't depend on
  82  * any particular GDT layout, because we load our own as soon as we
  83  * can.
  84  */
  85 .section .text.head,"ax",@progbits
  86 ENTRY(startup_32)
  87         /* test KEEP_SEGMENTS flag to see if the bootloader is asking
  88                 us to not reload segments */
  89         testb $(1<<6), BP_loadflags(%esi)
  90         jnz 2f
  91
  92 /*
  93  * Set segments to known values.
  94  */
  95         lgdt pa(boot_gdt_descr)
  96         movl $(__BOOT_DS),%eax
  97         movl %eax,%ds
  98         movl %eax,%es
  99         movl %eax,%fs
 100         movl %eax,%gs
 101 2:
 102
 103 /*
 104  * Clear BSS first so that there are no surprises...
 105  */
 106         cld
 107         xorl %eax,%eax
 108         movl $pa(__bss_start),%edi
 109         movl $pa(__bss_stop),%ecx
 110         subl %edi,%ecx
 111         shrl $2,%ecx
 112         rep ; stosl
 113 /*
 114  * Copy bootup parameters out of the way.
 115  * Note: %esi still has the pointer to the real-mode data.
 116  * With the kexec as boot loader, parameter segment might be loaded beyond
 117  * kernel image and might not even be addressable by early boot page tables.
 118  * (kexec on panic case). Hence copy out the parameters before initializing
 119  * page tables.
 120  */
 121         movl $pa(boot_params),%edi
 122         movl $(PARAM_SIZE/4),%ecx
 123         cld
 124         rep
 125         movsl
 126         movl pa(boot_params) + NEW_CL_POINTER,%esi
 127         andl %esi,%esi
 128         jz 1f                   # No comand line
 129         movl $pa(boot_command_line),%edi
 130         movl $(COMMAND_LINE_SIZE/4),%ecx
 131         rep
 132         movsl
 133 1:
 134
 135 #ifdef CONFIG_PARAVIRT
 136         /* This is can only trip for a broken bootloader... */
 137         cmpw $0x207, pa(boot_params + BP_version)
 138         jb default_entry
 139
 140         /* Paravirt-compatible boot parameters.  Look to see what architecture
 141                 we're booting under. */
 142         movl pa(boot_params + BP_hardware_subarch), %eax
 143         cmpl $num_subarch_entries, %eax
 144         jae bad_subarch
 145
 146         movl pa(subarch_entries)(,%eax,4), %eax
 147         subl $__PAGE_OFFSET, %eax
 148         jmp *%eax
 149
 150 bad_subarch:
 151 WEAK(lguest_entry)
 152 WEAK(xen_entry)
 153         /* Unknown implementation; there's really
 154            nothing we can do at this point. */
 155         ud2a
 156
 157         __INITDATA
 158
 159 subarch_entries:
 160         .long default_entry             /* normal x86/PC */
 161         .long lguest_entry              /* lguest hypervisor */
 162         .long xen_entry                 /* Xen hypervisor */
 163 num_subarch_entries = (. - subarch_entries) / 4
 164 .previous
 165 #endif /* CONFIG_PARAVIRT */
 166
 167 /*
 168  * Initialize page tables.  This creates a PDE and a set of page
 169  * tables, which are located immediately beyond _end.  The variable
 170  * init_pg_tables_end is set up to point to the first "safe" location.
 171  * Mappings are created both at virtual address 0 (identity mapping)
 172  * and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
 173  *
 174  * Note that the stack is not yet set up!
 175  */
 176 default_entry:
 177 #ifdef CONFIG_X86_PAE
 178
 179         /*
 180          * In PAE mode swapper_pg_dir is statically defined to contain enough
 181          * entries to cover the VMSPLIT option (that is the top 1, 2 or 3
 182          * entries). The identity mapping is handled by pointing two PGD
 183          * entries to the first kernel PMD.
 184          *
 185          * Note the upper half of each PMD or PTE are always zero at
 186          * this stage.
 187          */
 188
 189 #define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
 190
 191         xorl %ebx,%ebx                          /* %ebx is kept at zero */
 192
 193         movl $pa(pg0), %edi
 194         movl %edi, pa(init_pg_tables_start)
 195         movl $pa(swapper_pg_pmd), %edx
 196         movl $PTE_IDENT_ATTR, %eax
 197 10:
 198         leal PDE_IDENT_ATTR(%edi),%ecx          /* Create PMD entry */
 199         movl %ecx,(%edx)                        /* Store PMD entry */
 200                                                 /* Upper half already zero */
 201         addl $8,%edx
 202         movl $512,%ecx
 203 11:
 204         stosl
 205         xchgl %eax,%ebx
 206         stosl
 207         xchgl %eax,%ebx
 208         addl $0x1000,%eax
 209         loop 11b
 210
 211         /*
 212          * End condition: we must map up to and including INIT_MAP_BEYOND_END
 213          * bytes beyond the end of our own page tables.
 214          */
 215         leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
 216         cmpl %ebp,%eax
 217         jb 10b
 218 1:
 219         movl %edi,pa(init_pg_tables_end)
 220         shrl $12, %eax
 221         movl %eax, pa(max_pfn_mapped)
 222
 223         /* Do early initialization of the fixmap area */
 224         movl $pa(swapper_pg_fixmap)+PDE_IDENT_ATTR,%eax
 225         movl %eax,pa(swapper_pg_pmd+0x1000*KPMDS-8)
 226 #else   /* Not PAE */
 227
 228 page_pde_offset = (__PAGE_OFFSET >> 20);
 229
 230         movl $pa(pg0), %edi
 231         movl %edi, pa(init_pg_tables_start)
 232         movl $pa(swapper_pg_dir), %edx
 233         movl $PTE_IDENT_ATTR, %eax
 234 10:
 235         leal PDE_IDENT_ATTR(%edi),%ecx          /* Create PDE entry */
 236         movl %ecx,(%edx)                        /* Store identity PDE entry */
 237         movl %ecx,page_pde_offset(%edx)         /* Store kernel PDE entry */
 238         addl $4,%edx
 239         movl $1024, %ecx
 240 11:
 241         stosl
 242         addl $0x1000,%eax
 243         loop 11b
 244         /*
 245          * End condition: we must map up to and including INIT_MAP_BEYOND_END
 246          * bytes beyond the end of our own page tables; the +0x007 is
 247          * the attribute bits
 248          */
 249         leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
 250         cmpl %ebp,%eax
 251         jb 10b
 252         movl %edi,pa(init_pg_tables_end)
 253         shrl $12, %eax
 254         movl %eax, pa(max_pfn_mapped)
 255
 256         /* Do early initialization of the fixmap area */
 257         movl $pa(swapper_pg_fixmap)+PDE_IDENT_ATTR,%eax
 258         movl %eax,pa(swapper_pg_dir+0xffc)
 259 #endif
 260         jmp 3f
 261 /*
 262  * Non-boot CPU entry point; entered from trampoline.S
 263  * We can't lgdt here, because lgdt itself uses a data segment, but
 264  * we know the trampoline has already loaded the boot_gdt for us.
 265  *
 266  * If cpu hotplug is not supported then this code can go in init section
 267  * which will be freed later
 268  */
 269
 270 #ifndef CONFIG_HOTPLUG_CPU
 271 .section .init.text,"ax",@progbits
 272 #endif
 273
 274 #ifdef CONFIG_SMP
 275 ENTRY(startup_32_smp)
 276         cld
 277         movl $(__BOOT_DS),%eax
 278         movl %eax,%ds
 279         movl %eax,%es
 280         movl %eax,%fs
 281         movl %eax,%gs
 282 #endif /* CONFIG_SMP */
 283 3:
 284
 285 /*
 286  *      New page tables may be in 4Mbyte page mode and may
 287  *      be using the global pages.
 288  *
 289  *      NOTE! If we are on a 486 we may have no cr4 at all!
 290  *      So we do not try to touch it unless we really have
 291  *      some bits in it to set.  This won't work if the BSP
 292  *      implements cr4 but this AP does not -- very unlikely
 293  *      but be warned!  The same applies to the pse feature
 294  *      if not equally supported. --macro
 295  *
 296  *      NOTE! We have to correct for the fact that we're
 297  *      not yet offset PAGE_OFFSET..
 298  */
 299 #define cr4_bits pa(mmu_cr4_features)
 300         movl cr4_bits,%edx
 301         andl %edx,%edx
 302         jz 6f
 303         movl %cr4,%eax          # Turn on paging options (PSE,PAE,..)
 304         orl %edx,%eax
 305         movl %eax,%cr4
 306
 307         btl $5, %eax            # check if PAE is enabled
 308         jnc 6f
 309
 310         /* Check if extended functions are implemented */
 311         movl $0x80000000, %eax
 312         cpuid
 313         cmpl $0x80000000, %eax
 314         jbe 6f
 315         mov $0x80000001, %eax
 316         cpuid
 317         /* Execute Disable bit supported? */
 318         btl $20, %edx
 319         jnc 6f
 320
 321         /* Setup EFER (Extended Feature Enable Register) */
 322         movl $0xc0000080, %ecx
 323         rdmsr
 324
 325         btsl $11, %eax
 326         /* Make changes effective */
 327         wrmsr
 328
 329 6:
 330
 331 /*
 332  * Enable paging
 333  */
 334         movl $pa(swapper_pg_dir),%eax
 335         movl %eax,%cr3          /* set the page table pointer.. */
 336         movl %cr0,%eax
 337         orl  $X86_CR0_PG,%eax
 338         movl %eax,%cr0          /* ..and set paging (PG) bit */
 339         ljmp $__BOOT_CS,$1f     /* Clear prefetch and normalize %eip */
 340 1:
 341         /* Set up the stack pointer */
 342         lss stack_start,%esp
 343
 344 /*
 345  * Initialize eflags.  Some BIOS's leave bits like NT set.  This would
 346  * confuse the debugger if this code is traced.
 347  * XXX - best to initialize before switching to protected mode.
 348  */
 349         pushl $0
 350         popfl
 351
 352 #ifdef CONFIG_SMP
 353         cmpb $0, ready
 354         jz  1f                          /* Initial CPU cleans BSS */
 355         jmp checkCPUtype
 356 1:
 357 #endif /* CONFIG_SMP */
 358
 359 /*
 360  * start system 32-bit setup. We need to re-do some of the things done
 361  * in 16-bit mode for the "real" operations.
 362  */
 363         call setup_idt
 364
 365 checkCPUtype:
 366
 367         movl $-1,X86_CPUID              #  -1 for no CPUID initially
 368
 369 /* check if it is 486 or 386. */
 370 /*
 371  * XXX - this does a lot of unnecessary setup.  Alignment checks don't
 372  * apply at our cpl of 0 and the stack ought to be aligned already, and
 373  * we don't need to preserve eflags.
 374  */
 375
 376         movb $3,X86             # at least 386
 377         pushfl                  # push EFLAGS
 378         popl %eax               # get EFLAGS
 379         movl %eax,%ecx          # save original EFLAGS
 380         xorl $0x240000,%eax     # flip AC and ID bits in EFLAGS
 381         pushl %eax              # copy to EFLAGS
 382         popfl                   # set EFLAGS
 383         pushfl                  # get new EFLAGS
 384         popl %eax               # put it in eax
 385         xorl %ecx,%eax          # change in flags
 386         pushl %ecx              # restore original EFLAGS
 387         popfl
 388         testl $0x40000,%eax     # check if AC bit changed
 389         je is386
 390
 391         movb $4,X86             # at least 486
 392         testl $0x200000,%eax    # check if ID bit changed
 393         je is486
 394
 395         /* get vendor info */
 396         xorl %eax,%eax                  # call CPUID with 0 -> return vendor ID
 397         cpuid
 398         movl %eax,X86_CPUID             # save CPUID level
 399         movl %ebx,X86_VENDOR_ID         # lo 4 chars
 400         movl %edx,X86_VENDOR_ID+4       # next 4 chars
 401         movl %ecx,X86_VENDOR_ID+8       # last 4 chars
 402
 403         orl %eax,%eax                   # do we have processor info as well?
 404         je is486
 405
 406         movl $1,%eax            # Use the CPUID instruction to get CPU type
 407         cpuid
 408         movb %al,%cl            # save reg for future use
 409         andb $0x0f,%ah          # mask processor family
 410         movb %ah,X86
 411         andb $0xf0,%al          # mask model
 412         shrb $4,%al
 413         movb %al,X86_MODEL
 414         andb $0x0f,%cl          # mask mask revision
 415         movb %cl,X86_MASK
 416         movl %edx,X86_CAPABILITY
 417
 418 is486:  movl $0x50022,%ecx      # set AM, WP, NE and MP
 419         jmp 2f
 420
 421 is386:  movl $2,%ecx            # set MP
 422 2:      movl %cr0,%eax
 423         andl $0x80000011,%eax   # Save PG,PE,ET
 424         orl %ecx,%eax
 425         movl %eax,%cr0
 426
 427         call check_x87
 428         lgdt early_gdt_descr
 429         lidt idt_descr
 430         ljmp $(__KERNEL_CS),$1f
 431 1:      movl $(__KERNEL_DS),%eax        # reload all the segment registers
 432         movl %eax,%ss                   # after changing gdt.
 433
 434         movl $(__USER_DS),%eax          # DS/ES contains default USER segment
 435         movl %eax,%ds
 436         movl %eax,%es
 437
 438         movl $(__KERNEL_PERCPU), %eax
 439         movl %eax,%fs                   # set this cpu's percpu
 440
 441 #ifdef CONFIG_CC_STACKPROTECTOR
 442         /*
 443          * The linker can't handle this by relocation.  Manually set
 444          * base address in stack canary segment descriptor.
 445          */
 446         cmpb $0,ready
 447         jne 1f
 448         movl $per_cpu__gdt_page,%eax
 449         movl $per_cpu__stack_canary,%ecx
 450         subl $20, %ecx
 451         movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
 452         shrl $16, %ecx
 453         movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
 454         movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
 455 1:
 456 #endif
 457         movl $(__KERNEL_STACK_CANARY),%eax
 458         movl %eax,%gs
 459
 460         xorl %eax,%eax                  # Clear LDT
 461         lldt %ax
 462
 463         cld                     # gcc2 wants the direction flag cleared at all times
 464         pushl $0                # fake return address for unwinder
 465 #ifdef CONFIG_SMP
 466         movb ready, %cl
 467         movb $1, ready
 468         cmpb $0,%cl             # the first CPU calls start_kernel
 469         je   1f
 470         movl (stack_start), %esp
 471 1:
 472 #endif /* CONFIG_SMP */
 473         jmp *(initial_code)
 474
 475 /*
 476  * We depend on ET to be correct. This checks for 287/387.
 477  */
 478 check_x87:
 479         movb $0,X86_HARD_MATH
 480         clts
 481         fninit
 482         fstsw %ax
 483         cmpb $0,%al
 484         je 1f
 485         movl %cr0,%eax          /* no coprocessor: have to set bits */
 486         xorl $4,%eax            /* set EM */
 487         movl %eax,%cr0
 488         ret
 489         ALIGN
 490 1:      movb $1,X86_HARD_MATH
 491         .byte 0xDB,0xE4         /* fsetpm for 287, ignored by 387 */
 492         ret
 493
 494 /*
 495  *  setup_idt
 496  *
 497  *  sets up a idt with 256 entries pointing to
 498  *  ignore_int, interrupt gates. It doesn't actually load
 499  *  idt - that can be done only after paging has been enabled
 500  *  and the kernel moved to PAGE_OFFSET. Interrupts
 501  *  are enabled elsewhere, when we can be relatively
 502  *  sure everything is ok.
 503  *
 504  *  Warning: %esi is live across this function.
 505  */
 506 setup_idt:
 507         lea ignore_int,%edx
 508         movl $(__KERNEL_CS << 16),%eax
 509         movw %dx,%ax            /* selector = 0x0010 = cs */
 510         movw $0x8E00,%dx        /* interrupt gate - dpl=0, present */
 511
 512         lea idt_table,%edi
 513         mov $256,%ecx
 514 rp_sidt:
 515         movl %eax,(%edi)
 516         movl %edx,4(%edi)
 517         addl $8,%edi
 518         dec %ecx
 519         jne rp_sidt
 520
 521 .macro  set_early_handler handler,trapno
 522         lea \handler,%edx
 523         movl $(__KERNEL_CS << 16),%eax
 524         movw %dx,%ax
 525         movw $0x8E00,%dx        /* interrupt gate - dpl=0, present */
 526         lea idt_table,%edi
 527         movl %eax,8*\trapno(%edi)
 528         movl %edx,8*\trapno+4(%edi)
 529 .endm
 530
 531         set_early_handler handler=early_divide_err,trapno=0
 532         set_early_handler handler=early_illegal_opcode,trapno=6
 533         set_early_handler handler=early_protection_fault,trapno=13
 534         set_early_handler handler=early_page_fault,trapno=14
 535
 536         ret
 537
 538 early_divide_err:
 539         xor %edx,%edx
 540         pushl $0        /* fake errcode */
 541         jmp early_fault
 542
 543 early_illegal_opcode:
 544         movl $6,%edx
 545         pushl $0        /* fake errcode */
 546         jmp early_fault
 547
 548 early_protection_fault:
 549         movl $13,%edx
 550         jmp early_fault
 551
 552 early_page_fault:
 553         movl $14,%edx
 554         jmp early_fault
 555
 556 early_fault:
 557         cld
 558 #ifdef CONFIG_PRINTK
 559         pusha
 560         movl $(__KERNEL_DS),%eax
 561         movl %eax,%ds
 562         movl %eax,%es
 563         cmpl $2,early_recursion_flag
 564         je hlt_loop
 565         incl early_recursion_flag
 566         movl %cr2,%eax
 567         pushl %eax
 568         pushl %edx              /* trapno */
 569         pushl $fault_msg
 570         call printk
 571 #endif
 572         call dump_stack
 573 hlt_loop:
 574         hlt
 575         jmp hlt_loop
 576
 577 /* This is the default interrupt "handler" :-) */
 578         ALIGN
 579 ignore_int:
 580         cld
 581 #ifdef CONFIG_PRINTK
 582         pushl %eax
 583         pushl %ecx
 584         pushl %edx
 585         pushl %es
 586         pushl %ds
 587         movl $(__KERNEL_DS),%eax
 588         movl %eax,%ds
 589         movl %eax,%es
 590         cmpl $2,early_recursion_flag
 591         je hlt_loop
 592         incl early_recursion_flag
 593         pushl 16(%esp)
 594         pushl 24(%esp)
 595         pushl 32(%esp)
 596         pushl 40(%esp)
 597         pushl $int_msg
 598         call printk
 599
 600         call dump_stack
 601
 602         addl $(5*4),%esp
 603         popl %ds
 604         popl %es
 605         popl %edx
 606         popl %ecx
 607         popl %eax
 608 #endif
 609         iret
 610
 611 .section .cpuinit.data,"wa"
 612 .align 4
 613 ENTRY(initial_code)
 614         .long i386_start_kernel
 615
 616 .section .text
 617 /*
 618  * Real beginning of normal "text" segment
 619  */
 620 ENTRY(stext)
 621 ENTRY(_stext)
 622
 623 /*
 624  * BSS section
 625  */
 626 .section ".bss.page_aligned","wa"
 627         .align PAGE_SIZE_asm
 628 #ifdef CONFIG_X86_PAE
 629 swapper_pg_pmd:
 630         .fill 1024*KPMDS,4,0
 631 #else
 632 ENTRY(swapper_pg_dir)
 633         .fill 1024,4,0
 634 #endif
 635 swapper_pg_fixmap:
 636         .fill 1024,4,0
 637 ENTRY(empty_zero_page)
 638         .fill 4096,1,0
 639 /*
 640  * This starts the data section.
 641  */
 642 #ifdef CONFIG_X86_PAE
 643 .section ".data.page_aligned","wa"
 644         /* Page-aligned for the benefit of paravirt? */
 645         .align PAGE_SIZE_asm
 646 ENTRY(swapper_pg_dir)
 647         .long   pa(swapper_pg_pmd+PGD_IDENT_ATTR),0     /* low identity map */
 648 # if KPMDS == 3
 649         .long   pa(swapper_pg_pmd+PGD_IDENT_ATTR),0
 650         .long   pa(swapper_pg_pmd+PGD_IDENT_ATTR+0x1000),0
 651         .long   pa(swapper_pg_pmd+PGD_IDENT_ATTR+0x2000),0
 652 # elif KPMDS == 2
 653         .long   0,0
 654         .long   pa(swapper_pg_pmd+PGD_IDENT_ATTR),0
 655         .long   pa(swapper_pg_pmd+PGD_IDENT_ATTR+0x1000),0
 656 # elif KPMDS == 1
 657         .long   0,0
 658         .long   0,0
 659         .long   pa(swapper_pg_pmd+PGD_IDENT_ATTR),0
 660 # else
 661 #  error "Kernel PMDs should be 1, 2 or 3"
 662 # endif
 663         .align PAGE_SIZE_asm            /* needs to be page-sized too */
 664 #endif
 665
 666 .data
 667 ENTRY(stack_start)
 668         .long init_thread_union+THREAD_SIZE
 669         .long __BOOT_DS
 670
 671 ready:  .byte 0
 672
 673 early_recursion_flag:
 674         .long 0
 675
 676 int_msg:
 677         .asciz "Unknown interrupt or fault at: %p %p %p\n"
 678
 679 fault_msg:
 680 /* fault info: */
 681         .ascii "BUG: Int %d: CR2 %p\n"
 682 /* pusha regs: */
 683         .ascii "     EDI %p  ESI %p  EBP %p  ESP %p\n"
 684         .ascii "     EBX %p  EDX %p  ECX %p  EAX %p\n"
 685 /* fault frame: */
 686         .ascii "     err %p  EIP %p   CS %p  flg %p\n"
 687         .ascii "Stack: %p %p %p %p %p %p %p %p\n"
 688         .ascii "       %p %p %p %p %p %p %p %p\n"
 689         .asciz "       %p %p %p %p %p %p %p %p\n"
 690
 691 #include "../../x86/xen/xen-head.S"
 692
 693 /*
 694  * The IDT and GDT 'descriptors' are a strange 48-bit object
 695  * only used by the lidt and lgdt instructions. They are not
 696  * like usual segment descriptors - they consist of a 16-bit
 697  * segment size, and 32-bit linear address value:
 698  */
 699
 700 .globl boot_gdt_descr
 701 .globl idt_descr
 702
 703         ALIGN
 704 # early boot GDT descriptor (must use 1:1 address mapping)
 705         .word 0                         # 32 bit align gdt_desc.address
 706 boot_gdt_descr:
 707         .word __BOOT_DS+7
 708         .long boot_gdt - __PAGE_OFFSET
 709
 710         .word 0                         # 32-bit align idt_desc.address
 711 idt_descr:
 712         .word IDT_ENTRIES*8-1           # idt contains 256 entries
 713         .long idt_table
 714
 715 # boot GDT descriptor (later on used by CPU#0):
 716         .word 0                         # 32 bit align gdt_desc.address
 717 ENTRY(early_gdt_descr)
 718         .word GDT_ENTRIES*8-1
 719         .long per_cpu__gdt_page         /* Overwritten for secondary CPUs */
 720
 721 /*
 722  * The boot_gdt must mirror the equivalent in setup.S and is
 723  * used only for booting.
 724  */
 725         .align L1_CACHE_BYTES
 726 ENTRY(boot_gdt)
 727         .fill GDT_ENTRY_BOOT_CS,8,0
 728         .quad 0x00cf9a000000ffff        /* kernel 4GB code at 0x00000000 */
 729         .quad 0x00cf92000000ffff        /* kernel 4GB data at 0x00000000 */