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