root/arch/x86/kernel/head_32.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  Enhanced CPU detection and feature setting code by Mike Jagdis
   7  *  and Martin Mares, November 1997.
   8  */
   9 
  10 .text
  11 #include <linux/threads.h>
  12 #include <linux/init.h>
  13 #include <linux/linkage.h>
  14 #include <asm/segment.h>
  15 #include <asm/page_types.h>
  16 #include <asm/pgtable_types.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/msr-index.h>
  23 #include <asm/cpufeatures.h>
  24 #include <asm/percpu.h>
  25 #include <asm/nops.h>
  26 #include <asm/bootparam.h>
  27 #include <asm/export.h>
  28 #include <asm/pgtable_32.h>
  29 
  30 /* Physical address */
  31 #define pa(X) ((X) - __PAGE_OFFSET)
  32 
  33 /*
  34  * References to members of the new_cpu_data structure.
  35  */
  36 
  37 #define X86             new_cpu_data+CPUINFO_x86
  38 #define X86_VENDOR      new_cpu_data+CPUINFO_x86_vendor
  39 #define X86_MODEL       new_cpu_data+CPUINFO_x86_model
  40 #define X86_STEPPING    new_cpu_data+CPUINFO_x86_stepping
  41 #define X86_HARD_MATH   new_cpu_data+CPUINFO_hard_math
  42 #define X86_CPUID       new_cpu_data+CPUINFO_cpuid_level
  43 #define X86_CAPABILITY  new_cpu_data+CPUINFO_x86_capability
  44 #define X86_VENDOR_ID   new_cpu_data+CPUINFO_x86_vendor_id
  45 
  46 
  47 #define SIZEOF_PTREGS 17*4
  48 
  49 /*
  50  * Worst-case size of the kernel mapping we need to make:
  51  * a relocatable kernel can live anywhere in lowmem, so we need to be able
  52  * to map all of lowmem.
  53  */
  54 KERNEL_PAGES = LOWMEM_PAGES
  55 
  56 INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
  57 RESERVE_BRK(pagetables, INIT_MAP_SIZE)
  58 
  59 /*
  60  * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
  61  * %esi points to the real-mode code as a 32-bit pointer.
  62  * CS and DS must be 4 GB flat segments, but we don't depend on
  63  * any particular GDT layout, because we load our own as soon as we
  64  * can.
  65  */
  66 __HEAD
  67 ENTRY(startup_32)
  68         movl pa(initial_stack),%ecx
  69         
  70         /* test KEEP_SEGMENTS flag to see if the bootloader is asking
  71                 us to not reload segments */
  72         testb $KEEP_SEGMENTS, BP_loadflags(%esi)
  73         jnz 2f
  74 
  75 /*
  76  * Set segments to known values.
  77  */
  78         lgdt pa(boot_gdt_descr)
  79         movl $(__BOOT_DS),%eax
  80         movl %eax,%ds
  81         movl %eax,%es
  82         movl %eax,%fs
  83         movl %eax,%gs
  84         movl %eax,%ss
  85 2:
  86         leal -__PAGE_OFFSET(%ecx),%esp
  87 
  88 /*
  89  * Clear BSS first so that there are no surprises...
  90  */
  91         cld
  92         xorl %eax,%eax
  93         movl $pa(__bss_start),%edi
  94         movl $pa(__bss_stop),%ecx
  95         subl %edi,%ecx
  96         shrl $2,%ecx
  97         rep ; stosl
  98 /*
  99  * Copy bootup parameters out of the way.
 100  * Note: %esi still has the pointer to the real-mode data.
 101  * With the kexec as boot loader, parameter segment might be loaded beyond
 102  * kernel image and might not even be addressable by early boot page tables.
 103  * (kexec on panic case). Hence copy out the parameters before initializing
 104  * page tables.
 105  */
 106         movl $pa(boot_params),%edi
 107         movl $(PARAM_SIZE/4),%ecx
 108         cld
 109         rep
 110         movsl
 111         movl pa(boot_params) + NEW_CL_POINTER,%esi
 112         andl %esi,%esi
 113         jz 1f                   # No command line
 114         movl $pa(boot_command_line),%edi
 115         movl $(COMMAND_LINE_SIZE/4),%ecx
 116         rep
 117         movsl
 118 1:
 119 
 120 #ifdef CONFIG_OLPC
 121         /* save OFW's pgdir table for later use when calling into OFW */
 122         movl %cr3, %eax
 123         movl %eax, pa(olpc_ofw_pgd)
 124 #endif
 125 
 126 #ifdef CONFIG_MICROCODE
 127         /* Early load ucode on BSP. */
 128         call load_ucode_bsp
 129 #endif
 130 
 131         /* Create early pagetables. */
 132         call  mk_early_pgtbl_32
 133 
 134         /* Do early initialization of the fixmap area */
 135         movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
 136 #ifdef  CONFIG_X86_PAE
 137 #define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
 138         movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
 139 #else
 140         movl %eax,pa(initial_page_table+0xffc)
 141 #endif
 142 
 143 #ifdef CONFIG_PARAVIRT
 144         /* This is can only trip for a broken bootloader... */
 145         cmpw $0x207, pa(boot_params + BP_version)
 146         jb .Ldefault_entry
 147 
 148         /* Paravirt-compatible boot parameters.  Look to see what architecture
 149                 we're booting under. */
 150         movl pa(boot_params + BP_hardware_subarch), %eax
 151         cmpl $num_subarch_entries, %eax
 152         jae .Lbad_subarch
 153 
 154         movl pa(subarch_entries)(,%eax,4), %eax
 155         subl $__PAGE_OFFSET, %eax
 156         jmp *%eax
 157 
 158 .Lbad_subarch:
 159 WEAK(xen_entry)
 160         /* Unknown implementation; there's really
 161            nothing we can do at this point. */
 162         ud2a
 163 
 164         __INITDATA
 165 
 166 subarch_entries:
 167         .long .Ldefault_entry           /* normal x86/PC */
 168         .long xen_entry                 /* Xen hypervisor */
 169         .long .Ldefault_entry           /* Moorestown MID */
 170 num_subarch_entries = (. - subarch_entries) / 4
 171 .previous
 172 #else
 173         jmp .Ldefault_entry
 174 #endif /* CONFIG_PARAVIRT */
 175 
 176 #ifdef CONFIG_HOTPLUG_CPU
 177 /*
 178  * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
 179  * up already except stack. We just set up stack here. Then call
 180  * start_secondary().
 181  */
 182 ENTRY(start_cpu0)
 183         movl initial_stack, %ecx
 184         movl %ecx, %esp
 185         call *(initial_code)
 186 1:      jmp 1b
 187 ENDPROC(start_cpu0)
 188 #endif
 189 
 190 /*
 191  * Non-boot CPU entry point; entered from trampoline.S
 192  * We can't lgdt here, because lgdt itself uses a data segment, but
 193  * we know the trampoline has already loaded the boot_gdt for us.
 194  *
 195  * If cpu hotplug is not supported then this code can go in init section
 196  * which will be freed later
 197  */
 198 ENTRY(startup_32_smp)
 199         cld
 200         movl $(__BOOT_DS),%eax
 201         movl %eax,%ds
 202         movl %eax,%es
 203         movl %eax,%fs
 204         movl %eax,%gs
 205         movl pa(initial_stack),%ecx
 206         movl %eax,%ss
 207         leal -__PAGE_OFFSET(%ecx),%esp
 208 
 209 #ifdef CONFIG_MICROCODE
 210         /* Early load ucode on AP. */
 211         call load_ucode_ap
 212 #endif
 213 
 214 .Ldefault_entry:
 215         movl $(CR0_STATE & ~X86_CR0_PG),%eax
 216         movl %eax,%cr0
 217 
 218 /*
 219  * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
 220  * bits like NT set. This would confuse the debugger if this code is traced. So
 221  * initialize them properly now before switching to protected mode. That means
 222  * DF in particular (even though we have cleared it earlier after copying the
 223  * command line) because GCC expects it.
 224  */
 225         pushl $0
 226         popfl
 227 
 228 /*
 229  * New page tables may be in 4Mbyte page mode and may be using the global pages.
 230  *
 231  * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
 232  * if and only if CPUID exists and has flags other than the FPU flag set.
 233  */
 234         movl $-1,pa(X86_CPUID)          # preset CPUID level
 235         movl $X86_EFLAGS_ID,%ecx
 236         pushl %ecx
 237         popfl                           # set EFLAGS=ID
 238         pushfl
 239         popl %eax                       # get EFLAGS
 240         testl $X86_EFLAGS_ID,%eax       # did EFLAGS.ID remained set?
 241         jz .Lenable_paging              # hw disallowed setting of ID bit
 242                                         # which means no CPUID and no CR4
 243 
 244         xorl %eax,%eax
 245         cpuid
 246         movl %eax,pa(X86_CPUID)         # save largest std CPUID function
 247 
 248         movl $1,%eax
 249         cpuid
 250         andl $~1,%edx                   # Ignore CPUID.FPU
 251         jz .Lenable_paging              # No flags or only CPUID.FPU = no CR4
 252 
 253         movl pa(mmu_cr4_features),%eax
 254         movl %eax,%cr4
 255 
 256         testb $X86_CR4_PAE, %al         # check if PAE is enabled
 257         jz .Lenable_paging
 258 
 259         /* Check if extended functions are implemented */
 260         movl $0x80000000, %eax
 261         cpuid
 262         /* Value must be in the range 0x80000001 to 0x8000ffff */
 263         subl $0x80000001, %eax
 264         cmpl $(0x8000ffff-0x80000001), %eax
 265         ja .Lenable_paging
 266 
 267         /* Clear bogus XD_DISABLE bits */
 268         call verify_cpu
 269 
 270         mov $0x80000001, %eax
 271         cpuid
 272         /* Execute Disable bit supported? */
 273         btl $(X86_FEATURE_NX & 31), %edx
 274         jnc .Lenable_paging
 275 
 276         /* Setup EFER (Extended Feature Enable Register) */
 277         movl $MSR_EFER, %ecx
 278         rdmsr
 279 
 280         btsl $_EFER_NX, %eax
 281         /* Make changes effective */
 282         wrmsr
 283 
 284 .Lenable_paging:
 285 
 286 /*
 287  * Enable paging
 288  */
 289         movl $pa(initial_page_table), %eax
 290         movl %eax,%cr3          /* set the page table pointer.. */
 291         movl $CR0_STATE,%eax
 292         movl %eax,%cr0          /* ..and set paging (PG) bit */
 293         ljmp $__BOOT_CS,$1f     /* Clear prefetch and normalize %eip */
 294 1:
 295         /* Shift the stack pointer to a virtual address */
 296         addl $__PAGE_OFFSET, %esp
 297 
 298 /*
 299  * start system 32-bit setup. We need to re-do some of the things done
 300  * in 16-bit mode for the "real" operations.
 301  */
 302         movl setup_once_ref,%eax
 303         andl %eax,%eax
 304         jz 1f                           # Did we do this already?
 305         call *%eax
 306 1:
 307 
 308 /*
 309  * Check if it is 486
 310  */
 311         movb $4,X86                     # at least 486
 312         cmpl $-1,X86_CPUID
 313         je .Lis486
 314 
 315         /* get vendor info */
 316         xorl %eax,%eax                  # call CPUID with 0 -> return vendor ID
 317         cpuid
 318         movl %eax,X86_CPUID             # save CPUID level
 319         movl %ebx,X86_VENDOR_ID         # lo 4 chars
 320         movl %edx,X86_VENDOR_ID+4       # next 4 chars
 321         movl %ecx,X86_VENDOR_ID+8       # last 4 chars
 322 
 323         orl %eax,%eax                   # do we have processor info as well?
 324         je .Lis486
 325 
 326         movl $1,%eax            # Use the CPUID instruction to get CPU type
 327         cpuid
 328         movb %al,%cl            # save reg for future use
 329         andb $0x0f,%ah          # mask processor family
 330         movb %ah,X86
 331         andb $0xf0,%al          # mask model
 332         shrb $4,%al
 333         movb %al,X86_MODEL
 334         andb $0x0f,%cl          # mask mask revision
 335         movb %cl,X86_STEPPING
 336         movl %edx,X86_CAPABILITY
 337 
 338 .Lis486:
 339         movl $0x50022,%ecx      # set AM, WP, NE and MP
 340         movl %cr0,%eax
 341         andl $0x80000011,%eax   # Save PG,PE,ET
 342         orl %ecx,%eax
 343         movl %eax,%cr0
 344 
 345         lgdt early_gdt_descr
 346         ljmp $(__KERNEL_CS),$1f
 347 1:      movl $(__KERNEL_DS),%eax        # reload all the segment registers
 348         movl %eax,%ss                   # after changing gdt.
 349 
 350         movl $(__USER_DS),%eax          # DS/ES contains default USER segment
 351         movl %eax,%ds
 352         movl %eax,%es
 353 
 354         movl $(__KERNEL_PERCPU), %eax
 355         movl %eax,%fs                   # set this cpu's percpu
 356 
 357         movl $(__KERNEL_STACK_CANARY),%eax
 358         movl %eax,%gs
 359 
 360         xorl %eax,%eax                  # Clear LDT
 361         lldt %ax
 362 
 363         call *(initial_code)
 364 1:      jmp 1b
 365 ENDPROC(startup_32_smp)
 366 
 367 #include "verify_cpu.S"
 368 
 369 /*
 370  *  setup_once
 371  *
 372  *  The setup work we only want to run on the BSP.
 373  *
 374  *  Warning: %esi is live across this function.
 375  */
 376 __INIT
 377 setup_once:
 378 #ifdef CONFIG_STACKPROTECTOR
 379         /*
 380          * Configure the stack canary. The linker can't handle this by
 381          * relocation.  Manually set base address in stack canary
 382          * segment descriptor.
 383          */
 384         movl $gdt_page,%eax
 385         movl $stack_canary,%ecx
 386         movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
 387         shrl $16, %ecx
 388         movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
 389         movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
 390 #endif
 391 
 392         andl $0,setup_once_ref  /* Once is enough, thanks */
 393         ret
 394 
 395 ENTRY(early_idt_handler_array)
 396         # 36(%esp) %eflags
 397         # 32(%esp) %cs
 398         # 28(%esp) %eip
 399         # 24(%rsp) error code
 400         i = 0
 401         .rept NUM_EXCEPTION_VECTORS
 402         .if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
 403         pushl $0                # Dummy error code, to make stack frame uniform
 404         .endif
 405         pushl $i                # 20(%esp) Vector number
 406         jmp early_idt_handler_common
 407         i = i + 1
 408         .fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
 409         .endr
 410 ENDPROC(early_idt_handler_array)
 411         
 412 early_idt_handler_common:
 413         /*
 414          * The stack is the hardware frame, an error code or zero, and the
 415          * vector number.
 416          */
 417         cld
 418 
 419         incl %ss:early_recursion_flag
 420 
 421         /* The vector number is in pt_regs->gs */
 422 
 423         cld
 424         pushl   %fs             /* pt_regs->fs (__fsh varies by model) */
 425         pushl   %es             /* pt_regs->es (__esh varies by model) */
 426         pushl   %ds             /* pt_regs->ds (__dsh varies by model) */
 427         pushl   %eax            /* pt_regs->ax */
 428         pushl   %ebp            /* pt_regs->bp */
 429         pushl   %edi            /* pt_regs->di */
 430         pushl   %esi            /* pt_regs->si */
 431         pushl   %edx            /* pt_regs->dx */
 432         pushl   %ecx            /* pt_regs->cx */
 433         pushl   %ebx            /* pt_regs->bx */
 434 
 435         /* Fix up DS and ES */
 436         movl    $(__KERNEL_DS), %ecx
 437         movl    %ecx, %ds
 438         movl    %ecx, %es
 439 
 440         /* Load the vector number into EDX */
 441         movl    PT_GS(%esp), %edx
 442 
 443         /* Load GS into pt_regs->gs (and maybe clobber __gsh) */
 444         movw    %gs, PT_GS(%esp)
 445 
 446         movl    %esp, %eax      /* args are pt_regs (EAX), trapnr (EDX) */
 447         call    early_fixup_exception
 448 
 449         popl    %ebx            /* pt_regs->bx */
 450         popl    %ecx            /* pt_regs->cx */
 451         popl    %edx            /* pt_regs->dx */
 452         popl    %esi            /* pt_regs->si */
 453         popl    %edi            /* pt_regs->di */
 454         popl    %ebp            /* pt_regs->bp */
 455         popl    %eax            /* pt_regs->ax */
 456         popl    %ds             /* pt_regs->ds (always ignores __dsh) */
 457         popl    %es             /* pt_regs->es (always ignores __esh) */
 458         popl    %fs             /* pt_regs->fs (always ignores __fsh) */
 459         popl    %gs             /* pt_regs->gs (always ignores __gsh) */
 460         decl    %ss:early_recursion_flag
 461         addl    $4, %esp        /* pop pt_regs->orig_ax */
 462         iret
 463 ENDPROC(early_idt_handler_common)
 464 
 465 /* This is the default interrupt "handler" :-) */
 466 ENTRY(early_ignore_irq)
 467         cld
 468 #ifdef CONFIG_PRINTK
 469         pushl %eax
 470         pushl %ecx
 471         pushl %edx
 472         pushl %es
 473         pushl %ds
 474         movl $(__KERNEL_DS),%eax
 475         movl %eax,%ds
 476         movl %eax,%es
 477         cmpl $2,early_recursion_flag
 478         je hlt_loop
 479         incl early_recursion_flag
 480         pushl 16(%esp)
 481         pushl 24(%esp)
 482         pushl 32(%esp)
 483         pushl 40(%esp)
 484         pushl $int_msg
 485         call printk
 486 
 487         call dump_stack
 488 
 489         addl $(5*4),%esp
 490         popl %ds
 491         popl %es
 492         popl %edx
 493         popl %ecx
 494         popl %eax
 495 #endif
 496         iret
 497 
 498 hlt_loop:
 499         hlt
 500         jmp hlt_loop
 501 ENDPROC(early_ignore_irq)
 502 
 503 __INITDATA
 504         .align 4
 505 GLOBAL(early_recursion_flag)
 506         .long 0
 507 
 508 __REFDATA
 509         .align 4
 510 ENTRY(initial_code)
 511         .long i386_start_kernel
 512 ENTRY(setup_once_ref)
 513         .long setup_once
 514 
 515 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 516 #define PGD_ALIGN       (2 * PAGE_SIZE)
 517 #define PTI_USER_PGD_FILL       1024
 518 #else
 519 #define PGD_ALIGN       (PAGE_SIZE)
 520 #define PTI_USER_PGD_FILL       0
 521 #endif
 522 /*
 523  * BSS section
 524  */
 525 __PAGE_ALIGNED_BSS
 526         .align PGD_ALIGN
 527 #ifdef CONFIG_X86_PAE
 528 .globl initial_pg_pmd
 529 initial_pg_pmd:
 530         .fill 1024*KPMDS,4,0
 531 #else
 532 .globl initial_page_table
 533 initial_page_table:
 534         .fill 1024,4,0
 535 #endif
 536         .align PGD_ALIGN
 537 initial_pg_fixmap:
 538         .fill 1024,4,0
 539 .globl swapper_pg_dir
 540         .align PGD_ALIGN
 541 swapper_pg_dir:
 542         .fill 1024,4,0
 543         .fill PTI_USER_PGD_FILL,4,0
 544 .globl empty_zero_page
 545 empty_zero_page:
 546         .fill 4096,1,0
 547 EXPORT_SYMBOL(empty_zero_page)
 548 
 549 /*
 550  * This starts the data section.
 551  */
 552 #ifdef CONFIG_X86_PAE
 553 __PAGE_ALIGNED_DATA
 554         /* Page-aligned for the benefit of paravirt? */
 555         .align PGD_ALIGN
 556 ENTRY(initial_page_table)
 557         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0     /* low identity map */
 558 # if KPMDS == 3
 559         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
 560         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
 561         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
 562 # elif KPMDS == 2
 563         .long   0,0
 564         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
 565         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
 566 # elif KPMDS == 1
 567         .long   0,0
 568         .long   0,0
 569         .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
 570 # else
 571 #  error "Kernel PMDs should be 1, 2 or 3"
 572 # endif
 573         .align PAGE_SIZE                /* needs to be page-sized too */
 574 
 575 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 576         /*
 577          * PTI needs another page so sync_initial_pagetable() works correctly
 578          * and does not scribble over the data which is placed behind the
 579          * actual initial_page_table. See clone_pgd_range().
 580          */
 581         .fill 1024, 4, 0
 582 #endif
 583 
 584 #endif
 585 
 586 .data
 587 .balign 4
 588 ENTRY(initial_stack)
 589         /*
 590          * The SIZEOF_PTREGS gap is a convention which helps the in-kernel
 591          * unwinder reliably detect the end of the stack.
 592          */
 593         .long init_thread_union + THREAD_SIZE - SIZEOF_PTREGS - \
 594               TOP_OF_KERNEL_STACK_PADDING;
 595 
 596 __INITRODATA
 597 int_msg:
 598         .asciz "Unknown interrupt or fault at: %p %p %p\n"
 599 
 600 #include "../../x86/xen/xen-head.S"
 601 
 602 /*
 603  * The IDT and GDT 'descriptors' are a strange 48-bit object
 604  * only used by the lidt and lgdt instructions. They are not
 605  * like usual segment descriptors - they consist of a 16-bit
 606  * segment size, and 32-bit linear address value:
 607  */
 608 
 609         .data
 610 .globl boot_gdt_descr
 611 
 612         ALIGN
 613 # early boot GDT descriptor (must use 1:1 address mapping)
 614         .word 0                         # 32 bit align gdt_desc.address
 615 boot_gdt_descr:
 616         .word __BOOT_DS+7
 617         .long boot_gdt - __PAGE_OFFSET
 618 
 619 # boot GDT descriptor (later on used by CPU#0):
 620         .word 0                         # 32 bit align gdt_desc.address
 621 ENTRY(early_gdt_descr)
 622         .word GDT_ENTRIES*8-1
 623         .long gdt_page                  /* Overwritten for secondary CPUs */
 624 
 625 /*
 626  * The boot_gdt must mirror the equivalent in setup.S and is
 627  * used only for booting.
 628  */
 629         .align L1_CACHE_BYTES
 630 ENTRY(boot_gdt)
 631         .fill GDT_ENTRY_BOOT_CS,8,0
 632         .quad 0x00cf9a000000ffff        /* kernel 4GB code at 0x00000000 */
 633         .quad 0x00cf92000000ffff        /* kernel 4GB data at 0x00000000 */