arch/x86/boot/compressed/head_64.S

   1 /*
   2  *  linux/boot/head.S
   3  *
   4  *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
   5  */
   6
   7 /*
   8  *  head.S contains the 32-bit startup code.
   9  *
  10  * NOTE!!! Startup happens at absolute address 0x00001000, which is also where
  11  * the page directory will exist. The startup code will be overwritten by
  12  * the page directory. [According to comments etc elsewhere on a compressed
  13  * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
  14  *
  15  * Page 0 is deliberately kept safe, since System Management Mode code in
  16  * laptops may need to access the BIOS data stored there.  This is also
  17  * useful for future device drivers that either access the BIOS via VM86
  18  * mode.
  19  */
  20
  21 /*
  22  * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
  23  */
  24         .code32
  25         .text
  26
  27 #include <linux/init.h>
  28 #include <linux/linkage.h>
  29 #include <asm/segment.h>
  30 #include <asm/pgtable_types.h>
  31 #include <asm/page_types.h>
  32 #include <asm/boot.h>
  33 #include <asm/msr.h>
  34 #include <asm/processor-flags.h>
  35 #include <asm/asm-offsets.h>
  36
  37         __HEAD
  38         .code32
  39 ENTRY(startup_32)
  40         cld
  41         /*
  42          * Test KEEP_SEGMENTS flag to see if the bootloader is asking
  43          * us to not reload segments
  44          */
  45         testb $(1<<6), BP_loadflags(%esi)
  46         jnz 1f
  47
  48         cli
  49         movl    $(__KERNEL_DS), %eax
  50         movl    %eax, %ds
  51         movl    %eax, %es
  52         movl    %eax, %ss
  53 1:
  54
  55 /*
  56  * Calculate the delta between where we were compiled to run
  57  * at and where we were actually loaded at.  This can only be done
  58  * with a short local call on x86.  Nothing  else will tell us what
  59  * address we are running at.  The reserved chunk of the real-mode
  60  * data at 0x1e4 (defined as a scratch field) are used as the stack
  61  * for this calculation. Only 4 bytes are needed.
  62  */
  63         leal    (BP_scratch+4)(%esi), %esp
  64         call    1f
  65 1:      popl    %ebp
  66         subl    $1b, %ebp
  67
  68 /* setup a stack and make sure cpu supports long mode. */
  69         movl    $boot_stack_end, %eax
  70         addl    %ebp, %eax
  71         movl    %eax, %esp
  72
  73         call    verify_cpu
  74         testl   %eax, %eax
  75         jnz     no_longmode
  76
  77 /*
  78  * Compute the delta between where we were compiled to run at
  79  * and where the code will actually run at.
  80  *
  81  * %ebp contains the address we are loaded at by the boot loader and %ebx
  82  * contains the address where we should move the kernel image temporarily
  83  * for safe in-place decompression.
  84  */
  85
  86 #ifdef CONFIG_RELOCATABLE
  87         movl    %ebp, %ebx
  88         movl    BP_kernel_alignment(%esi), %eax
  89         decl    %eax
  90         addl    %eax, %ebx
  91         notl    %eax
  92         andl    %eax, %ebx
  93 #else
  94         movl    $LOAD_PHYSICAL_ADDR, %ebx
  95 #endif
  96
  97         /* Target address to relocate to for decompression */
  98         addl    $z_extract_offset, %ebx
  99
 100 /*
 101  * Prepare for entering 64 bit mode
 102  */
 103
 104         /* Load new GDT with the 64bit segments using 32bit descriptor */
 105         leal    gdt(%ebp), %eax
 106         movl    %eax, gdt+2(%ebp)
 107         lgdt    gdt(%ebp)
 108
 109         /* Enable PAE mode */
 110         movl    $(X86_CR4_PAE), %eax
 111         movl    %eax, %cr4
 112
 113  /*
 114   * Build early 4G boot pagetable
 115   */
 116         /* Initialize Page tables to 0 */
 117         leal    pgtable(%ebx), %edi
 118         xorl    %eax, %eax
 119         movl    $((4096*6)/4), %ecx
 120         rep     stosl
 121
 122         /* Build Level 4 */
 123         leal    pgtable + 0(%ebx), %edi
 124         leal    0x1007 (%edi), %eax
 125         movl    %eax, 0(%edi)
 126
 127         /* Build Level 3 */
 128         leal    pgtable + 0x1000(%ebx), %edi
 129         leal    0x1007(%edi), %eax
 130         movl    $4, %ecx
 131 1:      movl    %eax, 0x00(%edi)
 132         addl    $0x00001000, %eax
 133         addl    $8, %edi
 134         decl    %ecx
 135         jnz     1b
 136
 137         /* Build Level 2 */
 138         leal    pgtable + 0x2000(%ebx), %edi
 139         movl    $0x00000183, %eax
 140         movl    $2048, %ecx
 141 1:      movl    %eax, 0(%edi)
 142         addl    $0x00200000, %eax
 143         addl    $8, %edi
 144         decl    %ecx
 145         jnz     1b
 146
 147         /* Enable the boot page tables */
 148         leal    pgtable(%ebx), %eax
 149         movl    %eax, %cr3
 150
 151         /* Enable Long mode in EFER (Extended Feature Enable Register) */
 152         movl    $MSR_EFER, %ecx
 153         rdmsr
 154         btsl    $_EFER_LME, %eax
 155         wrmsr
 156
 157         /*
 158          * Setup for the jump to 64bit mode
 159          *
 160          * When the jump is performend we will be in long mode but
 161          * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1
 162          * (and in turn EFER.LMA = 1).  To jump into 64bit mode we use
 163          * the new gdt/idt that has __KERNEL_CS with CS.L = 1.
 164          * We place all of the values on our mini stack so lret can
 165          * used to perform that far jump.
 166          */
 167         pushl   $__KERNEL_CS
 168         leal    startup_64(%ebp), %eax
 169         pushl   %eax
 170
 171         /* Enter paged protected Mode, activating Long Mode */
 172         movl    $(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */
 173         movl    %eax, %cr0
 174
 175         /* Jump from 32bit compatibility mode into 64bit mode. */
 176         lret
 177 ENDPROC(startup_32)
 178
 179 no_longmode:
 180         /* This isn't an x86-64 CPU so hang */
 181 1:
 182         hlt
 183         jmp     1b
 184
 185 #include "../../kernel/verify_cpu_64.S"
 186
 187         /*
 188          * Be careful here startup_64 needs to be at a predictable
 189          * address so I can export it in an ELF header.  Bootloaders
 190          * should look at the ELF header to find this address, as
 191          * it may change in the future.
 192          */
 193         .code64
 194         .org 0x200
 195 ENTRY(startup_64)
 196         /*
 197          * We come here either from startup_32 or directly from a
 198          * 64bit bootloader.  If we come here from a bootloader we depend on
 199          * an identity mapped page table being provied that maps our
 200          * entire text+data+bss and hopefully all of memory.
 201          */
 202
 203         /* Setup data segments. */
 204         xorl    %eax, %eax
 205         movl    %eax, %ds
 206         movl    %eax, %es
 207         movl    %eax, %ss
 208         movl    %eax, %fs
 209         movl    %eax, %gs
 210         lldt    %ax
 211         movl    $0x20, %eax
 212         ltr     %ax
 213
 214         /*
 215          * Compute the decompressed kernel start address.  It is where
 216          * we were loaded at aligned to a 2M boundary. %rbp contains the
 217          * decompressed kernel start address.
 218          *
 219          * If it is a relocatable kernel then decompress and run the kernel
 220          * from load address aligned to 2MB addr, otherwise decompress and
 221          * run the kernel from LOAD_PHYSICAL_ADDR
 222          *
 223          * We cannot rely on the calculation done in 32-bit mode, since we
 224          * may have been invoked via the 64-bit entry point.
 225          */
 226
 227         /* Start with the delta to where the kernel will run at. */
 228 #ifdef CONFIG_RELOCATABLE
 229         leaq    startup_32(%rip) /* - $startup_32 */, %rbp
 230         movl    BP_kernel_alignment(%rsi), %eax
 231         decl    %eax
 232         addq    %rax, %rbp
 233         notq    %rax
 234         andq    %rax, %rbp
 235 #else
 236         movq    $LOAD_PHYSICAL_ADDR, %rbp
 237 #endif
 238
 239         /* Target address to relocate to for decompression */
 240         leaq    z_extract_offset(%rbp), %rbx
 241
 242         /* Set up the stack */
 243         leaq    boot_stack_end(%rbx), %rsp
 244
 245         /* Zero EFLAGS */
 246         pushq   $0
 247         popfq
 248
 249 /*
 250  * Copy the compressed kernel to the end of our buffer
 251  * where decompression in place becomes safe.
 252  */
 253         pushq   %rsi
 254         leaq    (_bss-8)(%rip), %rsi
 255         leaq    (_bss-8)(%rbx), %rdi
 256         movq    $_bss /* - $startup_32 */, %rcx
 257         shrq    $3, %rcx
 258         std
 259         rep     movsq
 260         cld
 261         popq    %rsi
 262
 263 /*
 264  * Jump to the relocated address.
 265  */
 266         leaq    relocated(%rbx), %rax
 267         jmp     *%rax
 268
 269         .text
 270 relocated:
 271
 272 /*
 273  * Clear BSS (stack is currently empty)
 274  */
 275         xorl    %eax, %eax
 276         leaq    _bss(%rip), %rdi
 277         leaq    _ebss(%rip), %rcx
 278         subq    %rdi, %rcx
 279         shrq    $3, %rcx
 280         rep     stosq
 281
 282 /*
 283  * Adjust our own GOT
 284  */
 285         leaq    _got(%rip), %rdx
 286         leaq    _egot(%rip), %rcx
 287 1:
 288         cmpq    %rcx, %rdx
 289         jae     2f
 290         addq    %rbx, (%rdx)
 291         addq    $8, %rdx
 292         jmp     1b
 293 2:
 294
 295 /*
 296  * Do the decompression, and jump to the new kernel..
 297  */
 298         pushq   %rsi                    /* Save the real mode argument */
 299         movq    %rsi, %rdi              /* real mode address */
 300         leaq    boot_heap(%rip), %rsi   /* malloc area for uncompression */
 301         leaq    input_data(%rip), %rdx  /* input_data */
 302         movl    $z_input_len, %ecx      /* input_len */
 303         movq    %rbp, %r8               /* output target address */
 304         call    decompress_kernel
 305         popq    %rsi
 306
 307 /*
 308  * Jump to the decompressed kernel.
 309  */
 310         jmp     *%rbp
 311
 312         .data
 313 gdt:
 314         .word   gdt_end - gdt
 315         .long   gdt
 316         .word   0
 317         .quad   0x0000000000000000      /* NULL descriptor */
 318         .quad   0x00af9a000000ffff      /* __KERNEL_CS */
 319         .quad   0x00cf92000000ffff      /* __KERNEL_DS */
 320         .quad   0x0080890000000000      /* TS descriptor */
 321         .quad   0x0000000000000000      /* TS continued */
 322 gdt_end:
 323
 324 /*
 325  * Stack and heap for uncompression
 326  */
 327         .bss
 328         .balign 4
 329 boot_heap:
 330         .fill BOOT_HEAP_SIZE, 1, 0
 331 boot_stack:
 332         .fill BOOT_STACK_SIZE, 1, 0
 333 boot_stack_end:
 334
 335 /*
 336  * Space for page tables (not in .bss so not zeroed)
 337  */
 338         .section ".pgtable","a",@nobits
 339         .balign 4096
 340 pgtable:
 341         .fill 6*4096, 1, 0