arch/x86/boot/compressed/head_32.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         .text
  25
  26 #include <linux/init.h>
  27 #include <linux/linkage.h>
  28 #include <asm/segment.h>
  29 #include <asm/page_types.h>
  30 #include <asm/boot.h>
  31 #include <asm/asm-offsets.h>
  32
  33         __HEAD
  34 ENTRY(startup_32)
  35 #ifdef CONFIG_EFI_STUB
  36         jmp     preferred_addr
  37
  38         /*
  39          * We don't need the return address, so set up the stack so
  40          * efi_main() can find its arguments.
  41          */
  42 ENTRY(efi_pe_entry)
  43         add     $0x4, %esp
  44
  45         call    1f
  46 1:      popl    %esi
  47         subl    $1b, %esi
  48
  49         popl    %ecx
  50         movl    %ecx, efi32_config(%esi)        /* Handle */
  51         popl    %ecx
  52         movl    %ecx, efi32_config+8(%esi)      /* EFI System table pointer */
  53
  54         /* Relocate efi_config->call() */
  55         leal    efi32_config(%esi), %eax
  56         add     %esi, 88(%eax)
  57         pushl   %eax
  58
  59         call    make_boot_params
  60         cmpl    $0, %eax
  61         je      fail
  62         popl    %ecx
  63         pushl   %eax
  64         pushl   %ecx
  65         jmp     2f              /* Skip efi_config initialization */
  66
  67 ENTRY(efi32_stub_entry)
  68         add     $0x4, %esp
  69         popl    %ecx
  70         popl    %edx
  71
  72         call    1f
  73 1:      popl    %esi
  74         subl    $1b, %esi
  75
  76         movl    %ecx, efi32_config(%esi)        /* Handle */
  77         movl    %edx, efi32_config+8(%esi)      /* EFI System table pointer */
  78
  79         /* Relocate efi_config->call() */
  80         leal    efi32_config(%esi), %eax
  81         add     %esi, 88(%eax)
  82         pushl   %eax
  83 2:
  84         call    efi_main
  85         cmpl    $0, %eax
  86         movl    %eax, %esi
  87         jne     2f
  88 fail:
  89         /* EFI init failed, so hang. */
  90         hlt
  91         jmp     fail
  92 2:
  93         call    3f
  94 3:
  95         popl    %eax
  96         subl    $3b, %eax
  97         subl    BP_pref_address(%esi), %eax
  98         add     BP_code32_start(%esi), %eax
  99         leal    preferred_addr(%eax), %eax
 100         jmp     *%eax
 101
 102 preferred_addr:
 103 #endif
 104         cld
 105         /*
 106          * Test KEEP_SEGMENTS flag to see if the bootloader is asking
 107          * us to not reload segments
 108          */
 109         testb   $(1<<6), BP_loadflags(%esi)
 110         jnz     1f
 111
 112         cli
 113         movl    $__BOOT_DS, %eax
 114         movl    %eax, %ds
 115         movl    %eax, %es
 116         movl    %eax, %fs
 117         movl    %eax, %gs
 118         movl    %eax, %ss
 119 1:
 120
 121 /*
 122  * Calculate the delta between where we were compiled to run
 123  * at and where we were actually loaded at.  This can only be done
 124  * with a short local call on x86.  Nothing  else will tell us what
 125  * address we are running at.  The reserved chunk of the real-mode
 126  * data at 0x1e4 (defined as a scratch field) are used as the stack
 127  * for this calculation. Only 4 bytes are needed.
 128  */
 129         leal    (BP_scratch+4)(%esi), %esp
 130         call    1f
 131 1:      popl    %ebp
 132         subl    $1b, %ebp
 133
 134 /*
 135  * %ebp contains the address we are loaded at by the boot loader and %ebx
 136  * contains the address where we should move the kernel image temporarily
 137  * for safe in-place decompression.
 138  */
 139
 140 #ifdef CONFIG_RELOCATABLE
 141         movl    %ebp, %ebx
 142         movl    BP_kernel_alignment(%esi), %eax
 143         decl    %eax
 144         addl    %eax, %ebx
 145         notl    %eax
 146         andl    %eax, %ebx
 147         cmpl    $LOAD_PHYSICAL_ADDR, %ebx
 148         jge     1f
 149 #endif
 150         movl    $LOAD_PHYSICAL_ADDR, %ebx
 151 1:
 152
 153         /* Target address to relocate to for decompression */
 154         addl    $z_extract_offset, %ebx
 155
 156         /* Set up the stack */
 157         leal    boot_stack_end(%ebx), %esp
 158
 159         /* Zero EFLAGS */
 160         pushl   $0
 161         popfl
 162
 163 /*
 164  * Copy the compressed kernel to the end of our buffer
 165  * where decompression in place becomes safe.
 166  */
 167         pushl   %esi
 168         leal    (_bss-4)(%ebp), %esi
 169         leal    (_bss-4)(%ebx), %edi
 170         movl    $(_bss - startup_32), %ecx
 171         shrl    $2, %ecx
 172         std
 173         rep     movsl
 174         cld
 175         popl    %esi
 176
 177 /*
 178  * Jump to the relocated address.
 179  */
 180         leal    relocated(%ebx), %eax
 181         jmp     *%eax
 182 ENDPROC(startup_32)
 183
 184         .text
 185 relocated:
 186
 187 /*
 188  * Clear BSS (stack is currently empty)
 189  */
 190         xorl    %eax, %eax
 191         leal    _bss(%ebx), %edi
 192         leal    _ebss(%ebx), %ecx
 193         subl    %edi, %ecx
 194         shrl    $2, %ecx
 195         rep     stosl
 196
 197 /*
 198  * Adjust our own GOT
 199  */
 200         leal    _got(%ebx), %edx
 201         leal    _egot(%ebx), %ecx
 202 1:
 203         cmpl    %ecx, %edx
 204         jae     2f
 205         addl    %ebx, (%edx)
 206         addl    $4, %edx
 207         jmp     1b
 208 2:
 209
 210 /*
 211  * Do the decompression, and jump to the new kernel..
 212  */
 213                                 /* push arguments for decompress_kernel: */
 214         pushl   $z_output_len   /* decompressed length */
 215         leal    z_extract_offset_negative(%ebx), %ebp
 216         pushl   %ebp            /* output address */
 217         pushl   $z_input_len    /* input_len */
 218         leal    input_data(%ebx), %eax
 219         pushl   %eax            /* input_data */
 220         leal    boot_heap(%ebx), %eax
 221         pushl   %eax            /* heap area */
 222         pushl   %esi            /* real mode pointer */
 223         call    decompress_kernel /* returns kernel location in %eax */
 224         addl    $24, %esp
 225
 226 /*
 227  * Jump to the decompressed kernel.
 228  */
 229         xorl    %ebx, %ebx
 230         jmp     *%eax
 231
 232 #ifdef CONFIG_EFI_STUB
 233         .data
 234 efi32_config:
 235         .fill 11,8,0
 236         .long efi_call_phys
 237         .long 0
 238         .byte 0
 239 #endif
 240
 241 /*
 242  * Stack and heap for uncompression
 243  */
 244         .bss
 245         .balign 4
 246 boot_heap:
 247         .fill BOOT_HEAP_SIZE, 1, 0
 248 boot_stack:
 249         .fill BOOT_STACK_SIZE, 1, 0
 250 boot_stack_end: