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         .balign 0x10
  39         /*
  40          * We don't need the return address, so set up the stack so
  41          * efi_main() can find its arugments.
  42          */
  43         add     $0x4, %esp
  44
  45         call    make_boot_params
  46         cmpl    $0, %eax
  47         je      1f
  48         movl    0x4(%esp), %esi
  49         movl    (%esp), %ecx
  50         pushl   %eax
  51         pushl   %esi
  52         pushl   %ecx
  53
  54         .org 0x30,0x90
  55         call    efi_main
  56         cmpl    $0, %eax
  57         movl    %eax, %esi
  58         jne     2f
  59 1:
  60         /* EFI init failed, so hang. */
  61         hlt
  62         jmp     1b
  63 2:
  64         call    3f
  65 3:
  66         popl    %eax
  67         subl    $3b, %eax
  68         subl    BP_pref_address(%esi), %eax
  69         add     BP_code32_start(%esi), %eax
  70         leal    preferred_addr(%eax), %eax
  71         jmp     *%eax
  72
  73 preferred_addr:
  74 #endif
  75         cld
  76         /*
  77          * Test KEEP_SEGMENTS flag to see if the bootloader is asking
  78          * us to not reload segments
  79          */
  80         testb   $(1<<6), BP_loadflags(%esi)
  81         jnz     1f
  82
  83         cli
  84         movl    $__BOOT_DS, %eax
  85         movl    %eax, %ds
  86         movl    %eax, %es
  87         movl    %eax, %fs
  88         movl    %eax, %gs
  89         movl    %eax, %ss
  90 1:
  91
  92 /*
  93  * Calculate the delta between where we were compiled to run
  94  * at and where we were actually loaded at.  This can only be done
  95  * with a short local call on x86.  Nothing  else will tell us what
  96  * address we are running at.  The reserved chunk of the real-mode
  97  * data at 0x1e4 (defined as a scratch field) are used as the stack
  98  * for this calculation. Only 4 bytes are needed.
  99  */
 100         leal    (BP_scratch+4)(%esi), %esp
 101         call    1f
 102 1:      popl    %ebp
 103         subl    $1b, %ebp
 104
 105 /*
 106  * %ebp contains the address we are loaded at by the boot loader and %ebx
 107  * contains the address where we should move the kernel image temporarily
 108  * for safe in-place decompression.
 109  */
 110
 111 #ifdef CONFIG_RELOCATABLE
 112         movl    %ebp, %ebx
 113         movl    BP_kernel_alignment(%esi), %eax
 114         decl    %eax
 115         addl    %eax, %ebx
 116         notl    %eax
 117         andl    %eax, %ebx
 118 #else
 119         movl    $LOAD_PHYSICAL_ADDR, %ebx
 120 #endif
 121
 122         /* Target address to relocate to for decompression */
 123         addl    $z_extract_offset, %ebx
 124
 125         /* Set up the stack */
 126         leal    boot_stack_end(%ebx), %esp
 127
 128         /* Zero EFLAGS */
 129         pushl   $0
 130         popfl
 131
 132 /*
 133  * Copy the compressed kernel to the end of our buffer
 134  * where decompression in place becomes safe.
 135  */
 136         pushl   %esi
 137         leal    (_bss-4)(%ebp), %esi
 138         leal    (_bss-4)(%ebx), %edi
 139         movl    $(_bss - startup_32), %ecx
 140         shrl    $2, %ecx
 141         std
 142         rep     movsl
 143         cld
 144         popl    %esi
 145
 146 /*
 147  * Jump to the relocated address.
 148  */
 149         leal    relocated(%ebx), %eax
 150         jmp     *%eax
 151 ENDPROC(startup_32)
 152
 153         .text
 154 relocated:
 155
 156 /*
 157  * Clear BSS (stack is currently empty)
 158  */
 159         xorl    %eax, %eax
 160         leal    _bss(%ebx), %edi
 161         leal    _ebss(%ebx), %ecx
 162         subl    %edi, %ecx
 163         shrl    $2, %ecx
 164         rep     stosl
 165
 166 /*
 167  * Adjust our own GOT
 168  */
 169         leal    _got(%ebx), %edx
 170         leal    _egot(%ebx), %ecx
 171 1:
 172         cmpl    %ecx, %edx
 173         jae     2f
 174         addl    %ebx, (%edx)
 175         addl    $4, %edx
 176         jmp     1b
 177 2:
 178
 179 /*
 180  * Do the decompression, and jump to the new kernel..
 181  */
 182         leal    z_extract_offset_negative(%ebx), %ebp
 183                                 /* push arguments for decompress_kernel: */
 184         pushl   %ebp            /* output address */
 185         pushl   $z_input_len    /* input_len */
 186         leal    input_data(%ebx), %eax
 187         pushl   %eax            /* input_data */
 188         leal    boot_heap(%ebx), %eax
 189         pushl   %eax            /* heap area */
 190         pushl   %esi            /* real mode pointer */
 191         call    decompress_kernel
 192         addl    $20, %esp
 193
 194 #if CONFIG_RELOCATABLE
 195 /*
 196  * Find the address of the relocations.
 197  */
 198         leal    z_output_len(%ebp), %edi
 199
 200 /*
 201  * Calculate the delta between where vmlinux was compiled to run
 202  * and where it was actually loaded.
 203  */
 204         movl    %ebp, %ebx
 205         subl    $LOAD_PHYSICAL_ADDR, %ebx
 206         jz      2f      /* Nothing to be done if loaded at compiled addr. */
 207 /*
 208  * Process relocations.
 209  */
 210
 211 1:      subl    $4, %edi
 212         movl    (%edi), %ecx
 213         testl   %ecx, %ecx
 214         jz      2f
 215         addl    %ebx, -__PAGE_OFFSET(%ebx, %ecx)
 216         jmp     1b
 217 2:
 218 #endif
 219
 220 /*
 221  * Jump to the decompressed kernel.
 222  */
 223         xorl    %ebx, %ebx
 224         jmp     *%ebp
 225
 226 /*
 227  * Stack and heap for uncompression
 228  */
 229         .bss
 230         .balign 4
 231 boot_heap:
 232         .fill BOOT_HEAP_SIZE, 1, 0
 233 boot_stack:
 234         .fill BOOT_STACK_SIZE, 1, 0
 235 boot_stack_end: