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