LXR linux/arch/arm/boot/bootp/init.S

   1/*
   2 *  linux/arch/arm/boot/bootp/init.S
   3 *
   4 *  Copyright (C) 2000-2003 Russell King.
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 *  "Header" file for splitting kernel + initrd.  Note that we pass
  11 *  r0 through to r3 straight through.
  12 *
  13 *  This demonstrates how to append code to the start of the kernel
  14 *  zImage, and boot the kernel without copying it around.  This
  15 *  example would be simpler; if we didn't have an object of unknown
  16 *  size immediately following the kernel, we could build this into
  17 *  a binary blob, and concatenate the zImage using the cat command.
  18 */
  19                .section .start,#alloc,#execinstr
  20                .type   _start, #function
  21                .globl  _start
  22
  23_start:         add     lr, pc, #-0x8           @ lr = current load addr
  24                adr     r13, data
  25                ldmia   r13!, {r4-r6}           @ r5 = dest, r6 = length
  26                add     r4, r4, lr              @ r4 = initrd_start + load addr
  27                bl      move                    @ move the initrd
  28
  29/*
  30 * Setup the initrd parameters to pass to the kernel.  This can only be
  31 * passed in via the tagged list.
  32 */
  33                ldmia   r13, {r5-r9}            @ get size and addr of initrd
  34                                                @ r5 = ATAG_CORE
  35                                                @ r6 = ATAG_INITRD2
  36                                                @ r7 = initrd start
  37                                                @ r8 = initrd end
  38                                                @ r9 = param_struct address
  39
  40                ldr     r10, [r9, #4]           @ get first tag
  41                teq     r10, r5                 @ is it ATAG_CORE?
  42/*
  43 * If we didn't find a valid tag list, create a dummy ATAG_CORE entry.
  44 */
  45                movne   r10, #0                 @ terminator
  46                movne   r4, #2                  @ Size of this entry (2 words)
  47                stmneia r9, {r4, r5, r10}       @ Size, ATAG_CORE, terminator
  48
  49/*
  50 * find the end of the tag list, and then add an INITRD tag on the end.
  51 * If there is already an INITRD tag, then we ignore it; the last INITRD
  52 * tag takes precedence.
  53 */
  54taglist:        ldr     r10, [r9, #0]           @ tag length
  55                teq     r10, #0                 @ last tag (zero length)?
  56                addne   r9, r9, r10, lsl #2
  57                bne     taglist
  58
  59                mov     r5, #4                  @ Size of initrd tag (4 words)
  60                stmia   r9, {r5, r6, r7, r8, r10}
  61                b       kernel_start            @ call kernel
  62
  63/*
  64 * Move the block of memory length r6 from address r4 to address r5
  65 */
  66move:           ldmia   r4!, {r7 - r10}         @ move 32-bytes at a time
  67                stmia   r5!, {r7 - r10}
  68                ldmia   r4!, {r7 - r10}
  69                stmia   r5!, {r7 - r10}
  70                subs    r6, r6, #8 * 4
  71                bcs     move
  72                mov     pc, lr
  73
  74                .size   _start, . - _start
  75
  76                .align
  77
  78                .type   data,#object
  79data:           .word   initrd_start            @ source initrd address
  80                .word   initrd_phys             @ destination initrd address
  81                .word   initrd_size             @ initrd size
  82
  83                .word   0x54410001              @ r5 = ATAG_CORE
  84                .word   0x54420005              @ r6 = ATAG_INITRD2
  85                .word   initrd_phys             @ r7
  86                .word   initrd_size             @ r8
  87                .word   params_phys             @ r9
  88                .size   data, . - data
  89