arch/ppc/boot/simple/relocate.S

   1 /*
   2  * arch/ppc/boot/simple/relocate.S
   3  *
   4  * This is the common part of the loader relocation and initialization
   5  * process.  All of the board/processor specific initialization is
   6  * done before we get here.
   7  *
   8  * Author: Tom Rini
   9  *         trini@mvista.com
  10  * Derived from arch/ppc/boot/prep/head.S (Cort Dougan, many others).
  11  *
  12  * 2001-2004 (c) MontaVista, Software, Inc.  This file is licensed under
  13  * the terms of the GNU General Public License version 2.  This program
  14  * is licensed "as is" without any warranty of any kind, whether express
  15  * or implied.
  16  */
  17
  18 #include <linux/config.h>
  19 #include <asm/cache.h>
  20 #include <asm/ppc_asm.h>
  21
  22 #define GETSYM(reg, sym)        \
  23         lis     reg, sym@h; ori reg, reg, sym@l
  24
  25         .text
  26         /* We get called from the early initialization code.
  27          * Register 3 has the address where we were loaded,
  28          * Register 4 contains any residual data passed from the
  29          * boot rom.
  30          */
  31         .globl  relocate
  32 relocate:
  33         /* Save r3, r4 for later.
  34          * The r8/r11 are legacy registers so I don't have to
  35          * rewrite the code below :-).
  36          */
  37         mr      r8, r3
  38         mr      r11, r4
  39
  40         /* compute the size of the whole image in words. */
  41         GETSYM(r4,start)
  42         GETSYM(r5,end)
  43
  44         addi    r5,r5,3         /* round up */
  45         sub     r5,r5,r4        /* end - start */
  46         srwi    r5,r5,2
  47         mr      r7,r5           /* Save for later use. */
  48
  49         /*
  50          * Check if we need to relocate ourselves to the link addr or were
  51          * we loaded there to begin with.
  52          */
  53         cmpw    cr0,r3,r4
  54         beq     start_ldr       /* If 0, we don't need to relocate */
  55
  56         /* Move this code somewhere safe.  This is max(load + size, end)
  57          * r8 == load address
  58          */
  59         GETSYM(r4, start)
  60         GETSYM(r5, end)
  61
  62         sub     r6,r5,r4
  63         add     r6,r8,r6        /* r6 == phys(load + size) */
  64
  65         cmpw    r5,r6
  66         bgt     1f
  67         b       2f
  68 1:
  69         mr      r6, r5
  70 2:
  71         /* dest is in r6 */
  72         /* Ensure alignment --- this code is precautionary */
  73         addi    r6,r6,4
  74         li      r5,0x0003
  75         andc    r6,r6,r5
  76
  77         /* Find physical address and size of do_relocate */
  78         GETSYM(r5, __relocate_start)
  79         GETSYM(r4, __relocate_end)
  80         GETSYM(r3, start)
  81
  82         /* Size to copy */
  83         sub     r4,r4,r5
  84         srwi    r4,r4,2
  85
  86         /* Src addr to copy (= __relocate_start - start + where_loaded) */
  87         sub     r3,r5,r3
  88         add     r5,r8,r3
  89
  90         /* Save dest */
  91         mr      r3, r6
  92
  93         /* Do the copy */
  94         mtctr   r4
  95 3:      lwz     r4,0(r5)
  96         stw     r4,0(r3)
  97         addi    r3,r3,4
  98         addi    r5,r5,4
  99         bdnz    3b
 100
 101         GETSYM(r4, __relocate_start)
 102         GETSYM(r5, do_relocate)
 103
 104         sub     r4,r5,r4        /* Get entry point for do_relocate in */
 105         add     r6,r6,r4        /* relocated section */
 106
 107         /* This will return to the relocated do_relocate */
 108         mtlr    r6
 109         b       flush_instruction_cache
 110
 111         .section ".relocate_code","xa"
 112
 113 do_relocate:
 114         /* We have 2 cases --- start < load, or start > load
 115          * This determines whether we copy from the end, or the start.
 116          * Its easier to have 2 loops than to have paramaterised
 117          * loops.  Sigh.
 118          */
 119         li      r6,0            /* Clear checksum */
 120         mtctr   r7              /* Setup for a loop */
 121
 122         GETSYM(r4, start)
 123         mr      r3,r8           /* Get the load addr */
 124
 125         cmpw    cr0,r4,r3       /* If we need to copy from the end, do so */
 126         bgt     do_relocate_from_end
 127
 128 do_relocate_from_start:
 129 1:      lwz     r5,0(r3)        /* Load and decrement */
 130         stw     r5,0(r4)        /* Store and decrement */
 131         addi    r3,r3,4
 132         addi    r4,r4,4
 133         xor     r6,r6,r5        /* Update checksum */
 134         bdnz    1b              /* Are we done? */
 135         b       do_relocate_out /* Finished */
 136
 137 do_relocate_from_end:
 138         GETSYM(r3, end)
 139         slwi    r4,r7,2
 140         add     r4,r8,r4        /* Get the physical end */
 141 1:      lwzu    r5,-4(r4)
 142         stwu    r5, -4(r3)
 143         xor     r6,r6,r5
 144         bdnz    1b
 145
 146 do_relocate_out:
 147         GETSYM(r3,start_ldr)
 148         mtlr    r3              /* Easiest way to do an absolute jump */
 149 /* Some boards don't boot up with the I-cache enabled.  Do that
 150  * now because the decompress runs much faster that way.
 151  * As a side effect, we have to ensure the data cache is not enabled
 152  * so we can access the serial I/O without trouble.
 153  */
 154         b       flush_instruction_cache
 155
 156         .previous
 157
 158 start_ldr:
 159 /* Clear all of BSS and set up stack for C calls */
 160         lis     r3,edata@h
 161         ori     r3,r3,edata@l
 162         lis     r4,end@h
 163         ori     r4,r4,end@l
 164         subi    r3,r3,4
 165         subi    r4,r4,4
 166         li      r0,0
 167 50:     stwu    r0,4(r3)
 168         cmpw    cr0,r3,r4
 169         bne     50b
 170 90:     mr      r9,r1           /* Save old stack pointer (in case it matters) */
 171         lis     r1,.stack@h
 172         ori     r1,r1,.stack@l
 173         addi    r1,r1,4096*2
 174         subi    r1,r1,256
 175         li      r2,0x000F       /* Mask pointer to 16-byte boundary */
 176         andc    r1,r1,r2
 177
 178         /*
 179          * Exec kernel loader
 180          */
 181         mr      r3,r8           /* Load point */
 182         mr      r4,r7           /* Program length */
 183         mr      r5,r6           /* Checksum */
 184         mr      r6,r11          /* Residual data */
 185         mr      r7,r25          /* Validated OFW interface */
 186         bl      load_kernel
 187
 188         /*
 189          * Make sure the kernel knows we don't have things set in
 190          * registers.  -- Tom
 191          */
 192         li      r4,0
 193         li      r5,0
 194         li      r6,0
 195
 196         /*
 197          * Start at the begining.
 198          */
 199 #ifdef CONFIG_PPC_MULTIPLATFORM
 200         li      r9,0xc
 201         mtlr    r9
 202         /* tell kernel we're prep, by putting 0xdeadc0de at KERNELLOAD,
 203          * and tell the kernel to start on the 4th instruction since we
 204          * overwrite the first 3 sometimes (which are 'nop').
 205          */
 206         lis     r10,0xdeadc0de@h
 207         ori     r10,r10,0xdeadc0de@l
 208         li      r9,0
 209         stw     r10,0(r9)
 210 #else
 211         li      r9,0
 212         mtlr    r9
 213 #endif
 214         blr
 215
 216         .comm   .stack,4096*2,4