hello_world/head.S

   1 /* Copyright 2013-2014 IBM Corp.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at
   6  *
   7  *      http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
  12  * implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #define STACK_TOP 0x2000
  18
  19 #define FIXUP_ENDIAN                                               \
  20         tdi   0,0,0x48;   /* Reverse endian of b . + 8          */ \
  21         b     191f;       /* Skip trampoline if endian is good  */ \
  22         .long 0xa600607d; /* mfmsr r11                          */ \
  23         .long 0x01006b69; /* xori r11,r11,1                     */ \
  24         .long 0x05009f42; /* bcl 20,31,$+4                      */ \
  25         .long 0xa602487d; /* mflr r10                           */ \
  26         .long 0x14004a39; /* addi r10,r10,20                    */ \
  27         .long 0xa64b5a7d; /* mthsrr0 r10                        */ \
  28         .long 0xa64b7b7d; /* mthsrr1 r11                        */ \
  29         .long 0x2402004c; /* hrfid                              */ \
  30 191:
  31
  32
  33 /* Load an immediate 64-bit value into a register */
  34 #define LOAD_IMM64(r, e)                        \
  35         lis     r,(e)@highest;                  \
  36         ori     r,r,(e)@higher;                 \
  37         rldicr  r,r, 32, 31;                    \
  38         oris    r,r, (e)@h;                     \
  39         ori     r,r, (e)@l;
  40
  41         .section ".head","ax"
  42
  43         /*
  44          * Microwatt currently enters in LE mode at 0x0, so we don't need to
  45          * do any endian fix ups>
  46          */
  47         . = 0
  48 .global _start
  49 _start:
  50         b       boot_entry
  51
  52         /* QEMU enters at 0x10 */
  53         . = 0x10
  54         FIXUP_ENDIAN
  55         b       boot_entry
  56
  57         . = 0x100
  58         FIXUP_ENDIAN
  59         b       boot_entry
  60
  61 .global boot_entry
  62 boot_entry:
  63         /* setup stack */
  64         LOAD_IMM64(%r1, STACK_TOP - 0x100)
  65         LOAD_IMM64(%r12, main)
  66         mtctr   %r12,
  67         bctrl
  68         b .
  69
  70 #define EXCEPTION(nr)           \
  71         .= nr                   ;\
  72         b       .
  73
  74         /* More exception stubs */
  75         EXCEPTION(0x300)
  76         EXCEPTION(0x380)
  77         EXCEPTION(0x400)
  78         EXCEPTION(0x480)
  79         EXCEPTION(0x500)
  80         EXCEPTION(0x600)
  81         EXCEPTION(0x700)
  82         EXCEPTION(0x800)
  83         EXCEPTION(0x900)
  84         EXCEPTION(0x980)
  85         EXCEPTION(0xa00)
  86         EXCEPTION(0xb00)
  87         EXCEPTION(0xc00)
  88         EXCEPTION(0xd00)
  89         EXCEPTION(0xe00)
  90         EXCEPTION(0xe20)
  91         EXCEPTION(0xe40)
  92         EXCEPTION(0xe60)
  93         EXCEPTION(0xe80)
  94         EXCEPTION(0xf00)
  95         EXCEPTION(0xf20)
  96         EXCEPTION(0xf40)
  97         EXCEPTION(0xf60)
  98         EXCEPTION(0xf80)
  99 #if 0
 100         EXCEPTION(0x1000)
 101         EXCEPTION(0x1100)
 102         EXCEPTION(0x1200)
 103         EXCEPTION(0x1300)
 104         EXCEPTION(0x1400)
 105         EXCEPTION(0x1500)
 106         EXCEPTION(0x1600)
 107 #endif