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microwatt/hello_world/head.S

83 lines
1.9 KiB
ArmAsm

/* Copyright 2013-2014 IBM Corp.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define STACK_TOP 0x2000
#define FIXUP_ENDIAN \
tdi 0,0,0x48; /* Reverse endian of b . + 8 */ \
b 191f; /* Skip trampoline if endian is good */ \
.long 0xa600607d; /* mfmsr r11 */ \
.long 0x01006b69; /* xori r11,r11,1 */ \
.long 0x05009f42; /* bcl 20,31,$+4 */ \
.long 0xa602487d; /* mflr r10 */ \
.long 0x14004a39; /* addi r10,r10,20 */ \
.long 0xa64b5a7d; /* mthsrr0 r10 */ \
.long 0xa64b7b7d; /* mthsrr1 r11 */ \
.long 0x2402004c; /* hrfid */ \
191:
/* Load an immediate 64-bit value into a register */
#define LOAD_IMM64(r, e) \
lis r,(e)@highest; \
ori r,r,(e)@higher; \
rldicr r,r, 32, 31; \
oris r,r, (e)@h; \
ori r,r, (e)@l;
.section ".head","ax"
/*
* Microwatt currently enters in LE mode at 0x0, so we don't need to
* do any endian fix ups>
*/
. = 0
.global _start
_start:
b boot_entry
/* QEMU enters at 0x10 */
. = 0x10
FIXUP_ENDIAN
b boot_entry
. = 0x100
FIXUP_ENDIAN
b boot_entry
.global boot_entry
boot_entry:
LOAD_IMM64(%r10,__bss_start)
LOAD_IMM64(%r11,__bss_end)
subf %r11,%r10,%r11
addi %r11,%r11,63
srdi. %r11,%r11,6
beq 2f
mtctr %r11
1: dcbz 0,%r10
addi %r10,%r10,64
bdnz 1b
/* setup stack */
2: LOAD_IMM64(%r1,__stack_top)
li %r0,0
stdu %r0,-32(%r1)
LOAD_IMM64(%r12, main)
mtctr %r12
bctrl
attn // terminate on exit
b .