mirror of
https://github.com/fail0verflow/mini.git
synced 2024-11-05 19:25:12 +01:00
127 lines
1.7 KiB
ArmAsm
127 lines
1.7 KiB
ArmAsm
.arm
|
|
|
|
.extern _main
|
|
.extern __got_start
|
|
.extern __got_end
|
|
.extern __bss_start
|
|
.extern __bss_end
|
|
.extern __stack_addr
|
|
.globl _start
|
|
.globl debug_output
|
|
.globl panic
|
|
.globl delay
|
|
|
|
.section .init
|
|
|
|
_vectors:
|
|
_start:
|
|
ldr pc, =v_reset
|
|
ldr pc, =v_undf
|
|
ldr pc, =v_swi
|
|
ldr pc, =v_instr_abrt
|
|
ldr pc, =v_data_abrt
|
|
ldr pc, =v_reserved
|
|
ldr pc, =v_irq
|
|
ldr pc, =v_fiq
|
|
|
|
.pool
|
|
|
|
v_reset:
|
|
@ Get loader base from ELF loader
|
|
mov r4, r0
|
|
|
|
@ Output 0x42 to the debug port
|
|
mov r0, #0x42
|
|
bl debug_output
|
|
|
|
@ Set up a stack
|
|
ldr sp, =__stack_addr
|
|
add sp, r4
|
|
|
|
@ clear BSS
|
|
ldr r1, =__bss_start
|
|
add r1, r4
|
|
ldr r2, =__bss_end
|
|
add r2, r4
|
|
mov r3, #0
|
|
bss_loop:
|
|
@ check for the end
|
|
cmp r1, r2
|
|
beq done_bss
|
|
@ clear the word and move on
|
|
str r3, [r1]
|
|
add r1, r1, #4
|
|
b bss_loop
|
|
|
|
done_bss:
|
|
mov r0, #0x84
|
|
bl debug_output
|
|
@ take the plunge
|
|
mov r0, r4
|
|
bl _main
|
|
@ _main returned! Go to whatever address it returned...
|
|
mov pc, r0
|
|
|
|
.pool
|
|
|
|
v_undf:
|
|
b v_undf
|
|
|
|
v_swi:
|
|
b v_swi
|
|
|
|
v_instr_abrt:
|
|
b v_instr_abrt
|
|
|
|
v_data_abrt:
|
|
b v_data_abrt
|
|
|
|
v_reserved:
|
|
b v_reserved
|
|
|
|
v_irq:
|
|
b v_irq
|
|
|
|
v_fiq:
|
|
b v_fiq
|
|
|
|
debug_output:
|
|
@ load address of port
|
|
mov r3, #0xd800000
|
|
@ load old value
|
|
ldr r2, [r3, #0xe0]
|
|
@ clear debug byte
|
|
bic r2, r2, #0xFF0000
|
|
@ insert new value
|
|
and r0, r0, #0xFF
|
|
orr r2, r2, r0, LSL #16
|
|
@ store back
|
|
str r2, [r3, #0xe0]
|
|
mov pc, lr
|
|
|
|
panic:
|
|
mov r4, r0
|
|
_panic:
|
|
mov r0, r4
|
|
bl debug_output
|
|
ldr r0, =6175000
|
|
bl delay
|
|
mov r0, #0x00
|
|
bl debug_output
|
|
ldr r0, =6175000
|
|
bl delay
|
|
b _panic
|
|
|
|
@ the speed of this seems to decrease wildly with certain (non-)alignments
|
|
@ probably some prefetch buffer / cache / DRAM junk
|
|
.balign 64
|
|
delay:
|
|
cmp r0, #0
|
|
moveq pc, lr
|
|
1:
|
|
subs r0, r0, #1
|
|
bne 1b
|
|
mov pc, lr
|
|
|
|
.pool
|