52 lines
1.2 KiB
ArmAsm
52 lines
1.2 KiB
ArmAsm
.text
|
|
.balign 4
|
|
.global _start
|
|
_start:
|
|
|
|
ld24 sp, _stack
|
|
ldi fp, #0
|
|
|
|
# Clear the BSS. Do it in two parts for efficiency: longwords first
|
|
# for most of it, then the remaining 0 to 3 bytes.
|
|
|
|
seth r2, #shigh(__bss_start)
|
|
add3 r2, r2, #low(__bss_start); R2 = start of BSS
|
|
seth r3, #shigh(_end)
|
|
add3 r3, r3, #low(_end) ; R3 = end of BSS + 1
|
|
|
|
sub r3, r2 ; R3 = BSS size in bytes
|
|
mv r4, r3
|
|
srli r4, #2 ; R4 = BSS size in longwords (rounded down)
|
|
ldi r1, #0 ; clear R1 for longword store
|
|
addi r2, #-4 ; account for pre-inc store
|
|
beqz r4, .Lendloop1 ; any more to go?
|
|
.Lloop1:
|
|
st r1, @+r2 ; yep, zero out another longword
|
|
addi r4, #-1 ; decrement count
|
|
bnez r4, .Lloop1 ; go do some more
|
|
.Lendloop1:
|
|
and3 r4, r3, #3 ; get no. of remaining BSS bytes to clear
|
|
addi r2, #4 ; account for pre-inc store
|
|
beqz r4, .Lendloop2 ; any more to go?
|
|
.Lloop2:
|
|
stb r1, @r2 ; yep, zero out another byte
|
|
addi r2, #1 ; bump address
|
|
addi r4, #-1 ; decrement count
|
|
bnez r4, .Lloop2 ; go do some more
|
|
.Lendloop2:
|
|
|
|
# Run code in the .init section.
|
|
# This will queue the .fini section to be run with atexit.
|
|
|
|
bl __init
|
|
|
|
# Call main, then exit.
|
|
|
|
bl main
|
|
bl exit
|
|
|
|
# If that fails just loop.
|
|
|
|
.Lexit:
|
|
bra .Lexit
|