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== code 0x80400000
main:
# print device tree info.
# OpenSBI calls us with a1 set to the start of the DTB
# load 0x10000000 (UART0) into a0
37/lui a/rd/a0 10000/imm20
13/opi 15/rd/s5 0/subop/add b/rs/a1 0/imm12
# check magic == 0xd00dfeed
37/lui 6/rd/t1 edfe1dd0/imm20hi
13/opi 6/rd/t1 0/subop/add 6/rs/t1 edfe0dd0/imm12lo
03/load 5/rd/t0 2/width/w 15/rs/s5 0/imm12
63/branch 1/subop/!= 5/rs/t0 6/rs/t1 err_magic/off13
37/lui b/rd/a1 S_TOTALSZ/imm20hi
13/opi b/rd/a1 0/subop/add b/rs/a1 S_TOTALSZ/imm12lo
6f/jal 1/rd/ra print/off21
03/load b/rd/a1 2/width/w 15/rs/s5 4/imm12
6f/jal 1/rd/ra bswapw/off21
6f/jal 1/rd/ra print_hex_word/off21
6f/jal 1/rd/ra printnl/off21
exit:
# system reset (via SBI extension SRST)
# a7 = ext id, a6 = fid, a0 = 0, a1 = 0
37/lui 11/rd/a7 53525/imm20
13/opi 11/rd/a7 0/subop/add 11/rs/a7 354/imm12
33/opr 0/mode/norm 10/rd/a6 0/subop/add 0/rs/x0 0/rs/x0
33/opr 0/mode/norm a/rd/a0 0/subop/add 0/rs/x0 0/rs/x0
33/opr 0/mode/norm b/rd/a1 0/subop/add 0/rs/x0 0/rs/x0
# ECALL
73/system 0/subop/priv 0/funct12/ecall
err_magic:
37/lui b/rd/a1 E_MAGIC/imm20hi
13/opi b/rd/a1 0/subop/add b/rs/a1 E_MAGIC/imm12lo
6f/jal 1/rd/ra print/off21
6f/jal 0/rd/x0 exit/off21
bswapw:
# byte-order-swap word in a1
# srli a1, a0, 8
# lui a2, 16
# addi a2, a2, -256
# and a1, a1, a2
13/opi 5/rd/t0 5/subop/srl b/rs/a1 8/imm12
37/lui 6/rd/t1 16/imm20
13/opi 6/rd/t1 0/subop/add 6/rs/t1 -100/imm12
33/opr 5/rd/t0 7/subop/and 0/mode/norm 5/rs/t0 6/rs/t1
# srli a2, a0, 24
# or a1, a1, a2
13/opi 6/rd/t1 5/subop/srl b/rs/a1 18/imm12
33/opr 5/rd/t0 6/subop/or 0/mode/norm 5/rs/t0 6/rs/t1
# slli a2, a0, 8
# lui a3, 4080
# and a2, a2, a3
13/opi 6/rd/t1 1/subop/sll 0/mode/norm b/rs/a1 8/imm5
37/lui 7/rd/t2 ff0/imm20
33/opr 6/rd/t1 7/subop/and 0/mode/norm 6/rs/t1 7/rs/t2
# slli a0, a0, 24
# or a0, a0, a2
# or a0, a0, a1
13/opi b/rd/a1 1/subop/sll 0/mode/norm b/rs/a1 18/imm5
33/opr b/rd/a1 6/subop/or 0/mode/norm b/rs/a1 6/rs/t1
33/opr b/rd/a1 6/subop/or 0/mode/norm b/rs/a1 5/rs/t0
# ret
67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
printnl:
13/opi 6/rd/t1 0/subop/add 0/rs/x0 0a/imm12
printnl:spin:
# spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
63/branch 0/subop/== 7/rs/t2 0/rs/x0 printnl:spin/off13
# print char
23/store 2/width/w a/rs/a0 0/off12 6/rs/t1
# return
67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
print:
print:loop:
# load unsigned byte at a1
03/load 6/rd/t1 4/width/bu b/rs/a1 0/imm12
# break loop if zero
63/branch 0/subop/== 6/rs/t1 0/rs/x0 print:break/off13
print:spin:
# spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
63/branch 0/subop/== 7/rs/t2 0/rs/x0 print:spin/off13
# print char
23/store 2/width/w a/rs/a0 0/off12 6/rs/t1
# increment a1
13/opi b/rd/a1 0/subop/add b/rs/a1 1/imm12
# jump back up
6f/jal 0/rd/x0 print:loop/off21
print:break:
# return
67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
print_hex_word:
13/opi 8/rd/s0 0/subop/add b/rs/a1 0/imm12
13/opi 9/rd/s1 0/subop/add 0/rs/x0 1c/imm12
13/opi 12/rd/s2 0/subop/add 1/rs/ra 0/imm12
print_hex_word:loop:
# shift
33/opr b/rd/a1 5/subop/srl 8/rs/s0 0/funct7/norm 9/rs/s1
6f/jal 1/rd/ra print_hex_dgt/off21
# break if last shift
63/branch 9/rs/s1 0/subop/== 0/rs/x0 print_hex_word:break/off13
# subtract shift count, loop
13/opi 9/rd/s1 0/subop/add 9/rs/s1 -4/imm12
6f/jal 0/rd/x0 print_hex_word:loop/off21
print_hex_word:break:
# return
67/jalr 0/rd/x0 0/subop 12/rs/s2 0/off12
print_hex_dgt:
# a1 = a1 & 0xf
13/opi b/rd/a1 7/subop/and b/rs/a1 f/imm12
# t1 = 0x40
13/opi 6/rd/t1 0/subop/add 0/rs/x0 40/imm12
# add 0x30 (ascii '0') / 0x61 (ascii 'a')
13/opi b/rd/a1 0/subop/add b/rs/a1 30/imm12
63/branch b/rs/a1 4/subop/< 6/rs/t1 print_hex_dgt:spin/off13
13/opi b/rd/a1 0/subop/add b/rs/a1 27/imm12
print_hex_dgt:spin:
# spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
63/branch 0/subop/== 7/rs/t2 0/rs/x0 print_hex_dgt:spin/off13
# print char
23/store 2/width/w a/rs/a0 0/off12 b/rs/a1
# return
67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
== data 0x80500000
E_MAGIC:
# "Invalid DTB magic!\n\0"
49/8 6e/8 76/8 61/8 6c/8 69/8 64/8 20/8 44/8 54/8 42/8 20/8 6d/8 61/8 67/8 69/8 63/8 21/8 0a/8 00/8
S_TOTALSZ:
54/8 6f/8 74/8 61/8 6c/8 20/8 53/8 69/8 7a/8 65/8 3a/8 20/8 00/8
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