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== code 0x80400000
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main:
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# print device tree info.
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# OpenSBI calls us with a1 set to the start of the DTB
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# load 0x10000000 (UART0) into a0
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5 |
37/lui a/rd/a0 10000/imm20
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6 |
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13/opi 15/rd/s5 0/subop/add b/rs/a1 0/imm12
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8 |
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# check magic == 0xd00dfeed
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10 |
37/lui 6/rd/t1 edfe1dd0/imm20hi
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13/opi 6/rd/t1 0/subop/add 6/rs/t1 edfe0dd0/imm12lo
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03/load 5/rd/t0 2/width/w 15/rs/s5 0/imm12
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63/branch 1/subop/!= 5/rs/t0 6/rs/t1 err_magic/off13
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14 |
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37/lui b/rd/a1 S_TOTALSZ/imm20hi
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13/opi b/rd/a1 0/subop/add b/rs/a1 S_TOTALSZ/imm12lo
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6f/jal 1/rd/ra print/off21
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18 |
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03/load b/rd/a1 2/width/w 15/rs/s5 4/imm12
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20 |
6f/jal 1/rd/ra bswapw/off21
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21 |
6f/jal 1/rd/ra print_hex_word/off21
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22 |
6f/jal 1/rd/ra printnl/off21
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23 |
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24 |
exit:
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# system reset (via SBI extension SRST)
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# a7 = ext id, a6 = fid, a0 = 0, a1 = 0
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37/lui 11/rd/a7 53525/imm20
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13/opi 11/rd/a7 0/subop/add 11/rs/a7 354/imm12
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29 |
33/opr 0/mode/norm 10/rd/a6 0/subop/add 0/rs/x0 0/rs/x0
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30 |
33/opr 0/mode/norm a/rd/a0 0/subop/add 0/rs/x0 0/rs/x0
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33/opr 0/mode/norm b/rd/a1 0/subop/add 0/rs/x0 0/rs/x0
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# ECALL
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73/system 0/subop/priv 0/funct12/ecall
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34 |
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err_magic:
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37/lui b/rd/a1 E_MAGIC/imm20hi
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37 |
13/opi b/rd/a1 0/subop/add b/rs/a1 E_MAGIC/imm12lo
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38 |
6f/jal 1/rd/ra print/off21
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6f/jal 0/rd/x0 exit/off21
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40 |
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bswapw:
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# byte-order-swap word in a1
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# srli a1, a0, 8
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# lui a2, 16
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# addi a2, a2, -256
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# and a1, a1, a2
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13/opi 5/rd/t0 5/subop/srl b/rs/a1 8/imm12
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37/lui 6/rd/t1 16/imm20
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13/opi 6/rd/t1 0/subop/add 6/rs/t1 -100/imm12
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33/opr 5/rd/t0 7/subop/and 0/mode/norm 5/rs/t0 6/rs/t1
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# srli a2, a0, 24
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# or a1, a1, a2
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13/opi 6/rd/t1 5/subop/srl b/rs/a1 18/imm12
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33/opr 5/rd/t0 6/subop/or 0/mode/norm 5/rs/t0 6/rs/t1
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# slli a2, a0, 8
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# lui a3, 4080
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# and a2, a2, a3
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13/opi 6/rd/t1 1/subop/sll 0/mode/norm b/rs/a1 8/imm5
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37/lui 7/rd/t2 ff0/imm20
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33/opr 6/rd/t1 7/subop/and 0/mode/norm 6/rs/t1 7/rs/t2
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# slli a0, a0, 24
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# or a0, a0, a2
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# or a0, a0, a1
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13/opi b/rd/a1 1/subop/sll 0/mode/norm b/rs/a1 18/imm5
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33/opr b/rd/a1 6/subop/or 0/mode/norm b/rs/a1 6/rs/t1
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33/opr b/rd/a1 6/subop/or 0/mode/norm b/rs/a1 5/rs/t0
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# ret
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67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
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69 |
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printnl:
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13/opi 6/rd/t1 0/subop/add 0/rs/x0 0a/imm12
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printnl:spin:
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# spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
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03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
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13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
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63/branch 0/subop/== 7/rs/t2 0/rs/x0 printnl:spin/off13
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# print char
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23/store 2/width/w a/rs/a0 0/off12 6/rs/t1
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# return
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67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
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81 |
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print:
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print:loop:
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# load unsigned byte at a1
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03/load 6/rd/t1 4/width/bu b/rs/a1 0/imm12
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# break loop if zero
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63/branch 0/subop/== 6/rs/t1 0/rs/x0 print:break/off13
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print:spin:
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# spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
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03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
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13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
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63/branch 0/subop/== 7/rs/t2 0/rs/x0 print:spin/off13
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# print char
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23/store 2/width/w a/rs/a0 0/off12 6/rs/t1
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# increment a1
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13/opi b/rd/a1 0/subop/add b/rs/a1 1/imm12
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# jump back up
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6f/jal 0/rd/x0 print:loop/off21
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print:break:
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# return
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67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
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102 |
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print_hex_word:
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13/opi 8/rd/s0 0/subop/add b/rs/a1 0/imm12
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13/opi 9/rd/s1 0/subop/add 0/rs/x0 1c/imm12
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13/opi 12/rd/s2 0/subop/add 1/rs/ra 0/imm12
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print_hex_word:loop:
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# shift
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33/opr b/rd/a1 5/subop/srl 8/rs/s0 0/funct7/norm 9/rs/s1
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6f/jal 1/rd/ra print_hex_dgt/off21
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111 |
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# break if last shift
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63/branch 9/rs/s1 0/subop/== 0/rs/x0 print_hex_word:break/off13
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# subtract shift count, loop
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13/opi 9/rd/s1 0/subop/add 9/rs/s1 -4/imm12
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6f/jal 0/rd/x0 print_hex_word:loop/off21
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print_hex_word:break:
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# return
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67/jalr 0/rd/x0 0/subop 12/rs/s2 0/off12
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121 |
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print_hex_dgt:
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# a1 = a1 & 0xf
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13/opi b/rd/a1 7/subop/and b/rs/a1 f/imm12
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# t1 = 0x40
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13/opi 6/rd/t1 0/subop/add 0/rs/x0 40/imm12
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127 |
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128 |
# add 0x30 (ascii '0') / 0x61 (ascii 'a')
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13/opi b/rd/a1 0/subop/add b/rs/a1 30/imm12
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63/branch b/rs/a1 4/subop/< 6/rs/t1 print_hex_dgt:spin/off13
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13/opi b/rd/a1 0/subop/add b/rs/a1 27/imm12
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print_hex_dgt:spin:
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# spin if FIFO is full (thr_emtpy = UART+5 & 0x20)
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03/load 7/rd/t2 4/width/bu a/rs/a0 5/imm12
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13/opi 7/rd/t2 7/subop/and 7/rs/t2 20/imm12
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63/branch 0/subop/== 7/rs/t2 0/rs/x0 print_hex_dgt:spin/off13
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# print char
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23/store 2/width/w a/rs/a0 0/off12 b/rs/a1
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# return
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67/jalr 0/rd/x0 0/subop 1/rs/ra 0/off12
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== data 0x80500000
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E_MAGIC:
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# "Invalid DTB magic!\n\0"
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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
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S_TOTALSZ:
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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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151 |
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