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mu/subx/examples/ex7.subx

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4530 - create an apps/ directory
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## example showing file syscalls
# Create a file, open it for writing, write a character to it, close it, open
# it for reading, read a character from it, close it, delete it, and return
# the character read.
4456 - example with function calls: factorial I found a bug with multiply in the process; another case (after the swap of call/jump opcodes in 4453) where there's no point improving testing. Unit tests can only tell us if our instructions are internally consistent. Validating against a real machine has to be manual. I'm definitely feeling the pain of debugging machine code now, that's for sure. Going over an instruction trace, comparing the state of registers line by line.
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#
# To run:
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# $ subx translate ex8.subx ex8
# $ subx run ex8
4456 - example with function calls: factorial I found a bug with multiply in the process; another case (after the swap of call/jump opcodes in 4453) where there's no point improving testing. Unit tests can only tell us if our instructions are internally consistent. Validating against a real machine has to be manual. I'm definitely feeling the pain of debugging machine code now, that's for sure. Going over an instruction trace, comparing the state of registers line by line.
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# Expected result:
# $ echo $?
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# 97
4456 - example with function calls: factorial I found a bug with multiply in the process; another case (after the swap of call/jump opcodes in 4453) where there's no point improving testing. Unit tests can only tell us if our instructions are internally consistent. Validating against a real machine has to be manual. I'm definitely feeling the pain of debugging machine code now, that's for sure. Going over an instruction trace, comparing the state of registers line by line.
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4531 - automatically compute segment addresses
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== code
4467
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# instruction effective address operand displacement immediate
# op subop mod rm32 base index scale r32
# 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes
4456 - example with function calls: factorial I found a bug with multiply in the process; another case (after the swap of call/jump opcodes in 4453) where there's no point improving testing. Unit tests can only tell us if our instructions are internally consistent. Validating against a real machine has to be manual. I'm definitely feeling the pain of debugging machine code now, that's for sure. Going over an instruction trace, comparing the state of registers line by line.
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## creat(filename)
bb/copy . . . . . . . 0x08049131/imm32/fname # copy to EBX
b9/copy . . . . . . . 0x180/imm32/fixed-perms # copy 0 to ECX
b8/copy . . . . . . . 8/imm32/creat # copy 8 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
4456 - example with function calls: factorial I found a bug with multiply in the process; another case (after the swap of call/jump opcodes in 4453) where there's no point improving testing. Unit tests can only tell us if our instructions are internally consistent. Validating against a real machine has to be manual. I'm definitely feeling the pain of debugging machine code now, that's for sure. Going over an instruction trace, comparing the state of registers line by line.
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## fd = open(filename, O_WRONLY, 0)
bb/copy . . . . . . . 0x08049131/imm32/fname # copy to EBX
b9/copy . . . . . . . 1/imm32/wronly # copy 1 to ECX
ba/copy . . . . . . . 0x180/imm32/fixed-perms # copy 0 to EDX
b8/copy . . . . . . . 5/imm32/open # copy 5 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# save fd
bb/copy . . . . . . . 0x08049125/imm32/fd # copy to EBX
89/copy 0/mod/indirect 3/rm32/EBX 0/r32/EAX # copy EAX to *EBX
4456 - example with function calls: factorial I found a bug with multiply in the process; another case (after the swap of call/jump opcodes in 4453) where there's no point improving testing. Unit tests can only tell us if our instructions are internally consistent. Validating against a real machine has to be manual. I'm definitely feeling the pain of debugging machine code now, that's for sure. Going over an instruction trace, comparing the state of registers line by line.
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## write(fd, "a", 1)
# load fd
bb/copy . . . . . . . 0x08049125/imm32/fd # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b9/copy . . . . . . . 0x08049129/imm32/a # copy to ECX
ba/copy . . . . . . . 1/imm32/size # copy 1 to EDX
b8/copy . . . . . . . 4/imm32/write # copy 4 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
4456 - example with function calls: factorial I found a bug with multiply in the process; another case (after the swap of call/jump opcodes in 4453) where there's no point improving testing. Unit tests can only tell us if our instructions are internally consistent. Validating against a real machine has to be manual. I'm definitely feeling the pain of debugging machine code now, that's for sure. Going over an instruction trace, comparing the state of registers line by line.
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4530 - create an apps/ directory
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## close(fd)
# load fd
bb/copy . . . . . . . 0x08049125/imm32/fd # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b8/copy . . . . . . . 6/imm32/close # copy 6 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
## fd = open(filename, O_RDONLY, 0)
bb/copy . . . . . . . 0x08049131/imm32/fname # copy to EBX
b9/copy . . . . . . . 0/imm32/rdonly # copy 0 to ECX
ba/copy . . . . . . . 0x180/imm32/fixed-perms # copy 0 to EDX
b8/copy . . . . . . . 5/imm32/open # copy 5 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
# save fd
bb/copy . . . . . . . 0x08049125/imm32/fd # copy to EBX
89/copy 0/mod/indirect 3/rm32/EBX 0/r32/EAX # copy EAX to *EBX
## read(fd, b, 1)
# load fd
bb/copy . . . . . . . 0x08049125/imm32/fd # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b9/copy . . . . . . . 0x0804912d/imm32/b # copy to ECX
ba/copy . . . . . . . 1/imm32/size # copy 1 to EDX
b8/copy . . . . . . . 3/imm32/read # copy 3 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
## close(fd)
# load fd
bb/copy . . . . . . . 0x08049125/imm32/fd # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b8/copy . . . . . . . 6/imm32/close # copy 8 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
## unlink(filename)
bb/copy . . . . . . . 0x08049131/imm32/fname # copy to EBX
b8/copy . . . . . . . 0xa/imm32/unlink # copy 8 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
## exit(b)
# load b
bb/copy . . . . . . . 0x0804912d/imm32/b # copy to EBX
8b/copy 0/mod/indirect 3/rm32/EBX 3/r32/EBX # copy *EBX to EBX
#
b8/copy . . . . . . . 1/imm32/exit # copy 1 to EAX
cd/syscall . . . . . . . 0x80/imm8 # int 80h
== 0x08049125 # data segment
00 00 00 00 # fd
61 00 00 00 # a: string to write to file: 'a'
00 00 00 00 # b: space for string read from file
2e 66 6f 6f 00 00 00 00 # filename: '.foo'
# vim:ft=subx:nowrap:tw&