41 lines
1.6 KiB
Plaintext
41 lines
1.6 KiB
Plaintext
# Read a character from stdin, save it to a local on the stack, write it to stdout.
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#
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# To run:
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# $ bootstrap/bootstrap translate ex5.subx -o ex5
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# $ bootstrap/bootstrap run ex5
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== code
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# instruction effective address register displacement immediate
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# . op subop mod rm32 base index scale r32
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# . 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
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Entry:
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# allocate x on the stack
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81 5/subop/subtract 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # subtract from esp
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# read(stdin, x, 1)
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# . fd = 0 (stdin)
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bb/copy-to-ebx 0/imm32
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# . data = x (location to write result to)
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8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/esp 4/index/none 1/r32/ecx 4/disp8 . # copy esp+4 to ecx
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# . size = 1 character
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ba/copy-to-edx 1/imm32
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# . syscall
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e8/call syscall_read/disp32
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# syscall(write, stdout, x, 1)
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# . fd = 1 (stdout)
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bb/copy-to-ebx 1/imm32
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# . data = x (location to read from)
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8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/esp 4/index/none 1/r32/ecx 4/disp8 . # copy esp+4 to ecx
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# . size = 1 character
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ba/copy-to-edx 1/imm32
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# . syscall
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e8/call syscall_write/disp32
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# exit(ebx)
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e8/call syscall_exit/disp32
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# . . vim:nowrap:textwidth=0
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