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< title > Mu - linux/ex12.subx< / title >
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< a href = 'https://github.com/akkartik/mu/blob/main/linux/ex12.subx' > https://github.com/akkartik/mu/blob/main/linux/ex12.subx< / a >
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< pre id = 'vimCodeElement' >
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< span id = "L1" class = "LineNr" > 1 < / span > < span class = "subxComment" > # Example showing mmap syscall.< / span >
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< span id = "L2" class = "LineNr" > 2 < / span > < span class = "subxComment" > # Create a new segment using mmap, save the address, write to it.< / span >
< span id = "L3" class = "LineNr" > 3 < / span > < span class = "subxComment" > #< / span >
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< span id = "L4" class = "LineNr" > 4 < / span > < span class = "subxComment" > # To run:< / span >
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< span id = "L5" class = "LineNr" > 5 < / span > < span class = "subxComment" > # $ bootstrap/bootstrap translate ex12.subx -o ex12< / span >
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< span id = "L6" class = "LineNr" > 6 < / span > < span class = "subxComment" > # $ bootstrap/bootstrap run ex12< / span >
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< span id = "L7" class = "LineNr" > 7 < / span > < span class = "subxComment" > # You shouldn't get a segmentation fault.< / span >
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< span id = "L8" class = "LineNr" > 8 < / span >
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< span id = "L9" class = "LineNr" > 9 < / span > == code
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< span id = "L10" class = "LineNr" > 10 < / span > < span class = "subxComment" > # instruction effective address register displacement immediate< / span >
< span id = "L11" class = "LineNr" > 11 < / span > < span class = "subxS1Comment" > # . op subop mod rm32 base index scale r32< / span >
< span id = "L12" class = "LineNr" > 12 < / span > < span class = "subxS1Comment" > # . 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< / span >
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< span id = "L13" class = "LineNr" > 13 < / span >
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< span id = "L14" class = "LineNr" > 14 < / span > < span class = "SpecialChar" > Entry< / span > :
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< span id = "L15" class = "LineNr" > 15 < / span > < span class = "subxComment" > # mmap(Mmap-new-segment-> len)< / span >
< span id = "L16" class = "LineNr" > 16 < / span > bb/copy-to-ebx < span class = "SpecialChar" > < a href = 'ex12.subx.html#L29' > Mmap-new-segment< / a > < / span > /imm32
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< span id = "L17" class = "LineNr" > 17 < / span > e8/call < a href = '000init.subx.html#L71' > syscall_mmap< / a > /disp32
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< span id = "L18" class = "LineNr" > 18 < / span >
< span id = "L19" class = "LineNr" > 19 < / span > < span class = "subxComment" > # write to *eax to check that we have access to the newly-allocated segment< / span >
< span id = "L20" class = "LineNr" > 20 < / span > c7 0/subop/copy 0/mod/direct 0/rm32/eax < span class = "Normal" > . < / span > < span class = "Normal" > . < / span > < span class = "Normal" > . < / span > < span class = "Normal" > . < / span > < span class = "Normal" > . < / span > 0x34/imm32 < span class = "subxComment" > # copy to *eax< / span >
< span id = "L21" class = "LineNr" > 21 < / span >
< span id = "L22" class = "LineNr" > 22 < / span > < span class = "subxComment" > # exit(eax)< / span >
< span id = "L23" class = "LineNr" > 23 < / span > 89/copy 3/mod/direct 3/rm32/ebx < span class = "Normal" > . < / span > < span class = "Normal" > . < / span > < span class = "Normal" > . < / span > 0/r32/eax < span class = "Normal" > . < / span > < span class = "Normal" > . < / span > < span class = "subxComment" > # copy eax to ebx< / span >
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< span id = "L24" class = "LineNr" > 24 < / span > e8/call < a href = '000init.subx.html#L18' > syscall_exit< / a > /disp32
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< span id = "L25" class = "LineNr" > 25 < / span >
< span id = "L26" class = "LineNr" > 26 < / span > == data
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< span id = "L27" class = "LineNr" > 27 < / span >
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< span id = "L28" class = "LineNr" > 28 < / span > < span class = "subxComment" > # various constants used here were found in the Linux sources (search for file mman-common.h)< / span >
< span id = "L29" class = "LineNr" > 29 < / span > < span class = "SpecialChar" > Mmap-new-segment< / span > : < span class = "subxComment" > # type mmap_arg_struct< / span >
< span id = "L30" class = "LineNr" > 30 < / span > < span class = "subxComment" > # addr< / span >
< span id = "L31" class = "LineNr" > 31 < / span > 0/imm32
< span id = "L32" class = "LineNr" > 32 < / span > < span class = "subxComment" > # len< / span >
< span id = "L33" class = "LineNr" > 33 < / span > 0x100/imm32
< span id = "L34" class = "LineNr" > 34 < / span > < span class = "subxComment" > # protection flags< / span >
< span id = "L35" class = "LineNr" > 35 < / span > 3/imm32 < span class = "subxComment" > # PROT_READ | PROT_WRITE< / span >
< span id = "L36" class = "LineNr" > 36 < / span > < span class = "subxComment" > # sharing flags< / span >
< span id = "L37" class = "LineNr" > 37 < / span > 0x22/imm32 < span class = "subxComment" > # MAP_PRIVATE | MAP_ANONYMOUS< / span >
< span id = "L38" class = "LineNr" > 38 < / span > < span class = "subxComment" > # fd< / span >
< span id = "L39" class = "LineNr" > 39 < / span > -1/imm32 < span class = "subxComment" > # since MAP_ANONYMOUS is specified< / span >
< span id = "L40" class = "LineNr" > 40 < / span > < span class = "subxComment" > # offset< / span >
< span id = "L41" class = "LineNr" > 41 < / span > 0/imm32 < span class = "subxComment" > # since MAP_ANONYMOUS is specified< / span >
< span id = "L42" class = "LineNr" > 42 < / span >
< span id = "L43" class = "LineNr" > 43 < / span > < span class = "subxS2Comment" > # . . vim: nowrap:textwidth=0< / span >
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