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Diffstat (limited to 'subx/examples/ex5.subx')
| -rw-r--r-- | subx/examples/ex5.subx | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/subx/examples/ex5.subx b/subx/examples/ex5.subx new file mode 100644 index 00000000..e4a2db81 --- /dev/null +++ b/subx/examples/ex5.subx @@ -0,0 +1,45 @@ +## read a character from stdin, save it to a local on the stack, write it to stdout +# +# To run: +# $ subx translate ex5.subx ex5 +# $ subx run ex5 + +== 0x08048054 # code segment, after leaving room for ELF header and segment headers +# 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 + +## function main + # prolog + 55/push # push EBP + 89/copy 3/mod/direct 5/rm32/EBP 4/r32/ESP # copy ESP to EBP + # allocate x on the stack + 81 5/subop/subtract 3/mod/direct 4/rm32/ESP 4/imm32 # subtract 4 bytes from ESP + + ## read(stdin, x, 1) + # fd = 0 (stdin) + bb/copy 0/imm32 # copy 0 to EBX + # initialize x (location to write result to) + 89/copy 3/mod/direct 1/rm32/ECX 5/r32/EBP # copy EBP to ECX + # size = 1 character + ba/copy 1/imm32 # copy 1 to EDX + # read(fd, x, size) + b8/copy 3/imm32 # copy 3 to EAX + cd/syscall 0x80/imm8 # int 80h + + ## write(stdout, x, 1) + # fd = 1 (stdout) + bb/copy 1/imm32 # copy 1 to EBX + # initialize x (location to read from) + 89/copy 3/mod/direct 1/rm32/ECX 5/r32/EBP # copy EBP to ECX + # size = 1 character + ba/copy 1/imm32 # copy 1 to EDX + # write(fd, x, size) + b8/copy 4/imm32 # copy 4 to EAX + cd/syscall 0x80/imm8 # int 80h + + ## exit(EBX) + b8/copy 1/imm32 # copy 1 to EAX + cd/syscall 0x80/imm8 # int 80h + +# vim:ft=subx:nowrap |