diff options
Diffstat (limited to 'subx/examples/ex4.subx')
| -rw-r--r-- | subx/examples/ex4.subx | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/subx/examples/ex4.subx b/subx/examples/ex4.subx new file mode 100644 index 00000000..cd7003d3 --- /dev/null +++ b/subx/examples/ex4.subx @@ -0,0 +1,41 @@ +## read a character from stdin, save it to a global, write it to stdout +# +# To run: +# $ subx translate ex4.subx ex4 +# $ subx run ex4 + +== 0x08048074 # 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 + + ## read(stdin, x, 1) + # fd = 0 (stdin) + bb/copy 0/imm32 # copy 0 to EBX + # initialize x (location to write result to) + b9/copy 0x080490a7/imm32 # copy 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) + b9/copy 0x080490a7/imm32 # copy 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 + +== 0x080490a7 # data segment +00 00 00 00 # space for read() to write to + +# vim:ft=subx:nowrap |