diff options
Diffstat (limited to 'subx/ex4.subx')
| -rw-r--r-- | subx/ex4.subx | 27 |
1 files changed, 21 insertions, 6 deletions
diff --git a/subx/ex4.subx b/subx/ex4.subx index 378b1a35..f76f864e 100644 --- a/subx/ex4.subx +++ b/subx/ex4.subx @@ -1,15 +1,15 @@ ## read a character from stdin -== 0x08048054 # code segment, after leaving room for ELF header +== 0x08048074 # code segment, after leaving room for ELF header and segment headers # opcode ModR/M SIB displacement immediate # instruction mod, reg, Reg/Mem bits scale, index, base # 1-3 bytes 0/1 byte 0/1 byte 0/1/2/4 bytes 0/1/2/4 bytes -# 0: e_entry = 0x08048054 - ## read(1, x, 1) - # fd = 1 - bb 1/imm32 # copy 1 to EBX + + ## read(stdin, x, 1) + # fd = 0 (stdin) + bb 0/imm32 # copy 0 to EBX # set location to write to - b9 00 90 04 08 # copy 0x08040000 to ECX + b9 a7 90 04 08 # copy 0x080490a7 to ECX # size = 1 character ba 1/imm32 # copy 1 to EDX # syscall = read @@ -17,8 +17,23 @@ # call cd 128/imm8 # int 80h + ## write(stdout, x, 1) + # fd = 1 (stdout) + bb 1/imm32 # copy 1 to EBX + # set location to write to + b9 a7 90 04 08 # copy 0x080490a7 to ECX + # size = 1 character + ba 1/imm32 # copy 1 to EDX + # syscall = write + b8 4/imm32 # copy 3 to EAX + # call + cd 128/imm8 # int 80h + ## exit(EBX) b8 1/imm32 # copy 1 to EAX cd 128/imm8 # int 80h +== 0x080490a7 +00 00 00 00 # space for read() to write to + # vim:ft=subx:nowrap |