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Diffstat (limited to 'subx/examples/ex9.subx')
| -rw-r--r-- | subx/examples/ex9.subx | 61 |
1 files changed, 0 insertions, 61 deletions
diff --git a/subx/examples/ex9.subx b/subx/examples/ex9.subx deleted file mode 100644 index 9ea547f1..00000000 --- a/subx/examples/ex9.subx +++ /dev/null @@ -1,61 +0,0 @@ -# Example reading commandline arguments: compute length of first arg. -# -# To run: -# $ subx translate ex9.subx ex9 -# $ subx run ex9 abc de fghi -# Expected result: -# $ echo $? -# 3 # length of 'abc' -# -# At the start of a SubX program: -# argc: *ESP -# argv[0]: *(ESP+4) -# argv[1]: *(ESP+8) -# ... -# Locals start from ESP-4 downwards. - -== 0x08048054 # code segment, after leaving room for ELF header and segment headers -# instruction effective address operand displacement immediate -# op subop mod rm32 base index scale r32 -# 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes - # var s = argv[1] (EBX) - 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 3/r32/EBX 8/disp8 . # copy *(ESP+8) to EBX - # call ascii_length(EBX) - # prepare call - 55/push . . . . . . . . # push EBP - 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP - # push args - 53/push . . . . . . . . # push EBX - # call - e8/call . . . . . . ascii_length/disp32 - # discard args - 5a/pop . . . . . . . . # pop into EDX - # clean up after call - 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP - 5d/pop . . . . . . . . # pop to EBP - - # exit(EAX) - 89/copy 3/mod/direct 3/rm32/EBX . . . 0/r32/EAX . . # copy EAX to EBX - b8/copy . . . . . . . 1/imm32/exit # copy 1 to EAX - cd/syscall . . . . . . . 0x80/imm8 # int 80h - -ascii_length: # (s) - # initialize s (EDX) - 8b/copy 1/mod/*+disp8 4/rm32/sib 4/base/ESP 4/index/none 2/r32/EDX 4/disp8 # copy *(ESP+4) to EDX - # var result = 0 (EAX) - b8/copy . . . . . . . 0/imm32 # copy 1 to EAX -$al_loop: - # var c = *s (ECX) - 8a/copy 0/mod/* 2/rm32/EDX . . . 1/r32/ECX . . # copy byte at *EDX to lower byte of ECX - # if c == '\0' break - 81 7/subop/compare 3/mod/direct 1/rm32/ECX . . . . . 0/imm32 # compare ECX with 0 - 74/jump-if-zero . . . . . . . $al_ret/disp8 # jump if equal - # ++s - 81 0/subop/add 3/mod/direct 2/rm32/EDX . . . . . 1/imm32 # add 1 to EDX - # ++result - 81 0/subop/add 3/mod/direct 0/rm32/EAX . . . . . 1/imm32 # add 1 to EAX - # loop - eb/jump . . . . . . . $al_loop/disp8 # jump $al_loop -$al_ret: - # return (result in EAX) - c3/return |