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ASSEMBLER M. Antczak, S. Wąsik

ASSEMBLER M. Antczak, S. Wąsik. Debug session:. starting of the example.exe program debugging process debug example.exe. checking the value that is stored in the AX register - rax AX 0000 :. setting the value that will be stored in the AX register - rax AX 0000 : 1.

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ASSEMBLER M. Antczak, S. Wąsik

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  1. ASSEMBLER M. Antczak, S. Wąsik

  2. Debug session: • starting of the example.exe program debugging process • debug example.exe • checking the value that is stored in the AX register • -rax • AX 0000 • : • setting the value that will be stored in the AX register • -rax • AX 0000 • : 1 • program execution (go) • -g • debug session termination (quit) • -q

  3. DecDig 0 1 2 3 4 5 6 7 8 9 Base=10 HexDig 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 A  10 B  11 C  12 D  13 E  14 F  15 Base=16 HexDig Negation 0 F 1 E 2 D 3 C 4 B 5 A 6 9 7 8 8 7 9 6 A  5 B  4 C  3 D  2 E  1 F  0 Hexadecimal arithmetic: 1 1  1 A  10 4  4 ---------- 15 – F 8  8 C  12 ---------- 20 – 16 = 4 negation 5F4 4 F4 2 + 16 7 -------- 11 - B 7 + 16 8 -------- 15 - F 2 3 BF F 3BF

  4. Basic assembler instructions set: ADD AX, BX  AX = AX + BX SUB AX, BX  AX = AX - BX NEG AX  AX = (-1)*AX INC AX  AX = AX + 1 DEC AX  AX = AX – 1 MOV AX, BX  AX = BX IMUL BX  AX = AX * BX IDIV BX  AX = AX / BX and DX = AX % BX while(a==b) { instrs } Assume: a  AX; b  BX loop: instrs finish: int 3 Assume: a  AX; b  BX loop: CMP AX, BX instrs finish: int 3 Assume: a  AX; b  BX loop: CMP AX, BX instrs JMP loop finish: int 3 Assume: a  AX; b  BX loop: CMP AX, BX JNE finish instrs JMP loop finish: int 3 • Jump instructions – used to jump to the memory place identified by particular address (e.g. code block label) : • direct jump (without condition) • JMP loop • conditional jumps (when the condition is fulfilled) • CMP AX, BX ; flags setting • JNE finish • Differentpossibilities: JNE  != ; JE  == ; • JG  > ; JL  < ;JLE, JNG  <= ; JGE, JNL  >= ; Assume: a  AX; b  BX ifCond: instr1 elseCond: instr2 finish: int 3 Assume: a  AX; b  BX ifCond: CMP AX, BX instr1 elseCond: instr2 finish: int 3 Assume: a  AX; b  BX ifCond: CMP AX, BX JL elseCond instr1 elseCond: instr2 finish: int 3 Assume: a  AX; b  BX ifCond: CMP AX, BX JL elseCond instr1 JMP finish elseCond: instr2 finish: int 3 if(a>=b) instr1 else instr2

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