220 lines
9.8 KiB
Markdown
220 lines
9.8 KiB
Markdown
# AMD64 NASM Cheatsheet
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## Sizes
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| Size (bits) | Size (bytes) | Name | NASM Mnemonics / Directives |
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|-------------|--------------|--------|----------------------------------------|
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| 8 | 1 | byte | DB, RESB |
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| 16 | 2 | word | DW, RESW |
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| 32 | 4 | dword | DD, RESD |
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| 64 | 8 | qword | DQ, RESQ |
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| 80 | 10 | tword | DT, REST |
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| 128 | 16 | oword | DO, RESO, DDQ, RESDQ |
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| 256 | 32 | yword | DY, RESY |
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| 512 | 64 | zword | DZ, RESZ |
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## Registers
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| Register | Usage | Preserved Across Function Calls |
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|------------------|-------------------------------------------------------------------------------------------|-------------------------------|
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| %rax | Temporary register; with variable arguments passes information about the number of vector registers used; 1st return register | No |
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| %rbx | Callee-saved register; optionally used as base pointer | Yes |
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| %rcx | Used to pass 4th integer argument to functions | No |
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| %rdx | Used to pass 3rd argument to functions; 2nd return register | No |
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| %rsp | Stack pointer | Yes |
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| %rbp | Callee-saved register; optionally used as frame pointer | Yes |
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| %rsi | Used to pass 2nd argument to functions | No |
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| %rdi | Used to pass 1st argument to functions | No |
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| %r8 | Used to pass 5th argument to functions | No |
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| %r9 | Used to pass 6th argument to functions | No |
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| %r10 | Temporary register, used for passing a function’s static chain pointer | No |
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| %r11 | Temporary register | No |
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| %r12–%r15 | Callee-saved registers | Yes |
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| %xmm0–%xmm1 | Used to pass and return floating point arguments | No |
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| %xmm2–%xmm7 | Used to pass floating point arguments | No |
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| %xmm8–%xmm15 | Temporary registers | No |
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| %mmx0–%mmx7 | Temporary registers | No |
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| %st0, %st1 | Temporary registers; used to return long double arguments | No |
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| %st2–%st7 | Temporary registers | No |
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| %fs | Reserved for system (as thread specific data register) | No |
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| mxcsr | SSE2 control and status word | Partial |
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| x87 SW | x87 status word | No |
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| x87 CW | x87 control word | Yes |
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## Instructions
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### Conditional JUMP Instructions
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<table class="standard">
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<thead>
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<tr>
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<th> Instruction </th>
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<th> Description </th>
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<th> signed-ness </th>
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<th> Flags </th>
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<th> short <br> jump <br> opcodes </th>
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<th> near <br> jump <br> opcodes </th>
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</tr>
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</thead>
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<tr>
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<td class="insn"> JO </td>
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<td class="descr"> Jump if overflow </td>
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<td class="signed"> </td>
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<td class="flags"> OF = 1 </td>
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<td class="hex"> 70 </td>
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<td class="hex"> 0F 80 </td> </tr>
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<tr>
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<td class="insn"> JNO </td>
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<td class="descr"> Jump if not overflow </td>
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<td class="signed"> </td>
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<td class="flags"> OF = 0 </td>
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<td class="hex"> 71 </td>
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<td class="hex"> 0F 81 </td> </tr>
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<tr>
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<td class="insn"> JS </td>
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<td class="descr"> Jump if sign </td>
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<td class="signed"> </td>
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<td class="flags"> SF = 1 </td>
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<td class="hex"> 78 </td>
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<td class="hex"> 0F 88 </td> </tr>
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<tr>
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<td class="insn"> JNS </td>
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<td class="descr"> Jump if not sign </td>
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<td class="signed"> </td>
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<td class="flags"> SF = 0 </td>
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<td class="hex"> 79 </td>
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<td class="hex"> 0F 89 </td> </tr>
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<tr>
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<td class="insn"> JE <br> JZ </td>
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<td class="descr"> Jump if equal
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<br> Jump if zero </td>
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<td class="signed"> </td>
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<td class="flags"> ZF = 1 </td>
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<td class="hex"> 74 </td>
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<td class="hex"> 0F 84 </td> </tr>
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<tr>
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<td class="insn"> JNE
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<br> JNZ </td>
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<td class="descr"> Jump if not equal
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<br> Jump if not zero </td>
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<td class="signed"> </td>
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<td class="flags"> ZF = 0 </td>
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<td class="hex"> 75 </td>
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<td class="hex"> 0F 85 </td> </tr>
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<tr>
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<td class="insn"> JB
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<br> JNAE
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<br> JC </td>
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<td class="descr"> Jump if below
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<br> Jump if not above or equal
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<br> Jump if carry </td>
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<td class="signed"> unsigned </td>
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<td class="flags"> CF = 1 </td>
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<td class="hex"> 72 </td>
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<td class="hex"> 0F 82 </td> </tr>
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<tr>
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<td class="insn"> JNB
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<br> JAE
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<br> JNC </td>
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<td class="descr"> Jump if not below
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<br> Jump if above or equal
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<br> Jump if not carry </td>
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<td class="signed">unsigned </td>
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<td class="flags">CF = 0 </td>
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<td class="hex">73 </td>
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<td class="hex">0F 83 </td> </tr>
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<tr>
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<td class="insn"> JBE
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<br> JNA </td>
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<td class="descr"> Jump if below or equal
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<br> Jump if not above </td>
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<td class="signed"> unsigned </td>
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<td class="flags"> CF = 1 or ZF = 1 </td>
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<td class="hex"> 76 </td>
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<td class="hex"> 0F 86 </td> </tr>
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<tr>
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<td class="insn"> JA
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<br> JNBE </td>
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<td class="descr"> Jump if above
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<br> Jump if not below or equal </td>
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<td class="signed"> unsigned </td>
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<td class="flags"> CF = 0 and ZF = 0 </td>
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<td class="hex"> 77 </td>
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<td class="hex"> 0F 87 </td> </tr>
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<tr>
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<td class="insn"> JL
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<br> JNGE </td>
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<td class="descr"> Jump if less
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<br> Jump if not greater or equal </td>
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<td class="signed"> signed </td>
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<td class="flags"> SF <> OF </td>
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<td class="hex"> 7C </td>
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<td class="hex"> 0F 8C </td> </tr>
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<tr>
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<td class="insn"> JGE
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<br> JNL </td>
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<td class="descr"> Jump if greater or equal
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<br> Jump if not less </td>
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<td class="signed"> signed </td>
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<td class="flags"> SF = OF </td>
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<td class="hex"> 7D </td>
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<td class="hex"> 0F 8D </td> </tr>
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<tr>
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<td class="insn"> JLE
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<br> JNG </td>
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<td class="descr"> Jump if less or equal
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<br> Jump if not greater </td>
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<td class="signed"> signed </td>
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<td class="flags"> ZF = 1 or SF <> OF </td>
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<td class="hex"> 7E </td>
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<td class="hex"> 0F 8E </td> </tr>
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<tr>
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<td class="insn"> JG
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<br> JNLE </td>
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<td class="descr"> Jump if greater
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<br> Jump if not less or equal </td>
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<td class="signed"> signed </td>
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<td class="flags"> ZF = 0 and SF = OF </td>
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<td class="hex"> 7F </td>
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<td class="hex"> 0F 8F </td> </tr>
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<tr>
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<td class="insn"> JP
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<br> JPE </td>
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<td class="descr"> Jump if parity
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<br> Jump if parity even </td>
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<td class="signed"> </td>
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<td class="flags"> PF = 1 </td>
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<td class="hex"> 7A </td>
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<td class="hex"> 0F 8A </td> </tr>
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<tr>
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<td class="insn"> JNP
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<br> JPO </td>
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<td class="descr"> Jump if not parity
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<br> Jump if parity odd </td>
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<td class="signed"> </td>
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<td class="flags"> PF = 0 </td>
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<td class="hex"> 7B </td>
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<td class="hex"> 0F 8B </td> </tr>
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<tr>
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<td class="insn"> JCXZ
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<br> JECXZ </td>
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<td class="descr"> Jump if %CX register is 0
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<br> Jump if %ECX register is 0 </td>
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<td class="signed"> </td>
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<td class="flags"> %CX = 0
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<br> %ECX = 0 </td>
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<td class="hex"> E3 </td>
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<td class="hex"> </td> </tr>
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</table>
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Source: [Intel x86 JUMP quick reference](http://unixwiz.net/techtips/x86-jumps.html)
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## additional resources
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[Linux syscalls](https://blog.rchapman.org/posts/Linux_System_Call_Table_for_x86_64/)
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[System V AMD64 ABI](https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf)
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[Getting arguments](https://github.com/tonyOreglia/argument-counter/wiki/x86-64-Linux-Assembly-Part-1:-Printing-Command-Line-Arguments)
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[x86 and amd64 instruction reference](https://www.felixcloutier.com/x86/) |