5,050 users solved

Description

Can you figure out what is in the eax register? Put your answer in the picoCTF flag format: picoCTF{n} where n is the contents of the eax register in the decimal number base. If the answer was 0x11 your flag would be picoCTF{17}.Download the assembly dump here.

Hints

• Don't tell anyone I told you this, but you can solve this problem without understanding the compare/jump relationship.
• Of course, if you're really good, you'll only need one attempt to solve this problem.

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01. 解题过程

<+0>:     endbr64 
<+4>:     push   rbp
<+5>:     mov    rbp,rsp
<+8>:     mov    DWORD PTR [rbp-0x14],edi
<+11>:    mov    QWORD PTR [rbp-0x20],rsi
<+15>:    mov    DWORD PTR [rbp-0x4],0x9fe1a ;654,874
<+22>:    cmp    DWORD PTR [rbp-0x4],0x2710 ; 654,874 > 10,000 
<+29>:    jle    0x55555555514e <main+37>
<+31>:    sub    DWORD PTR [rbp-0x4],0x65 ; 9 FDB5> 654,773
<+35>:    jmp    0x555555555152 <main+41>
<+37>:    add    DWORD PTR [rbp-0x4],0x65
<+41>:    mov    eax,DWORD PTR [rbp-0x4]
<+44>:    pop    rbp
<+45>:    ret

解题过程在注释里，不难啊这题，cmp，具体知识点在汇编手册里