gdb和strncmp，寄存器的值是否存儲？

下面是我的代碼（test.c的）：gdb和strncmp，寄存器的值是否存儲？

#include <stdio.h> 
#include <string.h> 

int main(int argc, char **argv) { 

char passwd[] = "pass"; 

if (argc < 2) { 
     printf("usage: %s <given-password>\n", argv[0]); 
     return 0; 
} 

if (!strncmp(passwd, argv[1],4)) { 
     printf("Green light!\n"); 
     return 1; 
} 

printf("Red light!\n"); 
return 0; 
}

我使用編譯：

gcc -o test test.c 

    And I started debugger: `gdb ./test` 
    (gdb) disassemble main 
    Dump of assembler code for function main: 
    0x08048404 <main+0>: lea 0x4(%esp),%ecx 
    ...... 
    0x08048456 <main+82>: mov 0x4(%edx),%eax 
    0x08048459 <main+85>: add $0x4,%eax 
    0x0804845c <main+88>: mov (%eax),%eax 
    0x0804845e <main+90>: movl $0x4,0x8(%esp) 
    0x08048466 <main+98>: mov %eax,0x4(%esp) 
    0x0804846a <main+102>: lea -0x9(%ebp),%eax 
    0x0804846d <main+105>: mov %eax,(%esp) 
    0x08048470 <main+108>: call 0x8048318 <[email protected]> 
    0x08048475 <main+113>: test %eax,%eax 
    0x08048477 <main+115>: jne 0x804848e <main+138> 
    0x08048479 <main+117>: movl $0x804859c,(%esp) 
    0x08048480 <main+124>: call 0x8048308 <[email protected]> 
    0x08048485 <main+129>: movl $0x1,-0x18(%ebp) 
........... 
    0x080484a8 <main+164>: pop %ebp 
    0x080484a9 <main+165>: lea -0x4(%ecx),%esp 
    0x080484ac <main+168>: ret 
    End of assembler dump.

我在主+ 108和運行PROG設置斷點！

(gdb) break *main+108 
    Breakpoint 1 at 0x8048470 
    (gdb) run [email protected] 
    Starting program: /etc/hien/test [email protected] 

    Breakpoint 1, 0x08048470 in main() 
    eax   0xbfffe9ff  -1073747457 
    ecx   0xbfffea20  -1073747424 
    edx   0xbfffea20  -1073747424 
    ebx   0xaebff4 11452404 
    esp   0xbfffe9e0  0xbfffe9e0 
    ebp   0xbfffea08  0xbfffea08 
    esi   0x994ca0 10046624 
    edi   0x0  0 
    eip   0x8048470  0x8048470 <main+108> 
    eflags   0x282 [ SF IF ] 
    cs    0x73  115 
    ss    0x7b  123 
    ds    0x7b  123 
    es    0x7b  123 
    fs    0x0  0 
    gs    0x33  51 
    (gdb) x/s $eax 
    0xbfffe9ff:  "pass" 
    (gdb) x/s $ecx 
    0xbfffea20:  "\002" 
    (gdb)

哪個寄存器可以顯示「argv [1]」的值？請幫幫我！謝謝！

來源

2010-08-29 Mr.Hien

是否有某些原因需要註冊（可能不在註冊表中）？用'-g'選項編譯並在gdb中發佈「print argv [1]'是不夠的）？ – nos 2010-08-29 11:57:51

如果沒有使用-g選項，argv [1]的值會存儲在哪？ – 2010-08-29 12:04:16

調用約定應該是所有參數都被推送到堆棧。所以請嘗試

(gdb) x/s *(0 + (void**)$esp) 
# should show "pass" 
(gdb) x/s *(1 + (void**)$esp) 
# should show argv[1] 
(gdb) x/d *(2 + (void**)$esp) 
# should show 4

來源

2010-08-29 12:06:26 kennytm

非常好的答案！非常感謝！！ – 2010-08-29 12:10:04

gdb和strncmp，寄存器的值是否存儲？

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