Simple GDB case

to be added...

 

gdb a.out

 

[Inferior 1 (process 9718) exited with code 05]

(gdb) list

Line number 15 out of range; t.c has 14 lines.

(gdb) list 1

1       #include

2       char foo(char *s)

3       {

4         char *c=s;

5         return *(c+2);

6       }

7       int main()

8       {

9         char arr[5]="abc\n";

10        char b=foo(arr);

(gdb) 

11        printf("%c\n",b);

12        printf("%s\n",arr);

13

14      }

(gdb) disass /m

Dump of assembler code for function main:

8       {

   0x08048449 <+0>:     push   �p

   0x0804844a <+1>:     mov    %esp,�p

   0x0804844c <+3>:     and    $0xfffffff0,%esp

   0x0804844f <+6>:     sub    $0x20,%esp

 

9         char arr[5]="abc\n";

   0x08048452 <+9>:     movl   $0xa636261,0x1a(%esp)

   0x0804845a <+17>:    movb   $0x0,0x1e(%esp)

 

10        char b=foo(arr);

=> 0x0804845f <+22>:    lea    0x1a(%esp),�x //eip 

   0x08048463 <+26>:    mov    �x,(%esp)

   0x08048466 <+29>:    call   0x8048434

   0x0804846b <+34>:    mov    %al,0x1f(%esp)

(gdb) info registers esp

esp            0xbfffefb0       0xbfffefb0

#another shell

johv@linux-8f1f:~> echo $((0xbfffefb0+0x1a))

3221221322

 

johv@linux-8f1f:~> echo 'obase=16;base=10;3221221322' | bc

BFFFEFCA

(gdb) x /s 0xbfffefca

0xbfffefca:      "abc\n" //find the "abc\n"

(gdb) 

 

gdb) help catch

Set catchpoints to catch events.

 

List of catch subcommands:

 

catch assert -- Catch failed Ada assertions

catch catch -- Catch an exception

catch exception -- Catch Ada exceptions

catch exec -- Catch calls to exec

catch fork -- Catch calls to fork

catch syscall -- Catch system calls by their names and/or numbers

catch throw -- Catch an exception

catch vfork -- Catch calls to vfork

 

Type "help catch" followed by catch subcommand name for 

full documentation.

Type "apropos word" to search for commands related to "word".

Command name abbreviations are allowed if unambiguous.

(gdb) 

(gdb) info breakpoints 

Num     Type           Disp Enb Address    What

7       breakpoint     keep y   0x08048440 in foo 

                                           at t.c:5

        breakpoint already hit 1 time

8       catchpoint     keep y              syscall "" 

9       breakpoint     keep y    exception catch

10      catchpoint     keep y              fork

(gdb) disable breakpoints 7

(gdb) 

condition