I try to read the values from memory with using PTRACE_PEEKDATA.
To find the memory address of specific line I am using with objdump -
objdump --dwarf=decodedline ./exe_filename
and got the output:
test: file format elf64-x86-64
Contents of the .debug_line section:
test.c:
File name Line number Starting address View Stmt
test.c 23 0x1369 x
test.c 23 0x1385 x
test.c 28 0x1394 x
test.c 29 0x139d x
test.c 30 0x13c5 x
test.c 35 0x13cf x
test.c 36 0x13da x
test.c 37 0x13e3 x
test.c 38 0x13f2 x
test.c 42 0x13fc x
test.c 44 0x1405 x
test.c 44 0x1423 x
test.c 45 0x1429 x
test.c 46 0x1438 x
test.c 50 0x1442 x
test.c 50 0x144d x
test.c 50 0x1458 x
test.c 51 0x1466 x
test.c 52 0x1475 x
test.c 57 0x147f x
test.c 57 0x149b x
test.c 58 0x14a0 x
test.c 59 0x14af x
test.c 63 0x14b9 x
test.c 64 0x14df x
test.c 73 0x14fa x
test.c 73 0x1505 x
test.c 73 0x1508 x
test.c 73 0x1513 x
test.c 74 0x1528 x
test.c 75 0x1548 x
test.c 76 0x1556 x
test.c 77 0x1581 x
test.c 78 0x15a3 x
test.c 79 0x15ae x
test.c 79 0x15b2 x
test.c 79 0x15bc x
test.c 79 0x15db x
test.c 80 0x15e2 x
test.c 81 0x15ec x
test.c 82 0x15fb x
test.c 84 0x1605 x
test.c 84 0x1609 x
test.c 87 0x1635 x
test.c 87 0x163e x
test.c 88 0x1647 x
test.c 88 0x164e x
test.c 88 0x1652 x
test.c 88 0x165c x
test.c 91 0x167c x
test.c 91 0x169f x
test.c 92 0x16a6 x
test.c 97 0x16cb x
test.c 97 0x16ec x
test.c 98 0x16f2 x
test.c 99 0x1701 x
test.c 103 0x170b x
test.c 104 0x171a x
test.c 104 0x1723 x
test.c 105 0x1728 x
test.c 105 0x1731 x
test.c 108 0x1754 x
test.c 112 0x1763 x
test.c 113 0x1789 x
test.c 120 0x17a4 x
test.c 121 0x17c9 x
test.c 122 0x17d5 x
test.c 125 0x17fb x
test.c 127 0x181c x
test.c 128 0x182b x
test.c 128 0x1834 x
test.c 129 0x1838 x
test.c 132 0x1849 x
test.c 137 0x1858 x
Now, I use:
unsigned long long int addr = 0x13cf;
unsigned long long int orig_data = ptrace(PTRACE_PEEKTEXT, child_pid, (void *)addr, 0);
if (orig_data == -1) {
perror("ptrace2");
exit(EXIT_FAILURE);
}
and got the error: ptrace2: Input/output error
I thought maybe objdump return the offset, so I searched the base address to use the formula:
base address + offset = virtual address
I used with Detect It Easy and found that base address is 0. So, I don't know why it's now working.
I tried also to get the memory address from gdb debugger while run:
Breakpoint 1, main (argc=3, argv=0x7fffffffe038) at /home/vboxuser/Documents/CreateDebugger/test.c:35
35 child_pid = fork();
(gdb) disas main
Dump of assembler code for function main:
0x0000555555555369 <+0>: endbr64
0x000055555555536d <+4>: push %rbp
0x000055555555536e <+5>: mov %rsp,%rbp
0x0000555555555371 <+8>: sub $0x130,%rsp
0x0000555555555378 <+15>: mov %edi,-0x124(%rbp)
0x000055555555537e <+21>: mov %rsi,-0x130(%rbp)
0x0000555555555385 <+28>: mov %fs:0x28,%rax
0x000055555555538e <+37>: mov %rax,-0x8(%rbp)
0x0000555555555392 <+41>: xor %eax,%eax
0x0000555555555394 <+43>: cmpl $0x3,-0x124(%rbp)
0x000055555555539b <+50>: je 0x5555555553cf <main+102>
0x000055555555539d <+52>: mov -0x130(%rbp),%rax
0x00005555555553a4 <+59>: mov (%rax),%rdx
0x00005555555553a7 <+62>: mov 0x2c72(%rip),%rax
0x00005555555553ae <+69>: lea 0xc53(%rip),%rcx
0x00005555555553b5 <+76>: mov %rcx,%rsi
0x00005555555553b8 <+79>: mov %rax,%rdi
0x00005555555553bb <+82>: mov $0x0,%eax
0x00005555555553c0 <+87>: call 0x5555555551d0 <fprintf@plt>
0x00005555555553c5 <+92>: mov $0x1,%eax
0x00005555555553ca <+97>: jmp 0x55555555583e <main+1237>
=> 0x00005555555553cf <+102>: call 0x555555555270 <fork@plt>
0x00005555555553d4 <+107>: mov %eax,-0x11c(%rbp)
0x00005555555553da <+113>: cmpl $0xffffffff,-0x11c(%rbp)
0x00005555555553e1 <+120>: jne 0x5555555553fc <main+147>
0x00005555555553e3 <+122>: lea 0xc45(%rip),%rax
0x00005555555553ea <+129>: mov %rax,%rdi
0x00005555555553ed <+132>: call 0x555555555230 <perror@plt>
0x00005555555553f2 <+137>: mov $0x1,%eax
0x00005555555553f7 <+142>: jmp 0x55555555583e <main+1237>
0x00005555555553fc <+147>: cmpl $0x0,-0x11c(%rbp)
0x0000555555555403 <+154>: jne 0x55555555547f <main+278>
0x0000555555555405 <+156>: mov $0x0,%ecx
--Type <RET> for more, q to quit, c to continue without paging--
Also the addresses 0x00005555555553cf and 0x7fffffffe038 didn't work.
in PTRACE_PEEKTEXT, I need to put the virtual address of line from the source code? how to find him? can ASLR affect on the address memory or it's fixed? Or maybe the problem is in child_pid?
Please help, I am stuck a lot of time on the problem. Thanks for helps!
BTW, I using in virtual machine Ubuntu 22.04.
