How to rebase IDA to match GDB

Question

I would like to debug my elf file on linux using GDB and follow the disassembly in IDA, is this possible? And if it is how would I rebase IDA to match with GDB?

Thanks!

Answer 1

If you are trying to rebase an elf, you could do info proc mappings. This will show you all of the mapped addresses. (This could also be viewed by doing cat /proc/<pid>/map)

Then just rebase your IDA via EDIT->Segments->Rebase program and select Image Base from the radio buttons.

Ex:

(gdb) info proc mappings 
process 12383
Mapped address spaces:
    Start Addr   End Addr       Size     Offset objfile
     0x8048000  0x8049000     0x1000          0      /home/user/my_elf
     0x8049000  0x804a000     0x1000          0      /home/user/my_elf
     0x804a000  0x804b000     0x1000     0x1000      /home/user/my_elf
    0xb7e73000 0xb7e74000     0x1000          0
    0xb7e74000 0xb7fbd000   0x149000          0     /lib/i386-linux-gnu/libc-2.13.so
    0xb7fbd000 0xb7fbe000     0x1000   0x149000     /lib/i386-linux-gnu/libc-2.13.so
    0xb7fbe000 0xb7fc0000     0x2000   0x149000     /lib/i386-linux-gnu/libc-2.13.so
    0xb7fc0000 0xb7fc1000     0x1000   0x14b000     /lib/i386-linux-gnu/libc-2.13.so
    0xb7fc1000 0xb7fc4000     0x3000          0
    0xb7fdf000 0xb7fe1000     0x2000          0
    0xb7fe1000 0xb7fe2000     0x1000          0           [vdso]
    0xb7fe2000 0xb7ffe000    0x1c000          0     /lib/i386-linux-gnu/ld-2.13.so
    0xb7ffe000 0xb7fff000     0x1000    0x1b000     /lib/i386-linux-gnu/ld-2.13.so
    0xb7fff000 0xb8000000     0x1000    0x1c000     /lib/i386-linux-gnu/ld-2.13.so
    0xbffdf000 0xc0000000    0x21000          0           [stack]

If I would be looking at the elf in IDA i would use 0x8048000 for the base. If I would be looking at libc-2.13.so I would use 0xb7e74000.

Hope that helps.