## Building a libc offset database

Fetch all the configured libc versions and extract the symbol offsets.
It will not download anything twice, so you can also use it to update your
database:

    $ ./get

You can also add a custom libc to your database.

    $ ./add /usr/lib/libc-2.21.so

Find all the libc's in the database that have a given name at the given address.
Only the last 12 bits are checked, because randomization usually works on page
size level.

    $ ./find printf 260
    archive-glibc (id libc6_2.19-10ubuntu2_i386)

Find a libc from the leaked return address into __libc_start_main.

    $ ./find __libc_start_main_ret a83
    ubuntu-trusty-i386-libc6 (id libc6_2.19-0ubuntu6.6_i386)
    archive-eglibc (id libc6_2.19-0ubuntu6_i386)
    ubuntu-utopic-i386-libc6 (id libc6_2.19-10ubuntu2.3_i386)
    archive-glibc (id libc6_2.19-10ubuntu2_i386)
    archive-glibc (id libc6_2.19-15ubuntu2_i386)

Dump some useful offsets, given a libc ID. You can also provide your own names
to dump.

    $ ./dump libc6_2.19-0ubuntu6.6_i386
    offset___libc_start_main_ret = 0x19a83
    offset_system = 0x00040190
    offset_dup2 = 0x000db590
    offset_recv = 0x000ed2d0
    offset_str_bin_sh = 0x160a24