Question

When executing ldd on a file, it returns a hex number in parentheses for every library it found.

For example:

root@server> ldd wpa_supplicant
        linux-gate.so.1 =>  (0xb779b000)
        libnl.so.1 => /usr/lib/libnl.so.1 (0xb774d000)
        libssl.so.1.0.0 => not found
        libcrypto.so.1.0.0 => not found
        libdl.so.2 => /lib/i686/cmov/libdl.so.2 (0xb7748000)
        libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb75ed000)
        libm.so.6 => /lib/i686/cmov/libm.so.6 (0xb75c7000)
        /lib/ld-linux.so.2 (0xb779c000)

If the hex number is not the one of the library the executable once got linked against, a version information error may occur.

I got two questions:

1. Where does this value originate?
2. How can I find out which hex value the executable is looking for? (i.e. the one it originally got linked against)

Answer 1

The hexadecimal numbers are the memory addresses the respective library gets loaded into. See https://stackoverflow.com/a/5130690/637284 for further explanation.