Re: [Buildroot] question: used wrong librarys to build packages

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Stefan, All,

On 2024-05-03 07:42 +0000, Stefan Müller via buildroot spake thusly:
> how is it possible that buildroot builds packages and links them against
> libraries that do not exist in buildroot (only on the host system, not below
> the buildroot directory)? - i am a bit confused now.
> 
> i downloaded buildroot 2024.02.01 and just copied my configs into it.
> 
> many of the built packages are now linked against libssl.so.1.1 (but buidroot
> uses openssl 3):
> 
> example:
> 
> build@build:~/buildroot/output/target/usr/sbin$ ldd NetworkManager

Using the host 'ldd' does not work on target binaries, becasue it does
not know that they are not meant for the current machine.

In fact, 'ldd' is just a glorified wrapper that basically is equivlanet
to actually running the file with LD_TRACE_LOADED_OBJECTS=1 in the
environment:

    $ ldd /usr/bin/ls
        linux-vdso.so.1 (0x00007fff02d31000)
        libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f5f9564b000)
        libcap.so.2 => /lib64/libcap.so.2 (0x00007f5f95641000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f5f9545f000)
        libpcre2-8.so.0 => /lib64/libpcre2-8.so.0 (0x00007f5f953c4000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f5f956b6000)

    $ LD_TRACE_LOADED_OBJECTS=1 /usr/bin/ls
        linux-vdso.so.1 (0x00007fff0c345000)
        libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f7dc1b2c000)
        libcap.so.2 => /lib64/libcap.so.2 (0x00007f7dc1b22000)
        libc.so.6 => /lib64/libc.so.6 (0x00007f7dc1940000)
        libpcre2-8.so.0 => /lib64/libpcre2-8.so.0 (0x00007f7dc18a5000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f7dc1b71000)

So you can't use ldd on target executables: it won't work.

Also, using ldd is really a bad idea, as it is basically equivalent to
actually running the program you're inspecting; don't do it. Instead use
readelf to inspect a program:

    $ readelf -d /usr/bin/ls
    Dynamic section at offset 0x229d8 contains 29 entries:
      Tag        Type                         Name/Value
     0x0000000000000001 (NEEDED)             Shared library: [libselinux.so.1]
     0x0000000000000001 (NEEDED)             Shared library: [libcap.so.2]
     0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
    [...]

    $ readelf -p .interp /usr/bin/ls
    String dump of section '.interp':
      [     0]  /lib64/ld-linux-x86-64.so.2

> ./NetworkManager: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not
> found (required by ./NetworkManager)

As you can see:

 1. it uses your host system interpreter, /lib/x86_64-linux-gnu/libc.so.6
 2. it reports unknown versioned symbols, presumably because your system
    uses an older glibc than your target system.

> shouldn't buildroot use the libraries that are inside the buildroot directory?

It does, but you are using the wrong tools to check.

> Can anyone help me find out what is wrong?

I hope the above is providing enough hints at how to look.

Regards,
Yann E. MORIN.

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