weird output of ldd on arm64

[Oliver Grawert]

running ldd under fakechroot (we are building generic initrds in one of our packages where we have this setup in use) ldd returns a wrong library path (/lib64) instead of the actual path it returns under normal chroot conditions (/lib) on arm64:

running ldd under fakechroot inside a build chroot:

root@localhost:/# fakechroot chroot initramfs-tools-ubuntu-core-0.7.20/build ldd /usr/lib/initramfs-tools/bin/wait-for-root
 linux-vdso.so.1 => (0x0000000000000000)
 libfakechroot.so => /usr/lib/aarch64-linux-gnu/fakechroot/libfakechroot.so (0x0000000000000000)
 libudev.so.1 => /lib/aarch64-linux-gnu/libudev.so.1 (0x0000000000000000)
 libpthread.so.0 => /lib/aarch64-linux-gnu/libpthread.so.0 (0x0000000000000000)
 libc.so.6 => /lib/aarch64-linux-gnu/libc.so.6 (0x0000000000000000)
 /lib64/ld-linux-aarch64.so.1 (0x0000000000000000)

running ldd directly in the chroot:

root@localhost:/# ldd /usr/lib/initramfs-tools/bin/wait-for-root
 linux-vdso.so.1 => (0x0000007f9cefd000)
 libudev.so.1 => /lib/aarch64-linux-gnu/libudev.so.1 (0x0000007f9cec5000)
 libc.so.6 => /lib/aarch64-linux-gnu/libc.so.6 (0x0000007f9cd7c000)
 /lib/ld-linux-aarch64.so.1 (0x0000005591a15000)
 libpthread.so.0 => /lib/aarch64-linux-gnu/libpthread.so.0 (0x0000007f9cd50000)
root@localhost:/#

since there is no /lib64 directory at all on arm64 the copy_exec call from update-initrmfs fails in this case.

[Adam Conrad (adconrad)]

Looks like fakechroot wraps ldd with a perl script that makes silly assumptions:

                        if ($Format =~ /^elf64-/) {
                            push @Libs, 'linux-vdso.so.1';
                            $Libs{'linux-vdso.so.1'} = '';
                            $Ldsodir = "/lib64";
                        }

[Oliver Grawert (ogra)]

hmm, i just noticed that this seems to affect nearly every binary in our initrd (parted, sgdisk do not pull in their libs at all for example)

[Oliver Grawert (ogra)]

http://paste.ubuntu.com/15322243/ has the output of ldd vs ldd.REAL inside the build env, apart from the zeroed addresses they seem to match.
yet, if you check i.e. https://launchpadlibrarian.net/246864900/buildlog_ubuntu-xenial-arm64.initramfs-tools-ubuntu-core_0.7.35_BUILDING.txt.gz you will see that copy_exec /sbin/parted does not pull libs in at all.

[Oliver Grawert (ogra)]

also note this latter bit does not seem limited to arm64 at all ... these libs are missing on all arches for initramfs-tools-ubuntu-core