Re: Weird ldd problem

[Chavdar Ivanov <ci4ic4%gmail.com@localhost>]

On Sun, 18 Jul 2021 at 10:26, RVP <rvp%sdf.org@localhost> wrote:
>
> On Sun, 18 Jul 2021, Chavdar Ivanov wrote:
>
> > # file ksh93
> > ksh93: ELF 64-bit LSB executable, x86-64, version 1 (SYSV),
> > dynamically linked, interpreter /usr/libexec/ld.elf_so, for NetBSD
> > 9.99.45, with debug_info, not stripped
> > # ldd ./ksh93
> > ./ksh93:
> >        -lm.0 => /usr/lib/libm.so.0
> >        -lc.12 => /usr/lib/libc.so.12
> >        -lexecinfo.0 => /usr/lib/libexecinfo.so.0
> >        -lelf.2 => /usr/lib/libelf.so.2
> >        -lgcc_s.1 => /usr/lib/libgcc_s.so.1
> > # ldd ksh93
> > ldd: bad execname `ksh93' in AUX vector: No such file or directory
> >
>
> That's coming from the run-time linker:
>
> function expand() in src/libexec/ld.elf_so/expand.c when it tries
> to expand $ORIGIN. You can create such a binary yourself like this:
>
> ---
> $ cat foo.c
> #include <stdio.h>
>
> int
> main(int argc, char* argv[])
> {
>          printf("%s\n", *argv);
>          return 0;
> }
> $ cc -o foo foo.c -Wl,-rpath='$ORIGIN'
> $ ldd ./foo
> ./foo:
>          -lc.12 => /usr/lib/libc.so.12
> $ ldd foo
> ldd: bad execname `foo' in AUX vector: Undefined error: 0
> $ readelf -d foo
>
> Dynamic section at offset 0xbb8 contains 18 entries:
>    Tag        Type                         Name/Value
>   0x0000000000000001 (NEEDED)             Shared library: [libc.so.12]
>   0x000000000000000f (RPATH)              Library rpath: [$ORIGIN]
>   0x000000000000000c (INIT)               0x400530
>   0x000000000000000d (FINI)               0x4009b0
>   0x0000000000000004 (HASH)               0x400210
>   0x0000000000000005 (STRTAB)             0x4003c8
>   0x0000000000000006 (SYMTAB)             0x400260
>   0x000000000000000a (STRSZ)              158 (bytes)
>   0x000000000000000b (SYMENT)             24 (bytes)
>   0x0000000000000015 (DEBUG)              0x0
>   0x0000000000000003 (PLTGOT)             0x600d48
>   0x0000000000000002 (PLTRELSZ)           120 (bytes)
>   0x0000000000000014 (PLTREL)             RELA
>   0x0000000000000017 (JMPREL)             0x4004b0
>   0x0000000000000007 (RELA)               0x400468
>   0x0000000000000008 (RELASZ)             72 (bytes)
>   0x0000000000000009 (RELAENT)            24 (bytes)
>   0x0000000000000000 (NULL)               0x0
> ---
>
> Do a `readelf -d' on both ksh93s. You'll see the difference.

The main difference is indeed

... (RPATH)              Library rpath:
[$ORIGIN/:$ORIGIN/../../lib/libast:$ORIGIN/cmds:$ORIGIN/../../lib/libdll]

I have to read more to understand it though...

>
> -RVP
>

Thanks,

Chavdar


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