Re: [mjt@tls.msk.ru: ltrace can't trace binaries linked with ld-2.15]

[Alan Modra <amodra at bigpond dot net dot au>]

On Mon, Oct 11, 2004 at 11:44:49AM +0200, Simon Richter wrote:
> Hi,
> 
> Debian received the message below through the bug tracking system. Could
> somebody give me an executive summary on what has changed in the linker
> that would cause the output described below, so we get an idea on where
> to go with this bug?

It's a deliberate change in ld behaviour, to speed ld.so.  Search for
ELF_LINK_POINTER_EQUALITY_NEEDED on the binutils list.


> ----- Forwarded message from Michael Tokarev <mjt@tls.msk.ru> -----
> 
> Date: Tue, 05 Oct 2004 03:07:48 +0400
> From: Michael Tokarev <mjt@tls.msk.ru>
> To: Debian Bug Tracking System <submit@bugs.debian.org>
> Subject: ltrace can't trace binaries linked with ld-2.15
> 
> Package: ltrace,binutils
> Severity: grave
> Justification: renders ltrace package unusable
> 
> I'm not really sure for which package this bug/problem
> belongs, so filing against both.
> 
> After upgrading binutils to 2.15, I noticied ltrace stopped
> working on binaries compiled/linked after upgrade.  Ltrace
> produces one line of output -- the finall exit line only:
> 
> $ ltrace ./a.out
> +++ exited (status 0) +++
> 
> for every such binary.
> 
> After some digging, I found the difference between binaries
> *linked* (the problem is with ld only, the final link stage)
> in .dynsym section.  For example (objdump -T output):
> 
> executable produced by ld-2.15:
> 
> bad:     file format elf32-i386
> 
> DYNAMIC SYMBOL TABLE:
> 00000000      DF *UND*  0000007c  GLIBC_2.0   write
> 00000000      DF *UND*  0000003f  GLIBC_2.0   strcmp
> 00000000      DF *UND*  00000071  GLIBC_2.0   close
> ....
> 
> executable produced by pre-2.15 ld:
> 
> good:     file format elf32-i386
> 
> DYNAMIC SYMBOL TABLE:
> 0804859c      DF *UND*  0000007c  GLIBC_2.0   write
> 080485ac      DF *UND*  0000003f  GLIBC_2.0   strcmp
> 080485bc      DF *UND*  00000071  GLIBC_2.0   close
> ....
> 
> 
> That is, ld-2.15 fills first column with zeros, while
> ld-pre-2.15 places some non-zero numbers here.
> 
> I don't know ELF format, and don't even know what this
> first column in objdump output means.
> 
> -- System Information
> Debian Release: 3.0
> Architecture: i386
> Kernel: Linux paltus.tls.msk.ru 2.6.7-i686-2 #1 Mon Jul 26 18:54:34 MSD 2004 
> i686 GNU/Linux
> Locale: LANG=ru_RU.KOI8-R
> 
> Relevant packages:
> 
> ii  binutils       2.15-4         The GNU assembler, linker and binary 
> utiliti
> ii  ltrace         0.3.35         Tracks runtime library calls in dynamically
> ii  gcc-3.3        3.3.4-6sarge1. The GNU C compiler
> 
> 
> 
> ----- End forwarded message -----
> 
> -- 
>  GPG Fingerprint: 040E B5F7 84F1 4FBC CEAD  ADC6 18A0 CC8D 5706 A4B4



-- 
Alan Modra
IBM OzLabs - Linux Technology Centre