Re: gdb/633: fully qualified pathnames in solib_map_sections() and remote debugging

[Daniel Jacobowitz <drow at mvista dot com>]

On Tue, Aug 06, 2002 at 10:06:34AM -0000, jorma.laaksonen@hut.fi wrote:
> 
> >Number:         633
> >Category:       gdb
> >Synopsis:       fully qualified pathnames in solib_map_sections() and remote debugging
> >Confidential:   no
> >Severity:       non-critical
> >Priority:       medium
> >Responsible:    unassigned
> >State:          open
> >Class:          sw-bug
> >Submitter-Id:   net
> >Arrival-Date:   Tue Aug 06 03:08:01 PDT 2002
> >Closed-Date:
> >Last-Modified:
> >Originator:     jorma.laaksonen@hut.fi
> >Release:        gdb-5.2
> >Organization:
> >Environment:
> --host=i686-pc-linux-gnu --target=arm-linux
> >Description:
> When debugging remotely an application that runs
> in another type of platform, solib_map_sections() of solib.c gets called with fully qualified pathnames
> that are correct in the target system but not necessarily
> in the host system.  Or, the host system's solib versions
> are of incorrect file format for the cross-target gdb.
> 
> When such a solib doesn't exist in host's filesystem,
> a loop of errors like
> 
> > Error while mapping shared library sections:
> > /usr/lib/libxxx.so.1: No such file or directory.
> 
> is entered.
> >How-To-Repeat:
> 
> >Fix:
> Add a variable that specifies search path for solibs
> while debugging remotely ???

There already is one :)  Two in fact.  The normal solution to this is
to set solib-absolute-prefix to point at an image of the target
filesystem.

   GLOBAL FUNCTION

   solib_open -- Find a shared library file and open it.

   SYNOPSIS

   int solib_open (char *in_patname, char **found_pathname);

   DESCRIPTION

   Global variable SOLIB_ABSOLUTE_PREFIX is used as a prefix directory
   to search for shared libraries if they have an absolute path.

   Global variable SOLIB_SEARCH_PATH is used as a prefix directory
   (or set of directories, as in LD_LIBRARY_PATH) to search for all
   shared libraries if not found in SOLIB_ABSOLUTE_PREFIX.

   Search order:
   * If path is absolute, look in SOLIB_ABSOLUTE_PREFIX.
   * If path is absolute or relative, look for it literally (unmodified).
   * Look in SOLIB_SEARCH_PATH.
   * Look in inferior's $PATH.
   * Look in inferior's $LD_LIBRARY_PATH.


I think the search order needs some revision though:
 - A cross debugger should not search $PATH or $LD_LIBRARY_PATH
 - A cross debugger may, or may not, want to look for the unmodified
path; I suspect that we only want to look for unmodified relative
paths, not unmodified absolute ones.

With those changes you would have to explicitly specify the path to
DSOs in a cross debugger via solib-absolute-prefix and
solib-search-path, and GDB would stop picking up the host libpthread.so
and making gdbserver segfault...  any comments from the list?

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer