Re: Map offsets

[Daniel Jacobowitz <drow@mvista.com>]

On Sat, Mar 16, 2002 at 03:47:26PM +0000, B?ng-ha ? wrote:
> OK, now you made me curious... I've been thinking a long time about reading 
> about ELF, but please tell me what that number indicates, would you?
> I'm using gdb-5.0rh-5

VMA, or virtual memory address.  I would recommend a good ELF
reference, but I don't know of any.


> 
> ----Original Message Follows----
> From: Daniel Jacobowitz <drow@mvista.com>
> To: B?ng-ha ? <jpbarda@hotmail.com>
> CC: gdb@sources.redhat.com
> Subject: Re: Map offsets
> Date: Sat, 9 Mar 2002 11:09:53 -0500
> User-Agent: Mutt/1.3.23i
> 
> On Sat, Mar 09, 2002 at 03:52:34PM +0000, B?ng-ha ? wrote:
> > Hi!
> >
> > I'm sure this is a rather stupid question, but I'll ask it anyway:
> > I'm debugging a couple of processes under linux, and I want to load the
> > symbols from glibc. Now, the only way I've managed to figure out as to
> > perform the task of finding the base address of libc if to look at the
> > memory maps in /proc/?/maps, whence I get the base address of libc to be
> > e.g. 0x40020000 (this was for mingetty). So naturally, I do 
> add-symbol-file
> > /lib/libc-2.2.2.so 0x4002000, but as it turns, it should be loaded
> > 0x4003BCB0, i.e. at an offset of 0x1BCB0 from what /proc says. (I got the
> > exact offset from looking at the dynamically linked function tables and
> > comparing the read function to what was acutally loaded, if that would
> > somehow matter) Anyway, I guess I could live with this small annoyance, 
> if
> > it wasn't for that other libs wants to be loaded with other offsets. 
> 0x1BCB0
> >
> > didn't work with e.g. libresolv. And, I want to know the cause of this as
> > well, of
> > course.
> > So could someone tell me how to get the real offset, because I can't 
> imagine
> >
> > that there isn't an error-free way to get the address, right?
> 
> objdump -x /lib/libc.so.6:
> 
>  10 .text         000e1460  0001d500  0001d500  0001d500  2**4
>                   CONTENTS, ALLOC, LOAD, READONLY, CODE
> 
> That second number.
> 
> This should absolutely not be necessary!  GDB should do it
> automatically.  What version of GDB are you using?
> 
> --
> Daniel Jacobowitz                           Carnegie Mellon University
> MontaVista Software                         Debian GNU/Linux Developer
> 
> 
> _________________________________________________________________
> Chat with friends online, try MSN Messenger: http://messenger.msn.com
> 
> 

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