missing text segment in Elf dump

missing text segment in Elf dump

[Lucy Zhang]

Hi,

When GDB is debugging an ELF core dump, what is it use for the text segment.
I realized in the Elf core that I've created from another dump file, that
the text segment is cut off because the size is too big. The actual text
segment spans 0x8048000  - 0x98cc4e0, but I only included the first 8MB of
the area in the ELF dump. So I'm wondering what affects will this have on
GDB? what kind of information will be missing due to the incomplete text
segment?

Thanks,
Lucy

Re: missing text segment in Elf dump

[Daniel Jacobowitz]

On Thu, Aug 15, 2002 at 11:10:12AM -0700, Lucy Zhang wrote:
> Hi,
> 
> When GDB is debugging an ELF core dump, what is it use for the text segment.
> I realized in the Elf core that I've created from another dump file, that
> the text segment is cut off because the size is too big. The actual text
> segment spans 0x8048000  - 0x98cc4e0, but I only included the first 8MB of
> the area in the ELF dump. So I'm wondering what affects will this have on
> GDB? what kind of information will be missing due to the incomplete text
> segment?

Most ELF core dumps don't even include the text segment.  GDB gets it
from the application instead, and only writeable segments are in the
core file...

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

Re: missing text segment in Elf dump

[Lucy Zhang]

Can you elaborate on how GDB gets it from the application? and by
application do you mean the executable file?
Also, when I try to look at the source code using "list", does this have
anything to do with the text segment? I ask because it would work for some
source files and not for others. i.e.
(gdb) list condvar.c:88
83      condvar.c: No such file or directory.
          in condvar.c

thank you,
Lucy

----- Original Message -----
From: "Daniel Jacobowitz" <drow@mvista.com>
To: "Lucy Zhang" <lucyz@uclink4.berkeley.edu>
Cc: <gdb@sources.redhat.com>
Sent: Thursday, August 15, 2002 11:08 AM
Subject: Re: missing text segment in Elf dump


> On Thu, Aug 15, 2002 at 11:10:12AM -0700, Lucy Zhang wrote:
> > Hi,
> >
> > When GDB is debugging an ELF core dump, what is it use for the text
segment.
> > I realized in the Elf core that I've created from another dump file,
that
> > the text segment is cut off because the size is too big. The actual text
> > segment spans 0x8048000  - 0x98cc4e0, but I only included the first 8MB
of
> > the area in the ELF dump. So I'm wondering what affects will this have
on
> > GDB? what kind of information will be missing due to the incomplete text
> > segment?
>
> Most ELF core dumps don't even include the text segment.  GDB gets it
> from the application instead, and only writeable segments are in the
> core file...
>
> --
> Daniel Jacobowitz
> MontaVista Software                         Debian GNU/Linux Developer

Re: missing text segment in Elf dump

[Daniel Jacobowitz]

On Thu, Aug 15, 2002 at 11:30:56AM -0700, Lucy Zhang wrote:
> Can you elaborate on how GDB gets it from the application? and by
> application do you mean the executable file?

Yes.  They are both ELF binaries with mapped sections.  GDB can read
data directly from the application; and the kernel generally will not
dump it.

> Also, when I try to look at the source code using "list", does this have
> anything to do with the text segment? I ask because it would work for some
> source files and not for others. i.e.
> (gdb) list condvar.c:88
> 83      condvar.c: No such file or directory.
>           in condvar.c

No, this has nothing to do with segments, only with debug information.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer