[linuxsh-dev] RE: [linux-sh:02691] Re: Use of e_flags field in ELF header

[Thomas,Stephen <ste...@su...>]

Hi Daniel,

Thanks for your reply. What you suggest does appear to work, but I had =
to do:

gdb -c core
file prog

Using 'gdb -e prog -c core' (as suggested in the man page) doesn't work, =
the file prog just gets ignored.

But I think the core file ought to be correct if possible. Getting gdb =
to generate the correct e_flags proved to be easy - they can be set in =
the elf_backend_final_write_processing routine in the appropriate =
elf<arch>.c. The kernel mod is also easy, it just means modifying =
generic code.

Thanks,

Steve Thomas
SuperH (UK) Ltd.

-----Original Message-----
From: Daniel Jacobowitz [mailto:dr...@fa...]=20
Sent: 14 April 2003 15:21
To: kaz Kojima
Cc: Thomas,Stephen; McGoogan,Sean; =
lin...@li...; lin...@m1...; =
lin...@li...
Subject: Re: [linux-sh:02691] Re: Use of e_flags field in ELF header


On Mon, Apr 14, 2003 at 11:12:47PM +0900, kaz Kojima wrote:
> Hi,
>=20
> "Thomas,Stephen" <ste...@su...> wrote:
> >Apparently, the e_flags field of the ELF Header structure in ELF=20
> >files is used by SH architectures to indicate the CPU type. The lower =

> >5 bits  have the following meaning:
> >
> >     0  =3D unknown CPU type
> >     1  =3D SH1
> >     2  =3D SH2
> >     3  =3D SH3
> >     5  =3D SH3 with DSP
> >     8  =3D SH3E
> >     9  =3D SH4
> >    10  =3D SH5
> >
> >The e_flags field is designed to hold architecture specific info, but =

> >other architectures don't appear to use it in quite the same way,=20
> >i.e. to indicate different CPU types.
> >
> >Does anybody know why SH uses e_flags in this way?
>=20
> I don't know why SH does so, but MIPS uses the upper 4 bits of e_flags =

> to encode ISA. Perhaps there might be another examples.
>=20
> >The problem I have is in generating & interpreting core files. When=20
> >the kernel (V2.4)generates an ELF core dump, it just sets e_flags to=20
> >0 (hard coded constant) & dumps it. So to get it to generate a valid=20
> >SH5 core dump, I need to modify generic code. There are similar=20
> >problems with the gdb 'gcore' command.
>=20
> Your modification seems the right thing to do.

Why is this an issue?  If the core dump is marked "unknown", then the =
ISA should be taken from the executable during a GDB session, and it =
should do the right thing.


--=20
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer