Porting GDB - Where to start?

Porting GDB - Where to start?

[James Sampson]

Hello

In my GDB journey, I have now found out, that I need to port the GDB to C55x 
target. A recipe on how to do this, exists only in very light form. The best 
thing is to edit another port, and since I don't know which port to choose, I 
ask that exact question here.

Which port would be best to start from, when I'm porting to a C55x target 
which produces COFF files?.

Best Regards
James Sampson

Re: Porting GDB - Where to start?

[Daniel Jacobowitz]

On Mon, Nov 25, 2002 at 10:56:22AM +0100, James Sampson wrote:
> Hello
> 
> In my GDB journey, I have now found out, that I need to port the GDB to C55x 
> target. A recipe on how to do this, exists only in very light form. The best 
> thing is to edit another port, and since I don't know which port to choose, I 
> ask that exact question here.
> 
> Which port would be best to start from, when I'm porting to a C55x target 
> which produces COFF files?.

It's an ELF port, but xstormy16 is still probably your best bet.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

Re: Porting GDB - Where to start?

[Andrew Cagney]

> On Mon, Nov 25, 2002 at 10:56:22AM +0100, James Sampson wrote:
> 
>> Hello
>> 
>> In my GDB journey, I have now found out, that I need to port the GDB to C55x 
>> target. A recipe on how to do this, exists only in very light form. The best 
>> thing is to edit another port, and since I don't know which port to choose, I 
>> ask that exact question here.
>> 
>> Which port would be best to start from, when I'm porting to a C55x target 
>> which produces COFF files?.
> 
> 
> It's an ELF port, but xstormy16 is still probably your best bet.

Yes.

(GDB ports are object file netural.  Handling elf, xcoff, coff, ... is a 
bfd problem and as long as BFD can handle it, so can GDB. The only 
potential got-ya is the debug info, use GCC and you should be safe there.)

Re: Porting GDB - Where to start?

[Jim Blandy]

Andrew Cagney <ac131313@redhat.com> writes:
> (btw, anyone got an easier way of identifying the debug info?)

objdump -h?

Re: Porting GDB - Where to start?

[Eli Zaretskii]

> Date: Mon, 2 Dec 2002 09:29:03 -0500
> From: Daniel Jacobowitz <drow@mvista.com>
> > 
> > DWARF-2 is also supported with COFF binary format.  DJGPP uses that 
> > combination.
> 
> Really?  How does that work?

Quite frankly, I have no idea; I just know it does.  You could
probably find the details in the GCC sources, though.

> I suppose that if COFF has arbitrary named sections, it could work -
> but I thought only ECOFF did that.

FWIW, the DJGPP linker script has this snippet:

      /* DWARF 2 */
      .debug_aranges  0 : { *(.debug_aranges) }
      .debug_pubnames 0 : { *(.debug_pubnames) }
      .debug_info     0 : { *(.debug_info) *(.gnu.linkonce.wi.*) }
      .debug_abbrev   0 : { *(.debug_abbrev) }
      .debug_line     0 : { *(.debug_line) }
      .debug_frame    0 : { *(.debug_frame) }
      .debug_str      0 : { *(.debug_str) }
      .debug_loc      0 : { *(.debug_loc) }
      .debug_macinfo  0 : { *(.debug_macinfo) }

Re: Porting GDB - Where to start?

[Daniel Jacobowitz]

On Mon, Dec 02, 2002 at 08:16:17AM +0200, Eli Zaretskii wrote:
> 
> On Sun, 1 Dec 2002, Daniel Jacobowitz wrote:
> 
> > > In CCS you have the option to use COFF or DWARF. I was planning on using COFF, 
> > > because I have noticed some C54x COFF file thingies in the BFD, which could be 
> > > usable :-D. Do you know if they are?.
> > 
> > If those are the two switches that's pretty bizarre.  COFF is a file
> > format, DWARF a debug info format.
> 
> Not 100% accurate, AFAIK: there's also COFF debug info format.
> 
> > You probably want DWARF (DWARF-2) which implies ELF format files.
> 
> DWARF-2 is also supported with COFF binary format.  DJGPP uses that 
> combination.

Really?  How does that work?  I recall a number of blatant ELFisms in
dwarf2, both specification and implementation.  I suppose that if COFF
has arbitrary named sections, it could work - but I thought only ECOFF
did that.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

Re: Porting GDB - Where to start?

[Eli Zaretskii]

On Sun, 1 Dec 2002, Daniel Jacobowitz wrote:

> > In CCS you have the option to use COFF or DWARF. I was planning on using COFF, 
> > because I have noticed some C54x COFF file thingies in the BFD, which could be 
> > usable :-D. Do you know if they are?.
> 
> If those are the two switches that's pretty bizarre.  COFF is a file
> format, DWARF a debug info format.

Not 100% accurate, AFAIK: there's also COFF debug info format.

> You probably want DWARF (DWARF-2) which implies ELF format files.

DWARF-2 is also supported with COFF binary format.  DJGPP uses that 
combination.

Re: Porting GDB - Where to start?

[Daniel Jacobowitz]

On Tue, Nov 26, 2002 at 04:53:15PM +0100, James Sampson wrote:
> >> 1. Why is xstormy16 the best place to start?.
> >
> >Being fairly new, and for a relatively straightforward architecture, it
> >doesn't come with much baggage.  It's roughly 1000 lines long, while the
> >MIPS is a wopping 6000 lines!
> 
> Ok! - I had the impression it had more than 200Kb of source code. Is it 
> because a lot of the code is similar from target to target, and doesn't need 
> much change? (I assume you mean a 1000 lines of code which has to be more or 
> less produced)
> 
> 
> >> 2. Since I can't use GCC to make target specific code for a C55x I must use
> >> CCS (Code Composer Studio) from TI. What could a "got-ya" be?.
> >
> >There is a good chance that after you've kind of got the target `mostly'
> >working, you will spend time debugging problems in the symtab code.
> >This is because, when it comes to debug info, no two compilers are
> >alike.   Consequently, is a very good chance that GDB won't properly
> >handle the debug info being output by this compiler.
> >
> >Anyway, a first step is to find out what the debug info is and if GDB
> >has any support for it at all ....  One way is to compile a simple
> >program using `-g -S' and then look at the assembler that is created.
> >If it contains ``.stabn'' lines its stabs, if it contains ``.debug_...''
> >symbols it's dwarf2 (or dwarf1?).  Beyond that, you may want to post the
> >contents here.
> 
> In CCS you have the option to use COFF or DWARF. I was planning on using COFF, 
> because I have noticed some C54x COFF file thingies in the BFD, which could be 
> usable :-D. Do you know if they are?.

If those are the two switches that's pretty bizarre.  COFF is a file
format, DWARF a debug info format.  You probably want DWARF (DWARF-2)
which implies ELF format files.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

RE: Porting GDB - Where to start?

[James Sampson]

>> 1. Why is xstormy16 the best place to start?.
>
>Being fairly new, and for a relatively straightforward architecture, it
>doesn't come with much baggage.  It's roughly 1000 lines long, while the
>MIPS is a wopping 6000 lines!

Ok! - I had the impression it had more than 200Kb of source code. Is it 
because a lot of the code is similar from target to target, and doesn't need 
much change? (I assume you mean a 1000 lines of code which has to be more or 
less produced)


>> 2. Since I can't use GCC to make target specific code for a C55x I must use
>> CCS (Code Composer Studio) from TI. What could a "got-ya" be?.
>
>There is a good chance that after you've kind of got the target `mostly'
>working, you will spend time debugging problems in the symtab code.
>This is because, when it comes to debug info, no two compilers are
>alike.   Consequently, is a very good chance that GDB won't properly
>handle the debug info being output by this compiler.
>
>Anyway, a first step is to find out what the debug info is and if GDB
>has any support for it at all ....  One way is to compile a simple
>program using `-g -S' and then look at the assembler that is created.
>If it contains ``.stabn'' lines its stabs, if it contains ``.debug_...''
>symbols it's dwarf2 (or dwarf1?).  Beyond that, you may want to post the
>contents here.

In CCS you have the option to use COFF or DWARF. I was planning on using COFF, 
because I have noticed some C54x COFF file thingies in the BFD, which could be 
usable :-D. Do you know if they are?.


>(btw, anyone got an easier way of identifying the debug info?)

Not me :-D

Re: Porting GDB - Where to start?

[Andrew Cagney]

>>> It's an ELF port, but xstormy16 is still probably your best bet.
> 
>>
>>Yes.
>>
>>(GDB ports are object file netural.  Handling elf, xcoff, coff, ... is a
>>bfd problem and as long as BFD can handle it, so can GDB. The only
>>potential got-ya is the debug info, use GCC and you should be safe >there.)
> 
> 
> Ok then :-)
> 
> A couple of questions:
> 
> 1. Why is xstormy16 the best place to start?.

Being fairly new, and for a relatively straightforward architecture, it 
doesn't come with much baggage.  It's roughly 1000 lines long, while the 
MIPS is a wopping 6000 lines!

> 2. Since I can't use GCC to make target specific code for a C55x I must use 
> CCS (Code Composer Studio) from TI. What could a "got-ya" be?.

There is a good chance that after you've kind of got the target `mostly' 
working, you will spend time debugging problems in the symtab code. 
This is because, when it comes to debug info, no two compilers are 
alike.   Consequently, is a very good chance that GDB won't properly 
handle the debug info being output by this compiler.

Anyway, a first step is to find out what the debug info is and if GDB 
has any support for it at all ....  One way is to compile a simple 
program using `-g -S' and then look at the assembler that is created. 
If it contains ``.stabn'' lines its stabs, if it contains ``.debug_...'' 
symbols it's dwarf2 (or dwarf1?).  Beyond that, you may want to post the 
contents here.

(btw, anyone got an easier way of identifying the debug info?)

Andrew

RE: Porting GDB - Where to start?

[James Sampson]

>> It's an ELF port, but xstormy16 is still probably your best bet.
>
>Yes.
>
>(GDB ports are object file netural.  Handling elf, xcoff, coff, ... is a
>bfd problem and as long as BFD can handle it, so can GDB. The only
>potential got-ya is the debug info, use GCC and you should be safe >there.)

Ok then :-)

A couple of questions:

1. Why is xstormy16 the best place to start?.

2. Since I can't use GCC to make target specific code for a C55x I must use 
CCS (Code Composer Studio) from TI. What could a "got-ya" be?.

Best Regards
James