Re: [RFA] Testing REGISTER_NAME in mips-linux-nat.c

[Daniel Jacobowitz <drow at mvista dot com>]

On Sat, Jun 28, 2003 at 02:36:31PM -0400, Daniel Jacobowitz wrote:
> On Fri, Jun 27, 2003 at 03:31:18PM -0400, Andrew Cagney wrote:
> > >A recent change to mips_register_name to return a empty string for
> > >register numbers < NUM_REGS is causing problems with the native mips
> > >linux port.  The change in mips_register_name is:
> > 
> > Arrgh, they keep turning up :-(
> > 
> > >  +   /* Map [NUM_REGS .. 2*NUM_REGS) onto the raw registers, but then
> > >  +      don't make the raw register names visible.  */
> > >  +   int rawnum = regno % NUM_REGS;
> > >  +   if (regno < NUM_REGS)
> > >  +     return "";
> > >
> > >Now for example when mips_linux_cannot_fetch_register() is called with
> > >regno == PC_REGNUM, it will return 1 and reading of the PC will return
> > >zero as the PC value.
> > >
> > >I think this is the correct patch, but I'm not 100% sure.  Perhaps we
> > >can just eliminate the REGISTER_NAME check completely.
> > 
> > The assertion:
> > 
> > 	gdb_assert (regno >= 0 && regno < NUM_REGS);
> > 
> > holds so, yes, eliminating REGISTER_NAME would make sense.
> 
> Take a look at MIPS_REGISTER_NAMES in tm-mips.h, which is the generic
> registers.  Note lots of empty (unnamed) entries in there - we can't
> fetch or store those.  That's what the check is trying to avoid.
> 
> I don't think Fred's patch is right either, because this function
> shouldn't even be called for regno > NUM_REGS, so it just disables the
> check.  I think the right thing to do is either (ugh!) to call
> REGISTER_NAME (regno + NUM_REGS), or to switch to an inclusive list of
> available registers.  Which is easier, and cleaner.
> 
> Fred, my mips-linux box is offline at the moment, so I can't test this. 
> Could you try the attached patch and let me know if it works?
> 
> I think I'm going to try to get my own breed of automated testing
> going to cover this...
> 
> > Hmm, how come this doesn't just use PTRACE_GETREGS?
> 
> Because mips-linux doesn't implement that yet.
> 
> -- 
> Daniel Jacobowitz
> MontaVista Software                         Debian GNU/Linux Developer
> 
> 2003-06-28  Daniel Jacobowitz  <drow@mvista.com>
> 
> 	* mips-linux-nat.c (mips_linux_cannot_fetch_register)
> 	(mips_linux_cannot_store_register): List supported instead of
> 	unsupported registers.

I've checked this in everywhere.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer