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From: Andrew de Quincey <adq_dvb@lidskialf.net>
To: gdb@sources.redhat.com
Subject: Re: GDB 6.2.1 with powerpc platform and uclibc and user breakpoint problem
Date: Sun, 07 Nov 2004 05:18:00 -0000
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Cc: Daniel Jacobowitz <drow@false.org>
References: <200411061434.45201.adq_dvb@lidskialf.net> <20041107021019.GA26731@nevyn.them.org>
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On Sunday 07 Nov 2004 02:10, Daniel Jacobowitz wrote:
> On Sat, Nov 06, 2004 at 02:34:45PM +0000, Andrew de Quincey wrote:
> > -- this is the internal breakpoint on _dl_debug_state being triggered. I
> > see this in my kernel tracing in the trap handlers.
> >
> > RX: m10000548,4
> > TX: 7d821008
> > RX: M10000548,4:38000000
> > TX: OK
> > RX: m300018d4,4
> > TX: 7d821008
> > RX: M300018d4,4:801c005c
> > TX: OK
> >
> > -- GDB is clearing the breakpoints *INCLUDING MY USER BREAKPOINT* - it
> > has removed the trap instruction and set it back to 0x38000000. why is it
> > doing this!?!
>
> So that it can step past the breakpoint.
>
> > RX: m10010904,b0
> > TX:
> > 00000001000000010000000c1000036c0000000d1000089c0000000410000128000000051
> >00002680000000610000 RX: m30005004,4
> > TX: 00000000
> > RX: vCont;s
>
> That's a step request.
>
> > TX: T0b01:7ffffa60;40:1000056c;
>
> That's a segfault.  Your kernel has failed to implement
> PTRACE_SINGLESTEP correctly.  This is a common problem on older 4xx
> kernels.

Nice one! Thats it exactly. Thank you so much!

Interesting, this means our vendor has never had breakpoints working in GDB 
either. Hmmmm.....