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Re: Some questions w.r.t remote watchpoint support in i386
- From: Wu Zhou <woodzltc at cn dot ibm dot com>
- To: Daniel Jacobowitz <drow at false dot org>
- Cc: gdb at sources dot redhat dot com
- Date: Sun, 21 May 2006 22:17:55 +0800 (CST)
- Subject: Re: Some questions w.r.t remote watchpoint support in i386
- References: <Pine.LNX.4.64.0604251813170.10220@woodzltc> <20060425125422.GB21293@nevyn.them.org>
> > 1. The first error I encounter is: "Couldn't write debug register: No such
> > process".
> >
> > After some tracking, I found gdb client is calling target_insert_watchpoint
> > defined in config/i386/nm-i386.h, instead of the remote_insert_watchpoint
> > defined in remote.c
> >
> > I guess this is a more general problem. Whenever you change target under
> > i386 platform, you will always get the i386_insert_watchpoint (and other
> > three target operations) executed.
> >
> > Maybe we can put these target operation into the target_ops, instead of
> > defining them as macro in config/i386/nm-i386.h?
>
> Yes, someone needs to fix this.
I had a closer look at this. It seems this will involve quite a few gdb
configs. Almost all the native header files in config/i386 include
nm-i386.h, but their responsive native c source are very different. To
delete these macros in nm-i386.h, I believe we need to put their
counterpart target vectore into all these responsive native c source.
And we also need to test that all relevant configs are ok after the
changes. It seems hard to me. Anyone have any good idea?
>
> > 2. Following the above thought, I comment out these four macros in
> > config/i386/nm-i386.h, and add them into i386-linux-nat.c
> >
> > This time, local gdb will call remote_insert_watchpoint indeed, but I get
> > another error:
> >
> > Can't clear hardware watchpoints without the 'Z2' (write-watchpoint) packet.
> >
> > "set debug remote 1" tell me that Packet Z2 (write-watchpoint) is NOT
> > supported
> >
> > I tried to use "set remote write-watchpoint-packet 1", but it won't work
> > either:
> >
> > Enabled packet Z2 (write-watchpoint) not recognized by stub
> >
> > my question here is:
> >
> > What is the stub refered to here? Is it the gdbserver? And how can
> > gdbserver determine which packat he will support, which won't?
>
> The stub is gdbserver, yes. It supports what it supports, and does not
> support what no one has implemented! And no one has implemented i386
> watchpoints for gdbserver.
It seems that there is not many requirement for this? Maybe i386 is not a
very popular gdbserver platform. :-)
Regards
- Wu Zhou