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RE: [RFC] Enable GDB handle compressed target.xml returned by GDB stub
- From: "Terry Guo" <terry dot guo at arm dot com>
- To: "'Jonathan Larmour'" <jifl at ecoscentric dot com>, "Pedro Alves" <palves at redhat dot com>
- Cc: "Ulrich Weigand" <uweigand at de dot ibm dot com>, "Yao Qi" <yao at codesourcery dot com>, <gdb-patches at sourceware dot org>, <tromey at redhat dot com>, "Richard Earnshaw" <Richard dot Earnshaw at arm dot com>, "Joey Ye" <Joey dot Ye at arm dot com>
- Date: Tue, 19 Jun 2012 15:40:37 +0800
- Subject: RE: [RFC] Enable GDB handle compressed target.xml returned by GDB stub
- References: <201206131312.q5DDCUfK028160@d06av02.portsmouth.uk.ibm.com> <4FD9B96C.9020908@redhat.com> <4FDA0543.9030100@eCosCentric.com>
>
> > In that perspective, something like the
> > 'try qXfer:features:zread:target.xml first, then
> > qXfer:features:read:target.xml, etc.' alternative sounded attractive.
> > Or should we not bother?
>
> I have a fresh variant proposal derived from the existing suggestions
> which I think can accommodate all the concerns:
>
> 1) Remote stub can return compressedXML+ in qSupported response
>
> 2) The current syntax of qXfer:features:read is:
> qXfer:features:read:ANNEX:OFFSET,LENGTH
> I suggest instead:
> qXfer:features:read:ANNEX:OFFSET,LENGTH[,Z]
> where the ,Z is only attempted if the stub supports the compressedXML
> remote protocol feature.
>
I don't think it will work after I looked into some open source GDB servers like STLINk, OpenOCD. After they confirm that the packet is qXfer:features:read, they just extract information of ANNEX, OFFSET and LENGTH. Whether there is a "Z" doesn't impact their response behavior.
But the new "zread" can work because those existing gdb servers do check whether the op is "read". So for "zread", that check will fail and an error code will be returned to host gdb, thus host gdb knows the compressed xml file isn't supported. While for the new stub that knows "zread", the compressed xml file will be returned.
BR,
Terry