Re: Odd square bracket encoding in QOM names

[Mark Cave-Ayland]

On 30/11/2021 16:41, Peter Maydell wrote:

> On Tue, 30 Nov 2021 at 08:36, Mark Cave-Ayland
> <mark.cave-ayland@ilande.co.uk> wrote:
> > Has there been a recent change as to how square brackets are encoded within QOM
> > names? I noticed that the output has changed here in the "info qom-tree" output 
> > in
> > qemu-system-m68k for the q800 machine.
> >
> > The q800 machine has a set of 256 memory region aliases that used to appear in 
> > the
> > "info qom-tree" output as:
> >
> >       /mac_m68k.io[100] (memory-region)
> >       /mac_m68k.io[101] (memory-region)
> >       /mac_m68k.io[102] (memory-region)
> >
> > but they now appear as:
> >
> >       /mac_m68k.io\x5b100\x5d[0] (memory-region)
> >       /mac_m68k.io\x5b101\x5d[0] (memory-region)
> >       /mac_m68k.io\x5b102\x5d[0] (memory-region)
>
> I looked at info qom-tree for an Arm machine, and the [..] seem to be
> OK there. I tried to test with q800 but got stuck on finding a
> command line to get it to run. Do you have repro instructions?

A couple of tests this evening and I think I must have misremembered this - I tried a 
couple of older versions of my various q800 branches (one within the 6.0 dev cycle 
and another within 6.1) and both escape the QOM object name in "info qom-tree" the 
same way as above.

Easiest way to see this is to grab Finn's kernel from issue #611 like this:

$ wget 
https://gitlab.com/qemu-project/qemu/uploads/dead759323116fb22cf0f03b8cdbe15a/vmlinux-5.14-multi.xz
$ unxz vmlinux-5.14-multi.xz

And then start QEMU with this command line:

$ ./qemu-system-m68k -M q800 -kernel vmlinux-5.14-multi -monitor stdio -S

Obviously the cause is the use of square brackets within the memory region name as 
per https://gitlab.com/qemu-project/qemu/-/blob/master/hw/m68k/q800.c#L411, so given 
the escaping has been like this for some time then I guess everything is working as 
intended, and sorry for the noise.


ATB,

Mark.