[9fans] gdbfs

[9fans] gdbfs

[Steven Stallion]

[-- Attachment #1: Type: text/plain, Size: 1323 bytes --]

Evening 9fans,

While working on the Chromebook (nee exynos) port I ended up in a
situation where I needed to use a more sophisticated JTAG debugger to
find an issue. I ended up grabbing a RealView ICE since they are
relatively cheap on eBay (around 500.00USD) compared to other models
capable of debugging Cortex-A15 cores. Older firmware revisions of the
 RVI support the remote GDB protocol (in addition to the closed RDDI
protocol). I've written a simple 9P file server that translates
memory/register accesses to remote GDB targets. I haven't tried it
yet, but this should also work with OpenOCD as well.

At the moment this is little more than a toy, but it has been stable
enough for me to debug issues on the board reliably. I've added
support for ARM and i386 for now - adding additional register maps for
the other mach types is straightforward. If there is enough demand,
I'll write up a man page and submit a patch. The setup for this isn't
particularly obvious since it requires some messing about with RVI
firmware updates and downloading the right version of RVDS to setup
the board, so a wiki page is deserved as well.

For now, you can find the source in my contrib directory on sources:
/n/sources/contrib/stallion/src/gdbfs/

(Obligatory screenshot attached)

Cheers,

Steve

[-- Attachment #2: gdbfs.png --]
[-- Type: image/png, Size: 56093 bytes --]

Re: [9fans] gdbfs

[Shane Morris]

[-- Attachment #1: Type: text/plain, Size: 1537 bytes --]

An Exynos port of Plan 9 on a ChromeBook... that would be seriously cool!


On Thu, Dec 19, 2013 at 4:12 PM, Steven Stallion <sstallion@gmail.com>wrote:

> Evening 9fans,
>
> While working on the Chromebook (nee exynos) port I ended up in a
> situation where I needed to use a more sophisticated JTAG debugger to
> find an issue. I ended up grabbing a RealView ICE since they are
> relatively cheap on eBay (around 500.00USD) compared to other models
> capable of debugging Cortex-A15 cores. Older firmware revisions of the
>  RVI support the remote GDB protocol (in addition to the closed RDDI
> protocol). I've written a simple 9P file server that translates
> memory/register accesses to remote GDB targets. I haven't tried it
> yet, but this should also work with OpenOCD as well.
>
> At the moment this is little more than a toy, but it has been stable
> enough for me to debug issues on the board reliably. I've added
> support for ARM and i386 for now - adding additional register maps for
> the other mach types is straightforward. If there is enough demand,
> I'll write up a man page and submit a patch. The setup for this isn't
> particularly obvious since it requires some messing about with RVI
> firmware updates and downloading the right version of RVDS to setup
> the board, so a wiki page is deserved as well.
>
> For now, you can find the source in my contrib directory on sources:
> /n/sources/contrib/stallion/src/gdbfs/
>
> (Obligatory screenshot attached)
>
> Cheers,
>
> Steve
>

[-- Attachment #2: Type: text/html, Size: 1913 bytes --]

Re: [9fans] gdbfs

[Gorka Guardiola Muzquiz]

¿Have you taken a look at the jtag tar in my contrib?
It is described here
http://lsub.org/ls/export/jtag.pdf
I don´t know enough about the RealView ICE, but if you write
the right module for whatever drives the serial communications
maybe you can drive the jtag directly.
I don´t know if that would give you anything you don´t have already
but just in case you didn´t know :-)


> On 19 Dec 2013, at 06:12, Steven Stallion <sstallion@gmail.com> wrote:
> 
> Evening 9fans,
> 
> While working on the Chromebook (nee exynos) port I ended up in a
> situation where I needed to use a more sophisticated JTAG debugger to
> find an issue. I ended up grabbing a RealView ICE since they are
> relatively cheap on eBay (around 500.00USD) compared to other models
> capable of debugging Cortex-A15 cores. Older firmware revisions of the
> RVI support the remote GDB protocol (in addition to the closed RDDI
> protocol). I've written a simple 9P file server that translates
> memory/register accesses to remote GDB targets. I haven't tried it
> yet, but this should also work with OpenOCD as well.
> 
> At the moment this is little more than a toy, but it has been stable
> enough for me to debug issues on the board reliably. I've added
> support for ARM and i386 for now - adding additional register maps for
> the other mach types is straightforward. If there is enough demand,
> I'll write up a man page and submit a patch. The setup for this isn't
> particularly obvious since it requires some messing about with RVI
> firmware updates and downloading the right version of RVDS to setup
> the board, so a wiki page is deserved as well.
> 
> For now, you can find the source in my contrib directory on sources:
> /n/sources/contrib/stallion/src/gdbfs/
> 
> (Obligatory screenshot attached)
> 
> Cheers,
> 
> Steve
> <gdbfs.png>

Re: [9fans] gdbfs

[Steven Stallion]

On Thu, Dec 19, 2013 at 2:38 AM, Gorka Guardiola Muzquiz
<paurea@gmail.com> wrote:
> ¿Have you taken a look at the jtag tar in my contrib?
> It is described here
> http://lsub.org/ls/export/jtag.pdf
> I don´t know enough about the RealView ICE, but if you write
> the right module for whatever drives the serial communications
> maybe you can drive the jtag directly.
> I don´t know if that would give you anything you don´t have already
> but just in case you didn´t know :-)

I have indeed! I started with jtagfs and an Amontec JTAGkey. Much to
my chagrin, Cortex-A15s require more advanced hardware than the FTDI
debuggers. The RVI can't be driven directly unless you implement RDDI,
which is only distributed for Linux and Windows as precompiled
libraries. I played with the idea of reverse-engineering the library,
but after looking at a couple of packet traces, it would have been
more work than I will will to put out.

Cheers,

Steve

Re: [9fans] gdbfs

[Alex Ivanov]

Steven Stallion <sstallion <at> gmail.com> writes:

> While working on the Chromebook (nee exynos) port

Hi, Steven.

What is the state of the port? Do you plan to share code?

Thanks, Alex.

Re: [9fans] gdbfs

[Steven Stallion]

On Sat, Mar 15, 2014 at 6:19 AM, Alex Ivanov <gnidorah@p0n4ik.tk> wrote:
> Steven Stallion <sstallion <at> gmail.com> writes:
>
>> While working on the Chromebook (nee exynos) port
>
> Hi, Steven.
>
> What is the state of the port? Do you plan to share code?

The port is in progress, though it's been a touch slow the last couple
of months due to job changes/stresses. The code is the process of
being pushed out to googlecode - as soon as it's in a state that's
consumable I'll send a link out to folks.

Cheers,

Steve