[J-core] Equiv of a datasheet?

Don A. Bailey donb at securitymouse.com
Fri Jan 6 13:31:07 EST 2017

This is great! Thanks for the information.

Does gdb work on sh2 (j2)? I can't for the life of me seem to build gdb
that supports either sh2 or sh4. The closest I got was building gdbserver
from the gdb-5.3 package, but then I couldn't actually cross compile gdb,

Thank you,

Don A. Bailey
Founder / CEO
Lab Mouse Security
@InfoSecMouse <https://twitter.com/InfoSecMouse>

On Fri, Jan 6, 2017 at 10:47 AM, Rob Landley <rob at landley.net> wrote:

> Jeff's reply didn't go to the list properly...
> On 01/06/2017 02:07 AM, D. Jeff Dionne wrote:
> > Don A. Bailey wrote:
> >>
> >> Hi All,
> >>
> >> I'm very happy to have accidentally stumbled upon the j-core project
> >> today. I'm currently involved in RISC-V and it's wonderful to see
> >> another open source CPU project. I'm interested in using the j-core
> >> sh2 "clone". Is there the equivalent of a datasheet? I'd like to
> >> learn how to port my custom operating system to it, but I'm having
> >> trouble finding clear SH-2 architecture documents that describe more
> >> than the instruction set. E.g. what are the vectors
> >> in the VBR, what is the order, etc.?
> I'm usually a bit further down in the software stack on this project,
> and Rich is offline this week, but here's the patch series that added
> interrupt controller support to the Linux kernel?
>   http://lkml.iu.edu/hypermail/linux/kernel/1608.0/03337.html
> We've basically been using the Linux device tree to document this stuff:
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/
> linux.git/tree/arch/sh/boot/dts/j2_mimas_v2.dts
> >> Any advice is appreciated. Congrats on a very cool project!
> >> Best,
> >>
> >> Don A. Bailey
> >> Founder / CEO
> >> Lab Mouse Security
> >
> > We’ve got this.  It’s very out of date… that is, contains now completely
> > incorrect, not just incomplete, information.  But it could be a starting
> > point.  As for the ISA, we have relied on Hitachi documents, and
> > architecture is not documented (at least not completely).
> >
> > J
> The hitachi document is probably:
> http://koti.kapsi.fi/~antime/sega/files/h12p0.pdf
> Although for an ISA reference we've more recently been using:
> http://www.shared-ptr.com/sh_insns.html
> As the j-core web page says, our local changes for j2 are:
> > We've added two backported sh3 barrel shift instructions (SHAD and
> > SHLD) to make modern compilers happy, and a new cmpxchg (mnemonic
> > CAS.L Rm, Rn, @R0 opcode 0010-nnnn-mmmm-0011, based on the IBM 360
> > instruction).
> Current gcc/binutils has cpu "j2" which knows about these changes. We're
> using https://github.com/richfelker/musl-cross-make to build fdpic
> toolchains, using something vaguely like:
> make install OUTPUT=~/cross-sh2eb-linux-muslfdpic \
>   TARGET=sh2eb-linux-muslfdpic GCC_CONFIG=--disable-nls \
>   --disable-libquadmath --disable-decimal-float --with-cpu-mj2
> (I have wrapper scripts that build various static and native toolchains
> for different targets, that was me sticking an "echo" in front of the
> make call to build the simple j2 one, once the script had worked out the
> arguments.)
> There's a j2_defconfig under arch/sh in current Linux kernels you can
> use to build a kernel targeted for the Numato board with that toolchain.
> (Rich asked me to upload a dtb file and I forgot, but you can build it
> from above dts file using dtc.)
> As for root filesystem, we're just doing a simple initramfs on the open
> source side. (It's got mmc sdcard support but it's fairly slow.) I'm
> doing a talk on building tiny root filesystems at ELC next month, which
> should eventually be listed on here:
> http://events.linuxfoundation.org/events/embedded-linux-
> conference/program/schedule
> And presumably video will go up sometime after that?
> Rob
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