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Re: ymm register error


On 17/07/2018, Paul Topley <> wrote:
> When trying to run gdb server on a skylake-x HEDT platform (i9-7940X) I
> encounter the following error:
> regcache.c:264: A problem internal to GDBserver has been detected.
> Unknown register ymm0h requested

How exactly do you run it to get this error?

> From what I can tell from furious googling is that the ymm registers have
> changed location from broadwell-e to skylake-x.

Broadwell-E doesn't support AVX-512, while Skylake-X does. This might
be the difference, but on Bochs with AVX-512 and XSAVE support enabled
I failed to reproduce your problem. I tried to do it by running
gdbserver from git master on /bin/true and then attaching from another
VT and trying `info all-reg` command. Also `p $ymm0h` and `info reg
ymm0h` commands do succeed for me (as does `info reg zmm0`, which
confirms that AVX-512 support is working).

> I can see references to the ymm registers in gdb's codebase, with apparent
> positioning related to features like org.gnu.gdb.i386.avx &
> org.gnu.gdb.i386.avx512.
> Being a complete novice around gdb's codebase, I'm not sure if I need to
> enable or state something at configure stage so that the right ymm register
> location is referenced.
> gdb server 8 in ubuntu bionics repos works OK on the skylake-x platform, but
> when I compile myself it does not.
> Is there something specific I need to be stating at compile time to "get"
> gdbserver 8 to work on skylake-x

I simply configured gdb via `configure --prefix=$HOME/opt/gdb-git`,
without any additional options, and it works as described above. Could
you check that latest git master still has the problem?

> Paul


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