[v3,0/3] target/riscv: Expose "priv" register for GDB

Message

Jonathan Behrens Oct. 8, 2019, 12:13 a.m. UTC

The third patch in this series makes the priv virtual register writitable. I'm
not entirely sure this is a good idea, so I split it out into its own patch. In
particular, this change will conflict with the hypervisor extension work which
assumes that the privilege mode does not change in unexpected cases.

As pointed out in a previous version of this series, GDB actually contains some
support already for the accessing the privilege mode via a virtual "priv"
register, including to convert the values into human readable forms:

(gdb) info reg priv
priv           0x3	prv:3 [Machine]

Changlog V3:
- Break patch into series
- Make priv a virtual register

Changelog V2:
- Use PRV_H and PRV_S instead of integer literals

Jonathan Behrens (3)
  target/riscv: Tell gdbstub the correct number of CSRs
  target/riscv: Expose priv register for GDB for reads
  target/riscv: Make the priv register writable by GDB

 configure                       |  4 ++--
 gdb-xml/riscv-32bit-virtual.xml | 11 +++++++++++
 gdb-xml/riscv-64bit-virtual.xml | 11 +++++++++++
 target/riscv/gdbstub.c          | 36 ++++++++++++++++++++++++++++++++++--
 4 files changed, 58 insertions(+), 4 deletions(-)

Comments

Jonathan Behrens Oct. 8, 2019, 12:17 a.m. UTC | #1

The first paragraph seems to have gone missing. Repeated below:

> This series adds a new "priv" virtual register that reports the current
> privilege mode. This is helpful for debugging purposes because that information
> is not actually available in any of the real CSRs.


On Mon, Oct 7, 2019 at 8:15 PM Jonathan Behrens <[e-mail]> wrote:
>
> The third patch in this series makes the priv virtual register writitable. I'm
> not entirely sure this is a good idea, so I split it out into its own patch. In
> particular, this change will conflict with the hypervisor extension work which
> assumes that the privilege mode does not change in unexpected cases.
>
> As pointed out in a previous version of this series, GDB actually contains some
> support already for the accessing the privilege mode via a virtual "priv"
> register, including to convert the values into human readable forms:
>
> (gdb) info reg priv
> priv           0x3      prv:3 [Machine]
>
> Changlog V3:
> - Break patch into series
> - Make priv a virtual register
>
> Changelog V2:
> - Use PRV_H and PRV_S instead of integer literals
>
> Jonathan Behrens (3)
>   target/riscv: Tell gdbstub the correct number of CSRs
>   target/riscv: Expose priv register for GDB for reads
>   target/riscv: Make the priv register writable by GDB
>
>  configure                       |  4 ++--
>  gdb-xml/riscv-32bit-virtual.xml | 11 +++++++++++
>  gdb-xml/riscv-64bit-virtual.xml | 11 +++++++++++
>  target/riscv/gdbstub.c          | 36 ++++++++++++++++++++++++++++++++++--
>  4 files changed, 58 insertions(+), 4 deletions(-)
>
>