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[PATCH v17 00/14] plugins: Allow to read registers

From: Akihiko Odaki
Subject: [PATCH v17 00/14] plugins: Allow to read registers
Date: Wed, 13 Dec 2023 15:40:59 +0900

Based-on: <20231213-riscv-v7-0-a760156a337f@daynix.com>
("[PATCH v7 0/4] gdbstub and TCG plugin improvements")

I and other people in the University of Tokyo, where I research
processor design, found TCG plugins are very useful for processor design

The feature we find missing is the capability to read registers from
plugins. In this series, I propose to add such a capability by reusing
gdbstub code.

The reuse of gdbstub code ensures the long-term stability of the TCG
plugin interface for register access without incurring a burden to
maintain yet another interface for register access.

This process to add TCG plugin involves four major changes. The first
one is to add members to GDBFeature necessary for register

The second one is to make gdb_read_register/gdb_write_register usable
outside of gdbstub context.

The third one is to actually make registers readable for plugins.

The execlog plugin will have new options to demonstrate the new feature.
I also have a plugin that uses this new feature to generate execution
traces for Sniper processor simulator, which is available at:

The below is a summary of patches:
Patch [01, 09] changes to use GDBFeature for dynamic XMLs.
Patch 10 adds members useful to identify registers to GDBFeature.
Patch 11 makes registers readable outside of gdbstub context.
Patch [12, 14] add the feature to read registers from plugins.

V16 -> V17:

V15 -> V16:
  Added new plugin_dyn_cb_subtype and plugin_gen_cb to remove the global
  translator state change.

V14 -> V15:
  Added kdoc comments to include/exec/gdbstub.h.
  Changed to use g_array_append_val() in gdb_register_feature().
  Separated the CPU flags from event bitmap.

V13 -> V14:
  Fixed RISC-V CSR register numbers.

V12 -> V13:
  Rebased to "[PATCH v4 0/5] gdbstub and TCG plugin improvements".

V11 -> V12:
  Rebased to "[PATCH v2 0/3] gdbstub and TCG plugin improvements".

V10 -> V11:

V9 -> V10:
  Rebased to "[PATCH 0/4] gdbstub and TCG plugin improvements".
  Dropped patch "plugins: Support C++".
  Removed the unnecessary QEMU_PLUGIN_VERSION change.

V8 -> V9:
  Rebased to "[PATCH 00/25] October maintainer omnibus pre-PR (tests,
  gdbstub, plugins)".
  Added patch "target/riscv: Move MISA limits to class".
  Added patch "target/riscv: Remove misa_mxl validation".
  Added patch "target/riscv: Validate misa_mxl_max only once".
  Added patch "plugins: Use different helpers when reading".
  Moved contrib/plugins/cc.cc to tests/plugin/cc.cc.

V7 -> V8:
  Rebased to "[PATCH v3 00/12] gdbstub and TCG plugin improvements".
  Clarified that initialization and exit hooks affect TCG state.
  Simplified by adding the core feature to gdb_regs.

V6 -> V7:
  Rebased to "[PATCH v2 00/11] gdbstub and TCG plugin improvements".
  Replaced functions to get register identifiers.

V5 -> V6:
  Rebased to "[PATCH 0/8] gdbstub and TCG plugin improvements".

V4 -> V5:
  Corrected g_rw_lock_writer_lock() call. (Richard Henderson)
  Replaced abort() with g_assert_not_reached(). (Richard Henderson)
  Fixed CSR name leak in target/riscv. (Richard Henderson)
  Removed gdb_has_xml variable.

V3 -> V4:
  Added execlog changes I forgot to include in the last version.

V2 -> V3:
  Added patch "hw/core/cpu: Return static value with gdb_arch_name()".
  Added patch "gdbstub: Dynamically allocate target.xml buffer".
  (Alex Bennée)
  Added patch "gdbstub: Introduce GDBFeatureBuilder". (Alex Bennée)
  Dropped Reviewed-by tags for "target/*: Use GDBFeature for dynamic XML".
  Changed gdb_find_static_feature() to abort on failure. (Alex Bennée)
  Changed the execlog plugin to log the register value only when changed.
  (Alex Bennée)
  Dropped 0x prefixes for register value logs for conciseness.

V1 -> V2:
  Added SPDX-License-Identifier: GPL-2.0-or-later. (Philippe Mathieu-Daudé)
  Split long lines. (Philippe Mathieu-Daudé)
  Renamed gdb_features to gdb_static_features (Philippe Mathieu-Daudé)
  Dropped RFC.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Akihiko Odaki (14):
      target/arm: Use GDBFeature for dynamic XML
      target/ppc: Use GDBFeature for dynamic XML
      target/riscv: Use GDBFeature for dynamic XML
      gdbstub: Use GDBFeature for gdb_register_coprocessor
      gdbstub: Use GDBFeature for GDBRegisterState
      gdbstub: Change gdb_get_reg_cb and gdb_set_reg_cb
      gdbstub: Simplify XML lookup
      gdbstub: Infer number of core registers from XML
      hw/core/cpu: Remove gdb_get_dynamic_xml member
      gdbstub: Add members to identify registers to GDBFeature
      gdbstub: Expose functions to read registers
      plugins: Use different helpers when reading registers
      plugins: Allow to read registers
      contrib/plugins: Allow to log registers

 docs/devel/tcg-plugins.rst   |  10 +-
 accel/tcg/plugin-helpers.h   |   3 +-
 include/exec/gdbstub.h       |  44 ++++++++-
 include/hw/core/cpu.h        |   7 +-
 include/qemu/plugin.h        |   1 +
 include/qemu/qemu-plugin.h   |  50 +++++++++-
 target/arm/cpu.h             |  27 ++---
 target/arm/internals.h       |  14 +--
 target/hexagon/internal.h    |   4 +-
 target/microblaze/cpu.h      |   4 +-
 target/ppc/cpu-qom.h         |   1 +
 target/ppc/cpu.h             |   5 +-
 target/riscv/cpu.h           |   5 +-
 target/s390x/cpu.h           |   2 -
 accel/tcg/plugin-gen.c       |  43 +++++++-
 contrib/plugins/execlog.c    | 120 ++++++++++++++++------
 gdbstub/gdbstub.c            | 173 +++++++++++++++++++-------------
 hw/core/cpu-common.c         |   5 +-
 plugins/api.c                |  32 +++++-
 target/arm/cpu.c             |   2 -
 target/arm/cpu64.c           |   1 -
 target/arm/gdbstub.c         | 230 ++++++++++++++++++++++---------------------
 target/arm/gdbstub64.c       | 122 ++++++++++++-----------
 target/avr/cpu.c             |   1 -
 target/hexagon/cpu.c         |   4 +-
 target/hexagon/gdbstub.c     |  10 +-
 target/i386/cpu.c            |   2 -
 target/loongarch/cpu.c       |   2 -
 target/loongarch/gdbstub.c   |  13 ++-
 target/m68k/cpu.c            |   1 -
 target/m68k/helper.c         |  26 +++--
 target/microblaze/cpu.c      |   6 +-
 target/microblaze/gdbstub.c  |   9 +-
 target/ppc/cpu_init.c        |   7 --
 target/ppc/gdbstub.c         | 114 ++++++++++-----------
 target/riscv/cpu.c           |  15 ---
 target/riscv/gdbstub.c       | 139 ++++++++++++++------------
 target/rx/cpu.c              |   1 -
 target/s390x/cpu.c           |   1 -
 target/s390x/gdbstub.c       | 105 ++++++++++++--------
 plugins/qemu-plugins.symbols |   3 +
 scripts/feature_to_c.py      |  14 ++-
 42 files changed, 836 insertions(+), 542 deletions(-)
base-commit: 651f18e5def549b67df934e38c474963b884ccc7
change-id: 20231213-gdb-349db0da93f2

Best regards,
Akihiko Odaki <akihiko.odaki@daynix.com>

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