On 1/20/26 7:19 AM, Florian Hofhammer wrote:
Hi,
This patch series builds on top of the discussion from the thread at
https://lore.kernel.org/qemu-devel/[email protected]/
and adds a plugin API function to set the program counter of the guest,
as just writing to it via qemu_plugin_write_register() has no direct
effect.
Based on the discussion in the above thread, the series also introduces
a means to declare registers as read-only from the plugin side, which
prevents plugins from writing to them via qemu_plugin_write_register().
This for now is only applied to the PC, and finding the PC register is
done via some rather hacky strcmp()s. In the above thread, we also
discussed encoding the read-only property in a custom attribute in the
GDB XMLs, but that would (1) make syncing with GDB harder, (2) not
cover all architectures, as there's not an XML description of all
architectures available in the gdb-xml/ directory, and (3) require quite
some changes to the whole GDB infrastructure in gdbstub/ to even encode
the attribute in the correct structs and pass them on over the different
layers up into the plugin API.
This patch series does not (yet) bump the plugin API version, as I've
sent another patch yesterday (see
https://lore.kernel.org/qemu-devel/[email protected]/)
that makes some changes to qemu_plugin_{read,write}_register() as well
and I'll adjust the plugin API version bump and API usage in a v4 once I
have an idea whether the patches will make it into a release or not to
avoid conflicts later on.
Best regards,
Florian
Changes:
v3:
- make PC registers read-only across architectures
- add tests for read-only registers
- adjust test structure for qemu_plugin_set_pc() by moving
architecture-specific tests into corresponding directories
v2:
- add setjmp() in syscall handling path to allow PC redirection from
syscall callbacks (via longjmp(), the cpu_loop()'s setjmp() for
exiting a TB would not be live anymore in syscall handlers)
- add flags to ensure the qemu_plugin_set_pc() API is only called from
contexts where the CPU is live
- add test for qemu_plugin_set_pc() API
v1:
- initial version
Florian Hofhammer (5):
plugins: add PC diversion API function
plugins: add read-only property for registers
plugins: prohibit writing to read-only registers
tests/tcg: add test for qemu_plugin_set_pc API
tests/tcg/plugins: test register readonly feature
include/qemu/qemu-plugin.h | 17 +++++
linux-user/aarch64/cpu_loop.c | 2 +-
linux-user/alpha/cpu_loop.c | 2 +-
linux-user/arm/cpu_loop.c | 2 +-
linux-user/hexagon/cpu_loop.c | 2 +-
linux-user/hppa/cpu_loop.c | 4 ++
linux-user/i386/cpu_loop.c | 8 ++-
linux-user/include/special-errno.h | 8 +++
linux-user/loongarch64/cpu_loop.c | 5 +-
linux-user/m68k/cpu_loop.c | 2 +-
linux-user/microblaze/cpu_loop.c | 2 +-
linux-user/mips/cpu_loop.c | 5 +-
linux-user/openrisc/cpu_loop.c | 2 +-
linux-user/ppc/cpu_loop.c | 6 +-
linux-user/riscv/cpu_loop.c | 2 +-
linux-user/s390x/cpu_loop.c | 2 +-
linux-user/sh4/cpu_loop.c | 2 +-
linux-user/sparc/cpu_loop.c | 4 +-
linux-user/syscall.c | 8 +++
linux-user/xtensa/cpu_loop.c | 3 +
plugins/api.c | 41 +++++++++--
plugins/core.c | 25 ++++---
tests/tcg/arm/Makefile.target | 6 ++
tests/tcg/hexagon/Makefile.target | 7 ++
tests/tcg/mips/Makefile.target | 6 +-
tests/tcg/mips64/Makefile.target | 15 ++++
tests/tcg/mips64el/Makefile.target | 15 ++++
tests/tcg/mipsel/Makefile.target | 15 ++++
tests/tcg/multiarch/Makefile.target | 20 +++++-
.../{ => plugin}/check-plugin-output.sh | 0
.../{ => plugin}/test-plugin-mem-access.c | 0
.../plugin/test-plugin-skip-syscalls.c | 26 +++++++
tests/tcg/plugins/meson.build | 2 +-
tests/tcg/plugins/registers.c | 71 +++++++++++++++++++
tests/tcg/plugins/syscall.c | 6 ++
tests/tcg/sparc64/Makefile.target | 16 +++++
36 files changed, 321 insertions(+), 38 deletions(-)
create mode 100644 tests/tcg/mips64/Makefile.target
create mode 100644 tests/tcg/mips64el/Makefile.target
create mode 100644 tests/tcg/mipsel/Makefile.target
rename tests/tcg/multiarch/{ => plugin}/check-plugin-output.sh (100%)
rename tests/tcg/multiarch/{ => plugin}/test-plugin-mem-access.c (100%)
create mode 100644 tests/tcg/multiarch/plugin/test-plugin-skip-syscalls.c
create mode 100644 tests/tcg/plugins/registers.c
create mode 100644 tests/tcg/sparc64/Makefile.target
base-commit: 38879a667fbb4ef54c70de71494882615f600a64
Thanks for posting Florian.
I'll let Alex review it to see if it matches his original vision, and
the readonly approach for pc register.
Regards,
Pierrick
