On 2/24/26 7:46 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 version v4 of the patch series is more about small refactorings and
cleanups than changes in functionality.
Best regards,
Florian
Changes:
v4:
- switch strcmp out in favor of g_strcmp0
- split the patch introducing the qemu_plugin_set_pc() API into three
patches, two for preparing the plugin infrastructure and the syscall
handling code and a third introducing the actual plugin API
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 (7):
plugins: add flag to specify whether PC is rw
linux-user: make syscall emulation interruptible
plugins: add PC diversion API function
tests/tcg: add test for qemu_plugin_set_pc API
plugins: add read-only property for registers
plugins: prohibit writing to read-only registers
tests/tcg/plugins: test register readonly feature
include/plugins/qemu-plugin.h | 18 +++++
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/or1k/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 | 16 +++++
linux-user/xtensa/cpu_loop.c | 3 +
plugins/api.c | 43 ++++++++++--
plugins/core.c | 29 ++++----
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 | 22 +++++-
.../{ => 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 | 1 +
tests/tcg/plugins/registers.c | 68 +++++++++++++++++++
tests/tcg/plugins/syscall.c | 6 ++
tests/tcg/sparc64/Makefile.target | 16 +++++
36 files changed, 331 insertions(+), 41 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: afe653676dc6dfd49f0390239ff90b2f0052c2b8
A few small nits reported by checkpatch.
$ ./scripts/checkpatch.pl $(git merge-base upstream/master HEAD)..HEAD
1/8 Checking commit 23b2901d559b (plugins: add flag to specify whether
PC is rw)
2/8 Checking commit cf46ff49010c (linux-user: make syscall emulation
interruptible)
WARNING: Block comments use a leading /* on a separate line
#217: FILE: linux-user/mips/cpu_loop.c:144:
+ /* Returning from a successful sigreturn syscall or from
WARNING: Block comments use * on subsequent lines
#218: FILE: linux-user/mips/cpu_loop.c:145:
+ /* Returning from a successful sigreturn syscall or from
+ control flow diversion in a plugin callback.
WARNING: Block comments use a leading /* on a separate line
#247: FILE: linux-user/ppc/cpu_loop.c:345:
+ /* Returning from a successful sigreturn syscall or from
WARNING: Block comments use * on subsequent lines
#248: FILE: linux-user/ppc/cpu_loop.c:346:
+ /* Returning from a successful sigreturn syscall or from
+ control flow diversion in a plugin callback.
3/8 Checking commit 2bb085851ee5 (plugins: add PC diversion API function)
4/8 Checking commit 3001ad67e7e5 (tests/tcg: add test for
qemu_plugin_set_pc API)
ERROR: New file 'tests/tcg/mips64/Makefile.target' requires
'SPDX-License-Identifier'
ERROR: New file 'tests/tcg/mips64el/Makefile.target' requires
'SPDX-License-Identifier'
ERROR: New file 'tests/tcg/mipsel/Makefile.target' requires
'SPDX-License-Identifier'
ERROR: open brace '{' following function declarations go on the next line
#216: FILE: tests/tcg/multiarch/plugin/test-plugin-skip-syscalls.c:15:
+void exit_success(void) {
ERROR: open brace '{' following function declarations go on the next line
#220: FILE: tests/tcg/multiarch/plugin/test-plugin-skip-syscalls.c:19:
+int main(int argc, char *argv[]) {
ERROR: New file 'tests/tcg/sparc64/Makefile.target' requires
'SPDX-License-Identifier'
5/8 Checking commit c85ae80717dc (plugins: add read-only property for
registers)
ERROR: do not use C99 // comments
#45: FILE: plugins/api.c:413:
+static const char pc_str[] = "pc"; // generic name for program counter
ERROR: do not use C99 // comments
#46: FILE: plugins/api.c:414:
+static const char eip_str[] = "eip"; // x86 specific name for program
counter
ERROR: do not use C99 // comments
#47: FILE: plugins/api.c:415:
+static const char rip_str[] = "rip"; // x86_64 specific name for
program counter
ERROR: do not use C99 // comments
#48: FILE: plugins/api.c:416:
+static const char pswa_str[] = "pswa"; // s390x specific name for
program counter
ERROR: do not use C99 // comments
#49: FILE: plugins/api.c:417:
+static const char iaoq_str[] = "iaoq"; // HP/PA specific name for
program counter
ERROR: do not use C99 // comments
#50: FILE: plugins/api.c:418:
+static const char rpc_str[] = "rpc"; // microblaze specific name for
program counter
6/8 Checking commit 156dc74ab9a5 (plugins: prohibit writing to read-only
registers)
7/8 Checking commit dba748c1e46c (tests/tcg/plugins: test register
readonly feature)
ERROR: New file 'tests/tcg/plugins/registers.c' requires
'SPDX-License-Identifier'
ERROR: New file 'tests/tcg/plugins/registers.c' must not have license
boilerplate header text, only the SPDX-License-Identifier, unless this
file was copied from existing code already having such text.
Regards,
Pierrick
