Hi, I noticed that when we get a SEGV due to jumping to non-readable memory, sometimes si_addr and program counter in siginfo_t are slightly off. I tracked this down to the assumption that translators stop before the end of a page, while in reality they may stop right after it.
Patch 1 fixes a minor invalidation issue, which may prevent SEGV from happening altogether. Patch 2 introduces a helper function. Patches 3-4 fix the main issue on x86_64 and s390x. Many other architectures have fixed-size instructions and are not affected. Patch 5 adds tests. Best regards, Ilya v1: https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg00822.html v1 -> v2: Fix individual translators instead of translator_loop (Peter). v2: https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg01079.html v2 -> v3: Peek at the next instruction on s390x (Richard). Undo more on i386 (Richard). Check PAGE_EXEC, not PAGE_READ (Peter, Richard). v3: https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg01306.html v3 -> v4: Improve the commit message in patch 1 to better reflect what exactly is being fixed there. Factor out the is_same_page() patch (Richard). Do not touch the common code in the i386 fix (Richard). Ilya Leoshkevich (5): accel/tcg: Invalidate translations when clearing PAGE_EXEC accel/tcg: Introduce is_same_page() target/s390x: Make translator stop before the end of a page target/i386: Make translator stop before the end of a page tests/tcg: Test siginfo_t contents when jumping to non-readable pages accel/tcg/translate-all.c | 17 ++-- include/exec/translator.h | 10 +++ target/i386/tcg/translate.c | 25 +++++- target/s390x/tcg/translate.c | 15 +++- tests/tcg/multiarch/noexec.h | 114 ++++++++++++++++++++++++ tests/tcg/s390x/Makefile.target | 1 + tests/tcg/s390x/noexec.c | 145 +++++++++++++++++++++++++++++++ tests/tcg/x86_64/Makefile.target | 3 +- tests/tcg/x86_64/noexec.c | 116 +++++++++++++++++++++++++ 9 files changed, 435 insertions(+), 11 deletions(-) create mode 100644 tests/tcg/multiarch/noexec.h create mode 100644 tests/tcg/s390x/noexec.c create mode 100644 tests/tcg/x86_64/noexec.c -- 2.37.1
