|Subject:||Re: [PATCH v5 0/4] linux-user: Fix siginfo_t contents when jumping to non-readable pages|
|Date:||Fri, 19 Aug 2022 00:55:12 +0800|
|User-agent:||Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.0.3|
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.
Could this be related to issue 1155 ? On RISC-V, I'm getting incorrect [m|s]tval/[m|s]epc combinations for page faults in system emulation and incorrect si_addr and program counter on SIGSEGV in user emulation. Since it seems to only affect instructions that cross page boundaries, and RISC-V also has variable length instructions, it seems that I've run into the same problem as what is fixed here.
Could this fix be extended be extended to targets/riscv?
Patch 1 fixes an invalidation issue, which may prevent SEGV from happening altogether. Patches 2-3 fix the main issue on x86_64 and s390x. Many other architectures have fixed-size instructions and are not affected. Patch 4 adds tests. Note: this series depends on . 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). v4: https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg01747.html v4 -> v5: Drop patch 2. Use a different fix for the invalidation issue based on discussion with Richard .  https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg02472.html  https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg02556.html Ilya Leoshkevich (4): linux-user: Clear tb_jmp_cache on mprotect() 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 linux-user/mmap.c | 14 +++ 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 +++++++++++++++++++++++++ 8 files changed, 427 insertions(+), 6 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
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