[PATCH v5 0/4] linux-user: Fix siginfo_t contents when jumping to non-readable pages

[Ilya Leoshkevich]

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 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 [1].

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 [2].

[1] https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg02472.html
[2] 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

-- 
2.37.1