There are multiple issues with the implementation of shmat().
(1) With reserved_va, which is the default for 32-on-64-bit, we mmap the
entire guest address space. Unlike mmap, shmat refuses to replace an
existing mapping without setting SHM_REMAP. This is the original
subject of issue #115, though it quicky gets distracted by
something else.
(2) With target page size > host page size, and a shm area
that is not a multiple of the target page size, we leave
an unmapped hole that the target expects to be mapped.
This is the subject of
https://lore.kernel.org/qemu-devel/2no4imvz2zrar5kchz2l3oddqbgpj77jgwcuf7aritkn2ok763@i2mvpcihztho/
wherein qemu itself expects a mapping to exist, and
dies in open_self_maps_2.
So: reimplement the thing.
Changes for v2:
- Include Ilya's test case, which caught extra errors: Yay!
- Include x86_64 /proc/self/maps fix, which the test triggers.
- Dropped r-b for the shmat rewrite due to number of changes.
r~
Based-on: <20240222204323.268539-1-richard.hender...@linaro.org>
("[PULL 00/39] tcg and linux-user patch queue")
(Which is technically now out of date, waiting on the coredump
rewrite to solve -Wvla werrors.)
Ilya Leoshkevich (1):
tests/tcg: Check that shmat() does not break /proc/self/maps
Richard Henderson (4):
linux-user/x86_64: Handle the vsyscall page in open_self_maps_{2,4}
linux-user/loongarch64: Remove TARGET_FORCE_SHMLBA
linux-user: Add strace for shmat
linux-user: Rewrite target_shmat
linux-user/loongarch64/target_syscall.h | 7 -
linux-user/mmap.c | 172 +++++++++++++++----
linux-user/strace.c | 23 +++
linux-user/syscall.c | 16 ++
tests/tcg/multiarch/linux/linux-shmat-maps.c | 55 ++++++
linux-user/strace.list | 2 +-
6 files changed, 231 insertions(+), 44 deletions(-)
create mode 100644 tests/tcg/multiarch/linux/linux-shmat-maps.c
--
2.34.1
