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.
There are a number of target page size != host page size and
target SHMLBA != host SHMLBA corner cases that are not implementable
without softmmu and a non-linear host to target address space.
I simply bail out in these situations and return EINVAL.
Based-on: <20240222204323.268539-1-richard.hender...@linaro.org>
("[PULL 00/39] tcg and linux-user patch queue")
r~
Richard Henderson (3):
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 | 146 ++++++++++++++++++------
linux-user/strace.c | 23 ++++
linux-user/strace.list | 2 +-
4 files changed, 134 insertions(+), 44 deletions(-)
--
2.34.1
