linux-user: Rewrite target_shmat

Handle combined host and guest alignment requirements.
Handle host and guest page size differences.
Handle SHM_EXEC.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/115
Tested-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
1 file changed