SHM_RDONLY
if (arg == 0 || (arg & ~(IPC_FLAGS|SHM_RDONLY|SHM_RND|0777)) != 0)
if (arg & SHM_RDONLY)
((read_index) ? 0 : SHM_RDONLY));
if ((flags & SHM_RDONLY) == 0 &&
if (flags & SHM_RDONLY)
(SHM_R | SHM_W | SHM_RDONLY | SHM_RND | SHM_SHARE_MMU | SHM_PAGEABLE)