On 8/26/20 11:49 AM, Yu, Yu-cheng wrote: >> I would expect things like Go and various JITs to call it directly. >> >> If we wanted to be fancy and add a potentially more widely useful >> syscall, how about: >> >> mmap_special(void *addr, size_t length, int prot, int flags, int type); >> >> Where type is something like MMAP_SPECIAL_X86_SHSTK. Fundamentally, >> this is really just mmap() except that we want to map something a bit >> magical, and we don't want to require opening a device node to do it. > > One benefit of MMAP_SPECIAL_* is there are more free bits than MAP_*. > Does ARM have similar needs for memory mapping, Dave? No idea. But, mmap_special() is *basically* mmap2() with extra-big flags space. I suspect it will grow some more uses on top of shadow stacks. It could have, for instance, been used to allocate MPX bounds tables.
