On Wed, Aug 26, 2020 at 12:57 PM Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > 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. There is no reason we can't use long arch_prctl (int, unsigned long, unsigned long, unsigned long, ..); for ARCH_X86_CET_MMAP_SHSTK. We just need to use syscall (SYS_arch_prctl, ARCH_X86_CET_MMAP_SHSTK, ...); -- H.J.
