On 8/25/20 11:43 AM, Yu, Yu-cheng wrote: >>> arch_prctl(ARCH_X86_CET_MMAP_SHSTK, u64 *args) >>> Allocate a new shadow stack. >>> >>> The parameter 'args' is a pointer to a user buffer. >>> >>> *args = desired size >>> *(args + 1) = MAP_32BIT or MAP_POPULATE >>> >>> On returning, *args is the allocated shadow stack address. >> >> This is hideous. Would this be better as a new syscall? > > Could you point out why this is hideous, so that I can modify the > arch_prctl? Passing values in memory is hideous when we don't have to. A syscall would let you have separate arguments for size and flags and would also let you have a nice return value instead of needing to do that in memory too. > I think this is more arch-specific. Even if it becomes a new syscall, > we still need to pass the same parameters. Right, but without the copying in and out of memory.
