Messages in this thread | | | Subject | Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack | From | Dave Hansen <> | Date | Tue, 25 Aug 2020 12:19:39 -0700 |
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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.
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