Messages in this thread | | | Date | Fri, 12 Dec 2014 09:31:34 +0100 | From | Ingo Molnar <> | Subject | Re: [GIT pull] x86 mpx support for 3.19 |
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* Dave Hansen <dave.hansen@linux.intel.com> wrote:
> +config X86_INTEL_MPX > + prompt "Intel MPX (Memory Protection Extensions)" > + def_bool y > + depends on CPU_SUP_INTEL > + ---help--- > + MPX provides hardware features that can be used in > + conjunction with compiler-instrumented code to check > + memory references. It is designed to detect buffer > + overflow or underflow bugs. > + > + This option enables running applications which are > + instrumented or otherwise use MPX. It does not use MPX > + itself inside the kernel or to protect the kernel > + against bad memory references. > + > + Enabling this option will make the kernel larger: > + ~8k of kernel text and 36 bytes of data on a 64-bit > + defconfig. It adds a long to the 'mm_struct' which > + will increase the kernel memory overhead of each > + process and adds some branches to paths used during > + exec() and munmap(). > + > + If unsure, say Y.
That description looks pretty good to me.
Linus, what's your take on the default-y? To me it seems there's arguments both ways: usually we allow unprivileged ABIs to be disabled only under EXPERT and make them default-y (to help adaption and to define what the default ABI of 'Linux' is - we did a default-y for SECCOMP for example) - OTOH this is a new ABI, the processors aren't even out yet, and there's costs to the MM code even in the non-MPX case, so it's not as clear-cut as in the SECCOMP case which had essentially zero runtime cost.
Thanks,
Ingo
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