Messages in this thread | | | Subject | Re: [PATCH 31/32] x86, pkeys: execute-only support | From | Dave Hansen <> | Date | Mon, 14 Dec 2015 15:37:50 -0800 |
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On 12/14/2015 12:05 PM, Kees Cook wrote: > On Mon, Dec 14, 2015 at 11:06 AM, Dave Hansen <dave@sr71.net> wrote: >> > From: Dave Hansen <dave.hansen@linux.intel.com> >> > Protection keys provide new page-based protection in hardware. >> > But, they have an interesting attribute: they only affect data >> > accesses and never affect instruction fetches. That means that >> > if we set up some memory which is set as "access-disabled" via >> > protection keys, we can still execute from it. ... >> > I haven't found any userspace that does this today. > To realistically take advantage of this, it sounds like the linker > would need to know to keep bss and data page-aligned away from text, > and then set text to PROT_EXEC only? > > Do you have any example linker scripts for this?
Nope. My linker-fu is weak.
Can we even depend on the linker by itself? Even if the sections were marked --x, we can't actually use them with those permissions unless we have protection keys.
Do we need some special tag on the section to tell the linker to map it as --x under some conditions and r-x for others?
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