On 12/14/2015 12:05 PM, Kees Cook wrote: > On Mon, Dec 14, 2015 at 11:06 AM, Dave Hansen <dave@xxxxxxxx> wrote: >> > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> >> > 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? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>