On Tue, Jun 21, 2016 at 2:24 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Monday, June 20, 2016 4:43:30 PM CEST Andy Lutomirski wrote: >> >> On my laptop, this adds about 1.5µs of overhead to task creation, >> which seems to be mainly caused by vmalloc inefficiently allocating >> individual pages even when a higher-order page is available on the >> freelist. > > Would it help to have a fixed virtual address for the stack instead > and map the current stack to that during a task switch, similar to > how we handle fixmap pages? > > That would of course trade the allocation overhead for a task switch > overhead, which may be better or worse. It would also give "current" > a constant address, which may give a small performance advantage > but may also introduce a new attack vector unless we randomize it > again. Right: we don't want a fixed address. That makes attacks WAY easier. -Kees -- Kees Cook Chrome OS & Brillo Security -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
