Other operating systems

Posted Feb 24, 2022 4:02 UTC (Thu) by ncm (guest, #165)
Parent article: Shadow stacks for user space

Wondering... Linux doesn't use all the bits, so can claim one to label a COW page. But $other does use them all, already. So, $other can't use Linux's method. What can $other do, instead? Has it already used one of those bits to tag a COW page, i.e. it already does what Linux will do?

And, there is more than one $other. Does anybody know whether all of them can make this work? Can Intel have succeeded in quizzing everybody who has an OS that might want shadow stacks?

Other operating systems

Posted Mar 19, 2022 8:12 UTC (Sat) by cpitrat (subscriber, #116459) [Link]

IIUC, COW is purely software so Linux can do whatever it wants with the invalid bits combinations. Shadow stack requires hardware support too (unless I'm mistaken) so it's a different story.