On Fri, 2023-02-17 at 17:11 +0100, Borislav Petkov wrote: > On Fri, Feb 10, 2023 at 05:00:05PM +0000, Edgecombe, Rick P wrote: > > /* > > * Dirty bit is not preserved above so it can be done > > * in a special way for the shadow stack case, where it > > * may need to set _PAGE_SAVED_DIRTY. __pte_mkdirty() will > > do > > * this in the case of shadow stack. > > */ > > if (oldval & _PAGE_DIRTY) > > if (cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && > > !pte_write(pte_result)) > > pte_set_flags(pte_result, > > _PAGE_SAVED_DIRTY); > > else > > pte_set_flags(pte_result, _PAGE_DIRTY); > > } > > > > return pte_result; > > } > > > > So the later logic of doing the _PAGE_SAVED_DIRTY (_PAGE_COW) part > > is > > not centralized. It's ok? > > I think so. > > 1. If you have a single pte_mkdirty() and not also a __ helper, then > there's less confusion for callers as to which interface they > should be > using > > 2. The not centralized part is a single conditional so it's not like > you're saving on gazillion code lines > > So I'd prefer that. > > Fair enough, I'll adjust it. Thanks!
