Re: [PATCH v5 11/39] x86/mm: Update pte_modify for _PAGE_COW
From: Borislav Petkov <bp@alien8.de>
Date: 2023-02-10 13:57:29
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
On Thu, Feb 09, 2023 at 05:09:15PM +0000, Edgecombe, Rick P wrote:
What do you think, can we leave it or give it a new name? Maybe pte_set_dirty() to be more like the x86-only pte_set_flags() family of functions?
I'd do this (ontop of yours, not built, not tested, etc). It is short and sweet: pte_mkdirty() set both dirty flags pte_modifl() sets only _PAGE_DIRTY No special helpers to lookup what they do, no nothing. Plain and simple. ---
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 7942eff2af50..8ba37380966c 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h@@ -392,19 +392,10 @@ static inline pte_t pte_mkexec(pte_t pte) return pte_clear_flags(pte, _PAGE_NX); } -static inline pte_t __pte_mkdirty(pte_t pte, bool soft) -{ - pteval_t dirty = _PAGE_DIRTY; - - if (soft) - dirty |= _PAGE_SOFT_DIRTY; - - return pte_set_flags(pte, dirty); -} - +/* Set _PAGE_SOFT_DIRTY for shadow stack pages. */ static inline pte_t pte_mkdirty(pte_t pte) { - return __pte_mkdirty(pte, true); + return pte_set_flags(pte, _PAGE_DIRTY | _PAGE_SOFT_DIRTY); } static inline pte_t pte_mkyoung(pte_t pte)
@@ -749,14 +740,8 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) pte_result = __pte(val); - /* - * 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_COW. __pte_mkdirty() will do this in - * the case of shadow stack. - */ if (pte_dirty(pte)) - pte_result = __pte_mkdirty(pte_result, false); + pte_result = pte_set_flags(pte_result, _PAGE_DIRTY); return pte_result; }
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette