linux-kernel - [PATCH, RFC 14/62] x86/mm: Map zero pages into encrypted mappings correctly

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Message-Id: <20190508144422.13171-15-kirill.shutemov@linux.intel.com>
Date:   Wed,  8 May 2019 17:43:34 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH, RFC 14/62] x86/mm: Map zero pages into encrypted mappings correctly

Zero pages are never encrypted. Keep KeyID-0 for them.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/include/asm/pgtable.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 50b3e2d963c9..59c3dd50b8d5 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -803,6 +803,19 @@ static inline unsigned long pmd_index(unsigned long address)
  */
 #define mk_pte(page, pgprot)   pfn_pte(page_to_pfn(page), (pgprot))
 
+#define mk_zero_pte mk_zero_pte
+static inline pte_t mk_zero_pte(unsigned long addr, pgprot_t prot)
+{
+	extern unsigned long zero_pfn;
+	pte_t entry;
+
+	prot.pgprot &= ~mktme_keyid_mask;
+	entry = pfn_pte(zero_pfn, prot);
+	entry = pte_mkspecial(entry);
+
+	return entry;
+}
+
 /*
  * the pte page can be thought of an array like this: pte_t[PTRS_PER_PTE]
  *
@@ -1133,6 +1146,12 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm,
 
 #define mk_pmd(page, pgprot)   pfn_pmd(page_to_pfn(page), (pgprot))
 
+#define mk_zero_pmd(zero_page, prot)					\
+({									\
+	prot.pgprot &= ~mktme_keyid_mask;				\
+	pmd_mkhuge(mk_pmd(zero_page, prot));				\
+})
+
 #define  __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
 extern int pmdp_set_access_flags(struct vm_area_struct *vma,
 				 unsigned long address, pmd_t *pmdp,
-- 
2.20.1