linux-kernel - [PATCH 12/16] x86/mm/pae: Populate the user page-table with user pgd's

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Message-Id: <1516120619-1159-13-git-send-email-joro@8bytes.org>
Date:   Tue, 16 Jan 2018 17:36:55 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, jroedel@...e.de,
        joro@...tes.org
Subject: [PATCH 12/16] x86/mm/pae: Populate the user page-table with user pgd's

From: Joerg Roedel <jroedel@...e.de>

This is the last part of the PAE page-table setup for PAE
before we can add the CR3 switch to the entry code.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/include/asm/pgtable-3level.h | 3 +++
 arch/x86/mm/pti.c                     | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index bc4af5453802..910f0b35370e 100644
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -98,6 +98,9 @@ static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
 
 static inline void native_set_pud(pud_t *pudp, pud_t pud)
 {
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+	pud.p4d.pgd = pti_set_user_pgd(&pudp->p4d.pgd, pud.p4d.pgd);
+#endif
 	set_64bit((unsigned long long *)(pudp), native_pud_val(pud));
 }
 
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 6b6bfd13350e..a561b5625d6c 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -122,6 +122,7 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
 	 */
 	kernel_to_user_pgdp(pgdp)->pgd = pgd.pgd;
 
+#ifdef CONFIG_X86_64
 	/*
 	 * If this is normal user memory, make it NX in the kernel
 	 * pagetables so that, if we somehow screw up and return to
@@ -134,10 +135,16 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
 	 *     may execute from it
 	 *  - we don't have NX support
 	 *  - we're clearing the PGD (i.e. the new pgd is not present).
+	 *  - We run on a 32 bit kernel. 2-level paging doesn't support NX at
+	 *    all and PAE paging does not support it on the PGD level. We can
+	 *    set it in the PMD level there in the future, but that means we
+	 *    need to unshare the PMDs between the kernel and the user
+	 *    page-tables.
 	 */
 	if ((pgd.pgd & (_PAGE_USER|_PAGE_PRESENT)) == (_PAGE_USER|_PAGE_PRESENT) &&
 	    (__supported_pte_mask & _PAGE_NX))
 		pgd.pgd |= _PAGE_NX;
+#endif
 
 	/* return the copy of the PGD we want the kernel to use: */
 	return pgd;
-- 
2.13.6