linux-kernel - [PATCH 29/35] x86/ldt: Reserve address-space range on 32 bit for the LDT

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Message-Id: <1521228593-3820-30-git-send-email-joro@8bytes.org>
Date:   Fri, 16 Mar 2018 20:29:47 +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>, Pavel Machek <pavel@....cz>,
        jroedel@...e.de, joro@...tes.org
Subject: [PATCH 29/35] x86/ldt: Reserve address-space range on 32 bit for the LDT

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

Reserve 2MB/4MB of address-space for mapping the LDT to
user-space on 32 bit PTI kernels.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/include/asm/pgtable_32_types.h | 7 +++++--
 arch/x86/mm/dump_pagetables.c           | 9 +++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_32_types.h b/arch/x86/include/asm/pgtable_32_types.h
index 0777e18..eb2e97a 100644
--- a/arch/x86/include/asm/pgtable_32_types.h
+++ b/arch/x86/include/asm/pgtable_32_types.h
@@ -48,13 +48,16 @@ extern bool __vmalloc_start_set; /* set once high_memory is set */
 	((FIXADDR_TOT_START - PAGE_SIZE * (CPU_ENTRY_AREA_PAGES + 1))   \
 	 & PMD_MASK)
 
-#define PKMAP_BASE		\
+#define LDT_BASE_ADDR		\
 	((CPU_ENTRY_AREA_BASE - PAGE_SIZE) & PMD_MASK)
 
+#define PKMAP_BASE		\
+	((LDT_BASE_ADDR - PAGE_SIZE) & PMD_MASK)
+
 #ifdef CONFIG_HIGHMEM
 # define VMALLOC_END	(PKMAP_BASE - 2 * PAGE_SIZE)
 #else
-# define VMALLOC_END	(CPU_ENTRY_AREA_BASE - 2 * PAGE_SIZE)
+# define VMALLOC_END	(LDT_BASE_ADDR - 2 * PAGE_SIZE)
 #endif
 
 #define MODULES_VADDR	VMALLOC_START
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 2151ebb..fdefdf0 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -117,6 +117,9 @@ enum address_markers_idx {
 #ifdef CONFIG_HIGHMEM
 	PKMAP_BASE_NR,
 #endif
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
+	LDT_NR,
+#endif
 	CPU_ENTRY_AREA_NR,
 	FIXADDR_START_NR,
 	END_OF_SPACE_NR,
@@ -130,6 +133,9 @@ static struct addr_marker address_markers[] = {
 #ifdef CONFIG_HIGHMEM
 	[PKMAP_BASE_NR]		= { 0UL,		"Persistent kmap() Area" },
 #endif
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
+	[LDT_NR]		= { 0UL,		"LDT remap" },
+#endif
 	[CPU_ENTRY_AREA_NR]	= { 0UL,		"CPU entry area" },
 	[FIXADDR_START_NR]	= { 0UL,		"Fixmap area" },
 	[END_OF_SPACE_NR]	= { -1,			NULL }
@@ -579,6 +585,9 @@ static int __init pt_dump_init(void)
 # endif
 	address_markers[FIXADDR_START_NR].start_address = FIXADDR_START;
 	address_markers[CPU_ENTRY_AREA_NR].start_address = CPU_ENTRY_AREA_BASE;
+# ifdef CONFIG_MODIFY_LDT_SYSCALL
+	address_markers[LDT_NR].start_address = LDT_BASE_ADDR;
+# endif
 #endif
 	return 0;
 }
-- 
2.7.4