From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 4 Dec 2017 15:07:36 +0100
Subject: [PATCH] x86/mm/pti: Add infrastructure for page table isolation
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CVE-2017-5754

Add the initial files for kernel page table isolation, with a minimal init
function and the boot time detection for this misfeature.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(backported from commit aa8c6248f8c75acfd610fe15d8cae23cf70d9d09)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit 50da124a01ed7a59f9b2c9551f622c5a27d1caec)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  2 +
 arch/x86/mm/Makefile                            |  7 ++-
 arch/x86/entry/calling.h                        |  7 +++
 arch/x86/include/asm/pti.h                      | 14 +++++
 include/linux/pti.h                             | 11 ++++
 arch/x86/boot/compressed/pagetable.c            |  3 +
 arch/x86/mm/init.c                              |  2 +
 arch/x86/mm/pti.c                               | 84 +++++++++++++++++++++++++
 init/main.c                                     |  3 +
 9 files changed, 130 insertions(+), 3 deletions(-)
 create mode 100644 arch/x86/include/asm/pti.h
 create mode 100644 include/linux/pti.h
 create mode 100644 arch/x86/mm/pti.c

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3510e255ef4c..e2a4608da5d2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2677,6 +2677,8 @@
 			steal time is computed, but won't influence scheduler
 			behaviour
 
+	nopti		[X86-64] Disable kernel page table isolation
+
 	nolapic		[X86-32,APIC] Do not enable or use the local APIC.
 
 	nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 76f5399a8356..7aa68fc18abe 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -35,7 +35,8 @@ obj-$(CONFIG_AMD_NUMA)		+= amdtopology.o
 obj-$(CONFIG_ACPI_NUMA)		+= srat.o
 obj-$(CONFIG_NUMA_EMU)		+= numa_emulation.o
 
-obj-$(CONFIG_X86_INTEL_MPX)	+= mpx.o
-obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) += pkeys.o
-obj-$(CONFIG_RANDOMIZE_MEMORY) += kaslr.o
+obj-$(CONFIG_X86_INTEL_MPX)			+= mpx.o
+obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)	+= pkeys.o
+obj-$(CONFIG_RANDOMIZE_MEMORY)			+= kaslr.o
+obj-$(CONFIG_PAGE_TABLE_ISOLATION)		+= pti.o
 
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index dde6262be0a3..bb56f5346ae8 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -204,18 +204,23 @@ For 32-bit we have the following conventions - kernel is built with
 .endm
 
 .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req
+	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
 	mov	%cr3, \scratch_reg
 	ADJUST_KERNEL_CR3 \scratch_reg
 	mov	\scratch_reg, %cr3
+.Lend_\@:
 .endm
 
 .macro SWITCH_TO_USER_CR3 scratch_reg:req
+	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
 	mov	%cr3, \scratch_reg
 	ADJUST_USER_CR3 \scratch_reg
 	mov	\scratch_reg, %cr3
+.Lend_\@:
 .endm
 
 .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req
+	ALTERNATIVE "jmp .Ldone_\@", "", X86_FEATURE_PTI
 	movq	%cr3, \scratch_reg
 	movq	\scratch_reg, \save_reg
 	/*
@@ -232,11 +237,13 @@ For 32-bit we have the following conventions - kernel is built with
 .endm
 
 .macro RESTORE_CR3 save_reg:req
+	ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI
 	/*
 	 * The CR3 write could be avoided when not changing its value,
 	 * but would require a CR3 read *and* a scratch register.
 	 */
 	movq	\save_reg, %cr3
+.Lend_\@:
 .endm
 
 #else /* CONFIG_PAGE_TABLE_ISOLATION=n: */
diff --git a/arch/x86/include/asm/pti.h b/arch/x86/include/asm/pti.h
new file mode 100644
index 000000000000..0b5ef05b2d2d
--- /dev/null
+++ b/arch/x86/include/asm/pti.h
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef _ASM_X86_PTI_H
+#define _ASM_X86_PTI_H
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+extern void pti_init(void);
+extern void pti_check_boottime_disable(void);
+#else
+static inline void pti_check_boottime_disable(void) { }
+#endif
+
+#endif /* __ASSEMBLY__ */
+#endif /* _ASM_X86_PTI_H */
diff --git a/include/linux/pti.h b/include/linux/pti.h
new file mode 100644
index 000000000000..0174883a935a
--- /dev/null
+++ b/include/linux/pti.h
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef _INCLUDE_PTI_H
+#define _INCLUDE_PTI_H
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+#include <asm/pti.h>
+#else
+static inline void pti_init(void) { }
+#endif
+
+#endif
diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c
index 28029be47fbb..21d8839cdaa7 100644
--- a/arch/x86/boot/compressed/pagetable.c
+++ b/arch/x86/boot/compressed/pagetable.c
@@ -15,6 +15,9 @@
 #define __pa(x)  ((unsigned long)(x))
 #define __va(x)  ((void *)((unsigned long)(x)))
 
+/* No PAGE_TABLE_ISOLATION support needed either: */
+#undef CONFIG_PAGE_TABLE_ISOLATION
+
 #include "misc.h"
 
 /* These actually do the work of building the kernel identity maps. */
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 020223420308..af75069fb116 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -20,6 +20,7 @@
 #include <asm/kaslr.h>
 #include <asm/hypervisor.h>
 #include <asm/cpufeature.h>
+#include <asm/pti.h>
 
 /*
  * We need to define the tracepoints somewhere, and tlb.c
@@ -630,6 +631,7 @@ void __init init_mem_mapping(void)
 {
 	unsigned long end;
 
+	pti_check_boottime_disable();
 	probe_page_size_mask();
 	setup_pcid();
 
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
new file mode 100644
index 000000000000..375f23a758bc
--- /dev/null
+++ b/arch/x86/mm/pti.c
@@ -0,0 +1,84 @@
+/*
+ * Copyright(c) 2017 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * This code is based in part on work published here:
+ *
+ *	https://github.com/IAIK/KAISER
+ *
+ * The original work was written by and and signed off by for the Linux
+ * kernel by:
+ *
+ *   Signed-off-by: Richard Fellner <richard.fellner@student.tugraz.at>
+ *   Signed-off-by: Moritz Lipp <moritz.lipp@iaik.tugraz.at>
+ *   Signed-off-by: Daniel Gruss <daniel.gruss@iaik.tugraz.at>
+ *   Signed-off-by: Michael Schwarz <michael.schwarz@iaik.tugraz.at>
+ *
+ * Major changes to the original code by: Dave Hansen <dave.hansen@intel.com>
+ * Mostly rewritten by Thomas Gleixner <tglx@linutronix.de> and
+ *		       Andy Lutomirsky <luto@amacapital.net>
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/bug.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+
+#include <asm/cpufeature.h>
+#include <asm/hypervisor.h>
+#include <asm/cmdline.h>
+#include <asm/pti.h>
+#include <asm/pgtable.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+#include <asm/desc.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt)     "Kernel/User page tables isolation: " fmt
+
+static void __init pti_print_if_insecure(const char *reason)
+{
+	if (boot_cpu_has_bug(X86_BUG_CPU_INSECURE))
+		pr_info("%s\n", reason);
+}
+
+void __init pti_check_boottime_disable(void)
+{
+	if (hypervisor_is_type(X86_HYPER_XEN_PV)) {
+		pti_print_if_insecure("disabled on XEN PV.");
+		return;
+	}
+
+	if (cmdline_find_option_bool(boot_command_line, "nopti")) {
+		pti_print_if_insecure("disabled on command line.");
+		return;
+	}
+
+	if (!boot_cpu_has_bug(X86_BUG_CPU_INSECURE))
+		return;
+
+	setup_force_cpu_cap(X86_FEATURE_PTI);
+}
+
+/*
+ * Initialize kernel page table isolation
+ */
+void __init pti_init(void)
+{
+	if (!static_cpu_has(X86_FEATURE_PTI))
+		return;
+
+	pr_info("enabled\n");
+}
diff --git a/init/main.c b/init/main.c
index de1c495da782..bb0896c24c08 100644
--- a/init/main.c
+++ b/init/main.c
@@ -75,6 +75,7 @@
 #include <linux/slab.h>
 #include <linux/perf_event.h>
 #include <linux/ptrace.h>
+#include <linux/pti.h>
 #include <linux/blkdev.h>
 #include <linux/elevator.h>
 #include <linux/sched_clock.h>
@@ -506,6 +507,8 @@ static void __init mm_init(void)
 	ioremap_huge_init();
 	/* Should be run before the first non-init thread is created */
 	init_espfix_bsp();
+	/* Should be run after espfix64 is set up. */
+	pti_init();
 }
 
 asmlinkage __visible void __init start_kernel(void)
-- 
2.14.2

