From: Thomas Gleixner 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 --- Documentation/admin-guide/kernel-parameters.txt | 2 arch/x86/boot/compressed/pagetable.c | 3 arch/x86/entry/calling.h | 7 ++ arch/x86/include/asm/kpti.h | 14 ++++ arch/x86/mm/Makefile | 7 +- arch/x86/mm/init.c | 2 arch/x86/mm/kpti.c | 76 ++++++++++++++++++++++++ include/linux/kpti.h | 11 +++ init/main.c | 2 9 files changed, 121 insertions(+), 3 deletions(-) --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2711,6 +2711,8 @@ steal time is computed, but won't influence scheduler behaviour + nokpti [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. --- a/arch/x86/boot/compressed/pagetable.c +++ b/arch/x86/boot/compressed/pagetable.c @@ -23,6 +23,9 @@ */ #undef CONFIG_AMD_MEM_ENCRYPT +/* No KERNEL_PAGE_TABLE_ISOLATION support needed either: */ +#undef CONFIG_KERNEL_PAGE_TABLE_ISOLATION + #include "misc.h" /* These actually do the work of building the kernel identity maps. */ --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -205,18 +205,23 @@ For 32-bit we have the following convent .endm .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req + ALTERNATIVE "jmp .Lend_\@", "", X86_BUG_CPU_SECURE_MODE_KPTI 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_BUG_CPU_SECURE_MODE_KPTI 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_BUG_CPU_SECURE_MODE_KPTI movq %cr3, \scratch_reg movq \scratch_reg, \save_reg /* @@ -233,11 +238,13 @@ For 32-bit we have the following convent .endm .macro RESTORE_CR3 save_reg:req + ALTERNATIVE "jmp .Lend_\@", "", X86_BUG_CPU_SECURE_MODE_KPTI /* * 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_KERNEL_PAGE_TABLE_ISOLATION=n: */ --- /dev/null +++ b/arch/x86/include/asm/kpti.h @@ -0,0 +1,14 @@ +// SPDX-License-Identifier: GPL-2.0 +#ifndef _ASM_X86_KPTI_H +#define _ASM_X86_KPTI_H +#ifndef __ASSEMBLY__ + +#ifdef CONFIG_KERNEL_PAGE_TABLE_ISOLATION +extern void kpti_init(void); +extern void kpti_check_boottime_disable(void); +#else +static inline void kpti_check_boottime_disable(void) { } +#endif + +#endif /* __ASSEMBLY__ */ +#endif /* _ASM_X86_KPTI_H */ --- a/arch/x86/mm/Makefile +++ b/arch/x86/mm/Makefile @@ -43,9 +43,10 @@ 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_KERNEL_PAGE_TABLE_ISOLATION) += kpti.o obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt.o obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt_boot.o --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -20,6 +20,7 @@ #include #include #include +#include /* * We need to define the tracepoints somewhere, and tlb.c @@ -630,6 +631,7 @@ void __init init_mem_mapping(void) { unsigned long end; + kpti_check_boottime_disable(); probe_page_size_mask(); setup_pcid(); --- /dev/null +++ b/arch/x86/mm/kpti.c @@ -0,0 +1,76 @@ +/* + * 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 + * Signed-off-by: Moritz Lipp + * Signed-off-by: Daniel Gruss + * Signed-off-by: Michael Schwarz + * + * Major changes to the original code by: Dave Hansen + * Mostly rewritten by Thomas Gleixner and + * Andy Lutomirsky + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include + +#undef pr_fmt +#define pr_fmt(fmt) "Kernel/User page tables isolation: " fmt + +void __init kpti_check_boottime_disable(void) +{ + bool enable = true; + + if (cmdline_find_option_bool(boot_command_line, "nokpti")) { + pr_info("disabled on command line.\n"); + enable = false; + } + if (hypervisor_is_type(X86_HYPER_XEN_PV)) { + pr_info("disabled on XEN_PV.\n"); + enable = false; + } + if (enable) + setup_force_cpu_bug(X86_BUG_CPU_SECURE_MODE_KPTI); +} + +/* + * Initialize kernel page table isolation + */ +void __init kpti_init(void) +{ + if (!static_cpu_has_bug(X86_BUG_CPU_SECURE_MODE_KPTI)) + return; + + pr_info("enabled\n"); +} --- /dev/null +++ b/include/linux/kpti.h @@ -0,0 +1,11 @@ +// SPDX-License-Identifier: GPL-2.0 +#ifndef _INCLUDE_KPTI_H +#define _INCLUDE_KPTI_H + +#ifdef CONFIG_KERNEL_PAGE_TABLE_ISOLATION +#include +#else +static inline void kpti_init(void) { } +#endif + +#endif --- a/init/main.c +++ b/init/main.c @@ -76,6 +76,7 @@ #include #include #include +#include #include #include #include @@ -505,6 +506,7 @@ static void __init mm_init(void) pgtable_init(); vmalloc_init(); ioremap_huge_init(); + kpti_init(); } asmlinkage __visible void __init start_kernel(void)