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Date: Thu, 14 Feb 2019 00:41:33 +0200
From: Igor Stoppa <igor.stoppa@...il.com>
To:
Cc: Igor Stoppa <igor.stoppa@...wei.com>,
Andy Lutomirski <luto@...capital.net>,
Nadav Amit <nadav.amit@...il.com>,
Matthew Wilcox <willy@...radead.org>,
Peter Zijlstra <peterz@...radead.org>,
Kees Cook <keescook@...omium.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Mimi Zohar <zohar@...ux.vnet.ibm.com>,
Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
Ahmed Soliman <ahmedsoliman@...a.vt.edu>,
linux-integrity@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH v5 04/12] __wr_after_init: x86_64: randomize mapping offset
x86_64 specialized way of defining the base address for the alternate
mapping used by write-rare.
Since the kernel address space spans across 64TB and it is mapped into a
used address space of 128TB, the kernel address space can be shifted by a
random offset that is up to 64TB and page aligned.
This is accomplished by providing arch-specific version of the function
__init_wr_base()
Signed-off-by: Igor Stoppa <igor.stoppa@...wei.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Nadav Amit <nadav.amit@...il.com>
CC: Matthew Wilcox <willy@...radead.org>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Kees Cook <keescook@...omium.org>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: Mimi Zohar <zohar@...ux.vnet.ibm.com>
CC: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
CC: Ahmed Soliman <ahmedsoliman@...a.vt.edu>
CC: linux-integrity@...r.kernel.org
CC: kernel-hardening@...ts.openwall.com
CC: linux-mm@...ck.org
CC: linux-kernel@...r.kernel.org
---
arch/x86/mm/Makefile | 2 ++
arch/x86/mm/prmem.c (new) | 20 ++++++++++++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 4b101dd6e52f..66652de1e2c7 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -53,3 +53,5 @@ obj-$(CONFIG_PAGE_TABLE_ISOLATION) += pti.o
obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt.o
obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt_identity.o
obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt_boot.o
+
+obj-$(CONFIG_PRMEM) += prmem.o
diff --git a/arch/x86/mm/prmem.c b/arch/x86/mm/prmem.c
new file mode 100644
index 000000000000..b04fc03f92fb
--- /dev/null
+++ b/arch/x86/mm/prmem.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * prmem.c: Memory Protection Library - x86_64 backend
+ *
+ * (C) Copyright 2018-2019 Huawei Technologies Co. Ltd.
+ * Author: Igor Stoppa <igor.stoppa@...wei.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/mmu_context.h>
+
+unsigned long __init __init_wr_base(void)
+{
+ /*
+ * Place 64TB of kernel address space within 128TB of user address
+ * space, at a random page aligned offset.
+ */
+ return (((unsigned long)kaslr_get_random_long("WR Poke")) &
+ PAGE_MASK) % (64 * _BITUL(40));
+}
--
2.19.1
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