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Message-Id: <1488228186-110679-6-git-send-email-keescook@chromium.org>
Date: Mon, 27 Feb 2017 12:43:03 -0800
From: Kees Cook <keescook@...omium.org>
To: kernel-hardening@...ts.openwall.com
Cc: Kees Cook <keescook@...omium.org>,
Mark Rutland <mark.rutland@....com>,
Andy Lutomirski <luto@...nel.org>,
Hoeun Ryu <hoeun.ryu@...il.com>,
PaX Team <pageexec@...email.hu>,
Emese Revfy <re.emese@...il.com>,
Russell King <linux@...linux.org.uk>,
x86@...nel.org
Subject: [RFC][PATCH 5/8] ARM: Implement __arch_rare_write_map/unmap()
Based on grsecurity's ARM pax_{open,close}_kernel() implementation, this
allows HAVE_ARCH_RARE_WRITE to work on ARM.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
arch/arm/Kconfig | 1 +
arch/arm/include/asm/domain.h | 3 ++-
arch/arm/include/asm/pgtable.h | 27 +++++++++++++++++++++++++++
3 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 186c4c214e0a..c3e1369e7429 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -39,6 +39,7 @@ config ARM
select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
select HAVE_ARCH_MMAP_RND_BITS if MMU
+ select HAVE_ARCH_RARE_WRITE if MMU && !ARM_LPAE && !CPU_USE_DOMAINS
select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT)
select HAVE_ARCH_TRACEHOOK
select HAVE_ARM_SMCCC if CPU_V7
diff --git a/arch/arm/include/asm/domain.h b/arch/arm/include/asm/domain.h
index 99d9f630d6b6..6c72f533382c 100644
--- a/arch/arm/include/asm/domain.h
+++ b/arch/arm/include/asm/domain.h
@@ -53,6 +53,7 @@
#define DOMAIN_MANAGER 3
#else
#define DOMAIN_MANAGER 1
+#define DOMAIN_RARE_WRITE 3
#endif
#define domain_mask(dom) ((3) << (2 * (dom)))
@@ -115,7 +116,7 @@ static inline void set_domain(unsigned val)
}
#endif
-#ifdef CONFIG_CPU_USE_DOMAINS
+#if defined(CONFIG_CPU_USE_DOMAINS) || defined(CONFIG_HAVE_ARCH_RARE_WRITE)
#define modify_domain(dom,type) \
do { \
unsigned int domain = get_domain(); \
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index a8d656d9aec7..c9492f3e9581 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -56,6 +56,33 @@ extern void __pgd_error(const char *file, int line, pgd_t);
#define pmd_ERROR(pmd) __pmd_error(__FILE__, __LINE__, pmd)
#define pgd_ERROR(pgd) __pgd_error(__FILE__, __LINE__, pgd)
+#ifdef CONFIG_HAVE_ARCH_RARE_WRITE
+#include <asm/domain.h>
+#include <linux/preempt.h>
+
+static inline int test_domain(int domain, int domaintype)
+{
+ return (get_domain() & domain_val(domain, 3)) ==
+ domain_val(domain, domaintype);
+}
+
+static inline unsigned long __arch_rare_write_map(void)
+{
+ preempt_disable();
+ BUG_ON(test_domain(DOMAIN_KERNEL, DOMAIN_RARE_WRITE));
+ modify_domain(DOMAIN_KERNEL, DOMAIN_RARE_WRITE);
+ return 0;
+}
+
+static inline unsigned long __arch_rare_write_unmap(void)
+{
+ BUG_ON(test_domain(DOMAIN_KERNEL, DOMAIN_MANAGER));
+ modify_domain(DOMAIN_KERNEL, DOMAIN_MANAGER);
+ preempt_enable_no_resched();
+ return 0;
+}
+#endif
+
/*
* This is the lowest virtual address we can permit any user space
* mapping to be mapped at. This is particularly important for
--
2.7.4
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