arm64: Add CONFIG_DEBUG_SET_MODULE_RONX support

In a similar fashion to other architecture, add the infrastructure
and Kconfig to enable DEBUG_SET_MODULE_RONX support. When
enabled, module ranges will be marked read-only/no-execute as
appropriate.

Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
[will: fixed off-by-one in module end check]
Signed-off-by: Will Deacon <will.deacon@arm.com>

4 files changed, 112 insertions, 1 deletions

diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 4ee8e90b7a45..0a12933e50ed 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -43,4 +43,15 @@ config ARM64_RANDOMIZE_TEXT_OFFSET
           of TEXT_OFFSET and platforms must not require a specific
           value.
 
+config DEBUG_SET_MODULE_RONX
+        bool "Set loadable kernel module data as NX and text as RO"
+        depends on MODULES
+        help
+          This option helps catch unintended modifications to loadable
+          kernel module's text and read-only data. It also prevents execution
+          of module data. Such protection may interfere with run-time code
+          patching and dynamic kernel tracing - and they might also protect
+          against certain classes of kernel exploits.
+          If in doubt, say "N".
+
 endmenu
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index f2defe1c380c..689b6379188c 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -148,4 +148,8 @@ static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
 {
 }
 
+int set_memory_ro(unsigned long addr, int numpages);
+int set_memory_rw(unsigned long addr, int numpages);
+int set_memory_x(unsigned long addr, int numpages);
+int set_memory_nx(unsigned long addr, int numpages);
 #endif
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index 3ecb56c624d3..c56179ed2c09 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -1,5 +1,5 @@
 obj-y                           := dma-mapping.o extable.o fault.o init.o \
                                    cache.o copypage.o flush.o \
                                    ioremap.o mmap.o pgd.o mmu.o \
-                                   context.o proc.o
+                                   context.o proc.o pageattr.o
 obj-$(CONFIG_HUGETLB_PAGE)      += hugetlbpage.o
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
new file mode 100644
index 000000000000..75e744e4cec5
--- /dev/null
+++ b/arch/arm64/mm/pageattr.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 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.
+ */
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+
+#include <asm/pgtable.h>
+#include <asm/tlbflush.h>
+
+struct page_change_data {
+        pgprot_t set_mask;
+        pgprot_t clear_mask;
+};
+
+static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
+                        void *data)
+{
+        struct page_change_data *cdata = data;
+        pte_t pte = *ptep;
+
+        pte = clear_pte_bit(pte, cdata->clear_mask);
+        pte = set_pte_bit(pte, cdata->set_mask);
+
+        set_pte(ptep, pte);
+        return 0;
+}
+
+static int change_memory_common(unsigned long addr, int numpages,
+                                pgprot_t set_mask, pgprot_t clear_mask)
+{
+        unsigned long start = addr;
+        unsigned long size = PAGE_SIZE*numpages;
+        unsigned long end = start + size;
+        int ret;
+        struct page_change_data data;
+
+        if (!IS_ALIGNED(addr, PAGE_SIZE)) {
+                addr &= PAGE_MASK;
+                WARN_ON_ONCE(1);
+        }
+
+        if (!is_module_address(start) || !is_module_address(end - 1))
+                return -EINVAL;
+
+        data.set_mask = set_mask;
+        data.clear_mask = clear_mask;
+
+        ret = apply_to_page_range(&init_mm, start, size, change_page_range,
+                                        &data);
+
+        flush_tlb_kernel_range(start, end);
+        return ret;
+}
+
+int set_memory_ro(unsigned long addr, int numpages)
+{
+        return change_memory_common(addr, numpages,
+                                        __pgprot(PTE_RDONLY),
+                                        __pgprot(PTE_WRITE));
+}
+EXPORT_SYMBOL_GPL(set_memory_ro);
+
+int set_memory_rw(unsigned long addr, int numpages)
+{
+        return change_memory_common(addr, numpages,
+                                        __pgprot(PTE_WRITE),
+                                        __pgprot(PTE_RDONLY));
+}
+EXPORT_SYMBOL_GPL(set_memory_rw);
+
+int set_memory_nx(unsigned long addr, int numpages)
+{
+        return change_memory_common(addr, numpages,
+                                        __pgprot(PTE_PXN),
+                                        __pgprot(0));
+}
+EXPORT_SYMBOL_GPL(set_memory_nx);
+
+int set_memory_x(unsigned long addr, int numpages)
+{
+        return change_memory_common(addr, numpages,
+                                        __pgprot(0),
+                                        __pgprot(PTE_PXN));
+}
+EXPORT_SYMBOL_GPL(set_memory_x);