Subject: [PATCH v3 7/9] powerpc/mm/hash: Implement mark_rodata_ro() for hash

From: Balbir Singh <[email-masked]>
Date: Tue, 6 Jun 2017 14:29:43 +1000

With hash we update the bolted pte to mark it read-only. We rely
on the MMU_FTR_KERNEL_RO to generate the correct permissions
for read-only text. The radix implementation just prints a warning
in this implementation

Signed-off-by: Balbir Singh <[email-masked]>
---
 arch/powerpc/include/asm/book3s/64/hash.h  |  3 +++
 arch/powerpc/include/asm/book3s/64/radix.h |  4 ++++
 arch/powerpc/mm/pgtable-hash64.c           | 35 ++++++++++++++++++++++++++++++
 arch/powerpc/mm/pgtable-radix.c            |  7 ++++++
 arch/powerpc/mm/pgtable_64.c               |  9 ++++++++
 5 files changed, 58 insertions(+)

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 4e957b0..0ce513f 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -89,6 +89,9 @@ static inline int hash__pgd_bad(pgd_t pgd)
 {
 	return (pgd_val(pgd) == 0);
 }
+#ifdef CONFIG_STRICT_KERNEL_RWX
+extern void hash__mark_rodata_ro(void);
+#endif
 
 extern void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
 			    pte_t *ptep, unsigned long pte, int huge);
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index ac16d19..368cb54 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -116,6 +116,10 @@
 #define RADIX_PUD_TABLE_SIZE	(sizeof(pud_t) << RADIX_PUD_INDEX_SIZE)
 #define RADIX_PGD_TABLE_SIZE	(sizeof(pgd_t) << RADIX_PGD_INDEX_SIZE)
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
+extern void radix__mark_rodata_ro(void);
+#endif
+
 static inline unsigned long __radix_pte_update(pte_t *ptep, unsigned long clr,
 					       unsigned long set)
 {
diff --git a/arch/powerpc/mm/pgtable-hash64.c b/arch/powerpc/mm/pgtable-hash64.c
index 8b85a14..dda808b 100644
--- a/arch/powerpc/mm/pgtable-hash64.c
+++ b/arch/powerpc/mm/pgtable-hash64.c
@@ -11,8 +11,12 @@
 
 #include <linux/sched.h>
 #include <linux/mm_types.h>
+#include <linux/mm.h>
 
 #include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/sections.h>
+#include <asm/mmu.h>
 #include <asm/tlb.h>
 
 #include "mmu_decl.h"
@@ -342,3 +346,34 @@ int hash__has_transparent_hugepage(void)
 	return 1;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+#ifdef CONFIG_STRICT_KERNEL_RWX
+void hash__mark_rodata_ro(void)
+{
+	unsigned long start = (unsigned long)_stext;
+	unsigned long end = (unsigned long)__init_begin;
+	unsigned long idx;
+	unsigned int step, shift;
+	unsigned long newpp = PP_RXXX;
+
+	if (!mmu_has_feature(MMU_FTR_KERNEL_RO)) {
+		pr_info("R/O rodata not supported\n");
+		return;
+	}
+
+	shift = mmu_psize_defs[mmu_linear_psize].shift;
+	step = 1 << shift;
+
+	start = ((start + step - 1) >> shift) << shift;
+	end = (end >> shift) << shift;
+
+	pr_devel("marking ro start %lx, end %lx, step %x\n",
+			start, end, step);
+
+	for (idx = start; idx < end; idx += step)
+		/* Not sure if we can do much with the return value */
+		mmu_hash_ops.hpte_updateboltedpp(newpp, idx, mmu_linear_psize,
+							mmu_kernel_ssize);
+
+}
+#endif
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index c28165d..8f42309 100644
--- a/arch/powerpc/mm/pgtable-radix.c
+++ b/arch/powerpc/mm/pgtable-radix.c
@@ -108,6 +108,13 @@ int radix__map_kernel_page(unsigned long ea, unsigned long pa,
 	return 0;
 }
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
+void radix__mark_rodata_ro(void)
+{
+	pr_warn("Not yet implemented for radix\n");
+}
+#endif
+
 static inline void __meminit print_mapping(unsigned long start,
 					   unsigned long end,
 					   unsigned long size)
diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
index db93cf7..a769e4f 100644
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -479,3 +479,12 @@ void mmu_partition_table_set_entry(unsigned int lpid, unsigned long dw0,
 }
 EXPORT_SYMBOL_GPL(mmu_partition_table_set_entry);
 #endif /* CONFIG_PPC_BOOK3S_64 */
+
+#ifdef CONFIG_STRICT_KERNEL_RWX
+void mark_rodata_ro(void)
+{
+	if (radix_enabled())
+		return radix__mark_rodata_ro();
+	return hash__mark_rodata_ro();
+}
+#endif
-- 
2.9.4