powerpc/mm/hash: Implement mark_rodata_ro() for hash

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 <bsingharora@gmail.com>
[mpe: Make the warning louder when we don't have MMU_FTR_KERNEL_RO]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 4e957b027fe0a3c9307fb72f921ada394fa002c5..0ce513f2926f12680ce1570266550eb8b2b09eeb 100644 (file)
--- 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 ba43754e96d2eff428c07ddbf1e0be18efa3c1c6..487709ff6875bd61d6b6cc7c8652c7e27f8404a2 100644 (file)
--- 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 a0facee5881141cdcef4eb88588d9f0e1cc0d37a..188b4107584d2a741645aac48382bffadbfb4116 100644 (file)
--- 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"
@@ -419,3 +423,35 @@ 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;
+
+       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);
+
+       if (start == end) {
+               pr_warn("could not set rodata ro, relocate the start"
+                       " of the kernel to a 0x%x boundary\n", step);
+               return;
+       }
+
+       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_64.c b/arch/powerpc/mm/pgtable_64.c
index bce0ed50789ce6cc77f2978dfcd6b5f5e844a86e..fc2e6def2eb7636d45313fe2e6b4a65c3df95e9a 100644 (file)
--- a/arch/powerpc/mm/pgtable_64.c
+++ b/arch/powerpc/mm/pgtable_64.c
@@ -491,3 +491,16 @@ 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 (!mmu_has_feature(MMU_FTR_KERNEL_RO)) {
+               pr_warn("Warning: Unable to mark rodata read only on this CPU.\n");
+               return;
+       }
+
+       if (!radix_enabled())
+               hash__mark_rodata_ro();
+}
+#endif