s390x/mmu: Add support for read-only regions

If the "DAT-protection" bit is set in the region table entry and EDAT is
enabled, only read accesses are allowed in the corresponding memory area.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index c0016b69fc0ef519bcbf9d3a47e346b7b021b7f6..08cdb1529edf4629aeecb414f893ad605b5ebe6f 100644 (file)
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -837,6 +837,7 @@ struct sysib_322 {
 #define _ASCE_TABLE_LENGTH      0x03      /* region table length              */
 
 #define _REGION_ENTRY_ORIGIN    ~0xfffULL /* region/segment table origin      */
+#define _REGION_ENTRY_RO        0x200     /* region/segment protection bit    */
 #define _REGION_ENTRY_TF        0xc0      /* region/segment table offset      */
 #define _REGION_ENTRY_INV       0x20      /* invalid region table entry       */
 #define _REGION_ENTRY_TYPE_MASK 0x0c      /* region/segment table type mask   */

diff --git a/target-s390x/mmu_helper.c b/target-s390x/mmu_helper.c
index 0c53ae92b321625770f71c780b75e1511ec1d542..702e8b82cb9deddc52be57e023d843ea8b906f6d 100644 (file)
--- a/target-s390x/mmu_helper.c
+++ b/target-s390x/mmu_helper.c
@@ -188,9 +188,6 @@ static int mmu_translate_region(CPUS390XState *env, target_ulong vaddr,
         return -1;
     }
 
-    /* XXX region protection flags */
-    /* *flags &= ~PAGE_WRITE */
-
     if (level == _ASCE_TYPE_SEGMENT) {
         return mmu_translate_segment(env, vaddr, asc, new_entry, raddr, flags,
                                      rw, exc);
@@ -205,6 +202,10 @@ static int mmu_translate_region(CPUS390XState *env, target_ulong vaddr,
         return -1;
     }
 
+    if ((env->cregs[0] & CR0_EDAT) && (new_entry & _REGION_ENTRY_RO)) {
+        *flags &= ~PAGE_WRITE;
+    }
+
     /* yet another region */
     return mmu_translate_region(env, vaddr, asc, new_entry, level - 4,
                                 raddr, flags, rw, exc);