2 files changed, 87 insertions, 22 deletions

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 4a2930844d43..75b8750a16ff 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -759,6 +759,8 @@ void gmap_disable(struct gmap *gmap);
 int gmap_map_segment(struct gmap *gmap, unsigned long from,
                      unsigned long to, unsigned long length);
 int gmap_unmap_segment(struct gmap *gmap, unsigned long to, unsigned long len);
+unsigned long __gmap_translate(unsigned long address, struct gmap *);
+unsigned long gmap_translate(unsigned long address, struct gmap *);
 unsigned long __gmap_fault(unsigned long address, struct gmap *);
 unsigned long gmap_fault(unsigned long address, struct gmap *);
 void gmap_discard(unsigned long from, unsigned long to, struct gmap *);
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index ae44d2a34313..2accf7113d13 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -379,45 +379,108 @@ out_unmap:
 }
 EXPORT_SYMBOL_GPL(gmap_map_segment);
 
+static unsigned long *gmap_table_walk(unsigned long address, struct gmap *gmap)
+{
+        unsigned long *table;
+
+        table = gmap->table + ((address >> 53) & 0x7ff);
+        if (unlikely(*table & _REGION_ENTRY_INV))
+                return ERR_PTR(-EFAULT);
+        table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
+        table = table + ((address >> 42) & 0x7ff);
+        if (unlikely(*table & _REGION_ENTRY_INV))
+                return ERR_PTR(-EFAULT);
+        table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
+        table = table + ((address >> 31) & 0x7ff);
+        if (unlikely(*table & _REGION_ENTRY_INV))
+                return ERR_PTR(-EFAULT);
+        table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
+        table = table + ((address >> 20) & 0x7ff);
+        return table;
+}
+
+/**
+ * __gmap_translate - translate a guest address to a user space address
+ * @address: guest address
+ * @gmap: pointer to guest mapping meta data structure
+ *
+ * Returns user space address which corresponds to the guest address or
+ * -EFAULT if no such mapping exists.
+ * This function does not establish potentially missing page table entries.
+ * The mmap_sem of the mm that belongs to the address space must be held
+ * when this function gets called.
+ */
+unsigned long __gmap_translate(unsigned long address, struct gmap *gmap)
+{
+        unsigned long *segment_ptr, vmaddr, segment;
+        struct gmap_pgtable *mp;
+        struct page *page;
+
+        current->thread.gmap_addr = address;
+        segment_ptr = gmap_table_walk(address, gmap);
+        if (IS_ERR(segment_ptr))
+                return PTR_ERR(segment_ptr);
+        /* Convert the gmap address to an mm address. */
+        segment = *segment_ptr;
+        if (!(segment & _SEGMENT_ENTRY_INV)) {
+                page = pfn_to_page(segment >> PAGE_SHIFT);
+                mp = (struct gmap_pgtable *) page->index;
+                return mp->vmaddr | (address & ~PMD_MASK);
+        } else if (segment & _SEGMENT_ENTRY_RO) {
+                vmaddr = segment & _SEGMENT_ENTRY_ORIGIN;
+                return vmaddr | (address & ~PMD_MASK);
+        }
+        return -EFAULT;
+}
+EXPORT_SYMBOL_GPL(__gmap_translate);
+
+/**
+ * gmap_translate - translate a guest address to a user space address
+ * @address: guest address
+ * @gmap: pointer to guest mapping meta data structure
+ *
+ * Returns user space address which corresponds to the guest address or
+ * -EFAULT if no such mapping exists.
+ * This function does not establish potentially missing page table entries.
+ */
+unsigned long gmap_translate(unsigned long address, struct gmap *gmap)
+{
+        unsigned long rc;
+
+        down_read(&gmap->mm->mmap_sem);
+        rc = __gmap_translate(address, gmap);
+        up_read(&gmap->mm->mmap_sem);
+        return rc;
+}
+EXPORT_SYMBOL_GPL(gmap_translate);
+
 /*
  * this function is assumed to be called with mmap_sem held
  */
 unsigned long __gmap_fault(unsigned long address, struct gmap *gmap)
 {
-        unsigned long *table, vmaddr, segment;
-        struct mm_struct *mm;
+        unsigned long *segment_ptr, vmaddr, segment;
+        struct vm_area_struct *vma;
         struct gmap_pgtable *mp;
         struct gmap_rmap *rmap;
-        struct vm_area_struct *vma;
+        struct mm_struct *mm;
         struct page *page;
         pgd_t *pgd;
         pud_t *pud;
         pmd_t *pmd;
 
         current->thread.gmap_addr = address;
-        mm = gmap->mm;
-        /* Walk the gmap address space page table */
-        table = gmap->table + ((address >> 53) & 0x7ff);
-        if (unlikely(*table & _REGION_ENTRY_INV))
-                return -EFAULT;
-        table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
-        table = table + ((address >> 42) & 0x7ff);
-        if (unlikely(*table & _REGION_ENTRY_INV))
+        segment_ptr = gmap_table_walk(address, gmap);
+        if (IS_ERR(segment_ptr))
                 return -EFAULT;
-        table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
-        table = table + ((address >> 31) & 0x7ff);
-        if (unlikely(*table & _REGION_ENTRY_INV))
-                return -EFAULT;
-        table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
-        table = table + ((address >> 20) & 0x7ff);
-
         /* Convert the gmap address to an mm address. */
-        segment = *table;
-        if (likely(!(segment & _SEGMENT_ENTRY_INV))) {
+        segment = *segment_ptr;
+        if (!(segment & _SEGMENT_ENTRY_INV)) {
                 page = pfn_to_page(segment >> PAGE_SHIFT);
                 mp = (struct gmap_pgtable *) page->index;
                 return mp->vmaddr | (address & ~PMD_MASK);
         } else if (segment & _SEGMENT_ENTRY_RO) {
+                mm = gmap->mm;
                 vmaddr = segment & _SEGMENT_ENTRY_ORIGIN;
                 vma = find_vma(mm, vmaddr);
                 if (!vma || vma->vm_start > vmaddr)
@@ -441,12 +504,12 @@ unsigned long __gmap_fault(unsigned long address, struct gmap *gmap)
                 /* Link gmap segment table entry location to page table. */
                 page = pmd_page(*pmd);
                 mp = (struct gmap_pgtable *) page->index;
-                rmap->entry = table;
+                rmap->entry = segment_ptr;
                 spin_lock(&mm->page_table_lock);
                 list_add(&rmap->list, &mp->mapper);
                 spin_unlock(&mm->page_table_lock);
                 /* Set gmap segment table entry to page table. */
-                *table = pmd_val(*pmd) & PAGE_MASK;
+                *segment_ptr = pmd_val(*pmd) & PAGE_MASK;
                 return vmaddr | (address & ~PMD_MASK);
         }
         return -EFAULT;