x86/mm: introduce l{1,2}t local variables to map_pages_to_xen

The pl2e and pl1e variables are heavily (ab)used in that function. It
is fine at the moment because all page tables are always mapped so
there is no need to track the life time of each variable.

We will soon have the requirement to map and unmap page tables. We
need to track the life time of each variable to avoid leakage.

Introduce some l{1,2}t variables with limited scope so that we can
track life time of pointers to xen page tables more easily.

No functional change.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index e2c8c3f3a1685cd6894aa037fc9d10b421e592ab..2ae8a7736f45686f9fa7bf64630849e62cedc40a 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5061,10 +5061,12 @@ int map_pages_to_xen(
                 }
                 else
                 {
-                    pl2e = l3e_to_l2e(ol3e);
+                    l2_pgentry_t *l2t;
+
+                    l2t = l3e_to_l2e(ol3e);
                     for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                     {
-                        ol2e = pl2e[i];
+                        ol2e = l2t[i];
                         if ( !(l2e_get_flags(ol2e) & _PAGE_PRESENT) )
                             continue;
                         if ( l2e_get_flags(ol2e) & _PAGE_PSE )
@@ -5072,21 +5074,22 @@ int map_pages_to_xen(
                         else
                         {
                             unsigned int j;
+                            l1_pgentry_t *l1t;
 
-                            pl1e = l2e_to_l1e(ol2e);
+                            l1t = l2e_to_l1e(ol2e);
                             for ( j = 0; j < L1_PAGETABLE_ENTRIES; j++ )
-                                flush_flags(l1e_get_flags(pl1e[j]));
+                                flush_flags(l1e_get_flags(l1t[j]));
                         }
                     }
                     flush_area(virt, flush_flags);
                     for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
                     {
-                        ol2e = pl2e[i];
+                        ol2e = l2t[i];
                         if ( (l2e_get_flags(ol2e) & _PAGE_PRESENT) &&
                              !(l2e_get_flags(ol2e) & _PAGE_PSE) )
                             free_xen_pagetable(l2e_to_l1e(ol2e));
                     }
-                    free_xen_pagetable(pl2e);
+                    free_xen_pagetable(l2t);
                 }
             }
 
@@ -5102,6 +5105,7 @@ int map_pages_to_xen(
         {
             unsigned int flush_flags =
                 FLUSH_TLB | FLUSH_ORDER(2 * PAGETABLE_ORDER);
+            l2_pgentry_t *l2t;
 
             /* Skip this PTE if there is no change. */
             if ( ((l3e_get_pfn(ol3e) & ~(L2_PAGETABLE_ENTRIES *
@@ -5123,12 +5127,12 @@ int map_pages_to_xen(
                 continue;
             }
 
-            pl2e = alloc_xen_pagetable();
-            if ( pl2e == NULL )
+            l2t = alloc_xen_pagetable();
+            if ( l2t == NULL )
                 return -ENOMEM;
 
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
-                l2e_write(pl2e + i,
+                l2e_write(l2t + i,
                           l2e_from_pfn(l3e_get_pfn(ol3e) +
                                        (i << PAGETABLE_ORDER),
                                        l3e_get_flags(ol3e)));
@@ -5141,15 +5145,15 @@ int map_pages_to_xen(
             if ( (l3e_get_flags(*pl3e) & _PAGE_PRESENT) &&
                  (l3e_get_flags(*pl3e) & _PAGE_PSE) )
             {
-                l3e_write_atomic(pl3e, l3e_from_mfn(virt_to_mfn(pl2e),
+                l3e_write_atomic(pl3e, l3e_from_mfn(virt_to_mfn(l2t),
                                                     __PAGE_HYPERVISOR));
-                pl2e = NULL;
+                l2t = NULL;
             }
             if ( locking )
                 spin_unlock(&map_pgdir_lock);
             flush_area(virt, flush_flags);
-            if ( pl2e )
-                free_xen_pagetable(pl2e);
+            if ( l2t )
+                free_xen_pagetable(l2t);
         }
 
         pl2e = virt_to_xen_l2e(virt);
@@ -5177,11 +5181,13 @@ int map_pages_to_xen(
                 }
                 else
                 {
-                    pl1e = l2e_to_l1e(ol2e);
+                    l1_pgentry_t *l1t;
+
+                    l1t = l2e_to_l1e(ol2e);
                     for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
-                        flush_flags(l1e_get_flags(pl1e[i]));
+                        flush_flags(l1e_get_flags(l1t[i]));
                     flush_area(virt, flush_flags);
-                    free_xen_pagetable(pl1e);
+                    free_xen_pagetable(l1t);
                 }
             }
 
@@ -5203,6 +5209,7 @@ int map_pages_to_xen(
             {
                 unsigned int flush_flags =
                     FLUSH_TLB | FLUSH_ORDER(PAGETABLE_ORDER);
+                l1_pgentry_t *l1t;
 
                 /* Skip this PTE if there is no change. */
                 if ( (((l2e_get_pfn(*pl2e) & ~(L1_PAGETABLE_ENTRIES - 1)) +
@@ -5222,12 +5229,12 @@ int map_pages_to_xen(
                     goto check_l3;
                 }
 
-                pl1e = alloc_xen_pagetable();
-                if ( pl1e == NULL )
+                l1t = alloc_xen_pagetable();
+                if ( l1t == NULL )
                     return -ENOMEM;
 
                 for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
-                    l1e_write(&pl1e[i],
+                    l1e_write(&l1t[i],
                               l1e_from_pfn(l2e_get_pfn(*pl2e) + i,
                                            lNf_to_l1f(l2e_get_flags(*pl2e))));
 
@@ -5239,15 +5246,15 @@ int map_pages_to_xen(
                 if ( (l2e_get_flags(*pl2e) & _PAGE_PRESENT) &&
                      (l2e_get_flags(*pl2e) & _PAGE_PSE) )
                 {
-                    l2e_write_atomic(pl2e, l2e_from_mfn(virt_to_mfn(pl1e),
+                    l2e_write_atomic(pl2e, l2e_from_mfn(virt_to_mfn(l1t),
                                                         __PAGE_HYPERVISOR));
-                    pl1e = NULL;
+                    l1t = NULL;
                 }
                 if ( locking )
                     spin_unlock(&map_pgdir_lock);
                 flush_area(virt, flush_flags);
-                if ( pl1e )
-                    free_xen_pagetable(pl1e);
+                if ( l1t )
+                    free_xen_pagetable(l1t);
             }
 
             pl1e  = l2e_to_l1e(*pl2e) + l1_table_offset(virt);
@@ -5272,6 +5279,7 @@ int map_pages_to_xen(
                     ((1u << PAGETABLE_ORDER) - 1)) == 0)) )
             {
                 unsigned long base_mfn;
+                l1_pgentry_t *l1t;
 
                 if ( locking )
                     spin_lock(&map_pgdir_lock);
@@ -5295,11 +5303,11 @@ int map_pages_to_xen(
                     goto check_l3;
                 }
 
-                pl1e = l2e_to_l1e(ol2e);
-                base_mfn = l1e_get_pfn(*pl1e) & ~(L1_PAGETABLE_ENTRIES - 1);
-                for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++, pl1e++ )
-                    if ( (l1e_get_pfn(*pl1e) != (base_mfn + i)) ||
-                         (l1e_get_flags(*pl1e) != flags) )
+                l1t = l2e_to_l1e(ol2e);
+                base_mfn = l1e_get_pfn(l1t[0]) & ~(L1_PAGETABLE_ENTRIES - 1);
+                for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
+                    if ( (l1e_get_pfn(l1t[i]) != (base_mfn + i)) ||
+                         (l1e_get_flags(l1t[i]) != flags) )
                         break;
                 if ( i == L1_PAGETABLE_ENTRIES )
                 {
@@ -5325,6 +5333,7 @@ int map_pages_to_xen(
                 ((1UL << (L3_PAGETABLE_SHIFT - PAGE_SHIFT)) - 1))) )
         {
             unsigned long base_mfn;
+            l2_pgentry_t *l2t;
 
             if ( locking )
                 spin_lock(&map_pgdir_lock);
@@ -5342,13 +5351,13 @@ int map_pages_to_xen(
                 continue;
             }
 
-            pl2e = l3e_to_l2e(ol3e);
-            base_mfn = l2e_get_pfn(*pl2e) & ~(L2_PAGETABLE_ENTRIES *
+            l2t = l3e_to_l2e(ol3e);
+            base_mfn = l2e_get_pfn(l2t[0]) & ~(L2_PAGETABLE_ENTRIES *
                                               L1_PAGETABLE_ENTRIES - 1);
-            for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ )
-                if ( (l2e_get_pfn(*pl2e) !=
+            for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
+                if ( (l2e_get_pfn(l2t[i]) !=
                       (base_mfn + (i << PAGETABLE_ORDER))) ||
-                     (l2e_get_flags(*pl2e) != l1f_to_lNf(flags)) )
+                     (l2e_get_flags(l2t[i]) != l1f_to_lNf(flags)) )
                     break;
             if ( i == L2_PAGETABLE_ENTRIES )
             {