diff mbox series

[v5,4/7] x86/mm: introduce l{1, 2}t local variables to modify_xen_mappings

Message ID ed7cc7c4b81e840dcee7705141058d3cd6747f09.1578397252.git.hongyxia@amazon.com (mailing list archive)
State New, archived
Headers show
Series Add alternative API for XEN PTEs | expand

Commit Message

Xia, Hongyan Jan. 7, 2020, 12:06 p.m. UTC 
From: Wei Liu <wei.liu2@citrix.com>

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>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
 xen/arch/x86/mm.c | 68 +++++++++++++++++++++++++++++++------------------------
 1 file changed, 38 insertions(+), 30 deletions(-)
diff mbox series

Patch

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 699aa6bbdf..7160ddcb67 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5575,6 +5575,8 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
 
         if ( l3e_get_flags(*pl3e) & _PAGE_PSE )
         {
+            l2_pgentry_t *l2t;
+
             if ( l2_table_offset(v) == 0 &&
                  l1_table_offset(v) == 0 &&
                  ((e - v) >= (1UL << L3_PAGETABLE_SHIFT)) )
@@ -5590,11 +5592,11 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
             }
 
             /* PAGE1GB: shatter the superpage and fall through. */
-            pl2e = alloc_xen_pagetable();
-            if ( !pl2e )
+            l2t = alloc_xen_pagetable();
+            if ( !l2t )
                 return -ENOMEM;
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
-                l2e_write(pl2e + i,
+                l2e_write(l2t + i,
                           l2e_from_pfn(l3e_get_pfn(*pl3e) +
                                        (i << PAGETABLE_ORDER),
                                        l3e_get_flags(*pl3e)));
@@ -5603,14 +5605,14 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
             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);
-            if ( pl2e )
-                free_xen_pagetable(pl2e);
+            if ( l2t )
+                free_xen_pagetable(l2t);
         }
 
         /*
@@ -5644,12 +5646,14 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
             }
             else
             {
+                l1_pgentry_t *l1t;
+
                 /* PSE: shatter the superpage and try again. */
-                pl1e = alloc_xen_pagetable();
-                if ( !pl1e )
+                l1t = alloc_xen_pagetable();
+                if ( !l1t )
                     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,
                                            l2e_get_flags(*pl2e) & ~_PAGE_PSE));
                 if ( locking )
@@ -5657,19 +5661,19 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
                 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);
-                if ( pl1e )
-                    free_xen_pagetable(pl1e);
+                if ( l1t )
+                    free_xen_pagetable(l1t);
             }
         }
         else
         {
-            l1_pgentry_t nl1e;
+            l1_pgentry_t nl1e, *l1t;
 
             /*
              * Ordinary 4kB mapping: The L2 entry has been verified to be
@@ -5716,9 +5720,9 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
                 continue;
             }
 
-            pl1e = l2e_to_l1e(*pl2e);
+            l1t = l2e_to_l1e(*pl2e);
             for ( i = 0; i < L1_PAGETABLE_ENTRIES; i++ )
-                if ( l1e_get_intpte(pl1e[i]) != 0 )
+                if ( l1e_get_intpte(l1t[i]) != 0 )
                     break;
             if ( i == L1_PAGETABLE_ENTRIES )
             {
@@ -5727,7 +5731,7 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
                 if ( locking )
                     spin_unlock(&map_pgdir_lock);
                 flush_area(NULL, FLUSH_TLB_GLOBAL); /* flush before free */
-                free_xen_pagetable(pl1e);
+                free_xen_pagetable(l1t);
             }
             else if ( locking )
                 spin_unlock(&map_pgdir_lock);
@@ -5756,21 +5760,25 @@  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
             continue;
         }
 
-        pl2e = l3e_to_l2e(*pl3e);
-        for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
-            if ( l2e_get_intpte(pl2e[i]) != 0 )
-                break;
-        if ( i == L2_PAGETABLE_ENTRIES )
         {
-            /* Empty: zap the L3E and free the L2 page. */
-            l3e_write_atomic(pl3e, l3e_empty());
-            if ( locking )
+            l2_pgentry_t *l2t;
+
+            l2t = l3e_to_l2e(*pl3e);
+            for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++ )
+                if ( l2e_get_intpte(l2t[i]) != 0 )
+                    break;
+            if ( i == L2_PAGETABLE_ENTRIES )
+            {
+                /* Empty: zap the L3E and free the L2 page. */
+                l3e_write_atomic(pl3e, l3e_empty());
+                if ( locking )
+                    spin_unlock(&map_pgdir_lock);
+                flush_area(NULL, FLUSH_TLB_GLOBAL); /* flush before free */
+                free_xen_pagetable(l2t);
+            }
+            else if ( locking )
                 spin_unlock(&map_pgdir_lock);
-            flush_area(NULL, FLUSH_TLB_GLOBAL); /* flush before free */
-            free_xen_pagetable(pl2e);
         }
-        else if ( locking )
-            spin_unlock(&map_pgdir_lock);
     }
 
     flush_area(NULL, FLUSH_TLB_GLOBAL);