[PATCH 6/8] x86/boot: Adjust .text/.rodata/etc permissions in one place

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

At the moment, we have two locations selecting restricted permissions, not
very far apart on boot, dependent on opposite answers from using_2M_mapping().
The later location however can shatter superpages if needed, while the former
cannot.

Collect together all the permission adjustments at the slightly later point in
boot, as we're may need to shatter a superpage to support __ro_after_init.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
---
 xen/arch/x86/setup.c | 74 ++++++++++++----------------------------------------
 1 file changed, 16 insertions(+), 58 deletions(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 0e0e706404a3..8329263430ed 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1281,55 +1281,16 @@ void __init noreturn __start_xen(unsigned long mbi_p)
                 }
             }
 
-            BUG_ON(using_2M_mapping() &&
-                   l2_table_offset((unsigned long)_erodata) ==
-                   l2_table_offset((unsigned long)_stext));
-
             /* Walk l2_xenmap[], relocating 2M superpage leaves. */
             pl2e = __va(__pa(l2_xenmap));
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ )
             {
-                unsigned int flags;
-
                 if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) ||
                      !(l2e_get_flags(*pl2e) & _PAGE_PSE) ||
                      (l2e_get_pfn(*pl2e) >= pte_update_limit) )
                     continue;
 
-                if ( !using_2M_mapping() )
-                {
-                    *pl2e = l2e_from_intpte(l2e_get_intpte(*pl2e) +
-                                            xen_phys_start);
-                    continue;
-                }
-
-                if ( i < l2_table_offset((unsigned long)&__2M_text_end) )
-                {
-                    flags = PAGE_HYPERVISOR_RX | _PAGE_PSE;
-                }
-                else if ( i >= l2_table_offset((unsigned 
long)&__2M_rodata_start) &&
-                          i <  l2_table_offset((unsigned 
long)&__2M_rodata_end) )
-                {
-                    flags = PAGE_HYPERVISOR_RO | _PAGE_PSE;
-                }
-                else if ( i >= l2_table_offset((unsigned 
long)&__2M_init_start) &&
-                          i <  l2_table_offset((unsigned long)&__2M_init_end) )
-                {
-                    flags = PAGE_HYPERVISOR_RWX | _PAGE_PSE;
-                }
-                else if ( (i >= l2_table_offset((unsigned 
long)&__2M_rwdata_start) &&
-                           i <  l2_table_offset((unsigned 
long)&__2M_rwdata_end)) )
-                {
-                    flags = PAGE_HYPERVISOR_RW | _PAGE_PSE;
-                }
-                else
-                {
-                    *pl2e = l2e_empty();
-                    continue;
-                }
-
-                *pl2e = l2e_from_paddr(
-                    l2e_get_paddr(*pl2e) + xen_phys_start, flags);
+                *pl2e = l2e_from_intpte(l2e_get_intpte(*pl2e) + 
xen_phys_start);
             }
 
             /* Re-sync the stack and then switch to relocated pagetables. */
@@ -1572,31 +1533,28 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 #endif
 
     /*
-     * If not using 2M mappings to gain suitable pagetable permissions
-     * directly from the relocation above, remap the code/data
-     * sections with decreased permissions.
+     * Restrict permissions on the Xen code/data.
+     *
+     * Mark .text as RX.
      */
-    if ( !using_2M_mapping() )
-    {
-        /* Mark .text as RX (avoiding the first 2M superpage). */
-        modify_xen_mappings(XEN_VIRT_START + MB(2),
-                            (unsigned long)&__2M_text_end,
-                            PAGE_HYPERVISOR_RX);
+    modify_xen_mappings((unsigned long)&_start,
+                        (unsigned long)&__2M_text_end,
+                        PAGE_HYPERVISOR_RX);
 
-        /* Mark .rodata as RO. */
-        modify_xen_mappings((unsigned long)&__2M_rodata_start,
-                            (unsigned long)&__2M_rodata_end,
-                            PAGE_HYPERVISOR_RO);
+    /* Mark .rodata as RO. */
+    modify_xen_mappings((unsigned long)&__2M_rodata_start,
+                        (unsigned long)&__2M_rodata_end,
+                        PAGE_HYPERVISOR_RO);
 
-        /* Mark .data and .bss as RW. */
-        modify_xen_mappings((unsigned long)&__2M_rwdata_start,
-                            (unsigned long)&__2M_rwdata_end,
-                            PAGE_HYPERVISOR_RW);
+    /* Mark .data and .bss as RW. */
+    modify_xen_mappings((unsigned long)&__2M_rwdata_start,
+                        (unsigned long)&__2M_rwdata_end,
+                        PAGE_HYPERVISOR_RW);
 
+    if ( !IS_ALIGNED((unsigned long)&__2M_rwdata_end, MB(2)) )
         /* Drop the remaining mappings in the shattered superpage. */
         destroy_xen_mappings((unsigned long)&__2M_rwdata_end,
                              ROUNDUP((unsigned long)&__2M_rwdata_end, MB(2)));
-    }
 
     nr_pages = 0;
     for ( i = 0; i < e820.nr_map; i++ )
-- 
2.11.0