[PATCH 1/2] xen/ppc: Fix opal.c's misaligned DT reads to avoid tripping UBSAN

[Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>]

Fix two misaligned reads from the FDT in the opal setup code to avoid
tripping UBSAN failures. Without this change, UBSAN-enabled builds on
PPC will fail on boot before the serial console is even initialized.

Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/ppc/opal.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/xen/arch/ppc/opal.c b/xen/arch/ppc/opal.c
index 1183b7d5ef..3d0e4daf27 100644
--- a/xen/arch/ppc/opal.c
+++ b/xen/arch/ppc/opal.c
@@ -34,8 +34,9 @@ static void opal_putchar(char c)
 void __init boot_opal_init(const void *fdt)
 {
     int opal_node;
-    const __be64 *opal_base;
-    const __be64 *opal_entry;
+    const __be64 *opal_base_p;
+    const __be64 *opal_entry_p;
+    __be64 opal_base, opal_entry;
 
     if ( fdt_check_header(fdt) < 0 )
     {
@@ -54,17 +55,20 @@ void __init boot_opal_init(const void *fdt)
         die();
     }
 
-    opal_base = fdt_getprop(fdt, opal_node, "opal-base-address", NULL);
-    opal_entry = fdt_getprop(fdt, opal_node, "opal-entry-address", NULL);
-    if ( !opal_base || !opal_entry )
+    opal_base_p = fdt_getprop(fdt, opal_node, "opal-base-address", NULL);
+    opal_entry_p = fdt_getprop(fdt, opal_node, "opal-entry-address", NULL);
+    if ( !opal_base_p || !opal_entry_p )
     {
         early_printk("Failed to get opal-base-address/opal-entry-address "
                      "property from DT!\n");
         die();
     }
 
-    opal.base = be64_to_cpu(*opal_base);
-    opal.entry = be64_to_cpu(*opal_entry);
+    memcpy(&opal_base, opal_base_p, sizeof(opal_base));
+    memcpy(&opal_entry, opal_entry_p, sizeof(opal_entry));
+
+    opal.base = be64_to_cpu(opal_base);
+    opal.entry = be64_to_cpu(opal_entry);
 
     early_printk_init(opal_putchar);
 
-- 
2.30.2