xen/arm: traps: report level 0 faults in panic_PAR()

decode_fsc() derives the fault level from the low two bits of the FSC, so
level 0 is a valid output: FSC_FLT_TRANS is 0x04, i.e. "translation fault,
level 0 or translation table base register".

This is reachable on arm64 because xen_pgtable is the zeroeth-level root,
but fsc_level_str() has no case for it and prints " (level invalid)"
instead. At the time the function was created Xen used only three levels.

Add the missing case. On arm32 the zeroeth level does not exist but FSC
0 denotes address size fault at translation table base register.

While at it, make decode_fsc() decode also address size faults.

Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
(cherry picked from commit 4e1f58ea1a)

xen/arch/arm/include/asm/processor.h

@@ -513,6 +513,7 @@ extern register_t __cpu_logical_map[];
 /*
  * 543210 BIT
  * 00XXLL -- XX Fault Level LL
+ * ..00LL -- Address Size Fault LL
  * ..01LL -- Translation Fault LL
  * ..10LL -- Access Fault LL
  * ..11LL -- Permission Fault LL
@@ -526,6 +527,7 @@ extern register_t __cpu_logical_map[];
 #define FSC_TYPE_OTH   (_AC(0x02,U)<<4)
 #define FSC_TYPE_IMPL  (_AC(0x03,U)<<4)
 
+#define FSC_FLT_ADDR_SIZE (0x00)
 #define FSC_FLT_TRANS  (0x04)
 #define FSC_FLT_ACCESS (0x08)
 #define FSC_FLT_PERM   (0x0c)

xen/arch/arm/traps.c

@@ -307,6 +307,10 @@ static const char *decode_fsc(uint32_t fsc, int *level)
 
     switch ( fsc & 0x3f )
     {
+    case FSC_FLT_ADDR_SIZE ... FSC_FLT_ADDR_SIZE + 3:
+        msg = "Address size fault";
+        *level = fsc & FSC_LL_MASK;
+        break;
     case FSC_FLT_TRANS ... FSC_FLT_TRANS + 3:
         msg = "Translation fault";
         *level = fsc & FSC_LL_MASK;
@@ -363,6 +367,7 @@ static const char *fsc_level_str(int level)
     switch ( level )
     {
     case -1: return "";
+    case 0:  return " at level 0 or TTBR";
     case 1:  return " at level 1";
     case 2:  return " at level 2";
     case 3:  return " at level 3";