kern/misc: Add STRING type for internal printf() format handling

Set printf() argument type for "%s" to new type STRING. This is in
preparation for a follow up patch to compare a printf() format string
against an expected printf() format string.

For "%s" the corresponding printf() argument is dereferenced as pointer
while all other argument types are defined as integer value. However,
when validating a printf() format it is necessary to differentiate "%s"
from "%p" and other integers. So, let's do that.

Signed-off-by: Thomas Frauendorfer | Miray Software <tf@miray.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/kern/misc.c

@@ -33,7 +33,8 @@ union printf_arg
   enum
     {
       INT, LONG, LONGLONG,
-      UNSIGNED_INT = 3, UNSIGNED_LONG, UNSIGNED_LONGLONG
+      UNSIGNED_INT = 3, UNSIGNED_LONG, UNSIGNED_LONGLONG,
+      STRING
     } type;
   long long ll;
 };
@@ -791,12 +792,14 @@ parse_printf_arg_fmt (const char *fmt0, struct printf_args *args)
 	  args->ptr[curn].type = INT + longfmt;
 	  break;
 	case 'p':
-	case 's':
 	  if (sizeof (void *) == sizeof (long long))
 	    args->ptr[curn].type = UNSIGNED_LONGLONG;
 	  else
 	    args->ptr[curn].type = UNSIGNED_INT;
 	  break;
+	case 's':
+	  args->ptr[curn].type = STRING;
+	  break;
 	case 'C':
 	case 'c':
 	  args->ptr[curn].type = INT;
@@ -831,6 +834,12 @@ parse_printf_args (const char *fmt0, struct printf_args *args, va_list args_in)
       case UNSIGNED_LONGLONG:
 	args->ptr[n].ll = va_arg (args_in, long long);
 	break;
+      case STRING:
+	if (sizeof (void *) == sizeof (long long))
+	  args->ptr[n].ll = va_arg (args_in, long long);
+	else
+	  args->ptr[n].ll = va_arg (args_in, unsigned int);
+	break;
       }
 }