[common] array: add ALIGN_PAD macro for common logic

ALIGN_PAD(x, a) returns x rounded up to the nearest multiple of a.

common/include/common/array.h

@@ -22,5 +22,6 @@
 #define _LG_ARRAY_H_
 
 #define ARRAY_LENGTH(arr) (sizeof(arr) / sizeof(*(arr)))
+#define ALIGN_PAD(value, align) (((value) + (align) - 1) & -(align))
 
 #endif

common/src/platform/linux/ivshmem.c

@@ -31,6 +31,7 @@
 #include <string.h>
 #include <errno.h>
 
+#include "common/array.h"
 #include "common/debug.h"
 #include "common/option.h"
 #include "common/sysinfo.h"
@@ -232,7 +233,7 @@ int ivshmemGetDMABuf(struct IVSHMEM * dev, uint64_t offset, uint64_t size)
     (struct IVSHMEMInfo *)dev->opaque;
 
   // align to the page size
-  size = (size + pageSize - 1) & -pageSize;
+  size = ALIGN_PAD(size, pageSize);
 
   const struct kvmfr_dmabuf_create create =
   {