x86_64: Align uint64_t/int64_t structure member to 8 bytes

To make sure the stature which pass between 32/64bit process have
same memory layout for 32/64bit.

Signed-off-by: Fengwei Yin <fengwei.yin@intel.com>
Co-Authored-by: Narayan Kamath <narayan@google.com> (Unit test only.)
Change-Id: I1bc2d12cce41ec0bc484adcaf968f274bec75c12

2 files changed, 16 insertions, 8 deletions

diff --git a/include/input/Input.h b/include/input/Input.h
index e778076..7c662a7 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -170,7 +170,7 @@ struct PointerCoords {
     enum { MAX_AXES = 14 }; // 14 so that sizeof(PointerCoords) == 64
 
     // Bitfield of axes that are present in this structure.
-    uint64_t bits;
+    uint64_t bits __attribute__((aligned(8)));
 
     // Values of axes that are stored in this structure packed in order by axis id
     // for each axis that is present in the structure according to 'bits'.
diff --git a/include/input/InputTransport.h b/include/input/InputTransport.h
index 8ffdfca..e7e383b 100644
--- a/include/input/InputTransport.h
+++ b/include/input/InputTransport.h
@@ -39,6 +39,9 @@ namespace android {
 
 /*
  * Intermediate representation used to send input events and related signals.
+ *
+ * Note that this structure is used for IPCs so its layout must be identical
+ * on 64 and 32 bit processes. This is tested in StructLayout_test.cpp.
  */
 struct InputMessage {
     enum {
@@ -49,13 +52,17 @@ struct InputMessage {
 
     struct Header {
         uint32_t type;
-        uint32_t padding; // 8 byte alignment for the body that follows
+        // We don't need this field in order to align the body below but we
+        // leave it here because InputMessage::size() and other functions
+        // compute the size of this structure as sizeof(Header) + sizeof(Body).
+        uint32_t padding;
     } header;
 
+    // Body *must* be 8 byte aligned.
     union Body {
         struct Key {
             uint32_t seq;
-            nsecs_t eventTime;
+            nsecs_t eventTime __attribute__((aligned(8)));
             int32_t deviceId;
             int32_t source;
             int32_t action;
@@ -64,7 +71,7 @@ struct InputMessage {
             int32_t scanCode;
             int32_t metaState;
             int32_t repeatCount;
-            nsecs_t downTime;
+            nsecs_t downTime __attribute__((aligned(8)));
 
             inline size_t size() const {
                 return sizeof(Key);
@@ -73,7 +80,7 @@ struct InputMessage {
 
         struct Motion {
             uint32_t seq;
-            nsecs_t eventTime;
+            nsecs_t eventTime __attribute__((aligned(8)));
             int32_t deviceId;
             int32_t source;
             int32_t action;
@@ -81,13 +88,14 @@ struct InputMessage {
             int32_t metaState;
             int32_t buttonState;
             int32_t edgeFlags;
-            nsecs_t downTime;
+            nsecs_t downTime __attribute__((aligned(8)));
             float xOffset;
             float yOffset;
             float xPrecision;
             float yPrecision;
             uint32_t pointerCount;
-            struct Pointer {
+            // Note that PointerCoords requires 8 byte alignment.
+            struct Pointer{
                 PointerProperties properties;
                 PointerCoords coords;
             } pointers[MAX_POINTERS];
@@ -112,7 +120,7 @@ struct InputMessage {
                 return sizeof(Finished);
             }
         } finished;
-    } body;
+    } __attribute__((aligned(8))) body;
 
     bool isValid(size_t actualSize) const;
     size_t size() const;