Xi: fix valuator alignment in DeepCopyDeviceClasses (#36119)

commit 678f5396c9 only fixed the
initialization, not the copy. After a slave device change, the valuator
were out of alignment again.

X.Org Bug 36119 <http://bugs.freedesktop.org/show_bug.cgi?id=36119>

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jeremy Huddleston <jeremyhu@apple.com>

Xi/exevents.c

@@ -535,6 +535,7 @@ DeepCopyPointerClasses(DeviceIntPtr from, DeviceIntPtr to)
     if (from->valuator)
     {
         ValuatorClassPtr v;
+
         if (!to->valuator)
         {
             classes = to->unused_classes;
@@ -543,18 +544,14 @@ DeepCopyPointerClasses(DeviceIntPtr from, DeviceIntPtr to)
                 classes->valuator = NULL;
         }
 
-        to->valuator = realloc(to->valuator, sizeof(ValuatorClassRec) +
-                from->valuator->numAxes * sizeof(AxisInfo) +
-                from->valuator->numAxes * sizeof(double));
-        v = to->valuator;
+        v = AllocValuatorClass(to->valuator, from->valuator->numAxes);
+
         if (!v)
             FatalError("[Xi] no memory for class shift.\n");
 
-        v->numAxes = from->valuator->numAxes;
-        v->axes = (AxisInfoPtr)&v[1];
+        to->valuator = v;
         memcpy(v->axes, from->valuator->axes, v->numAxes * sizeof(AxisInfo));
 
-        v->axisVal = (double*)(v->axes + from->valuator->numAxes);
         v->sourceid = from->id;
     } else if (to->valuator && !from->valuator)
     {

dix/devices.c

@@ -1221,13 +1221,46 @@ InitButtonClassDeviceStruct(DeviceIntPtr dev, int numButtons, Atom* labels,
     return TRUE;
 }
 
+/**
+ * Allocate a valuator class and set up the pointers for the axis values
+ * appropriately.
+ *
+ * @param src If non-NULL, the memory is reallocated from src. If NULL, the
+ * memory is calloc'd.
+ * @parma numAxes Number of axes to allocate.
+ * @return The allocated valuator struct.
+ */
+ValuatorClassPtr
+AllocValuatorClass(ValuatorClassPtr src, int numAxes)
+{
+    ValuatorClassPtr v;
+    /* force alignment with double */
+    union align_u { ValuatorClassRec valc; double d; } *align;
+    int size;
+
+    size = sizeof(union align_u) + numAxes * (sizeof(double) + sizeof(AxisInfo));
+    align = (union align_u *) realloc(src, size);
+
+    if (!align)
+        return NULL;
+
+    if (!src)
+        memset(align, 0, size);
+
+    v = &align->valc;
+    v->numAxes = numAxes;
+    v->axisVal = (double*)(align + 1);
+    v->axes = (AxisInfoPtr)(v->axisVal + numAxes);
+
+    return v;
+}
+
 Bool
 InitValuatorClassDeviceStruct(DeviceIntPtr dev, int numAxes, Atom *labels,
                               int numMotionEvents, int mode)
 {
     int i;
     ValuatorClassPtr valc;
-    union align_u { ValuatorClassRec valc; double d; } *align;
 
     if (!dev)
         return FALSE;
@@ -1240,13 +1273,10 @@ InitValuatorClassDeviceStruct(DeviceIntPtr dev, int numAxes, Atom *labels,
         numAxes = MAX_VALUATORS;
     }
 
-    align = (union align_u *) calloc(1, sizeof(union align_u) +
-				     numAxes * sizeof(double) +
-				     numAxes * sizeof(AxisInfo));
-    if (!align)
+    valc = AllocValuatorClass(NULL, numAxes);
+    if (!valc)
         return FALSE;
 
-    valc = &align->valc;
     valc->sourceid = dev->id;
     valc->motion = NULL;
     valc->first_motion = 0;
@@ -1254,9 +1284,6 @@ InitValuatorClassDeviceStruct(DeviceIntPtr dev, int numAxes, Atom *labels,
 
     valc->numMotionEvents = numMotionEvents;
     valc->motionHintWindow = NullWindow;
-    valc->numAxes = numAxes;
-    valc->axisVal = (double *)(align + 1);
-    valc->axes = (AxisInfoPtr)(valc->axisVal + numAxes);
 
     if (mode & OutOfProximity)
         InitProximityClassDeviceStruct(dev);

include/input.h

@@ -102,6 +102,7 @@ typedef unsigned long Leds;
 typedef struct _OtherClients *OtherClientsPtr;
 typedef struct _InputClients *InputClientsPtr;
 typedef struct _DeviceIntRec *DeviceIntPtr;
+typedef struct _ValuatorClassRec *ValuatorClassPtr;
 typedef struct _ClassesRec *ClassesPtr;
 typedef struct _SpriteRec *SpritePtr;
 typedef union _GrabMask GrabMask;
@@ -300,6 +301,10 @@ extern _X_EXPORT Bool InitButtonClassDeviceStruct(
     Atom* /* labels */,
     CARD8* /*map*/);
 
+extern _X_INTERNAL ValuatorClassPtr AllocValuatorClass(
+    ValuatorClassPtr src,
+    int numAxes);
+
 extern _X_EXPORT Bool InitValuatorClassDeviceStruct(
     DeviceIntPtr /*device*/,
     int /*numAxes*/,

include/inputstr.h

@@ -283,7 +283,7 @@ typedef struct _ValuatorClassRec {
     unsigned short	  numAxes;
     double		  *axisVal; /* always absolute, but device-coord system */
     ValuatorAccelerationRec	accelScheme;
-} ValuatorClassRec, *ValuatorClassPtr;
+} ValuatorClassRec;
 
 typedef struct _ButtonClassRec {
     int			sourceid;

test/input.c

@@ -1209,6 +1209,28 @@ static void include_bit_test_macros(void)
     }
 }
 
+/**
+ * Ensure that val->axisVal and val->axes are aligned on doubles.
+ */
+static void dix_valuator_alloc(void)
+{
+    ValuatorClassPtr v = NULL;
+    int num_axes = 0;
+
+    while (num_axes < 5)
+    {
+        v = AllocValuatorClass(v, num_axes);
+
+        g_assert(v);
+        g_assert(v->numAxes == num_axes);
+        g_assert(((void*)v->axisVal - (void*)v) % sizeof(double) == 0);
+        g_assert(((void*)v->axes - (void*)v) % sizeof(double) == 0);
+        num_axes ++;
+    }
+
+    free(v);
+}
+
 int main(int argc, char** argv)
 {
     g_test_init(&argc, &argv,NULL);
@@ -1226,7 +1248,7 @@ int main(int argc, char** argv)
     g_test_add_func("/include/byte_padding_macros", include_byte_padding_macros);
     g_test_add_func("/include/bit_test_macros", include_bit_test_macros);
     g_test_add_func("/Xi/xiproperty/register-unregister", xi_unregister_handlers);
-
+    g_test_add_func("/dix/input/valuator-alloc", dix_valuator_alloc);
 
     return g_test_run();
 }