fs/shm: alloc aligned memory if CPU has cache

For kernel builds, shared memory is automatically aligned to page size.
For flat and protected builds, we align the memory size to the CPU cache
line size.

Failure to align memory properly could result in partial data read/write
by the CPU and peripherals, potentially causing data corruption during
cache flushes or invalidations.

Signed-off-by: xuxingliang <[email protected]>

Author: XuNeo

fs/shm/shmfs_alloc.c

@@ -27,6 +27,7 @@
 #include <stdbool.h>
 
 #include <nuttx/arch.h>
+#include <nuttx/cache.h>
 #include <nuttx/kmalloc.h>
 #include <nuttx/pgalloc.h>
 
@@ -47,19 +48,23 @@ FAR struct shmfs_object_s *shmfs_alloc_object(size_t length)
    * chunk in kernel heap
    */
 
-  size_t alloc_size = sizeof(struct shmfs_object_s) + length;
-  if (alloc_size < length)
-    {
-      /* There must have been an integer overflow */
-
-      return NULL;
-    }
-
-  object = fs_heap_zalloc(alloc_size);
+  object = fs_heap_zalloc(sizeof(struct shmfs_object_s));
   if (object)
     {
-      object->paddr = (FAR char *)(object + 1);
-      allocated = true;
+      size_t cachesize = up_get_dcache_linesize();
+      if (cachesize > 0)
+        {
+          object->paddr = fs_heap_memalign(cachesize, length);
+        }
+      else
+        {
+          object->paddr = fs_heap_malloc(length);
+        }
+
+      if (object->paddr)
+        {
+           allocated = true;
+        }
     }
 
 #elif defined(CONFIG_BUILD_PROTECTED)
@@ -70,7 +75,15 @@ FAR struct shmfs_object_s *shmfs_alloc_object(size_t length)
   object = fs_heap_zalloc(sizeof(struct shmfs_object_s));
   if (object)
     {
-      object->paddr = kumm_zalloc(length);
+      size_t cachesize = up_get_dcache_linesize();
+      if (cachesize > 0)
+        {
+          object->paddr = kumm_memalign(cachesize, length);
+        }
+      else
+        {
+          object->paddr = kumm_malloc(length);
+        }
 
       if (object->paddr)
         {
@@ -140,7 +153,9 @@ void shmfs_free_object(FAR struct shmfs_object_s *object)
 
   if (object)
     {
-#if defined (CONFIG_BUILD_PROTECTED)
+#if defined(CONFIG_BUILD_FLAT)
+      fs_heap_free(object->paddr);
+#elif defined(CONFIG_BUILD_PROTECTED)
       kumm_free(object->paddr);
 #elif defined(CONFIG_BUILD_KERNEL)
       pages = &object->paddr;