regions_mm: Determine size of the mapped memory region before unmapping

The memory block allocated by the allocator may be larger than a requested
one. If the allocated block size exceeds the memory page size, only enough
pages are mapped to satisfy the request. Thanks to this optimization, it
don't map memory pages that will not be used. When freeing memory,
the allocator knows only size of the allocated block. Information about the
number of pages actually mapped isn't stored anywhere.

Before unmapping memory, determine the number of mapped pages to avoid
error when trying to unmap unmapped memory.

Signed-off-by: Adrian Warecki <[email protected]>

zephyr/lib/regions_mm.c

@@ -279,6 +279,44 @@ static bool vmh_get_map_region_boundaries(struct sys_mem_blocks *blocks, const v
 	return true;
 }
 
+/**
+ * @brief Determine the size of the mapped memory region.
+ *
+ * This function calculates the size of a mapped memory region starting from the given address.
+ * It uses a binary search algorithm to find the boundary of the mapped region by checking if
+ * pages are mapped or not.
+ *
+ * @param addr  Starting address of the memory region.
+ * @param size  Pointer to the size of the memory region. This value will be updated to reflect
+ *		the size of the mapped region.
+ *
+ * @retval None
+ */
+static void vmh_get_mapped_size(void *addr, size_t *size)
+{
+	int ret;
+	uintptr_t check, unused;
+	uintptr_t bottom, top;
+
+	if (*size <= CONFIG_MM_DRV_PAGE_SIZE)
+		return;
+
+	bottom = (POINTER_TO_UINT(addr));
+	top = bottom + *size;
+	check = top - CONFIG_MM_DRV_PAGE_SIZE;
+	while (top - bottom > CONFIG_MM_DRV_PAGE_SIZE) {
+		ret = sys_mm_drv_page_phys_get(UINT_TO_POINTER(check), &unused);
+		if (!ret)
+			bottom = check;	/* Page is mapped */
+		else
+			top = check;	/* Page is unmapped */
+
+		check = ALIGN_DOWN(bottom / 2 + top / 2, CONFIG_MM_DRV_PAGE_SIZE);
+	}
+
+	*size = top - POINTER_TO_UINT(addr);
+}
+
 /**
  * @brief Maps memory pages for a memory region if they have not been previously mapped for other
  *	  allocations.
@@ -326,8 +364,11 @@ static int vmh_unmap_region(struct sys_mem_blocks *region, void *ptr, size_t siz
 	const size_t block_size = 1 << region->info.blk_sz_shift;
 	uintptr_t begin;
 
-	if (block_size >= CONFIG_MM_DRV_PAGE_SIZE)
-		return sys_mm_drv_unmap_region(ptr, ALIGN_UP(size, CONFIG_MM_DRV_PAGE_SIZE));
+	if (block_size >= CONFIG_MM_DRV_PAGE_SIZE) {
+		size = ALIGN_UP(size, CONFIG_MM_DRV_PAGE_SIZE);
+		vmh_get_mapped_size(ptr, &size);
+		return sys_mm_drv_unmap_region(ptr, size);
+	}
 
 	if (vmh_get_map_region_boundaries(region, ptr, size, &begin, &size))
 		return sys_mm_drv_unmap_region((void *)begin, size);