xlat_tables_v2: find VA/idx with helper functions.

This patch introduces 2 helper functions 'xlat_tables_find_start_va' and
'xlat_tables_va_to_index' to find the first VA and table index affected by the
specified mmap region. it reduces code duplication and cyclomatic code
complexity in xlat_tables_map/unmap_region functions.

Cyclomatic complexity calculated using 'Coverity'

fixes arm-software/tf-issues#673
Signed-off-by: David Pu <dpu@nvidia.com>

lib/xlat_tables_v2/xlat_tables_core.c

@@ -231,6 +231,37 @@ typedef enum {
 
 } action_t;
 
+/*
+ * Function that returns the first VA of the table affected by the specified
+ * mmap region.
+ */
+static uintptr_t xlat_tables_find_start_va(mmap_region_t *mm,
+				   const uintptr_t table_base_va,
+				   const unsigned int level)
+{
+	uintptr_t table_idx_va;
+
+	if (mm->base_va > table_base_va) {
+		/* Find the first index of the table affected by the region. */
+		table_idx_va = mm->base_va & ~XLAT_BLOCK_MASK(level);
+	} else {
+		/* Start from the beginning of the table. */
+		table_idx_va = table_base_va;
+	}
+
+	return table_idx_va;
+}
+
+/*
+ * Function that returns table index for the given VA and level arguments.
+ */
+static inline unsigned int  xlat_tables_va_to_index(const uintptr_t table_base_va,
+						const uintptr_t va,
+						const unsigned int level)
+{
+	return (unsigned int)((va - table_base_va) >> XLAT_ADDR_SHIFT(level));
+}
+
 #if PLAT_XLAT_TABLES_DYNAMIC
 
 /*
@@ -316,19 +347,8 @@ static void xlat_tables_unmap_region(xlat_ctx_t *ctx, mmap_region_t *mm,
 
 	unsigned int table_idx;
 
-	if (mm->base_va > table_base_va) {
-		/* Find the first index of the table affected by the region. */
-		table_idx_va = mm->base_va & ~XLAT_BLOCK_MASK(level);
-
-		table_idx = (unsigned int)((table_idx_va - table_base_va) >>
-			    XLAT_ADDR_SHIFT(level));
-
-		assert(table_idx < table_entries);
-	} else {
-		/* Start from the beginning of the table. */
-		table_idx_va = table_base_va;
-		table_idx = 0;
-	}
+	table_idx_va = xlat_tables_find_start_va(mm, table_base_va, level);
+	table_idx = xlat_tables_va_to_index(table_base_va, table_idx_va, level);
 
 	while (table_idx < table_entries) {
 
@@ -540,19 +560,8 @@ static uintptr_t xlat_tables_map_region(xlat_ctx_t *ctx, mmap_region_t *mm,
 
 	unsigned int table_idx;
 
-	if (mm->base_va > table_base_va) {
-		/* Find the first index of the table affected by the region. */
-		table_idx_va = mm->base_va & ~XLAT_BLOCK_MASK(level);
-
-		table_idx = (unsigned int)((table_idx_va - table_base_va) >>
-			    XLAT_ADDR_SHIFT(level));
-
-		assert(table_idx < table_entries);
-	} else {
-		/* Start from the beginning of the table. */
-		table_idx_va = table_base_va;
-		table_idx = 0U;
-	}
+	table_idx_va = xlat_tables_find_start_va(mm, table_base_va, level);
+	table_idx = xlat_tables_va_to_index(table_base_va, table_idx_va, level);
 
 #if PLAT_XLAT_TABLES_DYNAMIC
 	if (level > ctx->base_level)