Add mem_region utility functions

This commit introduces a new type (mem_region_t) used to describe
memory regions and it adds two utility functions:

	- clear_mem_regions: This function clears (write 0) to a set
		of regions described with an array of mem_region_t.

	- mem_region_in_array_chk This function checks if a
		region is covered by some of the regions described
		with an array of mem_region_t.

Change-Id: I12ce549f5e81dd15ac0981645f6e08ee7c120811
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

include/lib/utils.h

@@ -19,6 +19,25 @@
 
 #include <types.h>
 
+typedef struct mem_region_t {
+	uintptr_t base;
+	size_t nbytes;
+} mem_region_t;
+
+/*
+ * zero_normalmem all the regions defined in tbl.
+ */
+void clear_mem_regions(mem_region_t *tbl, size_t nregions);
+
+
+/*
+ * checks that a region (addr + nbytes-1) of memory is totally covered by
+ * one of the regions defined in tbl. Caller must ensure that (addr+nbytes-1)
+ * doesn't overflow.
+ */
+int mem_region_in_array_chk(mem_region_t *tbl, size_t nregions,
+			    uintptr_t addr, size_t nbytes);
+
 /*
  * Fill a region of normal memory of size "length" in bytes with zero bytes.
  *

lib/utils/mem_region.c

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <utils.h>
+
+/*
+ * All the regions defined in mem_region_t must have the following properties
+ *
+ * - Any contiguous regions must be merged into a single entry.
+ * - The number of bytes of each region must be greater than zero.
+ * - The calculation of the highest address within the region (base + nbytes-1)
+ *   doesn't produce an overflow.
+ *
+ * These conditions must be fulfilled by the caller and they aren't checked
+ * at runtime.
+ */
+
+/*
+ * zero_normalmem all the regions defined in tbl.
+ * It assumes that MMU is enabled and the memory is Normal memory.
+ * tbl must be a valid pointer to a memory mem_region_t array,
+ * nregions is the size of the array.
+ */
+void clear_mem_regions(mem_region_t *tbl, size_t nregions)
+{
+	size_t i;
+
+	assert(tbl);
+	assert(nregions > 0);
+
+	for (i = 0; i < nregions; i++) {
+		assert(tbl->nbytes > 0);
+		assert(!check_uptr_overflow(tbl->base, tbl->nbytes-1));
+		zero_normalmem((void *) (tbl->base), tbl->nbytes);
+		tbl++;
+	}
+}
+
+/*
+ * This function checks that a region (addr + nbytes-1) of memory is totally
+ * covered by one of the regions defined in tbl.
+ * tbl must be a valid pointer to a memory mem_region_t array, nregions
+ * is the size of the array and the region described by addr and nbytes must
+ * not generate an overflow.
+ * Returns:
+ *  -1 means that the region is not covered by any of the regions
+ *     described in tbl.
+ *   0 the region (addr + nbytes-1) is covered by one of the regions described
+ *     in tbl
+ */
+int mem_region_in_array_chk(mem_region_t *tbl, size_t nregions,
+			    uintptr_t addr, size_t nbytes)
+{
+	uintptr_t region_start, region_end, start, end;
+	size_t i;
+
+	assert(tbl);
+	assert(nbytes > 0);
+	assert(!check_uptr_overflow(addr, nbytes-1));
+
+	region_start = addr;
+	region_end = addr + (nbytes - 1);
+	for (i = 0; i < nregions; i++) {
+		assert(tbl->nbytes > 0);
+		assert(!check_uptr_overflow(tbl->base, tbl->nbytes-1));
+		start = tbl->base;
+		end = start + (tbl->nbytes - 1);
+		if (region_start >= start && region_end <= end)
+			return 0;
+		tbl++;
+	}
+
+	return -1;
+}