platform: Add minimal libc support.

libfdt requires minimal libc support. Absoultely
minimum functions are added in libc.

Signed-off-by: Atish Patra <atish.patra@wdc.com>

platform/common/libc/objects.mk

@@ -0,0 +1,15 @@
+#
+# Copyright (c) 2018 Western Digital Corporation or its affiliates.
+#
+# Authors:
+#   Atish Patra<atish.patra@wdc.com>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+
+libc_files = string.o
+
+$(foreach file, $(libc_files), \
+	$(eval CFLAGS_$(file) = -I$(src)/../../common/libc))
+
+platform-common-objs-$(PLATFORM_INCLUDE_LIBC) += $(addprefix libc/,$(libc_files))

platform/common/libc/string.c

@@ -0,0 +1,170 @@
+/*
+ * Copyright (c) 2018 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Atish Patra <atish.patra@wdc.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+/*
+ * Simple libc functions. These are not optimized at all and might have some
+ * bugs as well. Use any optimized routines from newlib or glibc if required.
+ */
+
+#include <string.h>
+
+int strcmp(const char *a, const char *b)
+{
+	/* search first diff or end of string */
+	for (; *a == *b && *a != '\0'; a++, b++);
+	return *a - *b;
+}
+
+size_t strlen(const char *str)
+{
+	unsigned long ret = 0;
+
+	while (*str != '\0') {
+		ret++;
+		str++;
+	}
+
+	return ret;
+}
+
+size_t strnlen(const char *str, size_t count)
+{
+	unsigned long ret = 0;
+
+	while (*str != '\0' && ret < count) {
+		ret++;
+		str++;
+		count--;
+	}
+
+	return ret;
+}
+
+char * strcpy(char * dest,const char *src)
+{
+	char *ret = dest;
+
+	while(*src != '\0') {
+		*dest++ = *src++;
+	}
+
+	return ret;
+}
+
+char * strncpy(char * dest,const char *src,size_t count)
+{
+	char *ret = dest;
+
+	while(count-- && *src != '\0') {
+		*dest++ = *src++;
+	}
+
+	return ret;
+}
+
+char * strchr(const char * s, int c)
+{
+	while(*s != '\0' && *s != (char)c)
+		s++;
+
+	if (*s == '\0')
+		return NULL;
+	else
+		return (char *)s;
+}
+
+char * strrchr(const char * s, int c)
+{
+	const char *last = s + strlen(s);
+
+	while (last > s && *last != (char)c)
+		last--;
+
+	if (*last != (char)c)
+		return NULL;
+	else
+		return (char *)last;
+}
+void * memset(void * s,int c,size_t count)
+{
+	char *temp = s;
+
+	while(count > 0 ){
+		count--;
+		*temp++ = c;
+	}
+
+	return s;
+}
+
+void * memcpy(void *dest, const void *src, size_t count)
+{
+	char *temp1 = dest;
+	const char *temp2 = src;
+
+	while (count > 0) {
+		*temp1++ = *temp2++;
+		count--;
+	}
+
+	return dest;
+}
+
+void * memmove(void * dest,const void *src,size_t count)
+{
+	char *temp1 = (char *)dest;
+	const char *temp2 = (char *)src;
+
+	if (src == dest)
+		return dest;
+
+	if (dest < src) {
+		while(count > 0) {
+			*temp1++ = *temp2++;
+			count--;
+		}
+	} else {
+		temp1 = dest + count - 1;
+		temp2 = src + count - 1;
+
+		while(count > 0) {
+			*temp1-- = *temp2--;
+			count--;
+		}
+	}
+	return dest;
+}
+
+int memcmp(const void * s1,const void * s2,size_t count)
+{
+	const char *temp1 = s1;
+	const char *temp2 = s2;
+	for (; count > 0 && (*temp1 == *temp2); count--) {
+		temp1++;
+		temp2++;
+	}
+
+	if (count > 0)
+		return *(unsigned char *)temp1 - *(unsigned char *)temp2;
+	else
+		return 0;
+}
+
+void *memchr(const void *s, int c, size_t count)
+{
+	const unsigned char *temp = s;
+
+	while (count > 0) {
+		if ((unsigned char)c == *temp++) {
+			return (void *)(temp-1);
+		}
+		count--;
+	}
+	return NULL;
+}