tools: add tool to create empty flash image

Makefile

@@ -36,6 +36,8 @@ MAKE := make
 
 .SECONDARY:
 
+all: tools
+
 clean:
 	@echo "CLEAN"
 	@rm -rf $(BUILD)

scripts/Makefile.host

@@ -1,2 +1,9 @@
 obj-y += source/drivers/sandbox_flash.o
 obj-y += source/drivers/stdio_console.o
+
+tools: $(BUILD)/create-image
+
+$(BUILD)/create-image: $(BUILD)/source/tools/create_image.o
+	@echo "LD $@"
+	@mkdir -p $(dir $@)
+	@$(LD) -o $@ $(CFLAGS) $(LDFLAGS) $^

source/tools/create_image.c

@@ -0,0 +1,69 @@
+#include <ctype.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define min(x, y) ((x < y) ? (x) : (y))
+
+static int parse_size(size_t *size, const char *s)
+{
+	char *end;
+
+	if (!size || !s)
+		return -1;
+
+	*size = strtoul(s, &end, 10);
+
+	switch (toupper(*end)) {
+	case 'G': *size *= 1024;
+	case 'M': *size *= 1024;
+	case 'K': *size *= 1024;
+	case 'B': ++end; break;
+	case '\0': return 0;
+	default: return -1;
+	}
+
+	if (*end)
+		return -1;
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	uint8_t buf[4096];
+	FILE *fp;
+	size_t count, size;
+	int ret = 0;
+
+	if (argc < 3) {
+		fprintf(stderr, "usage: %s <size> <output>\n", argv[0]);
+		return -1;
+	}
+
+	if (parse_size(&size, argv[1]) != 0) {
+		fprintf(stderr, "error: size must be an integer with an optional K, M "
+			"or G suffix.\n");
+		return -1;
+	}
+
+	memset(buf, 0xFF, sizeof buf);
+
+	if (!(fp = fopen(argv[2], "wb"))) {
+		fprintf(stderr, "error: unable to open '%s' for writing.\n", argv[2]);
+		return -1;
+	}
+
+	for (; size; size -= count) {
+		count = min(sizeof buf, size);
+
+		if (fwrite(buf, sizeof *buf, count, fp) < count) {
+			fprintf(stderr, "error: unable to write to file.\n");
+			ret = -1;
+		}
+	}
+
+	fclose(fp);
+	return ret;
+}