diff --git a/jni/bootimgtools/Android.mk b/jni/bootimgtools/Android.mk
index 1862c5d80..6d6fc8f6f 100644
--- a/jni/bootimgtools/Android.mk
+++ b/jni/bootimgtools/Android.mk
@@ -3,6 +3,6 @@ LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 LOCAL_MODULE := bootimgtools
 LOCAL_MODULE_TAGS := optional
-LOCAL_SRC_FILES := main.c extract.c repack.c hexpatch.c
+LOCAL_SRC_FILES := main.c unpack.c repack.c hexpatch.c
 LOCAL_CFLAGS += -std=gnu11
 include $(BUILD_EXECUTABLE)
diff --git a/jni/bootimgtools/bootimg.h b/jni/bootimgtools/bootimg.h
index 65f81b34e..3a7e46353 100644
--- a/jni/bootimgtools/bootimg.h
+++ b/jni/bootimgtools/bootimg.h
@@ -93,7 +93,7 @@ struct boot_img_hdr
 **    else: jump to kernel_addr
 */
 
-int extract(const char *image);
+int unpack(const char *image);
 int repack(const char *image);
 int hexpatch(char *image, char *from, char *to);
 
diff --git a/jni/bootimgtools/hexpatch.c b/jni/bootimgtools/hexpatch.c
index 33a0ee10b..588e524cb 100644
--- a/jni/bootimgtools/hexpatch.c
+++ b/jni/bootimgtools/hexpatch.c
@@ -9,7 +9,7 @@
 
 #include "bootimg.h"
 
-int hex2int(char c) {
+static int hex2int(char c) {
 	int first = c / 16 - 3;
 	int second = c % 16;
 	int result = first * 10 + second;
@@ -17,13 +17,13 @@ int hex2int(char c) {
 	return result;
 }
 
-int hex2ascii(char c, char d) {
+static int hex2ascii(char c, char d) {
 	int high = hex2int(c) * 16;
 	int low = hex2int(d);
 	return high+low;
 }
 
-void hexstr2str(char *hex, char *str) {
+static void hexstr2str(char *hex, char *str) {
 	char buf = 0;
 	for(int i = 0, length = strlen(hex); i < length; ++i){
 		if(i % 2){
diff --git a/jni/bootimgtools/main.c b/jni/bootimgtools/main.c
index 3155bcefd..7ff39e5f9 100644
--- a/jni/bootimgtools/main.c
+++ b/jni/bootimgtools/main.c
@@ -7,22 +7,21 @@
   Patch Boot Image
 *********************/
 
-int usage(char *arg0) {
+static int usage(char *arg0) {
 	fprintf(stderr, "Boot Image Unpack/Repack Tool\n");
-	fprintf(stderr, "%s --extract <bootimage>\n", arg0);
+	fprintf(stderr, "%s --unpack <bootimage>\n", arg0);
 	fprintf(stderr, "  Unpack <bootimage> into current directory\n\n");
 	fprintf(stderr, "%s --repack <bootimage>\n", arg0);
-	fprintf(stderr, "  Repack kernel, dt, ramdisk... from current directory to new-image.img\n  <bootimage> is the image you've just unpacked\n\n");
+	fprintf(stderr, "  Repack kernel, dtb, ramdisk... from current directory to new-image.img\n  <bootimage> is the image you've just unpacked\n\n");
 	fprintf(stderr, "%s --hexpatch <bootimage> <hexpattern1> <hexpattern2>\n", arg0);
 	fprintf(stderr, "  Search <hexpattern1> in <bootimage>, and replace with <hexpattern2>\n\n");
 	return 1;
 }
 
-int main(int argc, char *argv[])
-{
+int main(int argc, char *argv[]) {
 	char ch;
 	struct option long_options[] = {
-		{"extract", required_argument, NULL, 'e'},
+		{"unpack", required_argument, NULL, 'u'},
 		{"repack", required_argument, NULL, 'r'},
 		{"hexpatch", required_argument, NULL, 'p'},
 		{NULL, 0, NULL, 0}
@@ -30,7 +29,7 @@ int main(int argc, char *argv[])
 	while ((ch = getopt_long(argc, argv, "e:r:p:", long_options, NULL)) != -1) {
 		switch (ch) {
 			case 'e':
-				return extract(optarg);
+				return unpack(optarg);
 			case 'r':
 				return repack(optarg);
 			case 'p':
@@ -42,4 +41,4 @@ int main(int argc, char *argv[])
 		}
 	}
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/jni/bootimgtools/repack.c b/jni/bootimgtools/repack.c
index 9c3ac2123..23c443bf7 100644
--- a/jni/bootimgtools/repack.c
+++ b/jni/bootimgtools/repack.c
@@ -12,8 +12,8 @@
 #include "bootimg.h"
 
 // Global pointer of current positions
-void *ibase, *ipos;
-int ofd, opos;
+static void *ibase, *ipos;
+static int ofd, opos;
 
 static size_t dump(const char *filename) {
 	int fd = open(filename, O_RDONLY);
@@ -60,7 +60,7 @@ static int aosp() {
 	printf("AOSP Boot Image Detected\n");
 
 	char *name;
-	struct boot_img_hdr hdr, ihdr;
+	boot_img_hdr hdr, ihdr;
 
 	// Read the original header
 	memcpy(&ihdr, ibase, sizeof(ihdr));
diff --git a/jni/bootimgtools/extract.c b/jni/bootimgtools/unpack.c
similarity index 97%
rename from jni/bootimgtools/extract.c
rename to jni/bootimgtools/unpack.c
index 71735781c..5b0e48bb3 100644
--- a/jni/bootimgtools/extract.c
+++ b/jni/bootimgtools/unpack.c
@@ -12,7 +12,7 @@
 #include "bootimg.h"
 
 // Global pointer of current positions
-unsigned char *base, *pos;
+static unsigned char *base, *pos;
 
 static void dump(size_t size, const char *filename) {
 	unlink(filename);
@@ -37,7 +37,7 @@ static int aosp() {
 	char name[PATH_MAX], *ext;
 
 	// Read the header
-	struct boot_img_hdr hdr;
+	boot_img_hdr hdr;
 	memcpy(&hdr, base, sizeof(hdr));
 
 	pos = base + hdr.page_size;
@@ -108,7 +108,7 @@ static int aosp() {
 	return 0;
 }
 
-int extract(const char* image) {
+int unpack(const char* image) {
 	int fd = open(image, O_RDONLY), ret = 0;
 	size_t size = lseek(fd, 0, SEEK_END);
 	lseek(fd, 0, SEEK_SET);