diff --git a/c/hw-file.c b/c/hw-file.c
index 7a9478d..afa62a0 100644
--- a/c/hw-file.c
+++ b/c/hw-file.c
@@ -14,6 +14,8 @@
 
 #include <stdint.h>
 #include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
@@ -21,9 +23,26 @@
 #define HW_FILE_READ	0x01
 #define HW_FILE_WRITE	0x02
 
+static size_t stat_length(size_t *const len, const size_t off, const int fd)
+{
+	struct stat statbuf;
+
+	if (*len == 0 && !fstat(fd, &statbuf)) {
+		if (statbuf.st_size == 0)
+			errno = EINVAL;
+		else if (statbuf.st_size - (off_t)off <= SIZE_MAX)
+			*len = (size_t)(statbuf.st_size - (off_t)off);
+		else
+			*len = SIZE_MAX;
+	}
+
+	return *len;
+}
+
 static int map_file(uint64_t *const addr,
 		    const char *const path,
-		    const uint32_t len,
+		    size_t len,
+		    const size_t off,
 		    const uint32_t mode)
 {
 	const int prot = (mode & HW_FILE_READ ? PROT_READ : 0) |
@@ -37,7 +56,12 @@
 	if (fd < 0)
 		return errno;
 
-	void *const mapped = mmap(NULL, len, prot, MAP_SHARED, fd, (off_t)0);
+	if (!stat_length(&len, off, fd)) {
+		close(fd);
+		return errno;
+	}
+
+	void *const mapped = mmap(NULL, len, prot, MAP_SHARED, fd, (off_t)off);
 	close(fd);
 	if (mapped == MAP_FAILED)
 		return errno;
@@ -48,23 +72,27 @@
 
 static int map_fill_from_file(uint64_t *const addr,
 			      const char *const path,
-			      const uint32_t len,
+			      size_t len,
+			      const size_t off,
 			      const uint32_t mode)
 {
-	uint32_t xferred;
+	size_t xferred;
 	ssize_t read_ret;
 
 	if (mode != HW_FILE_READ)
 		return EINVAL;
 
-	void *const mapped = mmap(NULL, len, PROT_READ | PROT_WRITE,
-				  MAP_ANONYMOUS | MAP_PRIVATE, -1, (off_t)0);
-	if (mapped == MAP_FAILED)
-		return errno;
-
 	const int fd = open(path, O_RDONLY);
 	if (fd < 0)
-		goto _munmap;
+		return errno;
+
+	if (!stat_length(&len, off, fd))
+		goto _close;
+
+	void *const mapped = mmap(NULL, len, PROT_READ | PROT_WRITE,
+				  MAP_ANONYMOUS | MAP_PRIVATE, -1, (off_t)off);
+	if (mapped == MAP_FAILED)
+		goto _close;
 
 	xferred = 0;
 	do {
@@ -73,7 +101,6 @@
 			xferred += read_ret;
 	} while ((read_ret > 0 || (read_ret == -1 && errno == EINTR))
 		 && xferred < len);
-	close(fd);
 
 	if (xferred < len)
 		goto _munmap;
@@ -81,22 +108,28 @@
 	if (mprotect(mapped, len, PROT_READ))
 		goto _munmap;
 
+	close(fd);
+
 	*addr = (uint64_t)(uintptr_t)mapped;
 	return 0;
 
 _munmap:
 	munmap(mapped, len);
+_close:
+	close(fd);
 	return errno;
 }
 
 int hw_file_map(uint64_t *const addr,
 		const char *const path,
 		const uint32_t len,
+		const uint32_t off,
 		const uint32_t mode,
 		const int copy)
 {
 	if (copy)
-		return map_fill_from_file(addr, path, len, mode);
+		return map_fill_from_file(
+				addr, path, (size_t)len, (size_t)off, mode);
 	else
-		return map_file(addr, path, len, mode);
+		return map_file(addr, path, (size_t)len, (size_t)off, mode);
 }