diff --git a/Cargo.lock b/Cargo.lock
index cc15281..2f6206b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -77,6 +77,18 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 
+[[package]]
+name = "bitvec"
+version = "0.22.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5237f00a8c86130a0cc317830e558b966dd7850d48a953d998c813f01a41b527"
+dependencies = [
+ "funty",
+ "radium",
+ "tap",
+ "wyz",
+]
+
 [[package]]
 name = "bootloader"
 version = "0.9.18"
@@ -211,6 +223,12 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "00b0228411908ca8685dba7fc2cdd70ec9990a6e753e89b6ac91a84c40fbaf4b"
 
+[[package]]
+name = "funty"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1847abb9cb65d566acd5942e94aea9c8f547ad02c98e1649326fc0e8910b8b1e"
+
 [[package]]
 name = "getrandom"
 version = "0.2.3"
@@ -353,6 +371,7 @@ name = "prefetcher_reverse"
 version = "0.1.0"
 dependencies = [
  "basic_timing_cache_channel",
+ "bitvec",
  "cache_side_channel",
  "cache_utils",
  "flush_flush",
@@ -362,6 +381,12 @@ dependencies = [
  "rand",
 ]
 
+[[package]]
+name = "radium"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "643f8f41a8ebc4c5dc4515c82bb8abd397b527fc20fd681b7c011c2aee5d44fb"
+
 [[package]]
 name = "rand"
 version = "0.8.3"
@@ -438,6 +463,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
 
+[[package]]
+name = "tap"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "55937e1799185b12863d447f42597ed69d9928686b8d88a1df17376a097d8369"
+
 [[package]]
 name = "turn_lock"
 version = "0.1.0"
@@ -481,6 +512,15 @@ version = "0.10.2+wasi-snapshot-preview1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6"
 
+[[package]]
+name = "wyz"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "129e027ad65ce1453680623c3fb5163cbf7107bfe1aa32257e7d0e63f9ced188"
+dependencies = [
+ "tap",
+]
+
 [[package]]
 name = "x86_64"
 version = "0.14.3"
diff --git a/prefetcher_reverse/Cargo.toml b/prefetcher_reverse/Cargo.toml
index c0a5528..e150af7 100644
--- a/prefetcher_reverse/Cargo.toml
+++ b/prefetcher_reverse/Cargo.toml
@@ -15,3 +15,4 @@ basic_timing_cache_channel = { path = "../basic_timing_cache_channel" }
 nix = "0.20.0"
 rand = "0.8.3"
 lazy_static = "1.4.0"
+bitvec = "0.22.3"
diff --git a/prefetcher_reverse/src/ip_tool.rs b/prefetcher_reverse/src/ip_tool.rs
index d8c384a..346c030 100644
--- a/prefetcher_reverse/src/ip_tool.rs
+++ b/prefetcher_reverse/src/ip_tool.rs
@@ -1,10 +1,11 @@
+use bitvec::prelude::*;
 use cache_utils::mmap::MMappedMemory;
 use lazy_static::lazy_static;
 use std::collections::LinkedList;
 use std::sync::Mutex;
 
 struct WXRange {
-    bitmap: Vec<bool>, // fixme bit vector
+    bitmap: BitVec, // fixme bit vector
     pages: Vec<MMappedMemory<u8>>,
 }
 
@@ -27,6 +28,13 @@ pub struct FunctionTemplate {
     ip: *const u8,
     end: *const u8,
 }
+
+pub struct Function {
+    fun: unsafe extern "C" fn(*const u8) -> u64,
+    ip: *const u8,
+    end: *const u8,
+    size: usize,
+}
 lazy_static! {
     static ref wx_allocator: Mutex<WXAllocator> = Mutex::new(WXAllocator::new());
 }
@@ -42,6 +50,10 @@ const TIMED_CLFLUSH: FunctionTemplate = FunctionTemplate {
     end: timed_clflush_template_end as *const u8,
 };
 
+pub fn allocate_function(align: usize, template: FunctionTemplate) -> Function {
+    unimplemented!()
+}
+
 global_asm!(
     ".global timed_maccess_template",
     "timed_maccess_template:",