libafl_libfuzzer: rename all symbols and allow mimalloc use (#1565)

* rename allocator symbols to avoid conflict with mimalloc

* re-add llvm-tools to CI

* rename everything

* fixup clippy lint

* make fuzzer entries more noticeable :)

* rabbit mode

* clippy

.github/workflows/build_and_test.yml

@@ -124,6 +124,7 @@ jobs:
       with:
         profile: minimal
         toolchain: stable
+        components: llvm-tools
     - name: Remove existing clang and LLVM
       run: sudo apt purge llvm* clang*
     - name: Install and cache deps

libafl_libfuzzer/Cargo.toml

@@ -35,6 +35,9 @@ introspection = []
 ## `-fsanitize=fuzzer-no-link -l:libafl_libfuzzer_runtime.a`
 embed-runtime = []
 
+## 🐇
+rabbit = []
+
 [dependencies]
 libfuzzer-sys = { version = "0.4.7", default-features = false }
 document-features = { version = "0.2" }

libafl_libfuzzer/build.rs

@@ -1,5 +1,17 @@
-use std::{path::PathBuf, process::Command};
+use std::{
+    fs::File,
+    io::{BufRead, BufReader, BufWriter, Write},
+    path::PathBuf,
+    process::{Command, Stdio},
+};
 
+#[cfg(feature = "rabbit")]
+const NAMESPACE: &str = "🐇";
+#[cfg(not(feature = "rabbit"))]
+const NAMESPACE: &str = "__libafl";
+const NAMESPACE_LEN: usize = NAMESPACE.as_bytes().len();
+
+#[allow(clippy::too_many_lines)]
 fn main() {
     if cfg!(any(feature = "cargo-clippy", docsrs)) {
         return; // skip when clippy or docs is running
@@ -69,20 +81,143 @@ fn main() {
     let mut lib_path = custom_lib_dir.join(std::env::var_os("TARGET").unwrap());
     lib_path.push("release");
 
-    #[cfg(all(feature = "embed-runtime", target_family = "unix"))]
+    if cfg!(target_family = "unix") {
+        use std::path::Path;
+
+        lib_path.push("libafl_libfuzzer_runtime.a");
+        let target_libdir = Command::new("rustc")
+            .args(["--print", "target-libdir"])
+            .output()
+            .expect("Couldn't find rustc's target-libdir");
+        let target_libdir = String::from_utf8(target_libdir.stdout).unwrap();
+        let target_libdir = Path::new(target_libdir.trim());
+
+        let rust_lld = target_libdir.join("../bin/rust-lld");
+        let rust_ar = target_libdir.join("../bin/llvm-ar"); // NOTE: depends on llvm-tools
+        let rust_objcopy = target_libdir.join("../bin/llvm-objcopy"); // NOTE: depends on llvm-tools
+        let nm = "nm"; // NOTE: we use system nm here because llvm-nm doesn't respect the encoding?
+
+        let redefined_symbols = custom_lib_dir.join("redefs.txt");
+
+        let objfile_orig = custom_lib_dir.join("libFuzzer.o");
+        let objfile_dest = custom_lib_dir.join("libFuzzer-mimalloc.o");
+
+        let mut command = Command::new(rust_lld);
+        command
+            .args(["-flavor", "gnu"])
+            .arg("-r")
+            .arg("--whole-archive")
+            .arg(lib_path)
+            .args(["-o", objfile_orig.to_str().expect("Invalid path characters present in your current directory prevent us from linking to the runtime")]);
+
+        assert!(
+            !command.status().map(|s| !s.success()).unwrap_or(true),
+            "Couldn't link runtime crate! Do you have the llvm-tools component installed?"
+        );
+
+        let mut child = Command::new(nm)
+            .arg(&objfile_orig)
+            .stdout(Stdio::piped())
+            .spawn()
+            .unwrap();
+
+        let mut redefinitions_file = BufWriter::new(File::create(&redefined_symbols).unwrap());
+
+        let replacement = format!("_ZN{NAMESPACE_LEN}{NAMESPACE}");
+
+        // redefine all the rust-mangled symbols we can
+        // TODO this will break when v0 mangling is stabilised
+        for line in BufReader::new(child.stdout.take().unwrap()).lines() {
+            let line = line.unwrap();
+            let (_, symbol) = line.rsplit_once(' ').unwrap();
+            if symbol.starts_with("_ZN") {
+                writeln!(
+                    redefinitions_file,
+                    "{} {}",
+                    symbol,
+                    symbol.replacen("_ZN", &replacement, 1)
+                )
+                .unwrap();
+            }
+        }
+        redefinitions_file.flush().unwrap();
+        drop(redefinitions_file);
+
+        assert!(
+            !child.wait().map(|s| !s.success()).unwrap_or(true),
+            "Couldn't link runtime crate! Do you have the llvm-tools component installed?"
+        );
+
+        let mut command = Command::new(rust_objcopy);
+
+        for symbol in [
+            "__rust_drop_panic",
+            "__rust_foreign_exception",
+            "rust_begin_unwind",
+            "rust_panic",
+            "rust_eh_personality",
+            "__rg_oom",
+            "__rdl_oom",
+            "__rdl_alloc",
+            "__rust_alloc",
+            "__rdl_dealloc",
+            "__rust_dealloc",
+            "__rdl_realloc",
+            "__rust_realloc",
+            "__rdl_alloc_zeroed",
+            "__rust_alloc_zeroed",
+            "__rust_alloc_error_handler",
+            "__rust_no_alloc_shim_is_unstable",
+            "__rust_alloc_error_handler_should_panic",
+        ] {
+            command
+                .arg("--redefine-sym")
+                .arg(format!("{symbol}={symbol}_libafl_libfuzzer_runtime"));
+        }
+
+        command
+            .arg("--redefine-syms")
+            .arg(redefined_symbols)
+            .args([&objfile_orig, &objfile_dest]);
+
+        assert!(
+            !command.status().map(|s| !s.success()).unwrap_or(true),
+            "Couldn't rename allocators in the runtime crate! Do you have the llvm-tools component installed?"
+        );
+
+        let mut command = Command::new(rust_ar);
+        command
+            .arg("cr")
+            .arg(custom_lib_dir.join("libFuzzer.a"))
+            .arg(objfile_dest);
+
+        assert!(
+            !command.status().map(|s| !s.success()).unwrap_or(true),
+            "Couldn't create runtime archive!"
+        );
+
+        #[cfg(feature = "embed-runtime")]
         {
             // NOTE: lib, .a are added always on unix-like systems as described in:
             // https://gist.github.com/novafacing/1389cbb2f0a362d7eb103e67b4468e2b
             println!(
                 "cargo:rustc-env=LIBAFL_LIBFUZZER_RUNTIME_PATH={}",
-            lib_path.join("libafl_libfuzzer_runtime.a").display()
+                custom_lib_dir.join("libFuzzer.a").display()
             );
         }
 
+        println!(
+            "cargo:rustc-link-search=native={}",
+            custom_lib_dir.to_str().unwrap()
+        );
+        println!("cargo:rustc-link-lib=static=Fuzzer");
+    } else {
         println!(
             "cargo:rustc-link-search=native={}",
             lib_path.to_str().unwrap()
         );
-    println!("cargo:rustc-link-lib=static=afl_libfuzzer_runtime");
+        println!("cargo:rustc-link-lib=static=afl_fuzzer_runtime");
+    }
+
     println!("cargo:rustc-link-lib=stdc++");
 }

libafl_libfuzzer/libafl_libfuzzer_runtime/Cargo.toml

@@ -37,7 +37,7 @@ libafl_targets = { path = "../../libafl_targets", features = ["sancov_8bit", "sa
 ahash = { version = "0.8.3", default-features = false }
 libc = "0.2.139"
 log = "0.4.17"
-mimalloc = { version = "0.1.34", default-features = false, optional = true }
+mimalloc = { version = "0.1.34", default-features = false }
 num-traits = "0.2.15"
 rand = "0.8.5"
 serde = { version = "1.0", features = ["derive"] } # serialization lib

libafl_libfuzzer/libafl_libfuzzer_runtime/build.rs

@@ -1,5 +1,6 @@
 use std::{env, path::Path};
 
+#[allow(clippy::too_many_lines)]
 fn main() {
     let out_dir = env::var_os("OUT_DIR").unwrap();
 

libafl_libfuzzer/libafl_libfuzzer_runtime/src/lib.rs

@@ -80,8 +80,11 @@ use libafl::{
 };
 use libafl_bolts::AsSlice;
 use libc::_exit;
+use mimalloc::MiMalloc;
 
 use crate::options::{LibfuzzerMode, LibfuzzerOptions};
+#[global_allocator]
+static GLOBAL: MiMalloc = MiMalloc;
 
 mod corpus;
 mod feedbacks;