Add basic object parsing and a rough TODO list of steps

Cargo.lock

@@ -1898,6 +1898,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "memmap2"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "00b6c2ebff6180198788f5db08d7ce3bc1d0b617176678831a7510825973e357"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "memoffset"
 version = "0.5.6"
@@ -3312,6 +3321,7 @@ version = "0.1.0"
 dependencies = [
  "bumpalo",
  "clap 3.0.0-beta.1",
+ "memmap2 0.3.1",
  "object 0.26.0",
 ]
 
@@ -3798,7 +3808,7 @@ dependencies = [
  "dlib 0.4.2",
  "lazy_static",
  "log",
- "memmap2",
+ "memmap2 0.1.0",
  "nix 0.18.0",
  "wayland-client",
  "wayland-cursor",

linker/Cargo.toml

@@ -18,7 +18,8 @@ test = false
 bench = false
 
 [dependencies]
+bumpalo = { version = "3.6.1", features = ["collections"] }
 # TODO switch to clap 3.0.0 once it's out. Tried adding clap = "~3.0.0-beta.1" and cargo wouldn't accept it
 clap = { git = "https://github.com/rtfeldman/clap", branch = "master" }
-object = { version = "0.26", features = ["read"] }
-bumpalo = { version = "3.6.1", features = ["collections"] }
+memmap2 = "0.3"
+object = { version = "0.26", features = ["read"] }

linker/src/lib.rs

@@ -1,4 +1,7 @@
-use clap::{App, AppSettings, Arg};
+use clap::{App, AppSettings, Arg, ArgMatches};
+use memmap2::Mmap;
+use object::Object;
+use std::fs;
 use std::io;
 
 pub const CMD_PREPROCESS: &str = "preprocess";
@@ -29,6 +32,46 @@ pub fn build_app<'a>() -> App<'a> {
         )
 }
 
-pub fn preprocess() -> io::Result<()> {
-    panic!("sad");
+pub fn preprocess(matches: &ArgMatches) -> io::Result<i32> {
+    let _app_functions = application_functions(&matches.value_of(SHARED_LIB).unwrap())?;
+
+    let exec_file = fs::File::open(&matches.value_of(EXEC).unwrap())?;
+    let exec_mmap = unsafe { Mmap::map(&exec_file)? };
+    let exec_obj = object::File::parse(&*exec_mmap).map_err(|err| {
+        io::Error::new(
+            io::ErrorKind::InvalidData,
+            format!("Failed to parse executable file: {}", err),
+        )
+    })?;
+
+    // TODO: Extract PLT related information for these functions.
+    // TODO: For all text sections check for function calls to app functions.
+    // TODO: Store all this data in a nice format.
+    // TODO: Potentially create a version of the executable with certain dynamic and PLT information deleted.
+    // It may be fine to just add some of this information to the metadata instead and deal with it on final exec creation.
+
+    Ok(0)
+}
+
+fn application_functions(shared_lib_name: &str) -> io::Result<Vec<String>> {
+    let shared_file = fs::File::open(&shared_lib_name)?;
+    let shared_mmap = unsafe { Mmap::map(&shared_file)? };
+    let shared_obj = object::File::parse(&*shared_mmap).map_err(|err| {
+        io::Error::new(
+            io::ErrorKind::InvalidData,
+            format!("Failed to parse shared library file: {}", err),
+        )
+    })?;
+    shared_obj
+        .exports()
+        .unwrap()
+        .into_iter()
+        .map(|export| String::from_utf8(export.name().to_vec()))
+        .collect::<Result<Vec<_>, _>>()
+        .map_err(|err| {
+            io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!("Failed to load function names from shared library: {}", err),
+            )
+        })
 }

linker/src/main.rs

@@ -7,8 +7,8 @@ fn main() -> io::Result<()> {
     let exit_code = match matches.subcommand_name() {
         None => Ok::<i32, io::Error>(-1),
         Some(CMD_PREPROCESS) => {
-            preprocess()?;
-            Ok(0)
+            let sub_matches = matches.subcommand_matches(CMD_PREPROCESS).unwrap();
+            preprocess(sub_matches)
         }
         Some(CMD_SURGERY) => Ok(0),
         _ => unreachable!(),