roc/linker/src/lib.rs
2021-08-19 21:07:45 -07:00

91 lines
4 KiB
Rust

use clap::{App, AppSettings, Arg, ArgMatches};
use memmap2::Mmap;
use object::Object;
use std::fs;
use std::io;
pub const CMD_PREPROCESS: &str = "preprocess";
pub const CMD_SURGERY: &str = "surgery";
pub const EXEC: &str = "EXEC";
pub const SHARED_LIB: &str = "SHARED_LIB";
pub fn build_app<'a>() -> App<'a> {
App::new("link")
.about("Preprocesses a platform and surgically links it to an application.")
.setting(AppSettings::SubcommandRequiredElseHelp)
.subcommand(
App::new(CMD_PREPROCESS)
.about("Preprocesses a dynamically linked platform to prepare for linking.")
.arg(
Arg::with_name(EXEC)
.help("The dynamically link platform executable")
.required(true),
)
.arg(
Arg::with_name(SHARED_LIB)
.help("The dummy shared library representing the Roc application")
.required(true),
),
)
.subcommand(
App::new(CMD_SURGERY).about("Links a preprocessed platform with a Roc application."),
)
}
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.
// The information need is really the address of each plt version of each application function.
// To find this, first get the dynmaic symbols for the app functions.
// Then reference them on the dynamic relocation table to figure out their plt function number.
// Then with the plt base address and that function number(or scanning the code), it should be possible to find the address.
// TODO: For all text sections check for function calls to app functions.
// This should just be disassembly and then scanning for jmp and call style ops that jump to the plt offsets we care about.
// The data well be store in a list for each function name.
// Not really sure if/how namespacing will lead to conflicts (i.e. naming an app function printf when c alread has printf).
// TODO: Store all this data in a nice format.
// TODO: Potentially create a version of the executable with certain dynamic and PLT information deleted.
// Remove shared library dependencies.
// Delete extra plt entries, dynamic symbols, and dynamic relocations (might require updating other plt entries, may not worth it).
// Add regular symbols pointing to 0 for the app functions (maybe not needed if it is just link metadata).
// It may be fine to just add some of this information to the metadata instead and deal with it on final exec creation.
// If we are copying the exec to a new location in the background anyway it may be basically free.
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),
)
})
}