Add symbol stripper binary

This will be used to take the kernel symbols and append it as payload to
the kernel itself.

That way the kernel will have the complete amount of information it
needs to perform symbolication.

Author: Javier-varez

Cargo.lock

@@ -3,7 +3,8 @@
 members = [
     "p1c0_kernel",
     "p1c0_macros",
-    "test_fwk"
+    "test_fwk",
+    "stripper"
 ]
 
 exclude = [

Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "stripper"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+structopt = "0.3.26"
+anyhow = "1.0.56"
+object = "0.28"
+rustc-demangle = "0.1.21"

stripper/Cargo.toml

@@ -0,0 +1,69 @@
+use object::{
+    elf, endian, read::elf::ElfFile, Object, ObjectSymbol, ObjectSymbolTable, SymbolKind,
+};
+use rustc_demangle::demangle;
+
+struct Symbol {
+    address: u64,
+    size: u64,
+    name_offset: u32,
+    name_length: u32,
+}
+
+pub fn symbols_from_elf_file(
+    elf: &ElfFile<elf::FileHeader64<endian::LittleEndian>>,
+    symbol_file: &mut impl std::io::Write,
+) -> anyhow::Result<()> {
+    let mut symbols = vec![];
+    let mut string_table: Vec<u8> = vec![];
+
+    if let Some(symbol_table) = elf.symbol_table() {
+        symbol_table
+            .symbols()
+            .filter(|symbol| symbol.kind() == SymbolKind::Text)
+            .for_each(|symbol| {
+                if let Ok(name) = symbol.name() {
+                    let name = demangle(name).to_string();
+
+                    let name_offset = string_table.len() as u32;
+                    let name_length = name.bytes().len() as u32;
+
+                    name.bytes().for_each(|byte| string_table.push(byte));
+
+                    symbols.push(Symbol {
+                        address: symbol.address(),
+                        size: symbol.size(),
+                        name_offset,
+                        name_length,
+                    });
+                } else {
+                    panic!("Symbol has invalid name!");
+                }
+            });
+    }
+
+    const MAGIC_BYTES: [u8; 4] = *b"Smbl";
+    const SYMBOL_TABLE_OFFSET: u32 = 0x14;
+    const SYMBOL_ENTRY_SIZE: u32 = 0x18;
+
+    let num_symbols = symbols.len() as u32;
+    let string_table_offset = SYMBOL_TABLE_OFFSET + num_symbols * SYMBOL_ENTRY_SIZE;
+    let filesize = string_table_offset + string_table.len() as u32;
+
+    symbol_file.write_all(&MAGIC_BYTES)?;
+    symbol_file.write_all(&u32::to_le_bytes(filesize))?;
+    symbol_file.write_all(&u32::to_le_bytes(symbols.len() as u32))?;
+    symbol_file.write_all(&u32::to_le_bytes(SYMBOL_TABLE_OFFSET))?;
+    symbol_file.write_all(&u32::to_le_bytes(string_table_offset))?;
+
+    for symbol in symbols {
+        symbol_file.write_all(&u32::to_le_bytes(symbol.name_offset))?;
+        symbol_file.write_all(&u32::to_le_bytes(symbol.name_length))?;
+        symbol_file.write_all(&u64::to_le_bytes(symbol.address))?;
+        symbol_file.write_all(&u64::to_le_bytes(symbol.size))?;
+    }
+
+    symbol_file.write_all(&string_table[..])?;
+
+    Ok(())
+}

stripper/src/lib.rs

@@ -0,0 +1,20 @@
+use std::fs;
+
+use object::read::elf::ElfFile;
+use structopt::StructOpt;
+
+#[derive(StructOpt, Debug)]
+struct Options {
+    elf_file: std::path::PathBuf,
+    symbol_file: std::path::PathBuf,
+}
+
+fn main() -> anyhow::Result<()> {
+    let options = Options::from_args();
+
+    let elf_file = fs::read(options.elf_file)?;
+    let elf_file = ElfFile::parse(&elf_file[..])?;
+    let mut symbol_file = fs::File::create(options.symbol_file)?;
+
+    stripper::symbols_from_elf_file(&elf_file, &mut symbol_file)
+}