initial commit
This commit is contained in:
208
src/main.rs
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208
src/main.rs
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mod ints;
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mod output;
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mod structs;
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use crate::{
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ints::BigEndian,
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output::Output,
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structs::{ElfHeader1, ElfHeader2, SectionHeaderEntry, SymbolTableEntry},
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};
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use bytemuck::from_bytes;
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use clap::{Parser, Subcommand};
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use core::str::from_utf8;
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use eyre::{bail, eyre, Context};
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use ints::{Decode, LittleEndian, U32, U64};
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use serde_json::Value;
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use std::{fs, mem::size_of, path::PathBuf};
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#[derive(Parser)]
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struct Opt {
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elf: PathBuf,
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#[clap(subcommand)]
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command: Command,
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}
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#[derive(Subcommand)]
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enum Command {
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/// List sections
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Sections {},
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/// List symbols
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Symbols {
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#[clap(short, long)]
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section: String,
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},
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}
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const HEADER1_LEN: usize = size_of::<ElfHeader1>();
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macro_rules! parse_elf {
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($endian:ty, $word:ty, $out:expr, $header1:expr, $elf:expr) => {{
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//let header1 = $header1;
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let out = $out;
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const HEADER2_LEN: usize = size_of::<ElfHeader2<$endian, $word>>();
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let elf = $elf;
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if elf.len() < HEADER1_LEN + HEADER2_LEN {
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bail!("not a valid elf file: file too small");
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}
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let header2: &[u8; HEADER2_LEN] = elf[HEADER1_LEN..][..HEADER2_LEN].try_into()?;
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let header2: ElfHeader2<$endian, $word> = *from_bytes(header2);
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out.write("header2", &header2)?;
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let e_shentsize = usize::from(header2.e_shentsize.to_native());
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if e_shentsize != size_of::<SectionHeaderEntry<$endian, $word>>() {
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bail!("wrong e_shentsize (0x{e_shentsize:x})");
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}
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let e_shnum = usize::from(header2.e_shnum.to_native());
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let section_header_table_size = e_shentsize * e_shnum;
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let section_header_table_start =
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usize::try_from(header2.e_shoff.to_native()).wrap_err("e_shoff bigger than usize")?;
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let section_header_table_end = section_header_table_start + section_header_table_size;
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if elf.len() < section_header_table_end {
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bail!("not a valid elf file: section table goes past eof");
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} else if elf.len() > section_header_table_end {
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bail!("not a valid elf file: section table doesn't end at eof");
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}
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let mut section_header_entries = vec![];
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for entry_start in
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(section_header_table_start..section_header_table_end).step_by(e_shentsize)
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{
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let entry = &elf[entry_start..][..e_shentsize];
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let entry: SectionHeaderEntry<$endian, $word> = *from_bytes(entry);
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section_header_entries.push(entry);
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}
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out.write("section_table", §ion_header_entries)?;
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let names_section_i = usize::from(header2.e_shstrndx.to_native());
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let names_section_entry = §ion_header_entries
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.get(names_section_i)
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.ok_or(eyre!("invalid e_shstrndx"))?;
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let names_section_start: usize = (names_section_entry.sh_offset.to_native().try_into())
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.wrap_err("sh_offset bigger than usize")?;
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let names_section_size: usize = (names_section_entry.sh_size.to_native().try_into())
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.wrap_err("sh_size bigger than usize")?;
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let names_section_end = names_section_start + names_section_size;
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let names_section = &elf[names_section_start..names_section_end];
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let mut symtab_i = None;
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let mut strtab = None;
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let mut section_header_entries_with_names = vec![];
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for (i, entry) in section_header_entries.iter().enumerate() {
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let name_start: usize = (entry.sh_name.to_native())
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.try_into()
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.wrap_err("sh_name bigger than usize")?;
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if name_start > names_section.len() {
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bail!("sh_name out of bounds for .names section");
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}
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let name_end = (name_start..names_section.len())
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.find(|&i| names_section[i] == b'\0')
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.ok_or(eyre!(".names entry missing null byte"))?;
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let name = &names_section[name_start..name_end];
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let name = from_utf8(name).wrap_err(eyre!(".names entry not valid utf-8"))?;
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let section_start = entry.start().wrap_err_with(|| name.to_string())?;
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let section_end = entry.end().wrap_err_with(|| name.to_string())?;
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if section_end > elf.len() {
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bail!("section {name:?} end is past eof");
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}
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match name {
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".symtab" => symtab_i = Some(i),
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".strtab" => {
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strtab = Some(&elf[section_start..section_end]);
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}
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_ => {}
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}
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let mut entry_json =
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serde_json::to_value(entry).wrap_err("failed to serialize section header")?;
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let Value::Object(fields) = &mut entry_json else {
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unreachable!()
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};
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fields.insert("name".to_string(), Value::String(name.to_string()));
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section_header_entries_with_names.push(entry_json);
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}
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let _ = out.write("section_table", §ion_header_entries_with_names);
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if let Some(symtab_i) = symtab_i {
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let symtab = §ion_header_entries[symtab_i];
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const ENTRY_SIZE: usize = size_of::<SymbolTableEntry<$word>>();
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if symtab.sh_size.to_native() as usize != ENTRY_SIZE {
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bail!(".symtab size not a multiple of symtab entry size");
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}
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let section_start: usize = symtab.start().wrap_err(".symtab")?;
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let section_end: usize = symtab.end().wrap_err(".symtab")?;
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for entry in elf[section_start..section_end].chunks_exact(ENTRY_SIZE) {
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let entry: &[u8; ENTRY_SIZE] = entry.try_into().unwrap();
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let entry: &SymbolTableEntry<$word> = from_bytes(entry);
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let name_start: usize = (entry.st_name.to_native().try_into())
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.wrap_err("symtab entry st_name too big to fit in usize")?;
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let name = (name_start != 0)
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.then(|| {
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strtab.map(|strtab| {
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eprintln!("{name_start} {}", strtab.len());
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let name_end = (name_start..strtab.len())
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.find(|&i| strtab[i] == b'\0')
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.ok_or(eyre!(".strtab entry missing null byte"))?;
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let name = &strtab[name_start..name_end];
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from_utf8(name).wrap_err(eyre!(
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".strtab entry at 0x{name_start:x} is not valid utf-8"
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))
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})
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})
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// Option<Option<Result>> to Result<Option>
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.flatten()
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.transpose()?;
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eprintln!("[.symtab] {name:?}: {entry:?}");
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}
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}
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}};
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}
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fn main() -> eyre::Result<()> {
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let opt = Opt::parse();
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color_eyre::install()?;
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let elf = fs::read(opt.elf).wrap_err("failed to read elf file")?;
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if elf.len() < HEADER1_LEN {
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bail!("not a valid elf file: file too small");
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}
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let header1: &[u8; HEADER1_LEN] = elf[..HEADER1_LEN].try_into()?;
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let header1: ElfHeader1 = *from_bytes(header1);
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let mut out = Output::default();
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out.write("header1", &header1)?;
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if &header1.ei_magic != b"\x7FELF" {
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bail!("not a valid elf file: invalid magic");
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}
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if header1.ei_version != 1 {
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bail!("unknown elf version: 0x{:x}", header1.ei_version);
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}
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match (header1.ei_class, header1.ei_data) {
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(1, 1) => parse_elf!(LittleEndian, U32<LittleEndian>, &mut out, header1, elf),
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(2, 1) => parse_elf!(LittleEndian, U64<LittleEndian>, &mut out, header1, elf),
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(1, 2) => parse_elf!(BigEndian, U32<BigEndian>, &mut out, header1, elf),
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(2, 2) => parse_elf!(BigEndian, U64<BigEndian>, &mut out, header1, elf),
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(1 | 2, ei_data) => bail!("unknown e_ident[EI_DATA]: 0x{ei_data:x}"),
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(ei_class, ..) => bail!("unknown e_ident[EI_CLASS]: 0x{ei_class:x}"),
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}
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Ok(())
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}
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