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-rw-r--r--src/main.rs142
1 files changed, 70 insertions, 72 deletions
diff --git a/src/main.rs b/src/main.rs
index 835fd62..6b2f382 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,18 +3,31 @@ use io::{BufRead, BufReader, BufWriter, Read, Seek, Write};
use std::collections::HashMap;
use std::{fmt, fs, io, mem, ptr};
-pub enum LinkError {}
+mod elf;
+
+pub enum LinkError {
+ IO(io::Error),
+ TooLarge,
+}
impl fmt::Display for LinkError {
- fn fmt(&self, _f: &mut fmt::Formatter) -> fmt::Result {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ use LinkError::*;
match self {
- _ => todo!(),
+ IO(e) => write!(f, "IO error: {e}"),
+ TooLarge => write!(f, "executable file would be too large."),
}
}
}
+impl From<io::Error> for LinkError {
+ fn from(e: io::Error) -> Self {
+ Self::IO(e)
+ }
+}
+
impl From<&LinkError> for String {
- fn from(e: &LinkError) -> String {
+ fn from(e: &LinkError) -> Self {
format!("{e}")
}
}
@@ -33,12 +46,11 @@ impl fmt::Display for LinkWarning {
}
impl From<&LinkWarning> for String {
- fn from(e: &LinkWarning) -> String {
+ fn from(e: &LinkWarning) -> Self {
format!("{e}")
}
}
-
pub enum ElfError {
NotAnElf,
Not32Bit,
@@ -145,7 +157,7 @@ struct SourceId(u32);
enum SymbolType {
Function,
Object,
- Other
+ Other,
}
#[derive(Copy, Clone, Debug)]
@@ -189,9 +201,10 @@ impl Symbols {
fn add_global(&mut self, name: SymbolName, info: SymbolInfo) {
self.global.insert(name, info);
}
-
+
fn get(&self, source: SourceId, name: SymbolName) -> Option<&SymbolInfo> {
- self.local.get(&(source, name))
+ self.local
+ .get(&(source, name))
.or_else(|| self.global.get(&name))
.or_else(|| self.weak.get(&name))
}
@@ -200,6 +213,7 @@ impl Symbols {
#[allow(dead_code)] // @TODO @TEMPORARY
#[derive(Debug, Clone, Copy)]
enum RelocationType {
+ Direct32,
Pc32,
GotOff32,
GotPc32,
@@ -209,6 +223,7 @@ impl RelocationType {
fn from_x86_u8(id: u8) -> Result<Self, ElfError> {
use RelocationType::*;
Ok(match id {
+ 1 => Direct32,
2 => Pc32,
9 => GotOff32,
10 => GotPc32,
@@ -250,21 +265,6 @@ impl Relocation {
}
}
-#[repr(C)]
-#[derive(Clone)]
-struct ElfShdr {
- name: u32,
- r#type: u32,
- flags: u32,
- addr: u32,
- offset: u32,
- size: u32,
- link: u32,
- info: u32,
- addralign: u32,
- entsize: u32,
-}
-
struct Linker {
strtab_offset: u64,
data: Vec<u8>, // contains all data from all objects.
@@ -272,7 +272,7 @@ struct Linker {
symbols: Symbols,
symbol_names: SymbolNames,
relocations: Vec<Relocation>,
- sections: Vec<ElfShdr>,
+ sections: Vec<elf::Shdr32>,
warnings: Vec<LinkWarning>,
bss_size: u64,
}
@@ -387,43 +387,9 @@ impl Linker {
let source_id = SourceId(self.source_count);
self.source_count += 1;
- #[repr(C)]
- struct ElfHeader {
- ident: [u8; 4],
- class: u8,
- data: u8,
- version: u8,
- abi: u8,
- abiversion: u8,
- pad: [u8; 7],
- r#type: u16,
- machine: u16,
- version2: u32,
- entry: u32,
- phoff: u32,
- shoff: u32,
- flags: u32,
- ehsize: u16,
- phentsize: u16,
- phnum: u16,
- shentsize: u16,
- shnum: u16,
- shstrndx: u16,
- }
-
- impl ElfHeader {
- fn section_offset(&self, ndx: u16) -> u64 {
- ndx as u64 * self.shentsize as u64 + self.shoff as u64
- }
-
- fn section_seek(&self, ndx: u16) -> io::SeekFrom {
- io::SeekFrom::Start(self.section_offset(ndx))
- }
- }
-
let mut elf = [0u8; 0x34];
reader.read_exact(&mut elf)?;
- let elf: ElfHeader = unsafe { mem::transmute(elf) };
+ let elf: elf::Header32 = unsafe { mem::transmute(elf) };
if elf.ident != [0x7f, b'E', b'L', b'F'] {
return Err(NotAnElf);
@@ -437,7 +403,7 @@ impl Linker {
if elf.version != 1 || elf.version2 != 1 {
return Err(BadVersion);
}
- if elf.r#type != 1 {
+ if elf.r#type != elf::ET_REL {
return Err(BadType);
}
if elf.machine != 3 {
@@ -449,7 +415,7 @@ impl Linker {
// read .strtab header
reader.seek(elf.section_seek(elf.shstrndx))?;
reader.read_exact(&mut shdr_buf)?;
- let shdr: ElfShdr = unsafe { mem::transmute(shdr_buf) };
+ let shdr: elf::Shdr32 = unsafe { mem::transmute(shdr_buf) };
shdr.offset as u64
};
@@ -458,7 +424,7 @@ impl Linker {
for s_idx in 0..elf.shnum {
reader.seek(elf.section_seek(s_idx))?;
reader.read_exact(&mut shdr_buf)?;
- let shdr: ElfShdr = unsafe { mem::transmute(shdr_buf) };
+ let shdr: elf::Shdr32 = unsafe { mem::transmute(shdr_buf) };
let name = self.get_str(reader, shdr.name)?;
sections_by_name.insert(name.clone(), shdr.clone());
self.sections.push(shdr);
@@ -486,14 +452,16 @@ impl Linker {
// we only process relocations relating to .symtab currently.
match self.sections.get(shdr.link as usize) {
None => continue,
- Some(h) => if self.get_str(reader, h.name)? != ".symtab" {
- continue
- },
+ Some(h) => {
+ if self.get_str(reader, h.name)? != ".symtab" {
+ continue;
+ }
+ }
}
-
+
fn read_relocations<RelType>(
reader: &mut BufReader<File>,
- shdr: &ElfShdr,
+ shdr: &elf::Shdr32,
) -> Result<Vec<RelType>, ElfError> {
let offset = shdr.offset as u64;
let size = shdr.size as u64;
@@ -587,7 +555,7 @@ impl Linker {
fn get_sym_name(&self, id: SymbolName) -> Option<&str> {
self.symbol_names.get_str(id)
}
-
+
// get symbol, producing a warning if it does not exist.
fn get_symbol(&mut self, source_id: SourceId, id: SymbolName) -> Option<&SymbolInfo> {
let sym = self.symbols.get(source_id, id);
@@ -603,16 +571,46 @@ impl Linker {
None => return Ok(()),
Some(sym) => sym,
};
- println!("{symbol:?}");
+ println!("{rel:?} {symbol:?}");
Ok(())
}
-
- pub fn link<T: Write>(&mut self, _writer: &mut BufWriter<T>) -> Result<Vec<LinkWarning>, LinkError> {
+
+ pub fn link<T: Write>(
+ &mut self,
+ out: &mut BufWriter<T>,
+ ) -> Result<Vec<LinkWarning>, LinkError> {
// we have to use an index because for all rust knows,
// apply_relocation modifies self.relocations (it doesn't).
for i in 0..self.relocations.len() {
self.apply_relocation(self.relocations[i].clone())?;
}
+
+ const SEGMENT_ADDR: u32 = 0x400000;
+
+ let data_size = 0;
+
+ let mut header = elf::Header32::default();
+ let header_size: u32 = header.ehsize.into();
+ let phdr_size: u32 = header.phentsize.into();
+ let file_size = header_size + phdr_size + data_size;
+ let entry_point = SEGMENT_ADDR + header_size + phdr_size;
+ header.phnum = 1;
+ header.phoff = header_size;
+ header.entry = entry_point;
+ out.write_all(&header.to_bytes())?;
+
+ let bss_size: u32 = self.bss_size.try_into().map_err(|_| LinkError::TooLarge)?;
+
+ let phdr = elf::Phdr32 {
+ flags: 0b111, // read, write, execute
+ offset: 0,
+ vaddr: SEGMENT_ADDR,
+ filesz: file_size,
+ memsz: file_size + bss_size,
+ ..Default::default()
+ };
+ out.write_all(&phdr.to_bytes())?;
+
Ok(mem::take(&mut self.warnings))
}
}
generated by cgit v1.2.3 (git 2.39.1) at 2025-07-01 05:11:03 +0000