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#![feature(no_std, core, core_prelude, core_slice_ext, custom_derive)]
#![no_std]
#![crate_name = "elfloader32"]
#![crate_type = "lib"]
#[cfg(test)]
#[macro_use]
extern crate std;
pub mod elf;
use core::fmt;
use core::mem::{transmute, size_of};
pub type PAddr = u64;
pub type VAddr = usize;
pub struct ElfBinary<'s> {
name: &'s str,
region: &'s [u8],
header: &'s elf::FileHeader,
}
impl<'s> fmt::Debug for ElfBinary<'s> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{} {}", self.name, self.header)
}
}
pub trait ElfLoader {
fn allocate(&mut self, base: VAddr, size: usize, flags: elf::ProgFlag);
fn load(&mut self, base: VAddr, region: &'static [u8]);
}
unsafe fn slice_pod<T>(region: &[u8], offset: usize, count: usize) -> &[T] {
assert!(region.len() - offset >= count * size_of::<T>());
core::slice::from_raw_parts(region[offset..].as_ptr() as *const T, count)
}
impl<'s> ElfBinary<'s> {
pub fn new(name: &'s str, region: &'s [u8]) -> Option<ElfBinary<'s>> {
if region.len() >= size_of::<elf::FileHeader>() && region.starts_with(elf::ELF_MAGIC) {
let header: &elf::FileHeader = unsafe { &slice_pod(region, 0, 1)[0] };
return Some(ElfBinary { name: name, region: region, header: header });
}
None
}
pub fn file_header(&self) -> &'s elf::FileHeader {
self.header
}
pub fn print_program_headers(&self) {
for p in self.program_headers() {
}
}
pub fn program_headers(&self) -> &'s [elf::ProgramHeader] {
let correct_header_size = self.header.phentsize as usize == size_of::<elf::ProgramHeader>();
let pheader_region_size = self.header.phoff as usize + self.header.phnum as usize * self.header.phentsize as usize;
let big_enough_region = self.region.len() >= pheader_region_size;
if self.header.phoff == 0 || !correct_header_size || !big_enough_region {
return &[];
}
unsafe {
slice_pod(self.region, self.header.phoff as usize, self.header.phnum as usize)
}
}
fn strtab_str(&self, strtab: &'s elf::SectionHeader, str_offset: elf::StrOffset) -> &'s str {
assert!(strtab.shtype == elf::SHT_STRTAB);
let data = self.section_data(strtab);
let offset = str_offset.0 as usize;
let mut end = offset;
while data[end] != 0 {
end += 1;
}
core::str::from_utf8(&data[offset..end]).unwrap()
}
pub fn symbol_name(&self, symbol: &'s elf::Symbol) -> &'s str {
let strtab = self.section_headers().iter().find(|s| s.shtype == elf::SHT_STRTAB && self.section_name(s) == ".strtab").unwrap();
self.strtab_str(strtab, symbol.name)
}
pub fn section_data(&self, section: &'s elf::SectionHeader) -> &'s [u8] {
&self.region[(section.offset as usize)..(section.offset as usize + section.size as usize)]
}
pub fn section_name(&self, section: &'s elf::SectionHeader) -> &'s str {
self.strtab_str(&self.section_headers()[self.header.shstrndx as usize], section.name)
}
fn section_symbols(&self, section: &'s elf::SectionHeader) -> &'s [elf::Symbol] {
assert!(section.shtype == elf::SHT_SYMTAB);
unsafe {
slice_pod(self.section_data(section), 0, section.size as usize / size_of::<elf::Symbol>())
}
}
pub fn for_each_symbol<F: FnMut(&'s elf::Symbol)>(&self, mut func: F) {
for sym in self.section_headers().iter().filter(|s| s.shtype == elf::SHT_SYMTAB).flat_map(|s| self.section_symbols(s).iter()) {
func(sym);
}
}
pub fn section_headers(&self) -> &'s [elf::SectionHeader] {
let correct_header_size = self.header.shentsize as usize == size_of::<elf::SectionHeader>();
let sheader_region_size = self.header.shoff as usize + self.header.shnum as usize * self.header.shentsize as usize;
let big_enough_region = self.region.len() >= sheader_region_size;
if self.header.shoff == 0 || !correct_header_size || !big_enough_region {
return &[];
}
unsafe {
slice_pod(self.region, self.header.shoff as usize, self.header.shnum as usize)
}
}
fn can_load(&self) -> bool {
let correct_class = self.header.ident.class == elf::ELFCLASS64;
let correct_elfversion = self.header.ident.version == elf::EV_CURRENT;
let correct_data = self.header.ident.data == elf::ELFDATA2LSB;
let correct_osabi = self.header.ident.osabi == elf::ELFOSABI_SYSV || self.header.ident.osabi == elf::ELFOSABI_LINUX;
let correct_type = self.header.elftype == elf::ET_EXEC || self.header.elftype == elf::ET_DYN;
let correct_machine = self.header.machine == elf::EM_X86_64;
correct_class && correct_data && correct_elfversion && correct_machine && correct_osabi && correct_type
}
fn load_header(&self, p: &elf::ProgramHeader, loader: &mut ElfLoader) {
let big_enough_region = self.region.len() >= (p.offset + p.filesz) as usize;
if !big_enough_region {
return;
}
loader.allocate(p.vaddr as usize, p.memsz as usize, p.flags);
let segment: &'static [u8] = unsafe {
core::slice::from_raw_parts(
transmute(&self.region[p.offset as usize]), p.filesz as usize)
};
loader.load(p.vaddr as usize, segment);
}
pub fn load(&self, loader: &mut ElfLoader) {
for p in self.program_headers() {
let x = match p.progtype {
elf::PT_LOAD => self.load_header(p, loader),
_ => ()
};
}
}
}