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libdyld: refactor

This commit is contained in:
Astro 2020-05-01 01:19:10 +02:00
parent c28c567e72
commit 895a3f47e2
4 changed files with 153 additions and 130 deletions
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2
firmware/libdyld/src/file.rs
View File

@ -1,4 +1,4 @@
use core::{mem, ptr, fmt, slice, str, convert, ops::{Deref, Range}};
use core::{mem, ptr, ops::{Deref, Range}};
use super::{
Arch,
elf::*,

139
firmware/libdyld/src/image.rs
View File

@ -9,64 +9,15 @@ use super::{
Error,
};
fn elf_hash(name: &[u8]) -> u32 {
let mut h: u32 = 0;
for c in name {
h = (h << 4) + *c as u32;
let g = h & 0xf0000000;
if g != 0 {
h ^= g >> 24;
h &= !g;
}
}
h
}
pub struct DynamicSection<'a> {
pub strtab: &'a [u8],
pub symtab: &'a [Elf32_Sym],
pub hash_bucket: &'a [Elf32_Word],
pub hash_chain: &'a [Elf32_Word],
pub rel: &'a [Elf32_Rel],
pub rela: &'a [Elf32_Rela],
pub pltrel: &'a [Elf32_Rel],
}
impl<'a> DynamicSection<'a> {
pub fn lookup(&self, name: &[u8]) -> Option<Elf32_Word> {
let hash = elf_hash(name);
let mut index = self.hash_bucket[hash as usize % self.hash_bucket.len()] as usize;
loop {
if index == STN_UNDEF { return None }
let sym = &self.symtab[index];
let sym_name_off = sym.st_name as usize;
match self.strtab.get(sym_name_off..sym_name_off + name.len()) {
Some(sym_name) if sym_name == name => {
if ELF32_ST_BIND(sym.st_info) & STB_GLOBAL == 0 {
return None
}
match sym.st_shndx {
SHN_UNDEF => return None,
SHN_ABS => return Some(sym.st_value),
_ => return Some(sym.st_value)
}
}
_ => (),
}
index = self.hash_chain[index] as usize;
}
}
pub fn name_starting_at(&self, offset: usize) -> Result<&'a [u8], Error> {
let size = self.strtab.iter().skip(offset).position(|&x| x == 0)
.ok_or("symbol in symbol table not null-terminated")?;
Ok(self.strtab.get(offset..offset + size)
.ok_or("cannot read symbol name")?)
}
pub struct DynamicSection {
pub strtab: Range<usize>,
pub symtab: Range<usize>,
pub hash: Range<usize>,
pub hash_bucket: Range<usize>,
pub hash_chain: Range<usize>,
pub rel: Range<usize>,
pub rela: Range<usize>,
pub pltrel: Range<usize>,
}
/// target memory image
@ -90,7 +41,7 @@ impl Image {
}
/// assumes that self.data is properly aligned
pub fn get_ref<T>(&self, offset: usize) -> Option<&T>
pub(crate) fn get_ref<T>(&self, offset: usize) -> Option<&T>
where
T: Copy,
{
@ -104,15 +55,15 @@ impl Image {
}
}
fn get_ref_slice<T: Copy>(&self, offset: usize, len: usize) -> Option<&[T]> {
if self.data.len() < offset + mem::size_of::<T>() * len {
None
} else if (self.data.as_ptr() as usize + offset) & (mem::align_of::<T>() - 1) != 0 {
None
} else {
let ptr = self.data.as_ptr().wrapping_offset(offset as isize) as *const T;
Some(unsafe { slice::from_raw_parts(ptr, len) })
}
/// assumes that self.data is properly aligned
///
/// range: in bytes
pub(crate) fn get_ref_slice_unchecked<T: Copy>(&self, range: &Range<usize>) -> &[T] {
let offset = range.start;
let len = (range.end - range.start) / mem::size_of::<T>();
let ptr = self.data.as_ptr().wrapping_offset(offset as isize) as *const T;
unsafe { slice::from_raw_parts(ptr, len) }
}
fn dyn_headers<'a>(&'a self, range: Range<usize>) ->
@ -148,13 +99,13 @@ impl Image {
DT_SYMTAB => symtab_off = val,
DT_SYMENT => sym_ent = val,
DT_REL => rel_off = val,
DT_RELSZ => rel_sz = val / mem::size_of::<Elf32_Rel>(),
DT_RELSZ => rel_sz = val,
DT_RELENT => rel_ent = val,
DT_RELA => rela_off = val,
DT_RELASZ => rela_sz = val / mem::size_of::<Elf32_Rela>(),
DT_RELASZ => rela_sz = val,
DT_RELAENT => rela_ent = val,
DT_JMPREL => pltrel_off = val,
DT_PLTRELSZ => pltrel_sz = val / mem::size_of::<Elf32_Rel>(),
DT_PLTRELSZ => pltrel_sz = val,
DT_HASH => {
nbucket = *self.get_ref::<Elf32_Word>(val + 0)
.ok_or("cannot read hash bucket count")? as usize;
@ -167,44 +118,44 @@ impl Image {
}
}
if strtab_off + strtab_sz > self.data.len() {
return Err("invalid strtab offset/size")?
}
if symtab_off + symtab_sz > self.data.len() {
return Err("invalid symtab offset/size")?
}
if sym_ent != mem::size_of::<Elf32_Sym>() {
return Err("incorrect symbol entry size")?
}
if rel_off + rel_sz > self.data.len() {
return Err("invalid rel offset/size")?
}
if rel_ent != 0 && rel_ent != mem::size_of::<Elf32_Rel>() {
return Err("incorrect relocation entry size")?
}
if rela_off + rela_sz > self.data.len() {
return Err("invalid rela offset/size")?
}
if rela_ent != 0 && rela_ent != mem::size_of::<Elf32_Rela>() {
return Err("incorrect relocation entry size")?
}
if pltrel_off + pltrel_sz > self.data.len() {
return Err("invalid pltrel offset/size")?
}
// These are the same--there are as many chains as buckets, and the chains only contain
// the symbols that overflowed the bucket.
symtab_sz = nchain;
let hash = self.get_ref_slice::<Elf32_Word>(hash_off, hash_sz)
.ok_or("cannot read hash entries")?;
let strtab = self.get_ref_slice(strtab_off, strtab_sz)
.ok_or("cannot read string table")?;
let symtab = self.get_ref_slice::<Elf32_Sym>(symtab_off, symtab_sz)
.ok_or("cannot read symbol table")?;
let hash_bucket = &hash[..nbucket];
let hash_chain = &hash[nbucket..nbucket + nchain];
let rel = self.get_ref_slice::<Elf32_Rel>(rel_off, rel_sz)
.ok_or("cannot read rel entries")?;
let rela = self.get_ref_slice::<Elf32_Rela>(rela_off, rela_sz)
.ok_or("cannot read rela entries")?;
let pltrel = self.get_ref_slice::<Elf32_Rel>(pltrel_off, pltrel_sz)
.ok_or("cannot read pltrel entries")?;
// debug!("ELF: {} rela, {} rel, {} pltrel entries", rela_sz, rel_sz, pltrel_sz);
Ok(DynamicSection {
strtab,
symtab,
hash_bucket,
hash_chain,
rel,
rela,
pltrel,
strtab: strtab_off..strtab_off + strtab_sz,
symtab: symtab_off..symtab_off + symtab_sz,
hash: hash_off..hash_off + hash_sz,
hash_bucket: 0..nbucket,
hash_chain: nbucket..nbucket + nchain,
rel: rel_off..rel_off + rel_sz,
rela: rela_off..rela_off + rela_sz,
pltrel: pltrel_off..pltrel_off + rela_sz,
})
}

119
firmware/libdyld/src/lib.rs
View File

@ -3,9 +3,9 @@
extern crate alloc;
extern crate log;
use core::{mem, ptr, fmt, slice, str, convert, ops::Range};
use core::{fmt, str, convert};
use alloc::string::String;
use log::{info, trace, error};
use log::{info, trace};
use elf::*;
pub mod elf;
@ -44,16 +44,90 @@ impl fmt::Display for Error {
}
}
fn elf_hash(name: &[u8]) -> u32 {
let mut h: u32 = 0;
for c in name {
h = (h << 4) + *c as u32;
let g = h & 0xf0000000;
if g != 0 {
h ^= g >> 24;
h &= !g;
}
}
h
}
pub struct Library {
image: Image,
dyn_range: Range<usize>,
dyn_section: DynamicSection<'static>,
dyn_section: DynamicSection,
}
impl Library {
pub fn lookup(&self, name: &[u8]) -> Option<u32> {
self.dyn_section.lookup(name)
.map(|addr| self.image.ptr() as u32 + addr)
fn strtab(&self) -> &[u8] {
self.image.get_ref_slice_unchecked(&self.dyn_section.strtab)
}
fn symtab(&self) -> &[Elf32_Sym] {
self.image.get_ref_slice_unchecked(&self.dyn_section.symtab)
}
fn hash(&self) -> &[Elf32_Word] {
self.image.get_ref_slice_unchecked(&self.dyn_section.hash)
}
fn hash_bucket(&self) -> &[Elf32_Word] {
&self.hash()[self.dyn_section.hash_bucket.clone()]
}
fn hash_chain(&self) -> &[Elf32_Word] {
&self.hash()[self.dyn_section.hash_chain.clone()]
}
fn rel(&self) -> &[Elf32_Rel] {
self.image.get_ref_slice_unchecked(&self.dyn_section.rel)
}
fn rela(&self) -> &[Elf32_Rela] {
self.image.get_ref_slice_unchecked(&self.dyn_section.rela)
}
fn pltrel(&self) -> &[Elf32_Rel] {
self.image.get_ref_slice_unchecked(&self.dyn_section.pltrel)
}
pub fn lookup(&self, name: &[u8]) -> Option<Elf32_Word> {
let hash = elf_hash(name);
let mut index = self.hash_bucket()[hash as usize % self.hash_bucket().len()] as usize;
loop {
if index == STN_UNDEF { return None }
let sym = &self.symtab()[index];
let sym_name_off = sym.st_name as usize;
match self.strtab().get(sym_name_off..sym_name_off + name.len()) {
Some(sym_name) if sym_name == name => {
if ELF32_ST_BIND(sym.st_info) & STB_GLOBAL == 0 {
return None
}
match sym.st_shndx {
SHN_UNDEF => return None,
SHN_ABS => return Some(self.image.ptr() as u32 + sym.st_value),
_ => return Some(self.image.ptr() as u32 + sym.st_value)
}
}
_ => (),
}
index = self.hash_chain()[index] as usize;
}
}
pub fn name_starting_at(&self, offset: usize) -> Result<&[u8], Error> {
let size = self.strtab().iter().skip(offset).position(|&x| x == 0)
.ok_or("symbol in symbol table not null-terminated")?;
Ok(self.strtab().get(offset..offset + size)
.ok_or("cannot read symbol name")?)
}
}
@ -113,23 +187,20 @@ pub fn load(
let dyn_section = image.dyn_section(dyn_range.clone())?;
info!("Relocating {} rela, {} rel, {} pltrel",
dyn_section.rela.len(), dyn_section.rel.len(), dyn_section.pltrel.len());
for rela in dyn_section.rela {
reloc::relocate(arch, &image, &dyn_section, rela, resolve)?;
}
for rel in dyn_section.rela {
reloc::relocate(arch, &image, &dyn_section, rel, resolve)?;
}
for pltrel in dyn_section.pltrel {
reloc::relocate(arch, &image, &dyn_section, pltrel, resolve)?;
}
let dyn_section = unsafe {
core::mem::transmute(dyn_section)
};
Ok(Library {
let lib = Library {
image,
dyn_range,
dyn_section,
})
};
for rela in lib.rela() {
reloc::relocate(arch, &lib, rela, resolve)?;
}
for rel in lib.rel() {
reloc::relocate(arch, &lib, rel, resolve)?;
}
for pltrel in lib.pltrel() {
reloc::relocate(arch, &lib, pltrel, resolve)?;
}
Ok(lib)
}

23
firmware/libdyld/src/reloc.rs
View File

@ -4,7 +4,8 @@ use super::{
Arch,
elf::*,
Error,
image::{DynamicSection, Image},
image::Image,
Library,
};
pub trait Relocatable {
@ -87,16 +88,16 @@ fn format_sym_name(sym_name: &[u8]) -> String {
.unwrap_or(String::from("<invalid symbol name>"))
}
pub fn relocate<'a, R: Relocatable>(
arch: Arch, image: &'a Image, dynamic_section: &'a DynamicSection<'a>,
rel: &'a R, resolve: &dyn Fn(&[u8]) -> Option<Elf32_Word>
pub fn relocate<R: Relocatable>(
arch: Arch, lib: &Library,
rel: &R, resolve: &dyn Fn(&[u8]) -> Option<Elf32_Word>
) -> Result<(), Error> {
// debug!("rel r_offset={:08X} r_info={:08X} r_addend={:08X}", rel.offset(), rel.r_info, rela.r_addend);
let sym;
if rel.sym_info() == 0 {
sym = None;
} else {
sym = Some(dynamic_section.symtab.get(rel.sym_info() as usize)
sym = Some(lib.symtab().get(rel.sym_info() as usize)
.ok_or("symbol out of bounds of symbol table")?)
}
@ -108,18 +109,18 @@ pub fn relocate<'a, R: Relocatable>(
return Ok(()),
RelType::Relative => {
let addend = rel.addend(image);
value = image.ptr().wrapping_offset(addend as isize) as Elf32_Word;
let addend = rel.addend(&lib.image);
value = lib.image.ptr().wrapping_offset(addend as isize) as Elf32_Word;
}
RelType::Lookup => {
let sym = sym.ok_or("relocation requires an associated symbol")?;
let sym_name = dynamic_section.name_starting_at(sym.st_name as usize)?;
let sym_name = lib.name_starting_at(sym.st_name as usize)?;
if let Some(addr) = dynamic_section.lookup(sym_name) {
if let Some(addr) = lib.lookup(sym_name) {
// First, try to resolve against itself.
trace!("looked up symbol {} in image", format_sym_name(sym_name));
value = image.ptr() as u32 + addr;
value = lib.image.ptr() as u32 + addr;
} else if let Some(addr) = resolve(sym_name) {
// Second, call the user-provided function.
trace!("resolved symbol {:?}", format_sym_name(sym_name));
@ -132,5 +133,5 @@ pub fn relocate<'a, R: Relocatable>(
}
debug!("rel_type={:?} write at {:08X} value {:08X}", rel_type, rel.offset(), value);
image.write(rel.offset(), value)
lib.image.write(rel.offset(), value)
}