forked from M-Labs/artiq-zynq
libdyld: refactor
This commit is contained in:
parent
c28c567e72
commit
895a3f47e2
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@ -1,4 +1,4 @@
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use core::{mem, ptr, fmt, slice, str, convert, ops::{Deref, Range}};
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use core::{mem, ptr, ops::{Deref, Range}};
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use super::{
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Arch,
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elf::*,
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@ -9,64 +9,15 @@ use super::{
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Error,
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};
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fn elf_hash(name: &[u8]) -> u32 {
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let mut h: u32 = 0;
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for c in name {
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h = (h << 4) + *c as u32;
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let g = h & 0xf0000000;
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if g != 0 {
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h ^= g >> 24;
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h &= !g;
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}
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}
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h
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}
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pub struct DynamicSection<'a> {
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pub strtab: &'a [u8],
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pub symtab: &'a [Elf32_Sym],
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pub hash_bucket: &'a [Elf32_Word],
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pub hash_chain: &'a [Elf32_Word],
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pub rel: &'a [Elf32_Rel],
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pub rela: &'a [Elf32_Rela],
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pub pltrel: &'a [Elf32_Rel],
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}
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impl<'a> DynamicSection<'a> {
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pub fn lookup(&self, name: &[u8]) -> Option<Elf32_Word> {
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let hash = elf_hash(name);
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let mut index = self.hash_bucket[hash as usize % self.hash_bucket.len()] as usize;
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loop {
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if index == STN_UNDEF { return None }
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let sym = &self.symtab[index];
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let sym_name_off = sym.st_name as usize;
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match self.strtab.get(sym_name_off..sym_name_off + name.len()) {
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Some(sym_name) if sym_name == name => {
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if ELF32_ST_BIND(sym.st_info) & STB_GLOBAL == 0 {
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return None
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}
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match sym.st_shndx {
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SHN_UNDEF => return None,
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SHN_ABS => return Some(sym.st_value),
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_ => return Some(sym.st_value)
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}
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}
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_ => (),
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}
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index = self.hash_chain[index] as usize;
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}
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}
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pub fn name_starting_at(&self, offset: usize) -> Result<&'a [u8], Error> {
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let size = self.strtab.iter().skip(offset).position(|&x| x == 0)
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.ok_or("symbol in symbol table not null-terminated")?;
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Ok(self.strtab.get(offset..offset + size)
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.ok_or("cannot read symbol name")?)
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}
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pub struct DynamicSection {
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pub strtab: Range<usize>,
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pub symtab: Range<usize>,
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pub hash: Range<usize>,
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pub hash_bucket: Range<usize>,
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pub hash_chain: Range<usize>,
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pub rel: Range<usize>,
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pub rela: Range<usize>,
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pub pltrel: Range<usize>,
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}
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/// target memory image
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@ -90,7 +41,7 @@ impl Image {
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}
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/// assumes that self.data is properly aligned
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pub fn get_ref<T>(&self, offset: usize) -> Option<&T>
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pub(crate) fn get_ref<T>(&self, offset: usize) -> Option<&T>
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where
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T: Copy,
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{
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@ -104,15 +55,15 @@ impl Image {
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}
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}
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fn get_ref_slice<T: Copy>(&self, offset: usize, len: usize) -> Option<&[T]> {
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if self.data.len() < offset + mem::size_of::<T>() * len {
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None
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} else if (self.data.as_ptr() as usize + offset) & (mem::align_of::<T>() - 1) != 0 {
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None
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} else {
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let ptr = self.data.as_ptr().wrapping_offset(offset as isize) as *const T;
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Some(unsafe { slice::from_raw_parts(ptr, len) })
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}
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/// assumes that self.data is properly aligned
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///
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/// range: in bytes
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pub(crate) fn get_ref_slice_unchecked<T: Copy>(&self, range: &Range<usize>) -> &[T] {
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let offset = range.start;
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let len = (range.end - range.start) / mem::size_of::<T>();
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let ptr = self.data.as_ptr().wrapping_offset(offset as isize) as *const T;
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unsafe { slice::from_raw_parts(ptr, len) }
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}
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fn dyn_headers<'a>(&'a self, range: Range<usize>) ->
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@ -148,13 +99,13 @@ impl Image {
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DT_SYMTAB => symtab_off = val,
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DT_SYMENT => sym_ent = val,
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DT_REL => rel_off = val,
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DT_RELSZ => rel_sz = val / mem::size_of::<Elf32_Rel>(),
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DT_RELSZ => rel_sz = val,
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DT_RELENT => rel_ent = val,
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DT_RELA => rela_off = val,
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DT_RELASZ => rela_sz = val / mem::size_of::<Elf32_Rela>(),
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DT_RELASZ => rela_sz = val,
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DT_RELAENT => rela_ent = val,
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DT_JMPREL => pltrel_off = val,
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DT_PLTRELSZ => pltrel_sz = val / mem::size_of::<Elf32_Rel>(),
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DT_PLTRELSZ => pltrel_sz = val,
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DT_HASH => {
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nbucket = *self.get_ref::<Elf32_Word>(val + 0)
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.ok_or("cannot read hash bucket count")? as usize;
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@ -167,44 +118,44 @@ impl Image {
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}
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}
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if strtab_off + strtab_sz > self.data.len() {
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return Err("invalid strtab offset/size")?
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}
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if symtab_off + symtab_sz > self.data.len() {
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return Err("invalid symtab offset/size")?
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}
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if sym_ent != mem::size_of::<Elf32_Sym>() {
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return Err("incorrect symbol entry size")?
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}
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if rel_off + rel_sz > self.data.len() {
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return Err("invalid rel offset/size")?
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}
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if rel_ent != 0 && rel_ent != mem::size_of::<Elf32_Rel>() {
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return Err("incorrect relocation entry size")?
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}
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if rela_off + rela_sz > self.data.len() {
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return Err("invalid rela offset/size")?
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}
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if rela_ent != 0 && rela_ent != mem::size_of::<Elf32_Rela>() {
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return Err("incorrect relocation entry size")?
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}
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if pltrel_off + pltrel_sz > self.data.len() {
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return Err("invalid pltrel offset/size")?
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}
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// These are the same--there are as many chains as buckets, and the chains only contain
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// the symbols that overflowed the bucket.
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symtab_sz = nchain;
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let hash = self.get_ref_slice::<Elf32_Word>(hash_off, hash_sz)
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.ok_or("cannot read hash entries")?;
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let strtab = self.get_ref_slice(strtab_off, strtab_sz)
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.ok_or("cannot read string table")?;
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let symtab = self.get_ref_slice::<Elf32_Sym>(symtab_off, symtab_sz)
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.ok_or("cannot read symbol table")?;
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let hash_bucket = &hash[..nbucket];
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let hash_chain = &hash[nbucket..nbucket + nchain];
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let rel = self.get_ref_slice::<Elf32_Rel>(rel_off, rel_sz)
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.ok_or("cannot read rel entries")?;
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let rela = self.get_ref_slice::<Elf32_Rela>(rela_off, rela_sz)
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.ok_or("cannot read rela entries")?;
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let pltrel = self.get_ref_slice::<Elf32_Rel>(pltrel_off, pltrel_sz)
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.ok_or("cannot read pltrel entries")?;
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// debug!("ELF: {} rela, {} rel, {} pltrel entries", rela_sz, rel_sz, pltrel_sz);
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Ok(DynamicSection {
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strtab,
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symtab,
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hash_bucket,
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hash_chain,
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rel,
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rela,
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pltrel,
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strtab: strtab_off..strtab_off + strtab_sz,
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symtab: symtab_off..symtab_off + symtab_sz,
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hash: hash_off..hash_off + hash_sz,
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hash_bucket: 0..nbucket,
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hash_chain: nbucket..nbucket + nchain,
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rel: rel_off..rel_off + rel_sz,
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rela: rela_off..rela_off + rela_sz,
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pltrel: pltrel_off..pltrel_off + rela_sz,
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})
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}
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@ -3,9 +3,9 @@
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extern crate alloc;
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extern crate log;
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use core::{mem, ptr, fmt, slice, str, convert, ops::Range};
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use core::{fmt, str, convert};
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use alloc::string::String;
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use log::{info, trace, error};
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use log::{info, trace};
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use elf::*;
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pub mod elf;
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@ -44,16 +44,90 @@ impl fmt::Display for Error {
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}
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}
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fn elf_hash(name: &[u8]) -> u32 {
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let mut h: u32 = 0;
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for c in name {
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h = (h << 4) + *c as u32;
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let g = h & 0xf0000000;
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if g != 0 {
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h ^= g >> 24;
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h &= !g;
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}
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}
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h
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}
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pub struct Library {
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image: Image,
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dyn_range: Range<usize>,
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dyn_section: DynamicSection<'static>,
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dyn_section: DynamicSection,
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}
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impl Library {
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pub fn lookup(&self, name: &[u8]) -> Option<u32> {
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self.dyn_section.lookup(name)
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.map(|addr| self.image.ptr() as u32 + addr)
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fn strtab(&self) -> &[u8] {
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self.image.get_ref_slice_unchecked(&self.dyn_section.strtab)
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}
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fn symtab(&self) -> &[Elf32_Sym] {
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self.image.get_ref_slice_unchecked(&self.dyn_section.symtab)
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}
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fn hash(&self) -> &[Elf32_Word] {
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self.image.get_ref_slice_unchecked(&self.dyn_section.hash)
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}
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fn hash_bucket(&self) -> &[Elf32_Word] {
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&self.hash()[self.dyn_section.hash_bucket.clone()]
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}
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fn hash_chain(&self) -> &[Elf32_Word] {
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&self.hash()[self.dyn_section.hash_chain.clone()]
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}
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fn rel(&self) -> &[Elf32_Rel] {
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self.image.get_ref_slice_unchecked(&self.dyn_section.rel)
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}
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fn rela(&self) -> &[Elf32_Rela] {
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self.image.get_ref_slice_unchecked(&self.dyn_section.rela)
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}
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fn pltrel(&self) -> &[Elf32_Rel] {
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self.image.get_ref_slice_unchecked(&self.dyn_section.pltrel)
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}
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pub fn lookup(&self, name: &[u8]) -> Option<Elf32_Word> {
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let hash = elf_hash(name);
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let mut index = self.hash_bucket()[hash as usize % self.hash_bucket().len()] as usize;
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loop {
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if index == STN_UNDEF { return None }
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let sym = &self.symtab()[index];
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let sym_name_off = sym.st_name as usize;
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match self.strtab().get(sym_name_off..sym_name_off + name.len()) {
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Some(sym_name) if sym_name == name => {
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if ELF32_ST_BIND(sym.st_info) & STB_GLOBAL == 0 {
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return None
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}
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match sym.st_shndx {
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SHN_UNDEF => return None,
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SHN_ABS => return Some(self.image.ptr() as u32 + sym.st_value),
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_ => return Some(self.image.ptr() as u32 + sym.st_value)
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}
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}
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_ => (),
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}
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index = self.hash_chain()[index] as usize;
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}
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}
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pub fn name_starting_at(&self, offset: usize) -> Result<&[u8], Error> {
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let size = self.strtab().iter().skip(offset).position(|&x| x == 0)
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.ok_or("symbol in symbol table not null-terminated")?;
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Ok(self.strtab().get(offset..offset + size)
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.ok_or("cannot read symbol name")?)
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}
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}
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@ -113,23 +187,20 @@ pub fn load(
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let dyn_section = image.dyn_section(dyn_range.clone())?;
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info!("Relocating {} rela, {} rel, {} pltrel",
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dyn_section.rela.len(), dyn_section.rel.len(), dyn_section.pltrel.len());
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for rela in dyn_section.rela {
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reloc::relocate(arch, &image, &dyn_section, rela, resolve)?;
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}
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for rel in dyn_section.rela {
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reloc::relocate(arch, &image, &dyn_section, rel, resolve)?;
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}
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for pltrel in dyn_section.pltrel {
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reloc::relocate(arch, &image, &dyn_section, pltrel, resolve)?;
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}
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let dyn_section = unsafe {
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core::mem::transmute(dyn_section)
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};
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Ok(Library {
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let lib = Library {
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image,
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dyn_range,
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dyn_section,
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})
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};
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for rela in lib.rela() {
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reloc::relocate(arch, &lib, rela, resolve)?;
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}
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for rel in lib.rel() {
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reloc::relocate(arch, &lib, rel, resolve)?;
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}
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for pltrel in lib.pltrel() {
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reloc::relocate(arch, &lib, pltrel, resolve)?;
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}
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Ok(lib)
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}
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@ -4,7 +4,8 @@ use super::{
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Arch,
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elf::*,
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Error,
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image::{DynamicSection, Image},
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image::Image,
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Library,
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};
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pub trait Relocatable {
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@ -87,16 +88,16 @@ fn format_sym_name(sym_name: &[u8]) -> String {
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.unwrap_or(String::from("<invalid symbol name>"))
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}
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pub fn relocate<'a, R: Relocatable>(
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arch: Arch, image: &'a Image, dynamic_section: &'a DynamicSection<'a>,
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rel: &'a R, resolve: &dyn Fn(&[u8]) -> Option<Elf32_Word>
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pub fn relocate<R: Relocatable>(
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arch: Arch, lib: &Library,
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rel: &R, resolve: &dyn Fn(&[u8]) -> Option<Elf32_Word>
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) -> Result<(), Error> {
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// debug!("rel r_offset={:08X} r_info={:08X} r_addend={:08X}", rel.offset(), rel.r_info, rela.r_addend);
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let sym;
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if rel.sym_info() == 0 {
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sym = None;
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} else {
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sym = Some(dynamic_section.symtab.get(rel.sym_info() as usize)
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sym = Some(lib.symtab().get(rel.sym_info() as usize)
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.ok_or("symbol out of bounds of symbol table")?)
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}
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@ -108,18 +109,18 @@ pub fn relocate<'a, R: Relocatable>(
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return Ok(()),
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RelType::Relative => {
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let addend = rel.addend(image);
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value = image.ptr().wrapping_offset(addend as isize) as Elf32_Word;
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let addend = rel.addend(&lib.image);
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value = lib.image.ptr().wrapping_offset(addend as isize) as Elf32_Word;
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}
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RelType::Lookup => {
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let sym = sym.ok_or("relocation requires an associated symbol")?;
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let sym_name = dynamic_section.name_starting_at(sym.st_name as usize)?;
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let sym_name = lib.name_starting_at(sym.st_name as usize)?;
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if let Some(addr) = dynamic_section.lookup(sym_name) {
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if let Some(addr) = lib.lookup(sym_name) {
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// First, try to resolve against itself.
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trace!("looked up symbol {} in image", format_sym_name(sym_name));
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value = image.ptr() as u32 + addr;
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value = lib.image.ptr() as u32 + addr;
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} else if let Some(addr) = resolve(sym_name) {
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// Second, call the user-provided function.
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trace!("resolved symbol {:?}", format_sym_name(sym_name));
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@ -132,5 +133,5 @@ pub fn relocate<'a, R: Relocatable>(
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}
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debug!("rel_type={:?} write at {:08X} value {:08X}", rel_type, rel.offset(), value);
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image.write(rel.offset(), value)
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lib.image.write(rel.offset(), value)
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}
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