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elf: use relocations to find number of dynamic symbols if hash is empty #112

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merged 2 commits into from
Oct 23, 2018
Merged

elf: use relocations to find number of dynamic symbols if hash is empty #112

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a901f08
elf: use relocations to find number of dynamic symbols if hash is empty
philipc Oct 22, 2018
2bc8d8e
elf: use relocation symbols even if the hash isn't empty
philipc Oct 23, 2018
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28 changes: 22 additions & 6 deletions src/elf/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ if_sylvan! {
use error;
use container::{Container, Ctx};
use alloc::vec::Vec;
use core::cmp;

pub type Header = header::Header;
pub type ProgramHeader = program_header::ProgramHeader;
Expand Down Expand Up @@ -276,19 +277,29 @@ if_sylvan! {
if dyn_info.needed_count > 0 {
libraries = dynamic.get_libraries(&dynstrtab);
}
let num_syms = if let Some(gnu_hash) = dyn_info.gnu_hash {
// parse the dynamic relocations
dynrelas = RelocSection::parse(bytes, dyn_info.rela, dyn_info.relasz, true, ctx)?;
dynrels = RelocSection::parse(bytes, dyn_info.rel, dyn_info.relsz, false, ctx)?;
let is_rela = dyn_info.pltrel as u64 == dyn::DT_RELA;
pltrelocs = RelocSection::parse(bytes, dyn_info.jmprel, dyn_info.pltrelsz, is_rela, ctx)?;

let mut num_syms = if let Some(gnu_hash) = dyn_info.gnu_hash {
gnu_hash_len(bytes, gnu_hash as usize, ctx)?
} else if let Some(hash) = dyn_info.hash {
hash_len(bytes, hash as usize, header.e_machine, ctx)?
} else {
0
};
if num_syms == 0 {
let max_reloc_sym = dynrelas.iter()
.chain(dynrels.iter())
.chain(pltrelocs.iter())
.fold(0, |num, reloc| cmp::max(num, reloc.r_sym));
if max_reloc_sym != 0 {
num_syms = max_reloc_sym + 1;
}
}
dynsyms = Symtab::parse(bytes, dyn_info.symtab, num_syms, ctx)?;
// parse the dynamic relocations
dynrelas = RelocSection::parse(bytes, dyn_info.rela, dyn_info.relasz, true, ctx)?;
dynrels = RelocSection::parse(bytes, dyn_info.rel, dyn_info.relsz, false, ctx)?;
let is_rela = dyn_info.pltrel as u64 == dyn::DT_RELA;
pltrelocs = RelocSection::parse(bytes, dyn_info.jmprel, dyn_info.pltrelsz, is_rela, ctx)?;
}

// iterate through shdrs again iff we're an ET_REL
Expand Down Expand Up @@ -349,6 +360,11 @@ if_sylvan! {
let buckets_num = bytes.pread_with::<u32>(offset, ctx.le)? as usize;
let min_chain = bytes.pread_with::<u32>(offset + 4, ctx.le)? as usize;
let bloom_size = bytes.pread_with::<u32>(offset + 8, ctx.le)? as usize;
// We could handle min_chain==0 if we really had to, but it shouldn't happen.
if buckets_num == 0 || min_chain == 0 || bloom_size == 0 {
return Err(error::Error::Malformed(format!("Invalid DT_GNU_HASH: buckets_num={} min_chain={} bloom_size={}",
buckets_num, min_chain, bloom_size)));
}
// Find the last bucket.
let buckets_offset = offset + 16 + bloom_size * if ctx.container.is_big() { 8 } else { 4 };
let mut max_chain = 0;
Expand Down