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libdyld: refactor and fix multiarch support

This commit is contained in:
Astro 2020-04-22 01:42:15 +02:00
parent 91085ca8d6
commit d9c58da1e9
1 changed files with 78 additions and 38 deletions
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116
libdyld/src/lib.rs
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@ -5,6 +5,33 @@ use elf::*;
pub mod elf;
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Arch {
Arm,
OpenRisc,
}
impl Arch {
fn detect(ehdr: &Elf32_Ehdr) -> Option<Self> {
const IDENT_OPENRISC: [u8; EI_NIDENT] = [
ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3,
ELFCLASS32, ELFDATA2MSB, EV_CURRENT, ELFOSABI_NONE,
/* ABI version */ 0, /* padding */ 0, 0, 0, 0, 0, 0, 0
];
const IDENT_ARM: [u8; EI_NIDENT] = [
ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3,
ELFCLASS32, ELFDATA2LSB, EV_CURRENT, ELFOSABI_NONE,
/* ABI version */ 0, /* padding */ 0, 0, 0, 0, 0, 0, 0
];
match (ehdr.e_ident, ehdr.e_machine) {
(IDENT_ARM, EM_ARM) => Some(Arch::Arm),
(IDENT_OPENRISC, EM_OPENRISC) => Some(Arch::OpenRisc),
_ => None,
}
}
}
fn read_unaligned<T: Copy>(data: &[u8], offset: usize) -> Result<T, ()> {
if data.len() < offset + mem::size_of::<T>() {
Err(())
@ -83,6 +110,7 @@ pub struct Library<'a> {
pltrel: &'a [Elf32_Rela],
hash_bucket: &'a [Elf32_Word],
hash_chain: &'a [Elf32_Word],
arch: Arch,
}
impl<'a> Library<'a> {
@ -133,20 +161,24 @@ impl<'a> Library<'a> {
// This is unsafe because it mutates global data (the PLT).
pub unsafe fn rebind(&self, name: &[u8], addr: Elf32_Word) -> Result<(), Error<'a>> {
for rela in self.pltrel.iter() {
match ELF32_R_TYPE(rela.r_info) {
R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT |
R_ARM_GLOB_DAT | R_ARM_JUMP_SLOT => {
let sym = self.symtab.get(ELF32_R_SYM(rela.r_info) as usize)
.ok_or("symbol out of bounds of symbol table")?;
let sym_name = self.name_starting_at(sym.st_name as usize)?;
let is_rebind_type = match ELF32_R_TYPE(rela.r_info) {
R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT
if self.arch == Arch::OpenRisc => true,
R_ARM_GLOB_DAT | R_ARM_JUMP_SLOT
if self.arch == Arch::Arm => true,
_ =>
// No associated symbols for other relocation types.
false,
};
if sym_name == name {
self.update_rela(rela, addr)?
}
if is_rebind_type {
let sym = self.symtab.get(ELF32_R_SYM(rela.r_info) as usize)
.ok_or("symbol out of bounds of symbol table")?;
let sym_name = self.name_starting_at(sym.st_name as usize)?;
if sym_name == name {
self.update_rela(rela, addr)?
}
// No associated symbols for other relocation types.
_ => ()
}
}
Ok(())
@ -162,16 +194,39 @@ impl<'a> Library<'a> {
.ok_or("symbol out of bounds of symbol table")?)
}
enum RelaType {
None,
Relative,
Lookup,
};
let rela_type = match ELF32_R_TYPE(rela.r_info) {
R_OR1K_NONE if self.arch == Arch::OpenRisc =>
RelaType::None,
R_ARM_NONE if self.arch == Arch::Arm =>
RelaType::None,
R_OR1K_RELATIVE if self.arch == Arch::OpenRisc =>
RelaType::Relative,
R_ARM_RELATIVE if self.arch == Arch::Arm =>
RelaType::Relative,
R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT
if self.arch == Arch::OpenRisc => RelaType::Lookup,
R_ARM_GLOB_DAT | R_ARM_JUMP_SLOT
if self.arch == Arch::Arm => RelaType::Lookup,
_ =>
return Err("unsupported relocation type")?,
};
let value;
match ELF32_R_TYPE(rela.r_info) {
R_OR1K_NONE | R_ARM_NONE =>
match rela_type {
RelaType::None =>
return Ok(()),
R_OR1K_RELATIVE | R_ARM_RELATIVE =>
RelaType::Relative =>
value = self.image_off + rela.r_addend as Elf32_Word,
R_OR1K_32 | R_OR1K_GLOB_DAT | R_OR1K_JMP_SLOT |
R_ARM_GLOB_DAT | R_ARM_JUMP_SLOT => {
RelaType::Lookup => {
let sym = sym.ok_or("relocation requires an associated symbol")?;
let sym_name = self.name_starting_at(sym.st_name as usize)?;
@ -190,9 +245,6 @@ impl<'a> Library<'a> {
}
}
}
_ =>
return Err("unsupported relocation type")?,
}
self.update_rela(rela, value)
@ -205,25 +257,12 @@ impl<'a> Library<'a> {
let ehdr = read_unaligned::<Elf32_Ehdr>(data, 0)
.map_err(|()| "cannot read ELF header")?;
const IDENT_OPENRISC: [u8; EI_NIDENT] = [
ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3,
ELFCLASS32, ELFDATA2MSB, EV_CURRENT, ELFOSABI_NONE,
/* ABI version */ 0, /* padding */ 0, 0, 0, 0, 0, 0, 0
];
const IDENT_ARM: [u8; EI_NIDENT] = [
ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3,
ELFCLASS32, ELFDATA2LSB, EV_CURRENT, ELFOSABI_NONE,
/* ABI version */ 0, /* padding */ 0, 0, 0, 0, 0, 0, 0
];
if ehdr.e_type != ET_DYN {
return Err("not a shared library")?
}
if !((ehdr.e_ident == IDENT_OPENRISC && ehdr.e_machine == EM_OPENRISC)
|| ((ehdr.e_ident == IDENT_ARM && ehdr.e_machine == EM_ARM))) {
return Err("not for a supported architecture")?
}
let arch = Arch::detect(&ehdr)
.ok_or("not for a supported architecture")?;
let mut dyn_off = None;
for i in 0..ehdr.e_phnum {
@ -324,11 +363,12 @@ impl<'a> Library<'a> {
let library = Library {
image_off: image.as_ptr() as Elf32_Word,
image_sz: image.len(),
strtab: strtab,
symtab: symtab,
pltrel: pltrel,
strtab,
symtab,
pltrel,
hash_bucket: &hash[..nbucket],
hash_chain: &hash[nbucket..nbucket + nchain],
arch,
};
// If a borrow exists anywhere, the borrowed memory cannot be mutated except