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Gary Guo 2021-08-25 02:55:49 +01:00
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.gitignore vendored Normal file
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.vscode/
target
Cargo.lock

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Cargo.toml Normal file
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[package]
name = "unwind"
version = "0.1.0"
authors = ["Gary Guo <gary@garyguo.net>"]
edition = "2018"
[dependencies]
gimli = { version = "0.25.0", default-features = false, features = ["read"] }
libc = "0.2"
fallible-iterator = "0.1"
log = "0.4"
once_cell = "1.8"
[profile.release]
debug = true

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Permission is hereby granted, free of charge, to any
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
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TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

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mod phdr;
mod registry;
use crate::util::*;
use gimli::{BaseAddresses, EhFrame, FrameDescriptionEntry};
pub struct FDESearchResult {
pub fde: FrameDescriptionEntry<StaticSlice>,
pub bases: BaseAddresses,
pub eh_frame: EhFrame<StaticSlice>,
}
pub trait FDEFinder {
fn find_fde(&self, pc: usize) -> Option<FDESearchResult>;
}
pub struct GlobalFinder(());
impl FDEFinder for GlobalFinder {
fn find_fde(&self, pc: usize) -> Option<FDESearchResult> {
if let Some(v) = registry::get_finder().find_fde(pc) {
return Some(v);
}
if let Some(v) = phdr::get_finder().find_fde(pc) {
return Some(v);
}
None
}
}
pub fn get_finder() -> &'static GlobalFinder {
&GlobalFinder(())
}

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use super::FDESearchResult;
use crate::util::{deref_pointer, get_unlimited_slice};
use core::mem;
use core::slice;
use gimli::{BaseAddresses, EhFrame, EhFrameHdr, NativeEndian, UnwindSection};
use libc::{c_int, c_void, dl_iterate_phdr, dl_phdr_info, PT_DYNAMIC, PT_GNU_EH_FRAME, PT_LOAD};
struct CallbackData {
pc: usize,
result: Option<FDESearchResult>,
}
pub struct PhdrFinder(());
pub fn get_finder() -> &'static PhdrFinder {
&PhdrFinder(())
}
impl super::FDEFinder for PhdrFinder {
fn find_fde(&self, pc: usize) -> Option<FDESearchResult> {
let mut data = CallbackData { pc, result: None };
unsafe { dl_iterate_phdr(Some(phdr_callback), &mut data as *mut CallbackData as _) };
data.result
}
}
unsafe extern "C" fn phdr_callback(
info: *mut dl_phdr_info,
_size: usize,
data: *mut c_void,
) -> c_int {
let data = &mut *(data as *mut CallbackData);
let phdrs = slice::from_raw_parts((*info).dlpi_phdr, (*info).dlpi_phnum as usize);
let mut text = None;
let mut eh_frame_hdr = None;
let mut dynamic = None;
for phdr in phdrs {
let start = (*info).dlpi_addr + phdr.p_vaddr;
match phdr.p_type {
PT_LOAD => {
let end = start + phdr.p_memsz;
let range = start..end;
if range.contains(&(data.pc as _)) {
text = Some(range);
}
}
PT_GNU_EH_FRAME => {
eh_frame_hdr = Some(start);
}
PT_DYNAMIC => {
dynamic = Some(start);
}
_ => (),
}
}
let text = match text {
Some(v) => v,
None => return 0,
};
let eh_frame_hdr = match eh_frame_hdr {
Some(v) => v,
None => return 0,
};
let mut bases = BaseAddresses::default()
.set_eh_frame_hdr(eh_frame_hdr as _)
.set_text(text.start as _);
// Find the GOT section.
if let Some(start) = dynamic {
const DT_NULL: usize = 0;
const DT_PLTGOT: usize = 3;
let mut tags = start as *const [usize; 2];
let mut tag = *tags;
while tag[0] != DT_NULL {
if tag[0] == DT_PLTGOT {
bases = bases.set_got(tag[1] as _);
break;
}
tags = tags.add(1);
tag = *tags;
}
}
// Parse .eh_frame_hdr section.
let eh_frame_hdr = EhFrameHdr::new(
get_unlimited_slice(eh_frame_hdr as usize as _),
NativeEndian,
)
.parse(&bases, mem::size_of::<usize>() as _);
let eh_frame_hdr = match eh_frame_hdr {
Ok(v) => v,
Err(_) => return 0,
};
let eh_frame = deref_pointer(eh_frame_hdr.eh_frame_ptr());
bases = bases.set_eh_frame(eh_frame as _);
let eh_frame = EhFrame::new(get_unlimited_slice(eh_frame as usize as _), NativeEndian);
// Use binary search table for address if available.
if let Some(table) = eh_frame_hdr.table() {
if let Ok(fde) =
table.fde_for_address(&eh_frame, &bases, data.pc as _, EhFrame::cie_from_offset)
{
data.result = Some(FDESearchResult {
fde,
bases,
eh_frame,
});
return 1;
}
}
// Otherwise do the linear search.
if let Ok(fde) = eh_frame.fde_for_address(&bases, data.pc as _, EhFrame::cie_from_offset) {
data.result = Some(FDESearchResult {
fde,
bases,
eh_frame,
});
return 1;
}
0
}

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use super::FDESearchResult;
use crate::util::get_unlimited_slice;
use core::mem::MaybeUninit;
use core::ptr;
use gimli::{BaseAddresses, EhFrame, NativeEndian, UnwindSection};
use libc::c_void;
use once_cell::sync::Lazy;
use std::sync::Mutex;
enum Table {
Single(*const c_void),
Multiple(*const *const c_void),
}
struct Object {
next: *mut Object,
tbase: usize,
dbase: usize,
table: Table,
}
struct RegistryInner {
object: *mut Object,
}
unsafe impl Send for RegistryInner {}
pub struct Registry {
inner: Mutex<RegistryInner>,
}
pub fn get_finder() -> &'static Registry {
static LAZY: Lazy<Registry> = Lazy::new(|| Registry {
inner: Mutex::new(RegistryInner {
object: ptr::null_mut(),
}),
});
&*LAZY
}
impl super::FDEFinder for Registry {
fn find_fde(&self, pc: usize) -> Option<FDESearchResult> {
let guard = get_finder().inner.lock().unwrap();
let mut cur = guard.object;
unsafe {
while !cur.is_null() {
let bases = BaseAddresses::default()
.set_text((*cur).tbase as _)
.set_got((*cur).dbase as _);
match (*cur).table {
Table::Single(addr) => {
let eh_frame = EhFrame::new(get_unlimited_slice(addr as _), NativeEndian);
let bases = bases.clone().set_eh_frame(addr as usize as _);
if let Ok(fde) =
eh_frame.fde_for_address(&bases, pc as _, EhFrame::cie_from_offset)
{
return Some(FDESearchResult {
fde,
bases,
eh_frame,
});
}
}
Table::Multiple(mut addrs) => {
let mut addr = *addrs;
while !addr.is_null() {
let eh_frame =
EhFrame::new(get_unlimited_slice(addr as _), NativeEndian);
let bases = bases.clone().set_eh_frame(addr as usize as _);
if let Ok(fde) =
eh_frame.fde_for_address(&bases, pc as _, EhFrame::cie_from_offset)
{
return Some(FDESearchResult {
fde,
bases,
eh_frame,
});
}
addrs = addrs.add(1);
addr = *addrs;
}
}
}
cur = (*cur).next;
}
}
None
}
}
#[no_mangle]
unsafe extern "C" fn __register_frame_info_bases(
begin: *const c_void,
ob: *mut Object,
tbase: *const c_void,
dbase: *const c_void,
) {
if begin.is_null() {
return;
}
ob.write(Object {
next: core::ptr::null_mut(),
tbase: tbase as _,
dbase: dbase as _,
table: Table::Single(begin),
});
let mut guard = get_finder().inner.lock().unwrap();
(*ob).next = guard.object;
guard.object = ob;
}
#[no_mangle]
unsafe extern "C" fn __register_frame_info(begin: *const c_void, ob: *mut Object) {
__register_frame_info_bases(begin, ob, core::ptr::null_mut(), core::ptr::null_mut());
}
#[no_mangle]
unsafe extern "C" fn __register_frame(begin: *const c_void) {
if begin.is_null() {
return;
}
let storage = Box::into_raw(Box::new(MaybeUninit::<Object>::uninit())) as *mut Object;
__register_frame_info(begin, storage);
}
#[no_mangle]
unsafe extern "C" fn __register_frame_info_table_bases(
begin: *const c_void,
ob: *mut Object,
tbase: *const c_void,
dbase: *const c_void,
) {
ob.write(Object {
next: core::ptr::null_mut(),
tbase: tbase as _,
dbase: dbase as _,
table: Table::Multiple(begin as _),
});
let mut guard = get_finder().inner.lock().unwrap();
(*ob).next = guard.object;
guard.object = ob;
}
#[no_mangle]
unsafe extern "C" fn __register_frame_info_table(begin: *const c_void, ob: *mut Object) {
__register_frame_info_table_bases(begin, ob, core::ptr::null_mut(), core::ptr::null_mut());
}
#[no_mangle]
unsafe extern "C" fn __register_frame_table(begin: *const c_void) {
if begin.is_null() {
return;
}
let storage = Box::into_raw(Box::new(MaybeUninit::<Object>::uninit())) as *mut Object;
__register_frame_info_table(begin, storage);
}
#[no_mangle]
unsafe extern "C" fn __deregister_frame_info_bases(begin: *const c_void) -> *mut Object {
if begin.is_null() {
return core::ptr::null_mut();
}
let mut guard = get_finder().inner.lock().unwrap();
let mut prev = &mut guard.object;
let mut cur = *prev;
while !cur.is_null() {
let found = match (*cur).table {
Table::Single(addr) => addr == begin,
_ => false,
};
if found {
*prev = (*cur).next;
return cur;
}
prev = &mut (*cur).next;
cur = *prev;
}
core::ptr::null_mut()
}
#[no_mangle]
unsafe extern "C" fn __deregister_frame_info(begin: *const c_void) -> *mut Object {
__deregister_frame_info_bases(begin)
}
#[no_mangle]
unsafe extern "C" fn __deregister_frame(begin: *const c_void) {
if begin.is_null() {
return;
}
let storage = __deregister_frame_info(begin);
drop(Box::from_raw(storage as *mut MaybeUninit<Object>))
}

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mod find_fde;
mod util;

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use gimli::{EndianSlice, NativeEndian, Pointer};
pub type StaticSlice = EndianSlice<'static, NativeEndian>;
pub unsafe fn get_unlimited_slice<'a>(start: *const u8) -> &'a [u8] {
// Create the largest possible slice for this address.
let start = start as usize;
let end = start.saturating_add(isize::MAX as _);
let len = end - start;
core::slice::from_raw_parts(start as *const _, len)
}
pub unsafe fn deref_pointer(ptr: Pointer) -> usize {
match ptr {
Pointer::Direct(x) => x as _,
Pointer::Indirect(x) => *(x as *const _),
}
}