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nora 2023-06-13 13:28:26 +02:00
parent 2875f34693
commit d1e561c665
7 changed files with 157 additions and 81 deletions
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65
src/dwarf/mod.rs
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@ -1,72 +1,11 @@
//! this implements the stuff necessary to get the uwutables for actual unwinding
//!
//! # how it works
//! first, we ask the dynamic linker to give us the `.eh_frame` for the current binary using
//! the GNU extension (`_dl_find_object`)[https://www.gnu.org/software/libc/manual/html_node/Dynamic-Linker-Introspection.html].
//! then, we parse that as beautiful DWARF call frame information, as god (or rather, the x86-64 psABI) intended.
//!
//! for this we need a DWARF parser and a DWARF call frame information interpreter (yes, that shit is basically a programming
//! language). See https://dwarfstd.org/doc/DWARF5.pdf for more information if more information is desired.
mod divination;
mod parse;
use core::ffi;
use std::fmt::Debug;
#[allow(non_camel_case_types)]
#[repr(C)]
struct dl_find_object {
dlfo_flags: ffi::c_ulonglong,
dlfo_map_start: *const ffi::c_void,
dlfo_map_end: *const ffi::c_void,
dlf_link_map: *const ffi::c_void,
dlfo_eh_frame: *const ffi::c_void,
}
//
extern "C" {
fn _dl_find_object(address: *const ffi::c_void, result: *mut dl_find_object) -> ffi::c_int;
}
#[derive(Debug, Clone, Copy)]
pub struct DwarfInfo {
/// The text segment
map: *const [u8],
/// PT_GNU_EH_FRAME
dwarf: *const u8,
}
pub fn dwarf_info(addr: *const ffi::c_void) -> Option<DwarfInfo> {
unsafe {
let mut out = core::mem::zeroed();
let ret = _dl_find_object(addr, &mut out);
trace!("dl_find_object returned {ret}");
if ret != 0 {
trace!("dl_find_object error: {}", std::io::Error::last_os_error());
return None;
}
if out.dlfo_eh_frame.is_null() {
return None;
}
let text_len = out.dlfo_map_end as usize - out.dlfo_map_start as usize;
trace!(
"dwarf info; map: ({:p}, {:x}), dwarf: {:p}",
out.dlfo_map_start,
text_len,
out.dlfo_eh_frame
);
if !(out.dlfo_map_start..out.dlfo_map_end).contains(&addr) {
trace!("dl_find_object returned object out of range for addr: {addr:p}");
return None;
}
Some(DwarfInfo {
map: core::ptr::slice_from_raw_parts(out.dlfo_map_start as _, text_len),
dwarf: out.dlfo_eh_frame as _,
})
}
}
pub use divination::{dwarf_info, DwarfInfo};
pub fn uwutables(_dwarf_info: DwarfInfo) {}