parse more (badly)

.cargo/config.toml

@@ -1,5 +1,4 @@
 [target.x86_64-unknown-linux-gnu]
 rustflags = [
         "-Cforce-frame-pointers=yes", # for the uwuwind fp stack walker
-        "-Clink-arg=-Wl,-E" # for dladdr
 ]

src/dwarf/divination.rs

@@ -103,8 +103,6 @@ pub(crate) fn eh_frame(addr: Addr) -> Option<*const u8> {
             core::slice::from_raw_parts(eh_frame_ptr as *const u8, 15)
         );
 
-        crate::dwarf::uwutables(eh_frame_ptr as *const u8);
-
         Some(eh_frame_ptr as *const u8)
     }
 }

src/dwarf/mod.rs

@@ -2,7 +2,10 @@
 //! unwinding
 //!
 //! 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.
+//! interpreter (yes, that shit is basically a programming language).
+//! See https://dwarfstd.org/doc/DWARF5.pdf §6.4 for more information if more information is desired.
+//! Note that https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
+//! contains more details on the precise format, which is slightly different from .debug_frame from DWARF.
 
 mod divination;
 mod parse;

src/dwarf/parse.rs

@@ -106,6 +106,7 @@ pub struct Cie<'a> {
     /// .debug_info section, the augmentation string always uses UTF-8
     /// encoding.
     pub augmentation: Option<AugmentationData>,
+    pub augmentation_string: &'a str,
     /// A constant that is factored out of all advance location instructions
     /// (see Section 6.4.2.1 on page 177). The resulting value is
     /// (operand * code_alignment_factor).
@@ -539,12 +540,14 @@ unsafe fn parse_frame_info<'a>(
 
     loop {
         let (cie_id, data, newer_ptr) = parse_frame_head(ptr)?;
+        trace!("cie id: {cie_id}");
         if cie_id != 0 {
             return Ok((cie, fdes, prev_ptr));
         }
         prev_ptr = newer_ptr;
         let data = &mut Cursor(data);
         let fde = parse_fde(data, cie_id, &cie)?;
+        trace!("FDE: {fde:?}");
         fdes.push(fde);
     }
 }
@@ -590,6 +593,7 @@ fn parse_cie<'a>(data: &mut Cursor<'a>) -> Result<Cie<'a>> {
 
     let cie = Cie {
         augmentation: augmentation_data,
+        augmentation_string: augmentation,
         code_alignment_factor,
         data_alignment_factor,
         return_address_register,
@@ -608,6 +612,8 @@ fn parse_fde<'a>(data: &mut Cursor<'a>, cie_id: u32, cie: &Cie<'_>) -> Result<Fd
         .as_ref()
         .ok_or_else(|| Error("augmentation data not present for CIE with FDEs".into()))?;
 
+    trace!("augmentation: {augmentation:?}");
+
     let pointer_encoding = augmentation.pointer_encoding.ok_or_else(|| {
         Error("pointer encoding not present in augmentation for CIE with FDEs".into())
     })?;
@@ -618,7 +624,12 @@ fn parse_fde<'a>(data: &mut Cursor<'a>, cie_id: u32, cie: &Cie<'_>) -> Result<Fd
     let (read_size, pc_range) = unsafe { read_encoded(data.0.as_ptr(), pointer_encoding) };
     data.0 = &data.0[read_size..];
 
+    // This is only present if the aug data of the CIE contains z. But that is
+    // always the case?
     let augmentation_len = read_uleb128(data)?;
+    let augmentation_data = &data.0[..(augmentation_len as usize)];
+    let data = parse_augmentation_data(cie.augmentation_string, augmentation_data)?;
+    trace!("debug data: {data:?}");
 
     Err(Error("aa".into()))
 }

src/dwarf/parse/tests.rs

@@ -24,6 +24,7 @@ fn parse_simple_cie() {
                 )),
                 personality: None
             }),
+            augmentation_string: "meow",
             code_alignment_factor: 1,
             data_alignment_factor: -8,
             return_address_register: 16,

src/lib.rs

@@ -31,7 +31,8 @@ pub unsafe extern "C" fn _UnwindRaiseException(
     exception_object: *mut uw::_Unwind_Exception,
 ) -> uw::_Unwind_Reason_Code {
     trace!("someone raised an exception with addr {exception_object:p}");
-    let _ = crate::dwarf::eh_frame(arch::get_rip()).unwrap();
+    let eh_frame = crate::dwarf::eh_frame(arch::get_rip()).unwrap();
+    crate::dwarf::uwutables(eh_frame);
 
     stdext::abort();
 }