read/cfi: always reset context in initialize (#684)

src/read/cfi.rs

@@ -1994,9 +1994,8 @@ impl<R: Reader, A: UnwindContextStorage<R>> UnwindContext<R, A> {
         bases: &BaseAddresses,
         cie: &CommonInformationEntry<R>,
     ) -> Result<()> {
-        if self.is_initialized {
-            self.reset();
-        }
+        // Always reset because previous initialization failure may leave dirty state.
+        self.reset();
 
         let mut table = UnwindTable::new_for_cie(section, bases, self, cie);
         while table.next_row()?.is_some() {}
@@ -5874,6 +5873,98 @@ mod tests {
         assert_eq!(Ok(None), table.next_row());
     }
 
+    #[test]
+    fn test_unwind_table_cie_invalid_rule() {
+        let initial_instructions1 = Section::with_endian(Endian::Little)
+            // Test that stack length is reset.
+            .D8(constants::DW_CFA_remember_state.0)
+            // Test that stack value is reset (different register from that used later).
+            .D8(constants::DW_CFA_offset.0 | 4)
+            .uleb(8)
+            // Invalid due to missing operands.
+            .D8(constants::DW_CFA_offset.0);
+        let initial_instructions1 = initial_instructions1.get_contents().unwrap();
+
+        let cie1 = CommonInformationEntry {
+            offset: 0,
+            length: 0,
+            format: Format::Dwarf32,
+            version: 4,
+            augmentation: None,
+            address_size: 8,
+            segment_size: 0,
+            code_alignment_factor: 1,
+            data_alignment_factor: 1,
+            return_address_register: Register(3),
+            initial_instructions: EndianSlice::new(&initial_instructions1, LittleEndian),
+        };
+
+        let initial_instructions2 = Section::with_endian(Endian::Little)
+            // Register 3 is 4 from the CFA.
+            .D8(constants::DW_CFA_offset.0 | 3)
+            .uleb(4)
+            .append_repeated(constants::DW_CFA_nop.0, 4);
+        let initial_instructions2 = initial_instructions2.get_contents().unwrap();
+
+        let cie2 = CommonInformationEntry {
+            offset: 0,
+            length: 0,
+            format: Format::Dwarf32,
+            version: 4,
+            augmentation: None,
+            address_size: 8,
+            segment_size: 0,
+            code_alignment_factor: 1,
+            data_alignment_factor: 1,
+            return_address_register: Register(3),
+            initial_instructions: EndianSlice::new(&initial_instructions2, LittleEndian),
+        };
+
+        let fde1 = FrameDescriptionEntry {
+            offset: 0,
+            length: 0,
+            format: Format::Dwarf32,
+            cie: cie1.clone(),
+            initial_segment: 0,
+            initial_address: 0,
+            address_range: 100,
+            augmentation: None,
+            instructions: EndianSlice::new(&[], LittleEndian),
+        };
+
+        let fde2 = FrameDescriptionEntry {
+            offset: 0,
+            length: 0,
+            format: Format::Dwarf32,
+            cie: cie2.clone(),
+            initial_segment: 0,
+            initial_address: 0,
+            address_range: 100,
+            augmentation: None,
+            instructions: EndianSlice::new(&[], LittleEndian),
+        };
+
+        let section = &DebugFrame::from(EndianSlice::default());
+        let bases = &BaseAddresses::default();
+        let mut ctx = Box::new(UnwindContext::new());
+
+        let table = fde1
+            .rows(section, bases, &mut ctx)
+            .map_eof(&initial_instructions1);
+        assert_eq!(table.err(), Some(Error::UnexpectedEof(ReaderOffsetId(4))));
+        assert!(!ctx.is_initialized);
+        assert_eq!(ctx.stack.len(), 2);
+        assert_eq!(ctx.initial_rule, None);
+
+        let _table = fde2
+            .rows(section, bases, &mut ctx)
+            .expect("Should run initial program OK");
+        assert!(ctx.is_initialized);
+        assert_eq!(ctx.stack.len(), 1);
+        let expected_initial_rule = (Register(3), RegisterRule::Offset(4));
+        assert_eq!(ctx.initial_rule, Some(expected_initial_rule));
+    }
+
     #[test]
     fn test_unwind_table_next_row() {
         let initial_instructions = Section::with_endian(Endian::Little)