gimli/write/
writer.rs

1use crate::common::{Format, SectionId};
2use crate::constants;
3use crate::endianity::Endianity;
4use crate::leb128;
5use crate::write::{Address, Error, Result};
6
7/// A trait for writing the data to a DWARF section.
8///
9/// All write operations append to the section unless otherwise specified.
10#[allow(clippy::len_without_is_empty)]
11pub trait Writer {
12    /// The endianity of bytes that are written.
13    type Endian: Endianity;
14
15    /// Return the endianity of bytes that are written.
16    fn endian(&self) -> Self::Endian;
17
18    /// Return the current section length.
19    ///
20    /// This may be used as an offset for future `write_at` calls.
21    fn len(&self) -> usize;
22
23    /// Write a slice.
24    fn write(&mut self, bytes: &[u8]) -> Result<()>;
25
26    /// Write a slice at a given offset.
27    ///
28    /// The write must not extend past the current section length.
29    fn write_at(&mut self, offset: usize, bytes: &[u8]) -> Result<()>;
30
31    /// Write an address.
32    ///
33    /// If the writer supports relocations, then it must provide its own implementation
34    /// of this method.
35    // TODO: use write_reference instead?
36    fn write_address(&mut self, address: Address, size: u8) -> Result<()> {
37        match address {
38            Address::Constant(val) => self.write_udata(val, size),
39            Address::Symbol { .. } => Err(Error::InvalidAddress),
40        }
41    }
42
43    /// Write an address with a `.eh_frame` pointer encoding.
44    ///
45    /// The given size is only used for `DW_EH_PE_absptr` formats.
46    ///
47    /// If the writer supports relocations, then it must provide its own implementation
48    /// of this method.
49    fn write_eh_pointer(
50        &mut self,
51        address: Address,
52        eh_pe: constants::DwEhPe,
53        size: u8,
54    ) -> Result<()> {
55        match address {
56            Address::Constant(val) => {
57                // Indirect doesn't matter here.
58                let val = match eh_pe.application() {
59                    constants::DW_EH_PE_absptr => val,
60                    constants::DW_EH_PE_pcrel => {
61                        // TODO: better handling of sign
62                        let offset = self.len() as u64;
63                        val.wrapping_sub(offset)
64                    }
65                    _ => {
66                        return Err(Error::UnsupportedPointerEncoding(eh_pe));
67                    }
68                };
69                self.write_eh_pointer_data(val, eh_pe.format(), size)
70            }
71            Address::Symbol { .. } => Err(Error::InvalidAddress),
72        }
73    }
74
75    /// Write a value with a `.eh_frame` pointer format.
76    ///
77    /// The given size is only used for `DW_EH_PE_absptr` formats.
78    ///
79    /// This must not be used directly for values that may require relocation.
80    fn write_eh_pointer_data(
81        &mut self,
82        val: u64,
83        format: constants::DwEhPe,
84        size: u8,
85    ) -> Result<()> {
86        match format {
87            constants::DW_EH_PE_absptr => self.write_udata(val, size),
88            constants::DW_EH_PE_uleb128 => self.write_uleb128(val),
89            constants::DW_EH_PE_udata2 => self.write_udata(val, 2),
90            constants::DW_EH_PE_udata4 => self.write_udata(val, 4),
91            constants::DW_EH_PE_udata8 => self.write_udata(val, 8),
92            constants::DW_EH_PE_sleb128 => self.write_sleb128(val as i64),
93            constants::DW_EH_PE_sdata2 => self.write_sdata(val as i64, 2),
94            constants::DW_EH_PE_sdata4 => self.write_sdata(val as i64, 4),
95            constants::DW_EH_PE_sdata8 => self.write_sdata(val as i64, 8),
96            _ => Err(Error::UnsupportedPointerEncoding(format)),
97        }
98    }
99
100    /// Write an offset that is relative to the start of the given section.
101    ///
102    /// If the writer supports relocations, then it must provide its own implementation
103    /// of this method.
104    fn write_offset(&mut self, val: usize, _section: SectionId, size: u8) -> Result<()> {
105        self.write_udata(val as u64, size)
106    }
107
108    /// Write an offset that is relative to the start of the given section.
109    ///
110    /// If the writer supports relocations, then it must provide its own implementation
111    /// of this method.
112    fn write_offset_at(
113        &mut self,
114        offset: usize,
115        val: usize,
116        _section: SectionId,
117        size: u8,
118    ) -> Result<()> {
119        self.write_udata_at(offset, val as u64, size)
120    }
121
122    /// Write a reference to a symbol.
123    ///
124    /// If the writer supports symbols, then it must provide its own implementation
125    /// of this method.
126    fn write_reference(&mut self, _symbol: usize, _size: u8) -> Result<()> {
127        Err(Error::InvalidReference)
128    }
129
130    /// Write a u8.
131    fn write_u8(&mut self, val: u8) -> Result<()> {
132        let bytes = [val];
133        self.write(&bytes)
134    }
135
136    /// Write a u16.
137    fn write_u16(&mut self, val: u16) -> Result<()> {
138        let mut bytes = [0; 2];
139        self.endian().write_u16(&mut bytes, val);
140        self.write(&bytes)
141    }
142
143    /// Write a u32.
144    fn write_u32(&mut self, val: u32) -> Result<()> {
145        let mut bytes = [0; 4];
146        self.endian().write_u32(&mut bytes, val);
147        self.write(&bytes)
148    }
149
150    /// Write a u64.
151    fn write_u64(&mut self, val: u64) -> Result<()> {
152        let mut bytes = [0; 8];
153        self.endian().write_u64(&mut bytes, val);
154        self.write(&bytes)
155    }
156
157    /// Write a u8 at the given offset.
158    fn write_u8_at(&mut self, offset: usize, val: u8) -> Result<()> {
159        let bytes = [val];
160        self.write_at(offset, &bytes)
161    }
162
163    /// Write a u16 at the given offset.
164    fn write_u16_at(&mut self, offset: usize, val: u16) -> Result<()> {
165        let mut bytes = [0; 2];
166        self.endian().write_u16(&mut bytes, val);
167        self.write_at(offset, &bytes)
168    }
169
170    /// Write a u32 at the given offset.
171    fn write_u32_at(&mut self, offset: usize, val: u32) -> Result<()> {
172        let mut bytes = [0; 4];
173        self.endian().write_u32(&mut bytes, val);
174        self.write_at(offset, &bytes)
175    }
176
177    /// Write a u64 at the given offset.
178    fn write_u64_at(&mut self, offset: usize, val: u64) -> Result<()> {
179        let mut bytes = [0; 8];
180        self.endian().write_u64(&mut bytes, val);
181        self.write_at(offset, &bytes)
182    }
183
184    /// Write unsigned data of the given size.
185    ///
186    /// Returns an error if the value is too large for the size.
187    /// This must not be used directly for values that may require relocation.
188    fn write_udata(&mut self, val: u64, size: u8) -> Result<()> {
189        match size {
190            1 => {
191                let write_val = val as u8;
192                if val != u64::from(write_val) {
193                    return Err(Error::ValueTooLarge);
194                }
195                self.write_u8(write_val)
196            }
197            2 => {
198                let write_val = val as u16;
199                if val != u64::from(write_val) {
200                    return Err(Error::ValueTooLarge);
201                }
202                self.write_u16(write_val)
203            }
204            4 => {
205                let write_val = val as u32;
206                if val != u64::from(write_val) {
207                    return Err(Error::ValueTooLarge);
208                }
209                self.write_u32(write_val)
210            }
211            8 => self.write_u64(val),
212            otherwise => Err(Error::UnsupportedWordSize(otherwise)),
213        }
214    }
215
216    /// Write signed data of the given size.
217    ///
218    /// Returns an error if the value is too large for the size.
219    /// This must not be used directly for values that may require relocation.
220    fn write_sdata(&mut self, val: i64, size: u8) -> Result<()> {
221        match size {
222            1 => {
223                let write_val = val as i8;
224                if val != i64::from(write_val) {
225                    return Err(Error::ValueTooLarge);
226                }
227                self.write_u8(write_val as u8)
228            }
229            2 => {
230                let write_val = val as i16;
231                if val != i64::from(write_val) {
232                    return Err(Error::ValueTooLarge);
233                }
234                self.write_u16(write_val as u16)
235            }
236            4 => {
237                let write_val = val as i32;
238                if val != i64::from(write_val) {
239                    return Err(Error::ValueTooLarge);
240                }
241                self.write_u32(write_val as u32)
242            }
243            8 => self.write_u64(val as u64),
244            otherwise => Err(Error::UnsupportedWordSize(otherwise)),
245        }
246    }
247
248    /// Write a word of the given size at the given offset.
249    ///
250    /// Returns an error if the value is too large for the size.
251    /// This must not be used directly for values that may require relocation.
252    fn write_udata_at(&mut self, offset: usize, val: u64, size: u8) -> Result<()> {
253        match size {
254            1 => {
255                let write_val = val as u8;
256                if val != u64::from(write_val) {
257                    return Err(Error::ValueTooLarge);
258                }
259                self.write_u8_at(offset, write_val)
260            }
261            2 => {
262                let write_val = val as u16;
263                if val != u64::from(write_val) {
264                    return Err(Error::ValueTooLarge);
265                }
266                self.write_u16_at(offset, write_val)
267            }
268            4 => {
269                let write_val = val as u32;
270                if val != u64::from(write_val) {
271                    return Err(Error::ValueTooLarge);
272                }
273                self.write_u32_at(offset, write_val)
274            }
275            8 => self.write_u64_at(offset, val),
276            otherwise => Err(Error::UnsupportedWordSize(otherwise)),
277        }
278    }
279
280    /// Write an unsigned LEB128 encoded integer.
281    fn write_uleb128(&mut self, val: u64) -> Result<()> {
282        let mut bytes = [0u8; 10];
283        // bytes is long enough so this will never fail.
284        let len = leb128::write::unsigned(&mut { &mut bytes[..] }, val).unwrap();
285        self.write(&bytes[..len])
286    }
287
288    /// Read an unsigned LEB128 encoded integer.
289    fn write_sleb128(&mut self, val: i64) -> Result<()> {
290        let mut bytes = [0u8; 10];
291        // bytes is long enough so this will never fail.
292        let len = leb128::write::signed(&mut { &mut bytes[..] }, val).unwrap();
293        self.write(&bytes[..len])
294    }
295
296    /// Write an initial length according to the given DWARF format.
297    ///
298    /// This will only write a length of zero, since the length isn't
299    /// known yet, and a subsequent call to `write_initial_length_at`
300    /// will write the actual length.
301    fn write_initial_length(&mut self, format: Format) -> Result<InitialLengthOffset> {
302        if format == Format::Dwarf64 {
303            self.write_u32(0xffff_ffff)?;
304        }
305        let offset = InitialLengthOffset(self.len());
306        self.write_udata(0, format.word_size())?;
307        Ok(offset)
308    }
309
310    /// Write an initial length at the given offset according to the given DWARF format.
311    ///
312    /// `write_initial_length` must have previously returned the offset.
313    fn write_initial_length_at(
314        &mut self,
315        offset: InitialLengthOffset,
316        length: u64,
317        format: Format,
318    ) -> Result<()> {
319        self.write_udata_at(offset.0, length, format.word_size())
320    }
321}
322
323/// The offset at which an initial length should be written.
324#[derive(Debug, Clone, Copy)]
325pub struct InitialLengthOffset(usize);
326
327#[cfg(test)]
328mod tests {
329    use super::*;
330    use crate::write;
331    use crate::{BigEndian, LittleEndian};
332
333    #[test]
334    fn test_writer() {
335        let mut w = write::EndianVec::new(LittleEndian);
336        w.write_address(Address::Constant(0x1122_3344), 4).unwrap();
337        assert_eq!(w.slice(), &[0x44, 0x33, 0x22, 0x11]);
338        assert_eq!(
339            w.write_address(
340                Address::Symbol {
341                    symbol: 0,
342                    addend: 0
343                },
344                4
345            ),
346            Err(Error::InvalidAddress)
347        );
348
349        let mut w = write::EndianVec::new(LittleEndian);
350        w.write_offset(0x1122_3344, SectionId::DebugInfo, 4)
351            .unwrap();
352        assert_eq!(w.slice(), &[0x44, 0x33, 0x22, 0x11]);
353        w.write_offset_at(1, 0x5566, SectionId::DebugInfo, 2)
354            .unwrap();
355        assert_eq!(w.slice(), &[0x44, 0x66, 0x55, 0x11]);
356
357        let mut w = write::EndianVec::new(LittleEndian);
358        w.write_u8(0x11).unwrap();
359        w.write_u16(0x2233).unwrap();
360        w.write_u32(0x4455_6677).unwrap();
361        w.write_u64(0x8081_8283_8485_8687).unwrap();
362        #[rustfmt::skip]
363        assert_eq!(w.slice(), &[
364            0x11,
365            0x33, 0x22,
366            0x77, 0x66, 0x55, 0x44,
367            0x87, 0x86, 0x85, 0x84, 0x83, 0x82, 0x81, 0x80,
368        ]);
369        w.write_u8_at(14, 0x11).unwrap();
370        w.write_u16_at(12, 0x2233).unwrap();
371        w.write_u32_at(8, 0x4455_6677).unwrap();
372        w.write_u64_at(0, 0x8081_8283_8485_8687).unwrap();
373        #[rustfmt::skip]
374        assert_eq!(w.slice(), &[
375            0x87, 0x86, 0x85, 0x84, 0x83, 0x82, 0x81, 0x80,
376            0x77, 0x66, 0x55, 0x44,
377            0x33, 0x22,
378            0x11,
379        ]);
380
381        let mut w = write::EndianVec::new(BigEndian);
382        w.write_u8(0x11).unwrap();
383        w.write_u16(0x2233).unwrap();
384        w.write_u32(0x4455_6677).unwrap();
385        w.write_u64(0x8081_8283_8485_8687).unwrap();
386        #[rustfmt::skip]
387        assert_eq!(w.slice(), &[
388            0x11,
389            0x22, 0x33,
390            0x44, 0x55, 0x66, 0x77,
391            0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
392        ]);
393        w.write_u8_at(14, 0x11).unwrap();
394        w.write_u16_at(12, 0x2233).unwrap();
395        w.write_u32_at(8, 0x4455_6677).unwrap();
396        w.write_u64_at(0, 0x8081_8283_8485_8687).unwrap();
397        #[rustfmt::skip]
398        assert_eq!(w.slice(), &[
399            0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
400            0x44, 0x55, 0x66, 0x77,
401            0x22, 0x33,
402            0x11,
403        ]);
404
405        let mut w = write::EndianVec::new(LittleEndian);
406        w.write_udata(0x11, 1).unwrap();
407        w.write_udata(0x2233, 2).unwrap();
408        w.write_udata(0x4455_6677, 4).unwrap();
409        w.write_udata(0x8081_8283_8485_8687, 8).unwrap();
410        #[rustfmt::skip]
411        assert_eq!(w.slice(), &[
412            0x11,
413            0x33, 0x22,
414            0x77, 0x66, 0x55, 0x44,
415            0x87, 0x86, 0x85, 0x84, 0x83, 0x82, 0x81, 0x80,
416        ]);
417        assert_eq!(w.write_udata(0x100, 1), Err(Error::ValueTooLarge));
418        assert_eq!(w.write_udata(0x1_0000, 2), Err(Error::ValueTooLarge));
419        assert_eq!(w.write_udata(0x1_0000_0000, 4), Err(Error::ValueTooLarge));
420        assert_eq!(w.write_udata(0x00, 3), Err(Error::UnsupportedWordSize(3)));
421        w.write_udata_at(14, 0x11, 1).unwrap();
422        w.write_udata_at(12, 0x2233, 2).unwrap();
423        w.write_udata_at(8, 0x4455_6677, 4).unwrap();
424        w.write_udata_at(0, 0x8081_8283_8485_8687, 8).unwrap();
425        #[rustfmt::skip]
426        assert_eq!(w.slice(), &[
427            0x87, 0x86, 0x85, 0x84, 0x83, 0x82, 0x81, 0x80,
428            0x77, 0x66, 0x55, 0x44,
429            0x33, 0x22,
430            0x11,
431        ]);
432        assert_eq!(w.write_udata_at(0, 0x100, 1), Err(Error::ValueTooLarge));
433        assert_eq!(w.write_udata_at(0, 0x1_0000, 2), Err(Error::ValueTooLarge));
434        assert_eq!(
435            w.write_udata_at(0, 0x1_0000_0000, 4),
436            Err(Error::ValueTooLarge)
437        );
438        assert_eq!(
439            w.write_udata_at(0, 0x00, 3),
440            Err(Error::UnsupportedWordSize(3))
441        );
442
443        let mut w = write::EndianVec::new(LittleEndian);
444        w.write_uleb128(0).unwrap();
445        assert_eq!(w.slice(), &[0]);
446
447        let mut w = write::EndianVec::new(LittleEndian);
448        w.write_uleb128(u64::MAX).unwrap();
449        assert_eq!(
450            w.slice(),
451            &[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 1]
452        );
453
454        let mut w = write::EndianVec::new(LittleEndian);
455        w.write_sleb128(0).unwrap();
456        assert_eq!(w.slice(), &[0]);
457
458        let mut w = write::EndianVec::new(LittleEndian);
459        w.write_sleb128(i64::MAX).unwrap();
460        assert_eq!(
461            w.slice(),
462            &[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0]
463        );
464
465        let mut w = write::EndianVec::new(LittleEndian);
466        w.write_sleb128(i64::MIN).unwrap();
467        assert_eq!(
468            w.slice(),
469            &[0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x7f]
470        );
471
472        let mut w = write::EndianVec::new(LittleEndian);
473        let offset = w.write_initial_length(Format::Dwarf32).unwrap();
474        assert_eq!(w.slice(), &[0, 0, 0, 0]);
475        w.write_initial_length_at(offset, 0x1122_3344, Format::Dwarf32)
476            .unwrap();
477        assert_eq!(w.slice(), &[0x44, 0x33, 0x22, 0x11]);
478        assert_eq!(
479            w.write_initial_length_at(offset, 0x1_0000_0000, Format::Dwarf32),
480            Err(Error::ValueTooLarge)
481        );
482
483        let mut w = write::EndianVec::new(LittleEndian);
484        let offset = w.write_initial_length(Format::Dwarf64).unwrap();
485        assert_eq!(w.slice(), &[0xff, 0xff, 0xff, 0xff, 0, 0, 0, 0, 0, 0, 0, 0]);
486        w.write_initial_length_at(offset, 0x1122_3344_5566_7788, Format::Dwarf64)
487            .unwrap();
488        assert_eq!(
489            w.slice(),
490            &[0xff, 0xff, 0xff, 0xff, 0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11]
491        );
492    }
493}
gimli/write/writer.rs

gimli/write/
writer.rs
