object/read/elf/
relocation.rs

1use alloc::fmt;
2use alloc::vec::Vec;
3use core::fmt::Debug;
4use core::slice;
5
6use crate::elf;
7use crate::endian::{self, Endianness};
8use crate::pod::Pod;
9use crate::read::{
10    self, Bytes, Error, ReadError, ReadRef, Relocation, RelocationEncoding, RelocationFlags,
11    RelocationKind, RelocationTarget, SectionIndex, SymbolIndex,
12};
13
14use super::{ElfFile, FileHeader, SectionHeader, SectionTable};
15
16/// A mapping from section index to associated relocation sections.
17#[derive(Debug, Default)]
18pub struct RelocationSections {
19    relocations: Vec<usize>,
20}
21
22impl RelocationSections {
23    /// Create a new mapping using the section table.
24    ///
25    /// Skips relocation sections that do not use the given symbol table section.
26    pub fn parse<'data, Elf: FileHeader, R: ReadRef<'data>>(
27        endian: Elf::Endian,
28        sections: &SectionTable<'data, Elf, R>,
29        symbol_section: SectionIndex,
30    ) -> read::Result<Self> {
31        let mut relocations = vec![0; sections.len()];
32        for (index, section) in sections.iter().enumerate().rev() {
33            let sh_type = section.sh_type(endian);
34            if sh_type == elf::SHT_REL || sh_type == elf::SHT_RELA || sh_type == elf::SHT_CREL {
35                // The symbol indices used in relocations must be for the symbol table
36                // we are expecting to use.
37                let sh_link = section.link(endian);
38                if sh_link != symbol_section {
39                    continue;
40                }
41
42                let sh_info = section.info_link(endian);
43                if sh_info == SectionIndex(0) {
44                    // Skip dynamic relocations.
45                    continue;
46                }
47                if sh_info.0 >= relocations.len() {
48                    return Err(Error("Invalid ELF sh_info for relocation section"));
49                }
50
51                // We don't support relocations that apply to other relocation sections
52                // because it interferes with the chaining of relocation sections below.
53                let sh_info_type = sections.section(sh_info)?.sh_type(endian);
54                if sh_info_type == elf::SHT_REL
55                    || sh_info_type == elf::SHT_RELA
56                    || sh_info_type == elf::SHT_CREL
57                {
58                    return Err(Error("Unsupported ELF sh_info for relocation section"));
59                }
60
61                // Handle multiple relocation sections by chaining them.
62                let next = relocations[sh_info.0];
63                relocations[sh_info.0] = index;
64                relocations[index] = next;
65            }
66        }
67        Ok(Self { relocations })
68    }
69
70    /// Given a section index, return the section index of the associated relocation section.
71    ///
72    /// This may also be called with a relocation section index, and it will return the
73    /// next associated relocation section.
74    pub fn get(&self, index: SectionIndex) -> Option<SectionIndex> {
75        self.relocations
76            .get(index.0)
77            .cloned()
78            .filter(|x| *x != 0)
79            .map(SectionIndex)
80    }
81}
82
83pub(super) enum ElfRelocationIterator<'data, Elf: FileHeader> {
84    Rel(slice::Iter<'data, Elf::Rel>, Elf::Endian),
85    Rela(slice::Iter<'data, Elf::Rela>, Elf::Endian, bool),
86    Crel(CrelIterator<'data>),
87}
88
89impl<'data, Elf: FileHeader> ElfRelocationIterator<'data, Elf> {
90    fn is_rel(&self) -> bool {
91        match self {
92            ElfRelocationIterator::Rel(..) => true,
93            ElfRelocationIterator::Rela(..) => false,
94            ElfRelocationIterator::Crel(i) => !i.is_rela(),
95        }
96    }
97}
98
99impl<'data, Elf: FileHeader> Iterator for ElfRelocationIterator<'data, Elf> {
100    type Item = Crel;
101
102    fn next(&mut self) -> Option<Self::Item> {
103        match self {
104            ElfRelocationIterator::Rel(ref mut i, endian) => {
105                i.next().map(|r| Crel::from_rel(r, *endian))
106            }
107            ElfRelocationIterator::Rela(ref mut i, endian, is_mips64el) => {
108                i.next().map(|r| Crel::from_rela(r, *endian, *is_mips64el))
109            }
110            ElfRelocationIterator::Crel(ref mut i) => i.next().and_then(Result::ok),
111        }
112    }
113}
114
115/// An iterator for the dynamic relocations in an [`ElfFile32`](super::ElfFile32).
116pub type ElfDynamicRelocationIterator32<'data, 'file, Endian = Endianness, R = &'data [u8]> =
117    ElfDynamicRelocationIterator<'data, 'file, elf::FileHeader32<Endian>, R>;
118/// An iterator for the dynamic relocations in an [`ElfFile64`](super::ElfFile64).
119pub type ElfDynamicRelocationIterator64<'data, 'file, Endian = Endianness, R = &'data [u8]> =
120    ElfDynamicRelocationIterator<'data, 'file, elf::FileHeader64<Endian>, R>;
121
122/// An iterator for the dynamic relocations in an [`ElfFile`].
123pub struct ElfDynamicRelocationIterator<'data, 'file, Elf, R = &'data [u8]>
124where
125    Elf: FileHeader,
126    R: ReadRef<'data>,
127{
128    /// The current relocation section index.
129    pub(super) section_index: SectionIndex,
130    pub(super) file: &'file ElfFile<'data, Elf, R>,
131    pub(super) relocations: Option<ElfRelocationIterator<'data, Elf>>,
132}
133
134impl<'data, 'file, Elf, R> Iterator for ElfDynamicRelocationIterator<'data, 'file, Elf, R>
135where
136    Elf: FileHeader,
137    R: ReadRef<'data>,
138{
139    type Item = (u64, Relocation);
140
141    fn next(&mut self) -> Option<Self::Item> {
142        let endian = self.file.endian;
143        loop {
144            if let Some(ref mut relocations) = self.relocations {
145                if let Some(reloc) = relocations.next() {
146                    let relocation =
147                        parse_relocation(self.file.header, endian, reloc, relocations.is_rel());
148                    return Some((reloc.r_offset, relocation));
149                }
150                self.relocations = None;
151            }
152
153            let section = self.file.sections.section(self.section_index).ok()?;
154            self.section_index.0 += 1;
155
156            if section.link(endian) != self.file.dynamic_symbols.section() {
157                continue;
158            }
159
160            match section.sh_type(endian) {
161                elf::SHT_REL => {
162                    if let Ok(relocations) = section.data_as_array(endian, self.file.data) {
163                        self.relocations =
164                            Some(ElfRelocationIterator::Rel(relocations.iter(), endian));
165                    }
166                }
167                elf::SHT_RELA => {
168                    if let Ok(relocations) = section.data_as_array(endian, self.file.data) {
169                        self.relocations = Some(ElfRelocationIterator::Rela(
170                            relocations.iter(),
171                            endian,
172                            self.file.header.is_mips64el(endian),
173                        ));
174                    }
175                }
176                elf::SHT_CREL => {
177                    if let Ok(data) = section.data(endian, self.file.data) {
178                        if let Ok(relocations) = CrelIterator::new(data) {
179                            self.relocations = Some(ElfRelocationIterator::Crel(relocations));
180                        }
181                    }
182                }
183                _ => {}
184            }
185        }
186    }
187}
188
189impl<'data, 'file, Elf, R> fmt::Debug for ElfDynamicRelocationIterator<'data, 'file, Elf, R>
190where
191    Elf: FileHeader,
192    R: ReadRef<'data>,
193{
194    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
195        f.debug_struct("ElfDynamicRelocationIterator").finish()
196    }
197}
198
199/// An iterator for the relocations for an [`ElfSection32`](super::ElfSection32).
200pub type ElfSectionRelocationIterator32<'data, 'file, Endian = Endianness, R = &'data [u8]> =
201    ElfSectionRelocationIterator<'data, 'file, elf::FileHeader32<Endian>, R>;
202/// An iterator for the relocations for an [`ElfSection64`](super::ElfSection64).
203pub type ElfSectionRelocationIterator64<'data, 'file, Endian = Endianness, R = &'data [u8]> =
204    ElfSectionRelocationIterator<'data, 'file, elf::FileHeader64<Endian>, R>;
205
206/// An iterator for the relocations for an [`ElfSection`](super::ElfSection).
207pub struct ElfSectionRelocationIterator<'data, 'file, Elf, R = &'data [u8]>
208where
209    Elf: FileHeader,
210    R: ReadRef<'data>,
211{
212    /// The current pointer in the chain of relocation sections.
213    pub(super) section_index: SectionIndex,
214    pub(super) file: &'file ElfFile<'data, Elf, R>,
215    pub(super) relocations: Option<ElfRelocationIterator<'data, Elf>>,
216}
217
218impl<'data, 'file, Elf, R> Iterator for ElfSectionRelocationIterator<'data, 'file, Elf, R>
219where
220    Elf: FileHeader,
221    R: ReadRef<'data>,
222{
223    type Item = (u64, Relocation);
224
225    fn next(&mut self) -> Option<Self::Item> {
226        let endian = self.file.endian;
227        loop {
228            if let Some(ref mut relocations) = self.relocations {
229                if let Some(reloc) = relocations.next() {
230                    let relocation =
231                        parse_relocation(self.file.header, endian, reloc, relocations.is_rel());
232                    return Some((reloc.r_offset, relocation));
233                }
234                self.relocations = None;
235            }
236            self.section_index = self.file.relocations.get(self.section_index)?;
237            // The construction of RelocationSections ensures section_index is valid.
238            let section = self.file.sections.section(self.section_index).unwrap();
239            match section.sh_type(endian) {
240                elf::SHT_REL => {
241                    if let Ok(relocations) = section.data_as_array(endian, self.file.data) {
242                        self.relocations =
243                            Some(ElfRelocationIterator::Rel(relocations.iter(), endian));
244                    }
245                }
246                elf::SHT_RELA => {
247                    if let Ok(relocations) = section.data_as_array(endian, self.file.data) {
248                        self.relocations = Some(ElfRelocationIterator::Rela(
249                            relocations.iter(),
250                            endian,
251                            self.file.header.is_mips64el(endian),
252                        ));
253                    }
254                }
255                elf::SHT_CREL => {
256                    if let Ok(data) = section.data(endian, self.file.data) {
257                        if let Ok(relocations) = CrelIterator::new(data) {
258                            self.relocations = Some(ElfRelocationIterator::Crel(relocations));
259                        }
260                    }
261                }
262                _ => {}
263            }
264        }
265    }
266}
267
268impl<'data, 'file, Elf, R> fmt::Debug for ElfSectionRelocationIterator<'data, 'file, Elf, R>
269where
270    Elf: FileHeader,
271    R: ReadRef<'data>,
272{
273    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
274        f.debug_struct("ElfSectionRelocationIterator").finish()
275    }
276}
277
278fn parse_relocation<Elf: FileHeader>(
279    header: &Elf,
280    endian: Elf::Endian,
281    reloc: Crel,
282    implicit_addend: bool,
283) -> Relocation {
284    use RelocationEncoding as E;
285    use RelocationKind as K;
286
287    let r_type = reloc.r_type;
288    let flags = RelocationFlags::Elf { r_type };
289    let g = E::Generic;
290    let unknown = (K::Unknown, E::Generic, 0);
291    let (kind, encoding, size) = match header.e_machine(endian) {
292        elf::EM_AARCH64 => {
293            if header.is_type_64() {
294                match r_type {
295                    elf::R_AARCH64_ABS64 => (K::Absolute, g, 64),
296                    elf::R_AARCH64_ABS32 => (K::Absolute, g, 32),
297                    elf::R_AARCH64_ABS16 => (K::Absolute, g, 16),
298                    elf::R_AARCH64_PREL64 => (K::Relative, g, 64),
299                    elf::R_AARCH64_PREL32 => (K::Relative, g, 32),
300                    elf::R_AARCH64_PREL16 => (K::Relative, g, 16),
301                    elf::R_AARCH64_CALL26 => (K::PltRelative, E::AArch64Call, 26),
302                    _ => unknown,
303                }
304            } else {
305                match r_type {
306                    elf::R_AARCH64_P32_ABS32 => (K::Absolute, g, 32),
307                    _ => unknown,
308                }
309            }
310        }
311        elf::EM_ALPHA => match r_type {
312            // Absolute
313            elf::R_ALPHA_REFLONG => (K::Absolute, g, 32),
314            elf::R_ALPHA_REFQUAD => (K::Absolute, g, 64),
315            // Relative to the PC
316            elf::R_ALPHA_SREL16 => (K::Relative, g, 16),
317            elf::R_ALPHA_SREL32 => (K::Relative, g, 32),
318            elf::R_ALPHA_SREL64 => (K::Relative, g, 64),
319            _ => unknown,
320        },
321        elf::EM_ARM => match r_type {
322            elf::R_ARM_ABS32 => (K::Absolute, g, 32),
323            _ => unknown,
324        },
325        elf::EM_AVR => match r_type {
326            elf::R_AVR_32 => (K::Absolute, g, 32),
327            elf::R_AVR_16 => (K::Absolute, g, 16),
328            _ => unknown,
329        },
330        elf::EM_BPF => match r_type {
331            elf::R_BPF_64_64 => (K::Absolute, g, 64),
332            elf::R_BPF_64_32 => (K::Absolute, g, 32),
333            _ => unknown,
334        },
335        elf::EM_CSKY => match r_type {
336            elf::R_CKCORE_ADDR32 => (K::Absolute, g, 32),
337            elf::R_CKCORE_PCREL32 => (K::Relative, g, 32),
338            _ => unknown,
339        },
340        elf::EM_MCST_ELBRUS => match r_type {
341            elf::R_E2K_32_ABS => (K::Absolute, g, 32),
342            elf::R_E2K_64_ABS => (K::Absolute, g, 64),
343            elf::R_E2K_64_ABS_LIT => (K::Absolute, E::E2KLit, 64),
344            elf::R_E2K_DISP => (K::Relative, E::E2KDisp, 28),
345            elf::R_E2K_GOT => (K::Got, g, 32),
346            _ => unknown,
347        },
348        elf::EM_386 => match r_type {
349            elf::R_386_32 => (K::Absolute, g, 32),
350            elf::R_386_PC32 => (K::Relative, g, 32),
351            elf::R_386_GOT32 => (K::Got, g, 32),
352            elf::R_386_PLT32 => (K::PltRelative, g, 32),
353            elf::R_386_GOTOFF => (K::GotBaseOffset, g, 32),
354            elf::R_386_GOTPC => (K::GotBaseRelative, g, 32),
355            elf::R_386_16 => (K::Absolute, g, 16),
356            elf::R_386_PC16 => (K::Relative, g, 16),
357            elf::R_386_8 => (K::Absolute, g, 8),
358            elf::R_386_PC8 => (K::Relative, g, 8),
359            _ => unknown,
360        },
361        elf::EM_X86_64 => match r_type {
362            elf::R_X86_64_64 => (K::Absolute, g, 64),
363            elf::R_X86_64_PC32 => (K::Relative, g, 32),
364            elf::R_X86_64_GOT32 => (K::Got, g, 32),
365            elf::R_X86_64_PLT32 => (K::PltRelative, g, 32),
366            elf::R_X86_64_GOTPCREL => (K::GotRelative, g, 32),
367            elf::R_X86_64_32 => (K::Absolute, g, 32),
368            elf::R_X86_64_32S => (K::Absolute, E::X86Signed, 32),
369            elf::R_X86_64_16 => (K::Absolute, g, 16),
370            elf::R_X86_64_PC16 => (K::Relative, g, 16),
371            elf::R_X86_64_8 => (K::Absolute, g, 8),
372            elf::R_X86_64_PC8 => (K::Relative, g, 8),
373            _ => unknown,
374        },
375        elf::EM_HEXAGON => match r_type {
376            elf::R_HEX_32 => (K::Absolute, g, 32),
377            _ => unknown,
378        },
379        elf::EM_LOONGARCH => match r_type {
380            elf::R_LARCH_32 => (K::Absolute, g, 32),
381            elf::R_LARCH_64 => (K::Absolute, g, 64),
382            elf::R_LARCH_32_PCREL => (K::Relative, g, 32),
383            elf::R_LARCH_64_PCREL => (K::Relative, g, 64),
384            elf::R_LARCH_B16 => (K::Relative, E::LoongArchBranch, 16),
385            elf::R_LARCH_B21 => (K::Relative, E::LoongArchBranch, 21),
386            elf::R_LARCH_B26 => (K::Relative, E::LoongArchBranch, 26),
387            _ => unknown,
388        },
389        elf::EM_68K => match r_type {
390            elf::R_68K_32 => (K::Absolute, g, 32),
391            elf::R_68K_16 => (K::Absolute, g, 16),
392            elf::R_68K_8 => (K::Absolute, g, 8),
393            elf::R_68K_PC32 => (K::Relative, g, 32),
394            elf::R_68K_PC16 => (K::Relative, g, 16),
395            elf::R_68K_PC8 => (K::Relative, g, 8),
396            elf::R_68K_GOT32O => (K::Got, g, 32),
397            elf::R_68K_GOT16O => (K::Got, g, 16),
398            elf::R_68K_GOT8O => (K::Got, g, 8),
399            elf::R_68K_GOT32 => (K::GotRelative, g, 32),
400            elf::R_68K_GOT16 => (K::GotRelative, g, 16),
401            elf::R_68K_GOT8 => (K::GotRelative, g, 8),
402            elf::R_68K_PLT32 => (K::PltRelative, g, 32),
403            elf::R_68K_PLT16 => (K::PltRelative, g, 16),
404            elf::R_68K_PLT8 => (K::PltRelative, g, 8),
405            _ => unknown,
406        },
407        elf::EM_MIPS => match r_type {
408            elf::R_MIPS_16 => (K::Absolute, g, 16),
409            elf::R_MIPS_32 => (K::Absolute, g, 32),
410            elf::R_MIPS_64 => (K::Absolute, g, 64),
411            _ => unknown,
412        },
413        elf::EM_MSP430 => match r_type {
414            elf::R_MSP430_32 => (K::Absolute, g, 32),
415            elf::R_MSP430_16_BYTE => (K::Absolute, g, 16),
416            _ => unknown,
417        },
418        elf::EM_PARISC => match r_type {
419            elf::R_PARISC_DIR32 => (K::Absolute, g, 32),
420            elf::R_PARISC_PCREL32 => (K::Relative, g, 32),
421            _ => unknown,
422        },
423        elf::EM_PPC => match r_type {
424            elf::R_PPC_ADDR32 => (K::Absolute, g, 32),
425            _ => unknown,
426        },
427        elf::EM_PPC64 => match r_type {
428            elf::R_PPC64_ADDR32 => (K::Absolute, g, 32),
429            elf::R_PPC64_ADDR64 => (K::Absolute, g, 64),
430            _ => unknown,
431        },
432        elf::EM_RISCV => match r_type {
433            elf::R_RISCV_32 => (K::Absolute, g, 32),
434            elf::R_RISCV_64 => (K::Absolute, g, 64),
435            _ => unknown,
436        },
437        elf::EM_S390 => match r_type {
438            elf::R_390_8 => (K::Absolute, g, 8),
439            elf::R_390_16 => (K::Absolute, g, 16),
440            elf::R_390_32 => (K::Absolute, g, 32),
441            elf::R_390_64 => (K::Absolute, g, 64),
442            elf::R_390_PC16 => (K::Relative, g, 16),
443            elf::R_390_PC32 => (K::Relative, g, 32),
444            elf::R_390_PC64 => (K::Relative, g, 64),
445            elf::R_390_PC16DBL => (K::Relative, E::S390xDbl, 16),
446            elf::R_390_PC32DBL => (K::Relative, E::S390xDbl, 32),
447            elf::R_390_PLT16DBL => (K::PltRelative, E::S390xDbl, 16),
448            elf::R_390_PLT32DBL => (K::PltRelative, E::S390xDbl, 32),
449            elf::R_390_GOT16 => (K::Got, g, 16),
450            elf::R_390_GOT32 => (K::Got, g, 32),
451            elf::R_390_GOT64 => (K::Got, g, 64),
452            elf::R_390_GOTENT => (K::GotRelative, E::S390xDbl, 32),
453            elf::R_390_GOTOFF16 => (K::GotBaseOffset, g, 16),
454            elf::R_390_GOTOFF32 => (K::GotBaseOffset, g, 32),
455            elf::R_390_GOTOFF64 => (K::GotBaseOffset, g, 64),
456            elf::R_390_GOTPC => (K::GotBaseRelative, g, 64),
457            elf::R_390_GOTPCDBL => (K::GotBaseRelative, E::S390xDbl, 32),
458            _ => unknown,
459        },
460        elf::EM_SBF => match r_type {
461            elf::R_SBF_64_64 => (K::Absolute, g, 64),
462            elf::R_SBF_64_32 => (K::Absolute, g, 32),
463            _ => unknown,
464        },
465        elf::EM_SHARC => match r_type {
466            elf::R_SHARC_ADDR24_V3 => (K::Absolute, E::SharcTypeA, 24),
467            elf::R_SHARC_ADDR32_V3 => (K::Absolute, E::SharcTypeA, 32),
468            elf::R_SHARC_ADDR_VAR_V3 => (K::Absolute, E::Generic, 32),
469            elf::R_SHARC_PCRSHORT_V3 => (K::Relative, E::SharcTypeA, 6),
470            elf::R_SHARC_PCRLONG_V3 => (K::Relative, E::SharcTypeA, 24),
471            elf::R_SHARC_DATA6_V3 => (K::Absolute, E::SharcTypeA, 6),
472            elf::R_SHARC_DATA16_V3 => (K::Absolute, E::SharcTypeA, 16),
473            elf::R_SHARC_DATA6_VISA_V3 => (K::Absolute, E::SharcTypeB, 6),
474            elf::R_SHARC_DATA7_VISA_V3 => (K::Absolute, E::SharcTypeB, 7),
475            elf::R_SHARC_DATA16_VISA_V3 => (K::Absolute, E::SharcTypeB, 16),
476            elf::R_SHARC_PCR6_VISA_V3 => (K::Relative, E::SharcTypeB, 16),
477            elf::R_SHARC_ADDR_VAR16_V3 => (K::Absolute, E::Generic, 16),
478            _ => unknown,
479        },
480        elf::EM_SPARC | elf::EM_SPARC32PLUS | elf::EM_SPARCV9 => match r_type {
481            elf::R_SPARC_32 | elf::R_SPARC_UA32 => (K::Absolute, g, 32),
482            elf::R_SPARC_64 | elf::R_SPARC_UA64 => (K::Absolute, g, 64),
483            _ => unknown,
484        },
485        elf::EM_SH => match r_type {
486            elf::R_SH_DIR32 => (K::Absolute, g, 32),
487            elf::R_SH_REL32 => (K::Relative, g, 32),
488            _ => unknown,
489        },
490        elf::EM_XTENSA => match r_type {
491            elf::R_XTENSA_32 => (K::Absolute, g, 32),
492            elf::R_XTENSA_32_PCREL => (K::Relative, g, 32),
493            _ => unknown,
494        },
495        _ => unknown,
496    };
497    let target = match reloc.symbol() {
498        None => RelocationTarget::Absolute,
499        Some(symbol) => RelocationTarget::Symbol(symbol),
500    };
501    Relocation {
502        kind,
503        encoding,
504        size,
505        target,
506        addend: reloc.r_addend,
507        implicit_addend,
508        flags,
509    }
510}
511
512/// A trait for generic access to [`elf::Rel32`] and [`elf::Rel64`].
513#[allow(missing_docs)]
514pub trait Rel: Debug + Pod + Clone {
515    type Word: Into<u64>;
516    type Sword: Into<i64>;
517    type Endian: endian::Endian;
518
519    fn r_offset(&self, endian: Self::Endian) -> Self::Word;
520    fn r_info(&self, endian: Self::Endian) -> Self::Word;
521    fn r_sym(&self, endian: Self::Endian) -> u32;
522    fn r_type(&self, endian: Self::Endian) -> u32;
523
524    /// Get the symbol index referenced by the relocation.
525    ///
526    /// Returns `None` for the null symbol index.
527    fn symbol(&self, endian: Self::Endian) -> Option<SymbolIndex> {
528        let sym = self.r_sym(endian);
529        if sym == 0 {
530            None
531        } else {
532            Some(SymbolIndex(sym as usize))
533        }
534    }
535}
536
537impl<Endian: endian::Endian> Rel for elf::Rel32<Endian> {
538    type Word = u32;
539    type Sword = i32;
540    type Endian = Endian;
541
542    #[inline]
543    fn r_offset(&self, endian: Self::Endian) -> Self::Word {
544        self.r_offset.get(endian)
545    }
546
547    #[inline]
548    fn r_info(&self, endian: Self::Endian) -> Self::Word {
549        self.r_info.get(endian)
550    }
551
552    #[inline]
553    fn r_sym(&self, endian: Self::Endian) -> u32 {
554        self.r_sym(endian)
555    }
556
557    #[inline]
558    fn r_type(&self, endian: Self::Endian) -> u32 {
559        self.r_type(endian)
560    }
561}
562
563impl<Endian: endian::Endian> Rel for elf::Rel64<Endian> {
564    type Word = u64;
565    type Sword = i64;
566    type Endian = Endian;
567
568    #[inline]
569    fn r_offset(&self, endian: Self::Endian) -> Self::Word {
570        self.r_offset.get(endian)
571    }
572
573    #[inline]
574    fn r_info(&self, endian: Self::Endian) -> Self::Word {
575        self.r_info.get(endian)
576    }
577
578    #[inline]
579    fn r_sym(&self, endian: Self::Endian) -> u32 {
580        self.r_sym(endian)
581    }
582
583    #[inline]
584    fn r_type(&self, endian: Self::Endian) -> u32 {
585        self.r_type(endian)
586    }
587}
588
589/// A trait for generic access to [`elf::Rela32`] and [`elf::Rela64`].
590#[allow(missing_docs)]
591pub trait Rela: Debug + Pod + Clone {
592    type Word: Into<u64>;
593    type Sword: Into<i64>;
594    type Endian: endian::Endian;
595
596    fn r_offset(&self, endian: Self::Endian) -> Self::Word;
597    fn r_info(&self, endian: Self::Endian, is_mips64el: bool) -> Self::Word;
598    fn r_addend(&self, endian: Self::Endian) -> Self::Sword;
599    fn r_sym(&self, endian: Self::Endian, is_mips64el: bool) -> u32;
600    fn r_type(&self, endian: Self::Endian, is_mips64el: bool) -> u32;
601
602    /// Get the symbol index referenced by the relocation.
603    ///
604    /// Returns `None` for the null symbol index.
605    fn symbol(&self, endian: Self::Endian, is_mips64el: bool) -> Option<SymbolIndex> {
606        let sym = self.r_sym(endian, is_mips64el);
607        if sym == 0 {
608            None
609        } else {
610            Some(SymbolIndex(sym as usize))
611        }
612    }
613}
614
615impl<Endian: endian::Endian> Rela for elf::Rela32<Endian> {
616    type Word = u32;
617    type Sword = i32;
618    type Endian = Endian;
619
620    #[inline]
621    fn r_offset(&self, endian: Self::Endian) -> Self::Word {
622        self.r_offset.get(endian)
623    }
624
625    #[inline]
626    fn r_info(&self, endian: Self::Endian, _is_mips64el: bool) -> Self::Word {
627        self.r_info.get(endian)
628    }
629
630    #[inline]
631    fn r_addend(&self, endian: Self::Endian) -> Self::Sword {
632        self.r_addend.get(endian)
633    }
634
635    #[inline]
636    fn r_sym(&self, endian: Self::Endian, _is_mips64el: bool) -> u32 {
637        self.r_sym(endian)
638    }
639
640    #[inline]
641    fn r_type(&self, endian: Self::Endian, _is_mips64el: bool) -> u32 {
642        self.r_type(endian)
643    }
644}
645
646impl<Endian: endian::Endian> Rela for elf::Rela64<Endian> {
647    type Word = u64;
648    type Sword = i64;
649    type Endian = Endian;
650
651    #[inline]
652    fn r_offset(&self, endian: Self::Endian) -> Self::Word {
653        self.r_offset.get(endian)
654    }
655
656    #[inline]
657    fn r_info(&self, endian: Self::Endian, is_mips64el: bool) -> Self::Word {
658        self.get_r_info(endian, is_mips64el)
659    }
660
661    #[inline]
662    fn r_addend(&self, endian: Self::Endian) -> Self::Sword {
663        self.r_addend.get(endian)
664    }
665
666    #[inline]
667    fn r_sym(&self, endian: Self::Endian, is_mips64el: bool) -> u32 {
668        self.r_sym(endian, is_mips64el)
669    }
670
671    #[inline]
672    fn r_type(&self, endian: Self::Endian, is_mips64el: bool) -> u32 {
673        self.r_type(endian, is_mips64el)
674    }
675}
676
677/// An iterator over the relative relocations in an ELF `SHT_RELR` section.
678///
679/// Returned by [`SectionHeader::relr`](super::SectionHeader::relr).
680#[derive(Debug)]
681pub struct RelrIterator<'data, Elf: FileHeader> {
682    offset: Elf::Word,
683    bits: Elf::Word,
684    count: u8,
685    iter: slice::Iter<'data, Elf::Relr>,
686    endian: Elf::Endian,
687}
688
689impl<'data, Elf: FileHeader> RelrIterator<'data, Elf> {
690    /// Create a new iterator given the `SHT_RELR` section data.
691    pub fn new(endian: Elf::Endian, data: &'data [Elf::Relr]) -> Self {
692        RelrIterator {
693            offset: Elf::Word::default(),
694            bits: Elf::Word::default(),
695            count: 0,
696            iter: data.iter(),
697            endian,
698        }
699    }
700}
701
702impl<'data, Elf: FileHeader> Iterator for RelrIterator<'data, Elf> {
703    type Item = Elf::Word;
704
705    fn next(&mut self) -> Option<Self::Item> {
706        loop {
707            while self.count > 0 {
708                self.count -= 1;
709                let offset = Elf::Relr::next(&mut self.offset, &mut self.bits);
710                if offset.is_some() {
711                    return offset;
712                }
713            }
714            let next = self.iter.next()?.get(self.endian);
715            if next.into() & 1 == 0 {
716                self.offset = next;
717                return Some(next);
718            }
719            self.bits = next;
720            self.count = Elf::Relr::COUNT;
721        }
722    }
723}
724
725/// A trait for generic access to [`elf::Relr32`] and [`elf::Relr64`].
726#[allow(missing_docs)]
727pub trait Relr: Debug + Pod + Clone {
728    type Word: Into<u64>;
729    type Endian: endian::Endian;
730
731    /// The number of bits in the bit mask, excluding the lowest bit.
732    const COUNT: u8;
733
734    /// Get the relocation entry.
735    ///
736    /// This value is an offset if the lowest bit is clear, or a bit mask if the lowest bit is set.
737    fn get(&self, endian: Self::Endian) -> Self::Word;
738
739    /// Return the offset corresponding to the next bit in the bit mask.
740    ///
741    /// Updates the offset and bit mask. This method should be called 31 times
742    /// for Relr32 and 63 times for Relr64 to iterate over all the bits.
743    ///
744    /// Returns `None` if the bit is not set.
745    fn next(offset: &mut Self::Word, bits: &mut Self::Word) -> Option<Self::Word>;
746}
747
748impl<Endian: endian::Endian> Relr for elf::Relr32<Endian> {
749    type Word = u32;
750    type Endian = Endian;
751    const COUNT: u8 = 31;
752
753    fn get(&self, endian: Self::Endian) -> Self::Word {
754        self.0.get(endian)
755    }
756
757    fn next(offset: &mut Self::Word, bits: &mut Self::Word) -> Option<Self::Word> {
758        *offset += 4;
759        *bits >>= 1;
760        if *bits & 1 != 0 {
761            Some(*offset)
762        } else {
763            None
764        }
765    }
766}
767
768impl<Endian: endian::Endian> Relr for elf::Relr64<Endian> {
769    type Word = u64;
770    type Endian = Endian;
771    const COUNT: u8 = 63;
772
773    fn get(&self, endian: Self::Endian) -> Self::Word {
774        self.0.get(endian)
775    }
776
777    fn next(offset: &mut Self::Word, bits: &mut Self::Word) -> Option<Self::Word> {
778        *offset += 8;
779        *bits >>= 1;
780        if *bits & 1 != 0 {
781            Some(*offset)
782        } else {
783            None
784        }
785    }
786}
787
788/// Compact relocation
789///
790/// The specification has been submited here: <https://groups.google.com/g/generic-abi/c/ppkaxtLb0P0/m/awgqZ_1CBAAJ>.
791#[derive(Debug, Clone, Copy)]
792pub struct Crel {
793    /// Relocation offset.
794    pub r_offset: u64,
795    /// Relocation symbol index.
796    pub r_sym: u32,
797    /// Relocation type.
798    pub r_type: u32,
799    /// Relocation addend.
800    ///
801    /// Only set if `CrelIterator::is_rela()` returns `true`.
802    pub r_addend: i64,
803}
804
805impl Crel {
806    /// Get the symbol index referenced by the relocation.
807    ///
808    /// Returns `None` for the null symbol index.
809    pub fn symbol(&self) -> Option<SymbolIndex> {
810        if self.r_sym == 0 {
811            None
812        } else {
813            Some(SymbolIndex(self.r_sym as usize))
814        }
815    }
816
817    /// Build Crel type from Rel.
818    pub fn from_rel<R: Rel>(r: &R, endian: R::Endian) -> Crel {
819        Crel {
820            r_offset: r.r_offset(endian).into(),
821            r_sym: r.r_sym(endian),
822            r_type: r.r_type(endian),
823            r_addend: 0,
824        }
825    }
826
827    /// Build Crel type from Rela.
828    pub fn from_rela<R: Rela>(r: &R, endian: R::Endian, is_mips64el: bool) -> Crel {
829        Crel {
830            r_offset: r.r_offset(endian).into(),
831            r_sym: r.r_sym(endian, is_mips64el),
832            r_type: r.r_type(endian, is_mips64el),
833            r_addend: r.r_addend(endian).into(),
834        }
835    }
836}
837
838#[derive(Debug, Clone)]
839struct CrelIteratorHeader {
840    /// The number of encoded relocations.
841    count: usize,
842    /// The number of flag bits each relocation uses.
843    flag_bits: u64,
844    /// Shift of the relocation value.
845    shift: u64,
846    /// True if the relocation format encodes addend.
847    is_rela: bool,
848}
849
850#[derive(Default, Debug, Clone)]
851struct CrelIteratorState {
852    /// Index of the current relocation.
853    index: usize,
854    /// Offset of the latest relocation.
855    offset: u64,
856    /// Addend of the latest relocation.
857    addend: i64,
858    /// Symbol index of the latest relocation.
859    symidx: u32,
860    /// Type of the latest relocation.
861    typ: u32,
862}
863
864/// Compact relocation iterator.
865#[derive(Debug, Clone)]
866pub struct CrelIterator<'data> {
867    /// Input stream reader.
868    data: Bytes<'data>,
869    /// Parsed header information.
870    header: CrelIteratorHeader,
871    /// State of the iterator.
872    state: CrelIteratorState,
873}
874
875impl<'data> CrelIterator<'data> {
876    /// Create a new CREL relocation iterator.
877    pub fn new(data: &'data [u8]) -> Result<Self, Error> {
878        const HEADER_ADDEND_BIT_MASK: u64 = 1 << 2;
879        const HEADER_SHIFT_MASK: u64 = 0x3;
880
881        let mut data = Bytes(data);
882        let header = data.read_uleb128().read_error("Invalid ELF CREL header")?;
883        let count = header >> 3;
884        let flag_bits = if header & HEADER_ADDEND_BIT_MASK != 0 {
885            3
886        } else {
887            2
888        };
889        let shift = header & HEADER_SHIFT_MASK;
890        let is_rela = header & HEADER_ADDEND_BIT_MASK != 0;
891
892        Ok(CrelIterator {
893            data,
894            header: CrelIteratorHeader {
895                count: count as usize,
896                flag_bits,
897                shift,
898                is_rela,
899            },
900            state: Default::default(),
901        })
902    }
903
904    /// True if the encoded relocations have addend.
905    pub fn is_rela(&self) -> bool {
906        self.header.is_rela
907    }
908
909    /// Return the number of encoded relocations.
910    pub fn len(&self) -> usize {
911        self.header.count - self.state.index
912    }
913
914    /// Return true if there are no more relocations to parse.
915    pub fn is_empty(&self) -> bool {
916        self.header.count == self.state.index
917    }
918
919    fn parse(&mut self) -> read::Result<Crel> {
920        const DELTA_SYMBOL_INDEX_MASK: u8 = 1 << 0;
921        const DELTA_TYPE_MASK: u8 = 1 << 1;
922        const DELTA_ADDEND_MASK: u8 = 1 << 2;
923
924        // The delta offset and flags combined may be larger than u64,
925        // so we handle the first byte separately.
926        let byte = *self
927            .data
928            .read::<u8>()
929            .read_error("Cannot read offset and flags of CREL relocation")?;
930        let flags = byte & ((1 << self.header.flag_bits) - 1);
931
932        let mut delta_offset = u64::from(byte & 0x7f) >> self.header.flag_bits;
933        if byte & 0x80 != 0 {
934            delta_offset |= self
935                .data
936                .read_uleb128()
937                .read_error("Cannot read offset and flags of CREL relocation")?
938                << (7 - self.header.flag_bits);
939        }
940        self.state.offset = self.state.offset.wrapping_add(delta_offset);
941
942        if flags & DELTA_SYMBOL_INDEX_MASK != 0 {
943            let delta_symidx = self
944                .data
945                .read_sleb128()
946                .read_error("Cannot read symidx of CREL relocation")?;
947            self.state.symidx = self.state.symidx.wrapping_add(delta_symidx as u32);
948        }
949        if flags & DELTA_TYPE_MASK != 0 {
950            let delta_typ = self
951                .data
952                .read_sleb128()
953                .read_error("Cannot read type of CREL relocation")?;
954            self.state.typ = self.state.typ.wrapping_add(delta_typ as u32);
955        }
956        if self.header.is_rela && flags & DELTA_ADDEND_MASK != 0 {
957            let delta_addend = self
958                .data
959                .read_sleb128()
960                .read_error("Cannot read addend of CREL relocation")?;
961            self.state.addend = self.state.addend.wrapping_add(delta_addend);
962        }
963        self.state.index += 1;
964        Ok(Crel {
965            r_offset: self.state.offset << self.header.shift,
966            r_sym: self.state.symidx,
967            r_type: self.state.typ,
968            r_addend: self.state.addend,
969        })
970    }
971}
972
973impl<'data> Iterator for CrelIterator<'data> {
974    type Item = read::Result<Crel>;
975
976    fn next(&mut self) -> Option<Self::Item> {
977        if self.state.index >= self.header.count {
978            return None;
979        }
980
981        let result = self.parse();
982        if result.is_err() {
983            self.state.index = self.header.count;
984        }
985        Some(result)
986    }
987
988    fn size_hint(&self) -> (usize, Option<usize>) {
989        (self.len(), Some(self.len()))
990    }
991}
object/read/elf/relocation.rs

object/read/elf/
relocation.rs
