| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // Delta encode and decode REL/RELA section of elf file. |
| // |
| // The encoded data format is sequence of elements of ElfAddr type (unsigned long): |
| // |
| // [00] relocation_count - the total count of relocations |
| // [01] initial r_offset - this is initial r_offset for the |
| // relocation table. |
| // followed by group structures: |
| // [02] group |
| // ... |
| // [nn] group |
| |
| // the generalized format of the group is (! - always present ? - depends on group_flags): |
| // -------------- |
| // ! group_size |
| // ! group_flags |
| // ? group_r_offset_delta when RELOCATION_GROUPED_BY_OFFSET_DELTA flag is set |
| // ? group_r_info when RELOCATION_GROUPED_BY_INFO flag is set |
| // ? group_r_addend_group_delta when RELOCATION_GROUP_HAS_ADDEND and RELOCATION_GROUPED_BY_ADDEND |
| // flag is set |
| // |
| // The group description is followed by individual relocations. |
| // please note that there is a case when individual relocation |
| // section could be empty - that is if every field ends up grouped. |
| // |
| // The format for individual relocations section is: |
| // ? r_offset_delta - when RELOCATION_GROUPED_BY_OFFSET_DELTA is not set |
| // ? r_info - when RELOCATION_GROUPED_BY_INFO flag is not set |
| // ? r_addend_delta - RELOCATION_GROUP_HAS_ADDEND is set and RELOCATION_GROUPED_BY_ADDEND is not set |
| // |
| // For example lets pack the following relocations: |
| // |
| // Relocation section '.rela.dyn' at offset 0xbf58 contains 939 entries: |
| // Offset Info Type Symbol's Value Symbol's Name + Addend |
| // 00000000000a2178 0000000000000403 R_AARCH64_RELATIVE 177a8 |
| // 00000000000a2180 0000000000000403 R_AARCH64_RELATIVE 177cc |
| // 00000000000a2188 0000000000000403 R_AARCH64_RELATIVE 177e0 |
| // 00000000000a2190 0000000000000403 R_AARCH64_RELATIVE 177f4 |
| // 00000000000a2198 0000000000000403 R_AARCH64_RELATIVE 17804 |
| // 00000000000a21a0 0000000000000403 R_AARCH64_RELATIVE 17818 |
| // 00000000000a21a8 0000000000000403 R_AARCH64_RELATIVE 1782c |
| // 00000000000a21b0 0000000000000403 R_AARCH64_RELATIVE 17840 |
| // 00000000000a21b8 0000000000000403 R_AARCH64_RELATIVE 17854 |
| // 00000000000a21c0 0000000000000403 R_AARCH64_RELATIVE 17868 |
| // 00000000000a21c8 0000000000000403 R_AARCH64_RELATIVE 1787c |
| // 00000000000a21d0 0000000000000403 R_AARCH64_RELATIVE 17890 |
| // 00000000000a21d8 0000000000000403 R_AARCH64_RELATIVE 178a4 |
| // 00000000000a21e8 0000000000000403 R_AARCH64_RELATIVE 178b8 |
| // |
| // The header is going to be |
| // [00] 14 <- count |
| // [01] 0x00000000000a2170 <- initial relocation (first relocation - delta, |
| // the delta is 8 in this case) |
| // -- starting the first and only group |
| // [03] 14 <- group size |
| // [03] 0xb <- flags RELOCATION_GROUP_HAS_ADDEND | RELOCATION_GROUPED_BY_OFFSET_DELTA |
| // | RELOCATION_GROUPED_BY_INFO |
| // [04] 8 <- offset delta |
| // [05] 0x403 <- r_info |
| // -- end of group definition, starting list of r_addend deltas |
| // [06] 0x177a8 |
| // [07] 0x24 = 177cc - 177a8 |
| // [08] 0x14 = 177e0 - 177cc |
| // [09] 0x14 = 177f4 - 177e0 |
| // [10] 0x10 = 17804 - 177f4 |
| // [11] 0x14 = 17818 - 17804 |
| // [12] 0x14 = 1782c - 17818 |
| // [13] 0x14 = 17840 - 1782c |
| // [14] 0x14 = 17854 - 17840 |
| // [15] 0x14 = 17868 - 17854 |
| // [16] 0x14 = 1787c - 17868 |
| // [17] 0x14 = 17890 - 1787c |
| // [18] 0x14 = 178a4 - 17890 |
| // [19] 0x14 = 178b8 - 178a4 |
| // -- the end. |
| |
| // TODO (dimitry): consider using r_addend_group_delta in the way we use group offset delta, it can |
| // save us more bytes... |
| |
| // The input ends when sum(group_size) == relocation_count |
| |
| #ifndef TOOLS_RELOCATION_PACKER_SRC_DELTA_ENCODER_H_ |
| #define TOOLS_RELOCATION_PACKER_SRC_DELTA_ENCODER_H_ |
| |
| #include <vector> |
| |
| #include "elf.h" |
| #include "elf_traits.h" |
| |
| namespace relocation_packer { |
| |
| // A RelocationDeltaCodec packs vectors of relative relocations with |
| // addends into more compact forms, and unpacks them to reproduce the |
| // pre-packed data. |
| template <typename ELF> |
| class RelocationDeltaCodec { |
| public: |
| typedef typename ELF::Addr ElfAddr; |
| typedef typename ELF::Rela ElfRela; |
| |
| // Encode relocations with addends into a more compact form. |
| // |relocations| is a vector of relative relocation with addend structs. |
| // |packed| is the vector of packed words into which relocations are packed. |
| static void Encode(const std::vector<ElfRela>& relocations, |
| std::vector<ElfAddr>* packed); |
| |
| // Decode relative relocations with addends from their more compact form. |
| // |packed| is the vector of packed relocations. |
| // |relocations| is a vector of unpacked relative relocations. |
| static void Decode(const std::vector<ElfAddr>& packed, |
| std::vector<ElfRela>* relocations); |
| |
| private: |
| static void DetectGroup(const std::vector<ElfRela>& relocations, |
| size_t group_starts_with, ElfAddr previous_offset, |
| ElfAddr* group_size, ElfAddr* group_flags, |
| ElfAddr* group_offset_delta, ElfAddr* group_info, |
| ElfAddr* group_addend); |
| |
| static void DetectGroupFields(const ElfRela& reloc_one, const ElfRela& reloc_two, |
| ElfAddr current_offset_delta, ElfAddr* group_flags, |
| ElfAddr* group_offset_delta, ElfAddr* group_info, |
| ElfAddr* group_addend); |
| }; |
| |
| } // namespace relocation_packer |
| |
| #endif // TOOLS_RELOCATION_PACKER_SRC_DELTA_ENCODER_H_ |
