| // Copyright 2016 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/eh-frame.h" |
| #include "src/objects-inl.h" |
| #include "src/objects.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| static const int DW_EH_PE_pcrel = 0x10; |
| static const int DW_EH_PE_datarel = 0x30; |
| static const int DW_EH_PE_udata4 = 0x03; |
| static const int DW_EH_PE_sdata4 = 0x0b; |
| |
| const int EhFrameHdr::kCIESize = 0; |
| |
| static const int kVersionSize = 1; |
| static const int kEncodingSpecifiersSize = 3; |
| |
| // |
| // In order to calculate offsets in the .eh_frame_hdr, we must know the layout |
| // of the DSO generated by perf inject, which is assumed to be the following: |
| // |
| // | ... | | |
| // +---------------+ <-- (F) --- | Larger offsets in file |
| // | | ^ | |
| // | Instructions | | .text v |
| // | | v |
| // +---------------+ <-- (E) --- |
| // |///////////////| |
| // |////Padding////| |
| // |///////////////| |
| // +---------------+ <-- (D) --- |
| // | | ^ |
| // | CIE | | |
| // | | | |
| // +---------------+ <-- (C) | .eh_frame |
| // | | | |
| // | FDE | | |
| // | | v |
| // +---------------+ <-- (B) --- |
| // | version | ^ |
| // +---------------+ | |
| // | encoding | | |
| // | specifiers | | |
| // +---------------+ <---(A) | .eh_frame_hdr |
| // | offset to | | |
| // | .eh_frame | | |
| // +---------------+ | |
| // | ... | ... |
| // |
| // (F) is aligned at a 16-byte boundary. |
| // (D) is aligned at a 8-byte boundary. |
| // (B) is aligned at a 4-byte boundary. |
| // (E), (C) and (A) have no alignment requirements. |
| // |
| // The distance between (A) and (B) is 4 bytes. |
| // |
| // The size of the .eh_frame is required to be a multiple of the pointer size, |
| // which means that (B) will be naturally aligned to a 4-byte boundary on all |
| // the architectures we support. |
| // |
| // Because (E) has no alignment requirements, there is padding between (E) and |
| // (D). (F) is aligned at a 16-byte boundary, thus to a 8-byte one as well. |
| // |
| EhFrameHdr::EhFrameHdr(Code* code) { |
| int code_size = code->is_crankshafted() ? code->safepoint_table_offset() |
| : code->instruction_size(); |
| version_ = 1; |
| eh_frame_ptr_encoding_ = DW_EH_PE_sdata4 | DW_EH_PE_pcrel; |
| lut_size_encoding_ = DW_EH_PE_udata4; |
| lut_entries_encoding_ = DW_EH_PE_sdata4 | DW_EH_PE_datarel; |
| |
| // .eh_frame pointer and LUT |
| if (code->has_unwinding_info()) { |
| DCHECK_GE(code->unwinding_info_size(), EhFrameHdr::kRecordSize); |
| int eh_frame_size = code->unwinding_info_size() - EhFrameHdr::kRecordSize; |
| |
| offset_to_eh_frame_ = |
| -(eh_frame_size + kVersionSize + kEncodingSpecifiersSize); // A -> D |
| lut_entries_number_ = 1; |
| offset_to_procedure_ = -(RoundUp(code_size, 8) + eh_frame_size); // B -> F |
| offset_to_fde_ = -(eh_frame_size - kCIESize); // B -> C |
| } else { |
| // Create a dummy table |
| offset_to_eh_frame_ = 0; |
| lut_entries_number_ = 0; |
| offset_to_procedure_ = 0; |
| offset_to_fde_ = 0; |
| } |
| } |
| |
| } // namespace internal |
| } // namespace v8 |