1 //===------------------------- EHHeaderParser.hpp -------------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
8 // Parses ELF .eh_frame_hdr sections.
10 //===----------------------------------------------------------------------===//
12 #ifndef __EHHEADERPARSER_HPP__
13 #define __EHHEADERPARSER_HPP__
15 #include "libunwind.h"
17 #include "DwarfParser.hpp"
21 /// \brief EHHeaderParser does basic parsing of an ELF .eh_frame_hdr section.
23 /// See DWARF spec for details:
24 /// http://refspecs.linuxbase.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
26 template <typename A> class EHHeaderParser {
28 typedef typename A::pint_t pint_t;
30 /// Information encoded in the EH frame header.
38 static bool decodeEHHdr(A &addressSpace, pint_t ehHdrStart, pint_t ehHdrEnd,
39 EHHeaderInfo &ehHdrInfo);
40 static bool findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart,
41 uint32_t sectionLength,
42 typename CFI_Parser<A>::FDE_Info *fdeInfo,
43 typename CFI_Parser<A>::CIE_Info *cieInfo);
46 static bool decodeTableEntry(A &addressSpace, pint_t &tableEntry,
47 pint_t ehHdrStart, pint_t ehHdrEnd,
49 typename CFI_Parser<A>::FDE_Info *fdeInfo,
50 typename CFI_Parser<A>::CIE_Info *cieInfo);
51 static size_t getTableEntrySize(uint8_t tableEnc);
55 bool EHHeaderParser<A>::decodeEHHdr(A &addressSpace, pint_t ehHdrStart,
56 pint_t ehHdrEnd, EHHeaderInfo &ehHdrInfo) {
57 pint_t p = ehHdrStart;
58 uint8_t version = addressSpace.get8(p++);
60 _LIBUNWIND_LOG0("Unsupported .eh_frame_hdr version");
64 uint8_t eh_frame_ptr_enc = addressSpace.get8(p++);
65 uint8_t fde_count_enc = addressSpace.get8(p++);
66 ehHdrInfo.table_enc = addressSpace.get8(p++);
68 ehHdrInfo.eh_frame_ptr =
69 addressSpace.getEncodedP(p, ehHdrEnd, eh_frame_ptr_enc, ehHdrStart);
71 fde_count_enc == DW_EH_PE_omit
73 : addressSpace.getEncodedP(p, ehHdrEnd, fde_count_enc, ehHdrStart);
80 bool EHHeaderParser<A>::decodeTableEntry(
81 A &addressSpace, pint_t &tableEntry, pint_t ehHdrStart, pint_t ehHdrEnd,
82 uint8_t tableEnc, typename CFI_Parser<A>::FDE_Info *fdeInfo,
83 typename CFI_Parser<A>::CIE_Info *cieInfo) {
84 // Have to decode the whole FDE for the PC range anyway, so just throw away
86 addressSpace.getEncodedP(tableEntry, ehHdrEnd, tableEnc, ehHdrStart);
88 addressSpace.getEncodedP(tableEntry, ehHdrEnd, tableEnc, ehHdrStart);
90 CFI_Parser<A>::decodeFDE(addressSpace, fde, fdeInfo, cieInfo);
91 if (message != NULL) {
92 _LIBUNWIND_DEBUG_LOG("EHHeaderParser::decodeTableEntry: bad fde: %s",
100 template <typename A>
101 bool EHHeaderParser<A>::findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart,
102 uint32_t sectionLength,
103 typename CFI_Parser<A>::FDE_Info *fdeInfo,
104 typename CFI_Parser<A>::CIE_Info *cieInfo) {
105 pint_t ehHdrEnd = ehHdrStart + sectionLength;
107 EHHeaderParser<A>::EHHeaderInfo hdrInfo;
108 if (!EHHeaderParser<A>::decodeEHHdr(addressSpace, ehHdrStart, ehHdrEnd,
112 size_t tableEntrySize = getTableEntrySize(hdrInfo.table_enc);
116 for (size_t len = hdrInfo.fde_count; len > 1;) {
117 size_t mid = low + (len / 2);
118 tableEntry = hdrInfo.table + mid * tableEntrySize;
119 pint_t start = addressSpace.getEncodedP(tableEntry, ehHdrEnd,
120 hdrInfo.table_enc, ehHdrStart);
125 } else if (start < pc) {
133 tableEntry = hdrInfo.table + low * tableEntrySize;
134 if (decodeTableEntry(addressSpace, tableEntry, ehHdrStart, ehHdrEnd,
135 hdrInfo.table_enc, fdeInfo, cieInfo)) {
136 if (pc >= fdeInfo->pcStart && pc < fdeInfo->pcEnd)
143 template <typename A>
144 size_t EHHeaderParser<A>::getTableEntrySize(uint8_t tableEnc) {
145 switch (tableEnc & 0x0f) {
146 case DW_EH_PE_sdata2:
147 case DW_EH_PE_udata2:
149 case DW_EH_PE_sdata4:
150 case DW_EH_PE_udata4:
152 case DW_EH_PE_sdata8:
153 case DW_EH_PE_udata8:
155 case DW_EH_PE_sleb128:
156 case DW_EH_PE_uleb128:
157 _LIBUNWIND_ABORT("Can't binary search on variable length encoded data.");
161 _LIBUNWIND_ABORT("Unknown DWARF encoding for search table.");