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1 //===-- DWARFCompileUnit.cpp ----------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "DWARFCompileUnit.h"
11 #include "DWARFContext.h"
12 #include "DWARFFormValue.h"
13 #include "llvm/Support/Dwarf.h"
14 #include "llvm/Support/Format.h"
15 #include "llvm/Support/raw_ostream.h"
16 using namespace llvm;
17 using namespace dwarf;
18 
getDebugInfoExtractor() const19 DataExtractor DWARFCompileUnit::getDebugInfoExtractor() const {
20   return DataExtractor(Context.getInfoSection(),
21                        Context.isLittleEndian(), getAddressByteSize());
22 }
23 
extract(DataExtractor debug_info,uint32_t * offset_ptr)24 bool DWARFCompileUnit::extract(DataExtractor debug_info, uint32_t *offset_ptr) {
25   clear();
26 
27   Offset = *offset_ptr;
28 
29   if (debug_info.isValidOffset(*offset_ptr)) {
30     uint64_t abbrOffset;
31     const DWARFDebugAbbrev *abbr = Context.getDebugAbbrev();
32     Length = debug_info.getU32(offset_ptr);
33     Version = debug_info.getU16(offset_ptr);
34     abbrOffset = debug_info.getU32(offset_ptr);
35     AddrSize = debug_info.getU8(offset_ptr);
36 
37     bool lengthOK = debug_info.isValidOffset(getNextCompileUnitOffset()-1);
38     bool versionOK = DWARFContext::isSupportedVersion(Version);
39     bool abbrOffsetOK = Context.getAbbrevSection().size() > abbrOffset;
40     bool addrSizeOK = AddrSize == 4 || AddrSize == 8;
41 
42     if (lengthOK && versionOK && addrSizeOK && abbrOffsetOK && abbr != NULL) {
43       Abbrevs = abbr->getAbbreviationDeclarationSet(abbrOffset);
44       return true;
45     }
46 
47     // reset the offset to where we tried to parse from if anything went wrong
48     *offset_ptr = Offset;
49   }
50 
51   return false;
52 }
53 
54 uint32_t
extract(uint32_t offset,DataExtractor debug_info_data,const DWARFAbbreviationDeclarationSet * abbrevs)55 DWARFCompileUnit::extract(uint32_t offset, DataExtractor debug_info_data,
56                           const DWARFAbbreviationDeclarationSet *abbrevs) {
57   clear();
58 
59   Offset = offset;
60 
61   if (debug_info_data.isValidOffset(offset)) {
62     Length = debug_info_data.getU32(&offset);
63     Version = debug_info_data.getU16(&offset);
64     bool abbrevsOK = debug_info_data.getU32(&offset) == abbrevs->getOffset();
65     Abbrevs = abbrevs;
66     AddrSize = debug_info_data.getU8 (&offset);
67 
68     bool versionOK = DWARFContext::isSupportedVersion(Version);
69     bool addrSizeOK = AddrSize == 4 || AddrSize == 8;
70 
71     if (versionOK && addrSizeOK && abbrevsOK &&
72         debug_info_data.isValidOffset(offset))
73       return offset;
74   }
75   return 0;
76 }
77 
clear()78 void DWARFCompileUnit::clear() {
79   Offset = 0;
80   Length = 0;
81   Version = 0;
82   Abbrevs = 0;
83   AddrSize = 0;
84   BaseAddr = 0;
85   DieArray.clear();
86 }
87 
dump(raw_ostream & OS)88 void DWARFCompileUnit::dump(raw_ostream &OS) {
89   OS << format("0x%08x", Offset) << ": Compile Unit:"
90      << " length = " << format("0x%08x", Length)
91      << " version = " << format("0x%04x", Version)
92      << " abbr_offset = " << format("0x%04x", Abbrevs->getOffset())
93      << " addr_size = " << format("0x%02x", AddrSize)
94      << " (next CU at " << format("0x%08x", getNextCompileUnitOffset())
95      << ")\n";
96 
97   getCompileUnitDIE(false)->dump(OS, this, -1U);
98 }
99 
setDIERelations()100 void DWARFCompileUnit::setDIERelations() {
101   if (DieArray.empty())
102     return;
103   DWARFDebugInfoEntryMinimal *die_array_begin = &DieArray.front();
104   DWARFDebugInfoEntryMinimal *die_array_end = &DieArray.back();
105   DWARFDebugInfoEntryMinimal *curr_die;
106   // We purposely are skipping the last element in the array in the loop below
107   // so that we can always have a valid next item
108   for (curr_die = die_array_begin; curr_die < die_array_end; ++curr_die) {
109     // Since our loop doesn't include the last element, we can always
110     // safely access the next die in the array.
111     DWARFDebugInfoEntryMinimal *next_die = curr_die + 1;
112 
113     const DWARFAbbreviationDeclaration *curr_die_abbrev =
114       curr_die->getAbbreviationDeclarationPtr();
115 
116     if (curr_die_abbrev) {
117       // Normal DIE
118       if (curr_die_abbrev->hasChildren())
119         next_die->setParent(curr_die);
120       else
121         curr_die->setSibling(next_die);
122     } else {
123       // NULL DIE that terminates a sibling chain
124       DWARFDebugInfoEntryMinimal *parent = curr_die->getParent();
125       if (parent)
126         parent->setSibling(next_die);
127     }
128   }
129 
130   // Since we skipped the last element, we need to fix it up!
131   if (die_array_begin < die_array_end)
132     curr_die->setParent(die_array_begin);
133 }
134 
extractDIEsIfNeeded(bool cu_die_only)135 size_t DWARFCompileUnit::extractDIEsIfNeeded(bool cu_die_only) {
136   const size_t initial_die_array_size = DieArray.size();
137   if ((cu_die_only && initial_die_array_size > 0) ||
138       initial_die_array_size > 1)
139     return 0; // Already parsed
140 
141   // Set the offset to that of the first DIE and calculate the start of the
142   // next compilation unit header.
143   uint32_t offset = getFirstDIEOffset();
144   uint32_t next_cu_offset = getNextCompileUnitOffset();
145 
146   DWARFDebugInfoEntryMinimal die;
147   // Keep a flat array of the DIE for binary lookup by DIE offset
148   uint32_t depth = 0;
149   // We are in our compile unit, parse starting at the offset
150   // we were told to parse
151 
152   const uint8_t *fixed_form_sizes =
153     DWARFFormValue::getFixedFormSizesForAddressSize(getAddressByteSize());
154 
155   while (offset < next_cu_offset &&
156          die.extractFast(this, fixed_form_sizes, &offset)) {
157 
158     if (depth == 0) {
159       uint64_t base_addr =
160         die.getAttributeValueAsUnsigned(this, DW_AT_low_pc, -1U);
161       if (base_addr == -1U)
162         base_addr = die.getAttributeValueAsUnsigned(this, DW_AT_entry_pc, 0);
163       setBaseAddress(base_addr);
164     }
165 
166     if (cu_die_only) {
167       addDIE(die);
168       return 1;
169     }
170     else if (depth == 0 && initial_die_array_size == 1) {
171       // Don't append the CU die as we already did that
172     } else {
173       addDIE (die);
174     }
175 
176     const DWARFAbbreviationDeclaration *abbrDecl =
177       die.getAbbreviationDeclarationPtr();
178     if (abbrDecl) {
179       // Normal DIE
180       if (abbrDecl->hasChildren())
181         ++depth;
182     } else {
183       // NULL DIE.
184       if (depth > 0)
185         --depth;
186       if (depth == 0)
187         break;  // We are done with this compile unit!
188     }
189 
190   }
191 
192   // Give a little bit of info if we encounter corrupt DWARF (our offset
193   // should always terminate at or before the start of the next compilation
194   // unit header).
195   if (offset > next_cu_offset) {
196     fprintf (stderr, "warning: DWARF compile unit extends beyond its bounds cu 0x%8.8x at 0x%8.8x'\n", getOffset(), offset);
197   }
198 
199   setDIERelations();
200   return DieArray.size();
201 }
202 
clearDIEs(bool keep_compile_unit_die)203 void DWARFCompileUnit::clearDIEs(bool keep_compile_unit_die) {
204   if (DieArray.size() > 1) {
205     // std::vectors never get any smaller when resized to a smaller size,
206     // or when clear() or erase() are called, the size will report that it
207     // is smaller, but the memory allocated remains intact (call capacity()
208     // to see this). So we need to create a temporary vector and swap the
209     // contents which will cause just the internal pointers to be swapped
210     // so that when "tmp_array" goes out of scope, it will destroy the
211     // contents.
212 
213     // Save at least the compile unit DIE
214     std::vector<DWARFDebugInfoEntryMinimal> tmpArray;
215     DieArray.swap(tmpArray);
216     if (keep_compile_unit_die)
217       DieArray.push_back(tmpArray.front());
218   }
219 }
220 
221 void
buildAddressRangeTable(DWARFDebugAranges * debug_aranges,bool clear_dies_if_already_not_parsed)222 DWARFCompileUnit::buildAddressRangeTable(DWARFDebugAranges *debug_aranges,
223                                          bool clear_dies_if_already_not_parsed){
224   // This function is usually called if there in no .debug_aranges section
225   // in order to produce a compile unit level set of address ranges that
226   // is accurate. If the DIEs weren't parsed, then we don't want all dies for
227   // all compile units to stay loaded when they weren't needed. So we can end
228   // up parsing the DWARF and then throwing them all away to keep memory usage
229   // down.
230   const bool clear_dies = extractDIEsIfNeeded(false) > 1;
231 
232   DieArray[0].buildAddressRangeTable(this, debug_aranges);
233 
234   // Keep memory down by clearing DIEs if this generate function
235   // caused them to be parsed.
236   if (clear_dies)
237     clearDIEs(true);
238 }
239