[DWARF v5] Rework of string offsets table reader
Reorganizes the DWARF consumer to derive the string offsets table
contribution's format from the contribution header instead of
(incorrectly) from the unit's format.
Reviewers: JDevliegehere, aprantl
Differential Revision: https://reviews.llvm.org/D41146
llvm-svn: 321295
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index a5defa9..5397994 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -88,70 +88,101 @@
}
}
-static void
-dumpDWARFv5StringOffsetsSection(raw_ostream &OS, StringRef SectionName,
- const DWARFObject &Obj,
- const DWARFSection &StringOffsetsSection,
- StringRef StringSection, bool LittleEndian) {
+using ContributionCollection =
+ std::vector<Optional<StrOffsetsContributionDescriptor>>;
+
+// Collect all the contributions to the string offsets table from all units,
+// sort them by their starting offsets and remove duplicates.
+static ContributionCollection
+collectContributionData(DWARFContext::cu_iterator_range CUs,
+ DWARFContext::tu_section_iterator_range TUSs) {
+ ContributionCollection Contributions;
+ for (const auto &CU : CUs)
+ Contributions.push_back(CU->getStringOffsetsTableContribution());
+ for (const auto &TUS : TUSs)
+ for (const auto &TU : TUS)
+ Contributions.push_back(TU->getStringOffsetsTableContribution());
+
+ // Sort the contributions so that any invalid ones are placed at
+ // the start of the contributions vector. This way they are reported
+ // first.
+ std::sort(Contributions.begin(), Contributions.end(),
+ [](const Optional<StrOffsetsContributionDescriptor> &L,
+ const Optional<StrOffsetsContributionDescriptor> &R) {
+ if (L && R) return L->Base < R->Base;
+ return R.hasValue();
+ });
+
+ // Uniquify contributions, as it is possible that units (specifically
+ // type units in dwo or dwp files) share contributions. We don't want
+ // to report them more than once.
+ Contributions.erase(
+ std::unique(Contributions.begin(), Contributions.end(),
+ [](const Optional<StrOffsetsContributionDescriptor> &L,
+ const Optional<StrOffsetsContributionDescriptor> &R) {
+ if (L && R)
+ return L->Base == R->Base && L->Size == R->Size;
+ return false;
+ }),
+ Contributions.end());
+ return Contributions;
+}
+
+static void dumpDWARFv5StringOffsetsSection(
+ raw_ostream &OS, StringRef SectionName, const DWARFObject &Obj,
+ const DWARFSection &StringOffsetsSection, StringRef StringSection,
+ DWARFContext::cu_iterator_range CUs,
+ DWARFContext::tu_section_iterator_range TUSs, bool LittleEndian) {
+ auto Contributions = collectContributionData(CUs, TUSs);
DWARFDataExtractor StrOffsetExt(Obj, StringOffsetsSection, LittleEndian, 0);
- uint32_t Offset = 0;
+ DataExtractor StrData(StringSection, LittleEndian, 0);
uint64_t SectionSize = StringOffsetsSection.Data.size();
-
- while (Offset < SectionSize) {
- unsigned Version = 0;
- DwarfFormat Format = DWARF32;
- unsigned EntrySize = 4;
- // Perform validation and extract the segment size from the header.
- if (!StrOffsetExt.isValidOffsetForDataOfSize(Offset, 4)) {
- OS << "error: invalid contribution to string offsets table in section ."
- << SectionName << ".\n";
- return;
- }
- uint32_t ContributionStart = Offset;
- uint64_t ContributionSize = StrOffsetExt.getU32(&Offset);
- // A contribution size of 0xffffffff indicates DWARF64, with the actual size
- // in the following 8 bytes. Otherwise, the DWARF standard mandates that
- // the contribution size must be at most 0xfffffff0.
- if (ContributionSize == 0xffffffff) {
- if (!StrOffsetExt.isValidOffsetForDataOfSize(Offset, 8)) {
- OS << "error: invalid contribution to string offsets table in section ."
- << SectionName << ".\n";
- return;
- }
- Format = DWARF64;
- EntrySize = 8;
- ContributionSize = StrOffsetExt.getU64(&Offset);
- } else if (ContributionSize > 0xfffffff0) {
+ uint32_t Offset = 0;
+ for (auto &Contribution : Contributions) {
+ // Report an ill-formed contribution.
+ if (!Contribution) {
OS << "error: invalid contribution to string offsets table in section ."
<< SectionName << ".\n";
return;
}
- // We must ensure that we don't read a partial record at the end, so we
- // validate for a multiple of EntrySize. Also, we're expecting a version
- // number and padding, which adds an additional 4 bytes.
- uint64_t ValidationSize =
- 4 + ((ContributionSize + EntrySize - 1) & (-(uint64_t)EntrySize));
- if (!StrOffsetExt.isValidOffsetForDataOfSize(Offset, ValidationSize)) {
- OS << "error: contribution to string offsets table in section ."
- << SectionName << " has invalid length.\n";
+ dwarf::DwarfFormat Format = Contribution->getFormat();
+ uint16_t Version = Contribution->getVersion();
+ uint64_t ContributionHeader = Contribution->Base;
+ // In DWARF v5 there is a contribution header that immediately precedes
+ // the string offsets base (the location we have previously retrieved from
+ // the CU DIE's DW_AT_str_offsets attribute). The header is located either
+ // 8 or 16 bytes before the base, depending on the contribution's format.
+ if (Version >= 5)
+ ContributionHeader -= Format == DWARF32 ? 8 : 16;
+
+ // Detect overlapping contributions.
+ if (Offset > ContributionHeader) {
+ OS << "error: overlapping contributions to string offsets table in "
+ "section ."
+ << SectionName << ".\n";
return;
}
-
- Version = StrOffsetExt.getU16(&Offset);
- Offset += 2;
- OS << format("0x%8.8x: ", ContributionStart);
- OS << "Contribution size = " << ContributionSize
+ // Report a gap in the table.
+ if (Offset < ContributionHeader) {
+ OS << format("0x%8.8x: Gap, length = ", Offset);
+ OS << (ContributionHeader - Offset) << "\n";
+ }
+ OS << format("0x%8.8x: ", ContributionHeader);
+ OS << "Contribution size = " << Contribution->Size
+ << ", Format = " << (Format == DWARF32 ? "DWARF32" : "DWARF64")
<< ", Version = " << Version << "\n";
- uint32_t ContributionBase = Offset;
- DataExtractor StrData(StringSection, LittleEndian, 0);
- while (Offset - ContributionBase < ContributionSize) {
+ Offset = Contribution->Base;
+ unsigned EntrySize = Contribution->getDwarfOffsetByteSize();
+ while (Offset - Contribution->Base < Contribution->Size) {
OS << format("0x%8.8x: ", Offset);
- // FIXME: We can only extract strings in DWARF32 format at the moment.
+ // FIXME: We can only extract strings if the offset fits in 32 bits.
uint64_t StringOffset =
StrOffsetExt.getRelocatedValue(EntrySize, &Offset);
- if (Format == DWARF32) {
+ // Extract the string if we can and display it. Otherwise just report
+ // the offset.
+ if (StringOffset <= std::numeric_limits<uint32_t>::max()) {
uint32_t StringOffset32 = (uint32_t)StringOffset;
OS << format("%8.8x ", StringOffset32);
const char *S = StrData.getCStr(&StringOffset32);
@@ -162,6 +193,11 @@
OS << "\n";
}
}
+ // Report a gap at the end of the table.
+ if (Offset < SectionSize) {
+ OS << format("0x%8.8x: Gap, length = ", Offset);
+ OS << (SectionSize - Offset) << "\n";
+ }
}
// Dump a DWARF string offsets section. This may be a DWARF v5 formatted
@@ -170,17 +206,18 @@
// a header containing size and version number. Alternatively, it may be a
// monolithic series of string offsets, as generated by the pre-DWARF v5
// implementation of split DWARF.
-static void dumpStringOffsetsSection(raw_ostream &OS, StringRef SectionName,
- const DWARFObject &Obj,
- const DWARFSection &StringOffsetsSection,
- StringRef StringSection, bool LittleEndian,
- unsigned MaxVersion) {
+static void dumpStringOffsetsSection(
+ raw_ostream &OS, StringRef SectionName, const DWARFObject &Obj,
+ const DWARFSection &StringOffsetsSection, StringRef StringSection,
+ DWARFContext::cu_iterator_range CUs,
+ DWARFContext::tu_section_iterator_range TUSs, bool LittleEndian,
+ unsigned MaxVersion) {
// If we have at least one (compile or type) unit with DWARF v5 or greater,
// we assume that the section is formatted like a DWARF v5 string offsets
// section.
if (MaxVersion >= 5)
dumpDWARFv5StringOffsetsSection(OS, SectionName, Obj, StringOffsetsSection,
- StringSection, LittleEndian);
+ StringSection, CUs, TUSs, LittleEndian);
else {
DataExtractor strOffsetExt(StringOffsetsSection.Data, LittleEndian, 0);
uint32_t offset = 0;
@@ -468,12 +505,14 @@
DObj->getStringOffsetSection().Data))
dumpStringOffsetsSection(
OS, "debug_str_offsets", *DObj, DObj->getStringOffsetSection(),
- DObj->getStringSection(), isLittleEndian(), getMaxVersion());
+ DObj->getStringSection(), compile_units(), type_unit_sections(),
+ isLittleEndian(), getMaxVersion());
if (shouldDump(ExplicitDWO, ".debug_str_offsets.dwo", DIDT_ID_DebugStrOffsets,
DObj->getStringOffsetDWOSection().Data))
dumpStringOffsetsSection(
OS, "debug_str_offsets.dwo", *DObj, DObj->getStringOffsetDWOSection(),
- DObj->getStringDWOSection(), isLittleEndian(), getMaxVersion());
+ DObj->getStringDWOSection(), dwo_compile_units(),
+ dwo_type_unit_sections(), isLittleEndian(), getMaxVersion());
if (shouldDump(Explicit, ".gnu_index", DIDT_ID_GdbIndex,
DObj->getGdbIndexSection())) {
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index c3d8ff2..e24ef90 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -79,8 +79,10 @@
bool DWARFUnit::getStringOffsetSectionItem(uint32_t Index,
uint64_t &Result) const {
- unsigned ItemSize = getDwarfOffsetByteSize();
- uint32_t Offset = StringOffsetSectionBase + Index * ItemSize;
+ if (!StringOffsetsTableContribution)
+ return false;
+ unsigned ItemSize = getDwarfStringOffsetsByteSize();
+ uint32_t Offset = getStringOffsetsBase() + Index * ItemSize;
if (StringOffsetSection.Data.size() < Offset + ItemSize)
return false;
DWARFDataExtractor DA(Context.getDWARFObj(), StringOffsetSection,
@@ -251,15 +253,28 @@
RangeSectionBase = toSectionOffset(UnitDie.find(DW_AT_rnglists_base), 0);
}
- // In general, we derive the offset of the unit's contibution to the
- // debug_str_offsets{.dwo} section from the unit DIE's
- // DW_AT_str_offsets_base attribute. In dwp files we add to it the offset
- // we get from the index table.
- StringOffsetSectionBase =
- toSectionOffset(UnitDie.find(DW_AT_str_offsets_base), 0);
+ // In general, in DWARF v5 and beyond we derive the start of the unit's
+ // contribution to the string offsets table from the unit DIE's
+ // DW_AT_str_offsets_base attribute. Split DWARF units do not use this
+ // attribute, so we assume that there is a contribution to the string
+ // offsets table starting at offset 0 of the debug_str_offsets.dwo section.
+ // In both cases we need to determine the format of the contribution,
+ // which may differ from the unit's format.
+ uint64_t StringOffsetsContributionBase =
+ isDWO ? 0 : toSectionOffset(UnitDie.find(DW_AT_str_offsets_base), 0);
if (IndexEntry)
if (const auto *C = IndexEntry->getOffset(DW_SECT_STR_OFFSETS))
- StringOffsetSectionBase += C->Offset;
+ StringOffsetsContributionBase += C->Offset;
+
+ DWARFDataExtractor DA(Context.getDWARFObj(), StringOffsetSection,
+ isLittleEndian, 0);
+ if (isDWO)
+ StringOffsetsTableContribution =
+ determineStringOffsetsTableContributionDWO(
+ DA, StringOffsetsContributionBase);
+ else if (getVersion() >= 5)
+ StringOffsetsTableContribution = determineStringOffsetsTableContribution(
+ DA, StringOffsetsContributionBase);
// Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
// skeleton CU DIE, so that DWARF users not aware of it are not broken.
@@ -466,3 +481,89 @@
Abbrevs = Abbrev->getAbbreviationDeclarationSet(AbbrOffset);
return Abbrevs;
}
+
+Optional<StrOffsetsContributionDescriptor>
+StrOffsetsContributionDescriptor::validateContributionSize(
+ DWARFDataExtractor &DA) {
+ uint8_t EntrySize = getDwarfOffsetByteSize();
+ // In order to ensure that we don't read a partial record at the end of
+ // the section we validate for a multiple of the entry size.
+ uint64_t ValidationSize = alignTo(Size, EntrySize);
+ // Guard against overflow.
+ if (ValidationSize >= Size)
+ if (DA.isValidOffsetForDataOfSize((uint32_t)Base, ValidationSize))
+ return *this;
+ return Optional<StrOffsetsContributionDescriptor>();
+}
+
+// Look for a DWARF64-formatted contribution to the string offsets table
+// starting at a given offset and record it in a descriptor.
+static Optional<StrOffsetsContributionDescriptor>
+parseDWARF64StringOffsetsTableHeader(DWARFDataExtractor &DA, uint32_t Offset) {
+ if (!DA.isValidOffsetForDataOfSize(Offset, 16))
+ return Optional<StrOffsetsContributionDescriptor>();
+
+ if (DA.getU32(&Offset) != 0xffffffff)
+ return Optional<StrOffsetsContributionDescriptor>();
+
+ uint64_t Size = DA.getU64(&Offset);
+ uint8_t Version = DA.getU16(&Offset);
+ (void)DA.getU16(&Offset); // padding
+ return StrOffsetsContributionDescriptor(Offset, Size, Version, DWARF64);
+ //return Optional<StrOffsetsContributionDescriptor>(Descriptor);
+}
+
+// Look for a DWARF32-formatted contribution to the string offsets table
+// starting at a given offset and record it in a descriptor.
+static Optional<StrOffsetsContributionDescriptor>
+parseDWARF32StringOffsetsTableHeader(DWARFDataExtractor &DA, uint32_t Offset) {
+ if (!DA.isValidOffsetForDataOfSize(Offset, 8))
+ return Optional<StrOffsetsContributionDescriptor>();
+ uint32_t ContributionSize = DA.getU32(&Offset);
+ if (ContributionSize >= 0xfffffff0)
+ return Optional<StrOffsetsContributionDescriptor>();
+ uint8_t Version = DA.getU16(&Offset);
+ (void)DA.getU16(&Offset); // padding
+ return StrOffsetsContributionDescriptor(Offset, ContributionSize, Version, DWARF32);
+ //return Optional<StrOffsetsContributionDescriptor>(Descriptor);
+}
+
+Optional<StrOffsetsContributionDescriptor>
+DWARFUnit::determineStringOffsetsTableContribution(DWARFDataExtractor &DA,
+ uint64_t Offset) {
+ Optional<StrOffsetsContributionDescriptor> Descriptor;
+ // Attempt to find a DWARF64 contribution 16 bytes before the base.
+ if (Offset >= 16)
+ Descriptor =
+ parseDWARF64StringOffsetsTableHeader(DA, (uint32_t)Offset - 16);
+ // Try to find a DWARF32 contribution 8 bytes before the base.
+ if (!Descriptor && Offset >= 8)
+ Descriptor = parseDWARF32StringOffsetsTableHeader(DA, (uint32_t)Offset - 8);
+ return Descriptor ? Descriptor->validateContributionSize(DA) : Descriptor;
+}
+
+Optional<StrOffsetsContributionDescriptor>
+DWARFUnit::determineStringOffsetsTableContributionDWO(DWARFDataExtractor &DA,
+ uint64_t Offset) {
+ if (getVersion() >= 5) {
+ // Look for a valid contribution at the given offset.
+ auto Descriptor =
+ parseDWARF64StringOffsetsTableHeader(DA, (uint32_t)Offset);
+ if (!Descriptor)
+ Descriptor = parseDWARF32StringOffsetsTableHeader(DA, (uint32_t)Offset);
+ return Descriptor ? Descriptor->validateContributionSize(DA) : Descriptor;
+ }
+ // Prior to DWARF v5, we derive the contribution size from the
+ // index table (in a package file). In a .dwo file it is simply
+ // the length of the string offsets section.
+ uint64_t Size = 0;
+ if (!IndexEntry)
+ Size = StringOffsetSection.Data.size();
+ else if (const auto *C = IndexEntry->getOffset(DW_SECT_STR_OFFSETS))
+ Size = C->Length;
+ // Return a descriptor with the given offset as base, version 4 and
+ // DWARF32 format.
+ //return Optional<StrOffsetsContributionDescriptor>(
+ //StrOffsetsContributionDescriptor(Offset, Size, 4, DWARF32));
+ return StrOffsetsContributionDescriptor(Offset, Size, 4, DWARF32);
+}