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[lld][ELF] Address last review comments.
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- Pulled body of loop that reads/parses IndexEntries into a
  separate function (readEntry)
- Removed unnecessary 'const' qualifiers on local vars
- Updated comment about handling type units
- Created getChunks accessor function; used it to eliminate use of
  'seq' in for-loop.
- Enhanced some error messages
- Update debug-names-bad.s test to handle udpated error messages
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@cmtice
cmtice committed Apr 18, 2024
1 parent 41580dd commit 254ceed
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Showing 3 changed files with 111 additions and 87 deletions.
190 changes: 105 additions & 85 deletions lld/ELF/SyntheticSections.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2734,14 +2734,99 @@ static uint32_t getDebugNamesHeaderSize(uint32_t augmentationStringSize) {
/* Augmentation string */ augmentationStringSize;
}

static Expected<DebugNamesBaseSection::IndexEntry *>
readEntry(uint64_t &offset, const DWARFDebugNames::NameIndex &ni,
uint64_t entriesBase, DWARFDataExtractor &namesExtractor,
const LLDDWARFSection &namesSec) {
std::string errMsg;
auto ie = makeThreadLocal<DebugNamesBaseSection::IndexEntry>();
ie->poolOffset = offset;
Error err = Error::success();
uint64_t ulebVal = namesExtractor.getULEB128(&offset, &err);
if (err) {
errMsg = ": invalid abbrev code in entry: ";
errMsg.append(toString(std::move(err)));
return createStringError(inconvertibleErrorCode(), errMsg.c_str());
}
if (ulebVal < UINT32_MAX)
ie->abbrevCode = static_cast<uint32_t>(ulebVal);
else {
errMsg = ": abbrev code in entry too large for DWARF32: ";
errMsg.append(std::to_string(ulebVal));
return createStringError(inconvertibleErrorCode(), errMsg.c_str());
}
auto it = ni.getAbbrevs().find_as(ie->abbrevCode);
if (it == ni.getAbbrevs().end()) {
errMsg = ": entry abbrev code not found in abbrev table: ";
errMsg.append(std::to_string(ie->abbrevCode));
return createStringError(inconvertibleErrorCode(), errMsg.c_str());
}

DebugNamesBaseSection::AttrValue attr, cuAttr = {0, 0};
for (DWARFDebugNames::AttributeEncoding a : it->Attributes) {
if (a.Index == dwarf::DW_IDX_parent) {
if (a.Form == dwarf::DW_FORM_ref4) {
attr.attrValue = namesExtractor.getU32(&offset, &err);
attr.attrSize = 4;
ie->parentOffset = entriesBase + attr.attrValue;
} else if (a.Form != DW_FORM_flag_present) {
errMsg = ": invalid form for DW_IDX_parent";
}
} else {
switch (a.Form) {
case DW_FORM_data1:
case DW_FORM_ref1: {
attr.attrValue = namesExtractor.getU8(&offset, &err);
attr.attrSize = 1;
break;
}
case DW_FORM_data2:
case DW_FORM_ref2: {
attr.attrValue = namesExtractor.getU16(&offset, &err);
attr.attrSize = 2;
break;
}
case DW_FORM_data4:
case DW_FORM_ref4: {
attr.attrValue = namesExtractor.getU32(&offset, &err);
attr.attrSize = 4;
break;
}
default:
errMsg = ": unrecognized form encoding ";
errMsg.append(std::to_string(a.Form));
errMsg.append(" in abbrev table");
return createStringError(inconvertibleErrorCode(), errMsg.c_str());
}
}
if (err) {
errMsg = ": error while reading attributes: ";
errMsg.append(toString(std::move(err)));
return createStringError(inconvertibleErrorCode(), errMsg.c_str());
}
if (a.Index == DW_IDX_compile_unit)
cuAttr = attr;
else if (a.Form != DW_FORM_flag_present)
ie->attrValues.push_back(attr);
}

// Canonicalize abbrev by placing the CU/TU index at the end.
ie->attrValues.push_back(cuAttr);

if (!errMsg.empty())
return createStringError(inconvertibleErrorCode(), errMsg.c_str());
else
return ie;
}

void DebugNamesBaseSection::parseDebugNames(
InputChunk &inputChunk, OutputChunk &chunk,
DWARFDataExtractor &namesExtractor, DataExtractor &strExtractor,
function_ref<SmallVector<uint32_t, 0>(
uint32_t numCus, const DWARFDebugNames::Header &,
const DWARFDebugNames::DWARFDebugNamesOffsets &)>
readOffsets) {
const LLDDWARFSection namesSec = inputChunk.section;
const LLDDWARFSection &namesSec = inputChunk.section;
DenseMap<uint32_t, IndexEntry *> offsetMap;
// Number of CUs seen in previous NameIndex sections within current chunk.
uint32_t numCus = 0;
Expand All @@ -2758,8 +2843,7 @@ void DebugNamesBaseSection::parseDebugNames(
Twine(nd.hdr.Version));
return;
}
const uint32_t dwarfSize =
dwarf::getDwarfOffsetByteSize(DwarfFormat::DWARF32);
uint32_t dwarfSize = dwarf::getDwarfOffsetByteSize(DwarfFormat::DWARF32);
DWARFDebugNames::DWARFDebugNamesOffsets locs = ni.getOffsets();
if (locs.EntriesBase > namesExtractor.getData().size()) {
errorOrWarn(toString(namesSec.sec) +
Expand All @@ -2782,83 +2866,23 @@ void DebugNamesBaseSection::parseDebugNames(
ne.hashValue = caseFoldingDjbHash(name);

// Read a series of index entries that end with abbreviation code 0.
const char *errMsg = nullptr;
std::string errMsg;
uint64_t offset = locs.EntriesBase + entryOffsets[i];
while (offset < namesSec.Data.size() && namesSec.Data[offset] != 0) {
// Read & store all entries (for the same string).
auto ie = makeThreadLocal<IndexEntry>();
ie->poolOffset = offset;
Error err = Error::success();
ie->abbrevCode =
static_cast<uint32_t>(namesExtractor.getULEB128(&offset, &err));
if (err) {
consumeError(std::move(err));
errMsg = ": invalid abbrev code in entry";
break;
Expected<IndexEntry *> ieOrErr =
readEntry(offset, ni, locs.EntriesBase, namesExtractor, namesSec);
if (!ieOrErr) {
errorOrWarn(toString(namesSec.sec) +
Twine(toString(ieOrErr.takeError())));
return;
}
auto it = ni.getAbbrevs().find_as(ie->abbrevCode);
if (it == ni.getAbbrevs().end()) {
errMsg = ": invalid abbrev code in entry";
break;
}

AttrValue attr, cuAttr = {0, 0};
for (DWARFDebugNames::AttributeEncoding a : it->Attributes) {
if (a.Index == dwarf::DW_IDX_parent) {
if (a.Form == dwarf::DW_FORM_ref4) {
attr.attrValue = namesExtractor.getU32(&offset, &err);
attr.attrSize = 4;
ie->parentOffset = locs.EntriesBase + attr.attrValue;
} else if (a.Form != DW_FORM_flag_present) {
errMsg = ": invalid form for DW_IDX_parent";
}
} else {
switch (a.Form) {
case DW_FORM_data1:
case DW_FORM_ref1: {
attr.attrValue = namesExtractor.getU8(&offset, &err);
attr.attrSize = 1;
break;
}
case DW_FORM_data2:
case DW_FORM_ref2: {
attr.attrValue = namesExtractor.getU16(&offset, &err);
attr.attrSize = 2;
break;
}
case DW_FORM_data4:
case DW_FORM_ref4: {
attr.attrValue = namesExtractor.getU32(&offset, &err);
attr.attrSize = 4;
break;
}
default:
errorOrWarn(toString(namesSec.sec) +
Twine(": unrecognized form encoding ") +
Twine(a.Form) + Twine(" in abbrev table"));
return;
}
}
if (err) {
errorOrWarn(toString(namesSec.sec) +
Twine(": error while reading attributes: ") +
toString(std::move(err)));
return;
}
if (a.Index == DW_IDX_compile_unit)
cuAttr = attr;
else if (a.Form != DW_FORM_flag_present)
ie->attrValues.push_back(attr);
}

// Canonicalize abbrev by placing the CU/TU index at the end.
ie->attrValues.push_back(cuAttr);
ne.indexEntries.push_back(std::move(ie));
ne.indexEntries.push_back(std::move(*ieOrErr));
}
if (offset >= namesSec.Data.size())
errMsg = ": index entry is out of bounds";
if (errMsg)
errorOrWarn(toString(namesSec.sec) + Twine(errMsg));
if (!errMsg.empty())
errorOrWarn(toString(namesSec.sec) + Twine(errMsg.c_str()));

for (IndexEntry &ie : ne.entries())
offsetMap[ie.poolOffset] = &ie;
Expand Down Expand Up @@ -2904,12 +2928,8 @@ void DebugNamesBaseSection::computeHdrAndAbbrevTable(
numCu += chunks[i].compUnits.size();
for (const NameData &nd : inputChunk.nameData) {
hdr.CompUnitCount += nd.hdr.CompUnitCount;
// We are not actually handling or emitting type units yet, so
// so non-zero type unit counts will crash LLD.
// TODO: Uncomment the two lines below when we implement this for
// type units & remove the following check/warning.
//hdr.LocalTypeUnitCount += nd.hdr.LocalTypeUnitCount;
//hdr.ForeignTypeUnitCount += nd.hdr.ForeignTypeUnitCount;
// TODO: We don't handle type units yet, so LocalTypeUnitCount &
// ForeignTypeUnitCount are left as 0.
if (nd.hdr.LocalTypeUnitCount || nd. hdr.ForeignTypeUnitCount)
warn(toString(inputChunk.section.sec) +
Twine(": type units are not implemented"));
Expand All @@ -2932,7 +2952,7 @@ void DebugNamesBaseSection::computeHdrAndAbbrevTable(
FoldingSet<Abbrev> abbrevSet;
// Determine the form for the DW_IDX_compile_unit attributes in the merged
// index. The input form may not be big enough for all CU indices.
const dwarf::Form cuAttrForm = getMergedCuCountForm(hdr.CompUnitCount).second;
dwarf::Form cuAttrForm = getMergedCuCountForm(hdr.CompUnitCount).second;
for (InputChunk &inputChunk : inputChunks) {
for (auto [i, ni] : enumerate(*inputChunk.llvmDebugNames)) {
for (const DWARFDebugNames::Abbrev &oldAbbrev : ni.getAbbrevs()) {
Expand Down Expand Up @@ -3003,10 +3023,10 @@ std::pair<uint32_t, uint32_t> DebugNamesBaseSection::computeEntryPool(
// Collect and de-duplicate all the names (preserving all the entries).
// Speed it up using multithreading, as the number of symbols can be in the
// order of millions.
const size_t concurrency =
size_t concurrency =
bit_floor(std::min<size_t>(config->threadCount, numShards));
const size_t shift = 32 - countr_zero(numShards);
const uint8_t cuAttrSize = getMergedCuCountForm(hdr.CompUnitCount).first;
size_t shift = 32 - countr_zero(numShards);
uint8_t cuAttrSize = getMergedCuCountForm(hdr.CompUnitCount).first;
DenseMap<CachedHashStringRef, size_t> maps[numShards];

parallelFor(0, concurrency, [&](size_t threadId) {
Expand Down Expand Up @@ -3237,8 +3257,8 @@ template <class ELFT> void DebugNamesSection<ELFT>::writeTo(uint8_t *buf) {
buf += hdr.AugmentationStringSize;

// Write the CU list.
for (auto i : seq(numChunks))
for (uint32_t cuOffset : chunks[i].compUnits)
for (auto &chunk : getChunks())
for (uint32_t cuOffset : chunk.compUnits)
endian::writeNext<uint32_t, ELFT::Endianness>(buf, cuOffset);

// TODO: Write the local TU list, then the foreign TU list..
Expand Down
4 changes: 4 additions & 0 deletions lld/ELF/SyntheticSections.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -892,6 +892,10 @@ class DebugNamesBaseSection : public SyntheticSection {
SmallVector<Abbrev *, 0> abbrevTable;
SmallVector<char, 0> abbrevTableBuf;

ArrayRef<OutputChunk> getChunks() {
return ArrayRef(chunks.get(), numChunks);
}

// Sharded name entries that will be used to compute bucket_count and the
// count name table.
static constexpr size_t numShards = 32;
Expand Down
4 changes: 2 additions & 2 deletions lld/test/ELF/debug-names-bad.s
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@
# RUN: llvm-mc -filetype=obj -triple=x86_64 bad-parent-form.s -o bad-parent-form.o
# RUN: not ld.lld --debug-names bad-parent-form.o 2>&1 | FileCheck %s --check-prefix=BAD-PARENT-FORM --implicit-check-not=error:

# BAD-PARENT-FORM-COUNT-2: error: bad-parent-form.o:(.debug_names): invalid form for DW_IDX_parent
# BAD-PARENT-FORM: error: bad-parent-form.o:(.debug_names): invalid form for DW_IDX_parent

# RUN: sed -E '/DW_IDX_die_offset/{n;s/[0-9]+.*DW_FORM_ref4/16/}' %S/Inputs/debug-names-a.s > bad-die-form.s
# RUN: llvm-mc -filetype=obj -triple=x86_64 bad-die-form.s -o bad-die-form.o
Expand All @@ -41,7 +41,7 @@
# RUN: ld.lld --debug-names bad-abbrev-code.o -o bad-abbrev-code --noinhibit-exec
# RUN: llvm-dwarfdump --debug-names bad-abbrev-code | FileCheck %s --check-prefix=BAD-ABBREV-CODE-DWARF

# BAD-ABBREV-CODE-COUNT-2: error: bad-abbrev-code.o:(.debug_names): invalid abbrev code in entry
# BAD-ABBREV-CODE: error: bad-abbrev-code.o:(.debug_names): entry abbrev code not found in abbrev table: 3

# BAD-ABBREV-CODE-DWARF: Abbreviations [
# BAD-ABBREV-CODE-DWARF-NEXT: Abbreviation 0x1 {
Expand Down

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