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DebugInfo: Rebuild dwp debug_info index column from v5 indexes more r…
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…obustly

the v4 rebuilding is a best-effort because it's not possible to reliably
parse the DWO ID as it requires the abbrev section (& if the index isn't
trustworthy then there's no way to find the associated abbrev section
contribution for a given info section contribution)

But in v5 the DWO ID/type signature is in the header and can be rebuilt
losslessly (only at the cost of performance of rescanning/parsing the
headers of all the units), so let's implement that.

the testing isn't /ideal/ - I think the testing should've been
implemented as a hardcoded dwp file with a corrupted/incorrect index,
then the test could've demonstrated that reparsing the index produces
the right answer - but this is a quick port of the existing v5 test back
to v4 so that we don't lose coverage on the v4 codepath now that it's
separated from the v5 codepath.

Differential Revision: https://reviews.llvm.org/D146662
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@dwblaikie
dwblaikie committed Mar 28, 2023
1 parent 4d4c0f9 commit 22afe19
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Showing 2 changed files with 132 additions and 4 deletions.
57 changes: 53 additions & 4 deletions llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
View file
Expand Up @@ -48,6 +48,7 @@
#include "llvm/Support/Error.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"
Expand Down Expand Up @@ -779,7 +780,7 @@ bool DWARFContext::verify(raw_ostream &OS, DIDumpOptions DumpOpts) {
return Success;
}

void fixupIndex(const DWARFObject &DObj, DWARFContext &C,
void fixupIndexV4(const DWARFObject &DObj, DWARFContext &C,
DWARFUnitIndex &Index) {
using EntryType = DWARFUnitIndex::Entry::SectionContribution;
using EntryMap = DenseMap<uint32_t, EntryType>;
Expand Down Expand Up @@ -847,14 +848,62 @@ void fixupIndex(const DWARFObject &DObj, DWARFContext &C,
return;
}

void fixupIndexV5(const DWARFObject &DObj, DWARFContext &C,
DWARFUnitIndex &Index) {
DenseMap<uint64_t, uint64_t> Map;

DObj.forEachInfoDWOSections([&](const DWARFSection &S) {
if (!(C.getParseCUTUIndexManually() ||
S.Data.size() >= std::numeric_limits<uint32_t>::max()))
return;
DWARFDataExtractor Data(DObj, S, C.isLittleEndian(), 0);
uint64_t Offset = 0;
while (Data.isValidOffset(Offset)) {
DWARFUnitHeader Header;
if (!Header.extract(C, Data, &Offset, DWARFSectionKind::DW_SECT_INFO)) {
logAllUnhandledErrors(
createError("Failed to parse unit header in DWP file"), errs());
break;
}
bool CU = Header.getUnitType() == DW_UT_split_compile;
uint64_t Sig = CU ? *Header.getDWOId() : Header.getTypeHash();
Map[Sig] = Header.getOffset();
Offset = Header.getNextUnitOffset();
}
});
for (DWARFUnitIndex::Entry &E : Index.getMutableRows()) {
if (!E.isValid())
continue;
DWARFUnitIndex::Entry::SectionContribution &CUOff = E.getContribution();
auto Iter = Map.find(E.getSignature());
if (Iter == Map.end()) {
logAllUnhandledErrors(
createError("Could not find unit with signature 0x" +
Twine::utohexstr(E.getSignature()) + " in the Map"),
errs());
break;
}
CUOff.setOffset(Iter->second);
}
}

void fixupIndex(const DWARFObject &DObj, DWARFContext &C,
DWARFUnitIndex &Index) {
if (Index.getVersion() < 5)
fixupIndexV4(DObj, C, Index);
else
fixupIndexV5(DObj, C, Index);
}

const DWARFUnitIndex &DWARFContext::getCUIndex() {
if (CUIndex)
return *CUIndex;

DataExtractor CUIndexData(DObj->getCUIndexSection(), isLittleEndian(), 0);
CUIndex = std::make_unique<DWARFUnitIndex>(DW_SECT_INFO);
CUIndex->parse(CUIndexData);
fixupIndex(*DObj, *this, *CUIndex.get());
bool IsParseSuccessful = CUIndex->parse(CUIndexData);
if (IsParseSuccessful)
fixupIndex(*DObj, *this, *CUIndex);
return *CUIndex;
}

Expand All @@ -868,7 +917,7 @@ const DWARFUnitIndex &DWARFContext::getTUIndex() {
// If we are parsing TU-index and for .debug_types section we don't need
// to do anything.
if (isParseSuccessful && TUIndex->getVersion() != 2)
fixupIndex(*DObj, *this, *TUIndex.get());
fixupIndex(*DObj, *this, *TUIndex);
return *TUIndex;
}

Expand Down
79 changes: 79 additions & 0 deletions llvm/test/tools/llvm-dwp/X86/cu_tu_units_manual_v4.s
View file
@@ -0,0 +1,79 @@
# This test checks if we can correctly parse manull cu and tu index for DWARF4.

# RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o %t.o \
# RUN: -split-dwarf-file=%t.dwo -dwarf-version=4
# RUN: llvm-dwp %t.dwo -o %t.dwp
# RUN: llvm-dwarfdump -debug-info -debug-types -debug-cu-index -debug-tu-index %t.dwp | FileCheck %s
# RUN: llvm-dwarfdump -debug-info -debug-types -debug-cu-index -debug-tu-index -manaully-generate-unit-index %t.dwp | FileCheck %s

## Note: In order to check whether the type unit index is generated
## there is no need to add the missing DIEs for the structure type of the type unit.

# CHECK-DAG: .debug_info.dwo contents:
# CHECK: 0x00000000: Compile Unit: length = 0x00000010, format = DWARF32, version = 0x0004, abbr_offset = 0x0000, addr_size = 0x08 (next unit at 0x00000014)
# CHECK: DW_AT_GNU_dwo_id ([[CUID1:.*]])
# CHECK-DAG: .debug_types.dwo contents:
# CHECK: 0x00000000: Type Unit: length = 0x00000016, format = DWARF32, version = 0x0004, abbr_offset = 0x0000, addr_size = 0x08, name = '', type_signature = [[TUID1:.*]], type_offset = 0x0019 (next unit at 0x0000001a)
# CHECK: 0x0000001a: Type Unit: length = 0x00000016, format = DWARF32, version = 0x0004, abbr_offset = 0x0000, addr_size = 0x08, name = '', type_signature = [[TUID2:.*]], type_offset = 0x0019 (next unit at 0x00000034)
# CHECK-DAG: .debug_cu_index contents:
# CHECK: version = 2, units = 1, slots = 2
# CHECK: Index Signature INFO ABBREV
# CHECK: 2 [[CUID1]] [0x0000000000000000, 0x0000000000000014) [0x00000000, 0x00000013)
# CHECK-DAG: .debug_tu_index contents:
# CHECK: version = 2, units = 2, slots = 4
# CHECK: Index Signature TYPES ABBREV
# CHECK: 1 [[TUID1]] [0x0000000000000000, 0x000000000000001a) [0x00000000, 0x00000013)
# CHECK: 4 [[TUID2]] [0x000000000000001a, 0x0000000000000034) [0x00000000, 0x00000013)

.section .debug_types.dwo,"e",@progbits
.long .Ldebug_info_dwo_end0-.Ldebug_info_dwo_start0 # Length of Unit
.Ldebug_info_dwo_start0:
.short 4 # DWARF version number
.long 0 # Offset Into Abbrev. Section
.byte 8 # Address Size (in bytes)
.quad 5657452045627120676 # Type Signature
.long 25 # Type DIE Offset
.byte 2 # Abbrev [2] DW_TAG_type_unit
.byte 3 # Abbrev [3] DW_TAG_structure_type
.byte 0 # End Of Children Mark
.Ldebug_info_dwo_end0:
.section .debug_types.dwo,"e",@progbits
.long .Ldebug_info_dwo_end1-.Ldebug_info_dwo_start1 # Length of Unit
.Ldebug_info_dwo_start1:
.short 4 # DWARF version number
.long 0 # Offset Into Abbrev. Section
.byte 8 # Address Size (in bytes)
.quad -8528522068957683993 # Type Signature
.long 25 # Type DIE Offset
.byte 2 # Abbrev [2] DW_TAG_type_unit
.byte 3 # Abbrev [3] DW_TAG_structure_type
.byte 0 # End Of Children Mark
.Ldebug_info_dwo_end1:
.section .debug_info.dwo,"e",@progbits
.long .Ldebug_info_dwo_end2-.Ldebug_info_dwo_start2 # Length of Unit
.Ldebug_info_dwo_start2:
.short 4 # DWARF version number
.long 0 # Offset Into Abbrev. Section
.byte 8 # Address Size (in bytes)
.byte 1 # Abbrev [1] DW_TAG_compile_unit
.quad -6619898858003450627 # DW_AT_GNU_dwo_id
.Ldebug_info_dwo_end2:
.section .debug_abbrev.dwo,"e",@progbits
.byte 1 # Abbreviation Code
.byte 17 # DW_TAG_compile_unit
.byte 0 # DW_CHILDREN_no
.ascii "\261B" # DW_AT_GNU_dwo_id
.byte 7 # DW_FORM_data8
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 2 # Abbreviation Code
.byte 65 # DW_TAG_type_unit
.byte 1 # DW_CHILDREN_yes
.byte 0 # EOM
.byte 0 # EOM
.byte 3 # Abbreviation Code
.byte 0x13 # DW_TAG_structure_unit
.byte 0 # DW_CHILDREN_no
.byte 0 # EOM
.byte 0 # EOM
.byte 0 # EOM

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