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libDebugInfoDWARF: Don't try to parse loclist[.dwo] headers when pars…
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…ing debug_info[.dwo]

There's no way to know whether there's a loclist contribution to parse
if there's no loclistx encoding - and if there is one, there's no need
to walk back from the loclist_base (or, uin the case of
info.dwo/loclist.dwo - starting at 0 in the contribution) to parse the
header, instead rely on the DWARF32/64 and address size in the CU
that's already available.

This would come up in split DWARF (non-split wouldn't try to read a
loclist header in the absence of a loclist_base) when one unit had
location lists and another does not (because the loclists.dwo section
would be non-empty in that case - in the case where it's empty the
parsing would silently skip).

Simplify the testing a bit, rather than needing a whole dwp, etc - by
creating a malformed loclists.dwo section (and use single file Split
DWARF) that would trip up any attempt to parse it - but no attempt
should be made.
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@dwblaikie
dwblaikie committed Oct 14, 2020
1 parent bd05afc commit 9670a45
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Showing 3 changed files with 265 additions and 76 deletions.
18 changes: 2 additions & 16 deletions llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
View file
Expand Up @@ -209,7 +209,6 @@ class DWARFUnit {
const DWARFDebugAbbrev *Abbrev;
const DWARFSection *RangeSection;
uint64_t RangeSectionBase;
const DWARFSection *LocSection;
uint64_t LocSectionBase;

/// Location table of this unit.
Expand All @@ -228,9 +227,6 @@ class DWARFUnit {
/// offsets table (DWARF v5).
Optional<StrOffsetsContributionDescriptor> StringOffsetsTableContribution;

/// A table of range lists (DWARF v5 and later).
Optional<DWARFListTableHeader> LoclistTableHeader;

mutable const DWARFAbbreviationDeclarationSet *Abbrevs;
llvm::Optional<object::SectionedAddress> BaseAddr;
/// The compile unit debug information entry items.
Expand Down Expand Up @@ -318,10 +314,6 @@ class DWARFUnit {
RangeSection = RS;
RangeSectionBase = Base;
}
void setLocSection(const DWARFSection *LS, uint64_t Base) {
LocSection = LS;
LocSectionBase = Base;
}

uint64_t getLocSectionBase() const {
return LocSectionBase;
Expand Down Expand Up @@ -418,14 +410,8 @@ class DWARFUnit {
/// DW_FORM_rnglistx.
Optional<uint64_t> getRnglistOffset(uint32_t Index);

Optional<uint64_t> getLoclistOffset(uint32_t Index) {
if (!LoclistTableHeader)
return None;
if (Optional<uint64_t> Off =
LoclistTableHeader->getOffsetEntry(LocTable->getData(), Index))
return *Off + getLocSectionBase();
return None;
}
Optional<uint64_t> getLoclistOffset(uint32_t Index);

Expected<DWARFAddressRangesVector> collectAddressRanges();

Expected<DWARFLocationExpressionsVector>
Expand Down
93 changes: 33 additions & 60 deletions llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
View file
Expand Up @@ -181,31 +181,6 @@ DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
StringOffsetSection(SOS), AddrOffsetSection(AOS), isLittleEndian(LE),
IsDWO(IsDWO), UnitVector(UnitVector) {
clear();
if (IsDWO) {
// If we are reading a package file, we need to adjust the location list
// data based on the index entries.
StringRef Data = Header.getVersion() >= 5
? Context.getDWARFObj().getLoclistsDWOSection().Data
: LocSection->Data;
if (auto *IndexEntry = Header.getIndexEntry())
if (const auto *C = IndexEntry->getContribution(
Header.getVersion() >= 5 ? DW_SECT_LOCLISTS : DW_SECT_EXT_LOC))
Data = Data.substr(C->Offset, C->Length);

DWARFDataExtractor DWARFData(Data, isLittleEndian, getAddressByteSize());
LocTable =
std::make_unique<DWARFDebugLoclists>(DWARFData, Header.getVersion());
} else if (Header.getVersion() >= 5) {
LocTable = std::make_unique<DWARFDebugLoclists>(
DWARFDataExtractor(Context.getDWARFObj(),
Context.getDWARFObj().getLoclistsSection(),
isLittleEndian, getAddressByteSize()),
Header.getVersion());
} else {
LocTable = std::make_unique<DWARFDebugLoc>(
DWARFDataExtractor(Context.getDWARFObj(), *LocSection, isLittleEndian,
getAddressByteSize()));
}
}

DWARFUnit::~DWARFUnit() = default;
Expand Down Expand Up @@ -492,8 +467,8 @@ Error DWARFUnit::tryExtractDIEsIfNeeded(bool CUDieOnly) {
// describe address ranges.
if (getVersion() >= 5) {
// In case of DWP, the base offset from the index has to be added.
uint64_t ContributionBaseOffset = 0;
if (IsDWO) {
uint64_t ContributionBaseOffset = 0;
if (auto *IndexEntry = Header.getIndexEntry())
if (auto *Contrib = IndexEntry->getContribution(DW_SECT_RNGLISTS))
ContributionBaseOffset = Contrib->Offset;
Expand All @@ -506,42 +481,33 @@ Error DWARFUnit::tryExtractDIEsIfNeeded(bool CUDieOnly) {
toSectionOffset(UnitDie.find(DW_AT_rnglists_base),
DWARFListTableHeader::getHeaderSize(
Header.getFormat())));
}

// In a split dwarf unit, there is no DW_AT_loclists_base attribute.
// Setting LocSectionBase to point past the table header.
if (IsDWO) {
auto &DWOSection = Context.getDWARFObj().getLoclistsDWOSection();
if (DWOSection.Data.empty())
return Error::success();
setLocSection(&DWOSection,
DWARFListTableHeader::getHeaderSize(Header.getFormat()));
} else if (auto X = UnitDie.find(DW_AT_loclists_base)) {
setLocSection(&Context.getDWARFObj().getLoclistsSection(),
toSectionOffset(X, 0));
} else {
return Error::success();
}
if (IsDWO) {
// If we are reading a package file, we need to adjust the location list
// data based on the index entries.
StringRef Data = Header.getVersion() >= 5
? Context.getDWARFObj().getLoclistsDWOSection().Data
: Context.getDWARFObj().getLocDWOSection().Data;
if (auto *IndexEntry = Header.getIndexEntry())
if (const auto *C = IndexEntry->getContribution(
Header.getVersion() >= 5 ? DW_SECT_LOCLISTS : DW_SECT_EXT_LOC))
Data = Data.substr(C->Offset, C->Length);

if (LocSection) {
if (IsDWO)
LoclistTableHeader.emplace(".debug_loclists.dwo", "locations");
else
LoclistTableHeader.emplace(".debug_loclists", "locations");

uint64_t HeaderSize = DWARFListTableHeader::getHeaderSize(Header.getFormat());
uint64_t Offset = getLocSectionBase();
const DWARFDataExtractor &Data = LocTable->getData();
if (Offset < HeaderSize)
return createStringError(errc::invalid_argument,
"did not detect a valid"
" list table with base = 0x%" PRIx64 "\n",
Offset);
Offset -= HeaderSize;
if (Error E = LoclistTableHeader->extract(Data, &Offset))
return createStringError(errc::invalid_argument,
"parsing a loclist table: " +
toString(std::move(E)));
}
DWARFDataExtractor DWARFData(Data, isLittleEndian, getAddressByteSize());
LocTable =
std::make_unique<DWARFDebugLoclists>(DWARFData, Header.getVersion());
LocSectionBase = DWARFListTableHeader::getHeaderSize(Header.getFormat());
} else if (getVersion() >= 5) {
LocTable = std::make_unique<DWARFDebugLoclists>(
DWARFDataExtractor(Context.getDWARFObj(),
Context.getDWARFObj().getLoclistsSection(),
isLittleEndian, getAddressByteSize()),
getVersion());
} else {
LocTable = std::make_unique<DWARFDebugLoc>(DWARFDataExtractor(
Context.getDWARFObj(), Context.getDWARFObj().getLocSection(),
isLittleEndian, getAddressByteSize()));
}

// Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
Expand Down Expand Up @@ -981,3 +947,10 @@ Optional<uint64_t> DWARFUnit::getRnglistOffset(uint32_t Index) {
return *Off + RangeSectionBase;
return None;
}

Optional<uint64_t> DWARFUnit::getLoclistOffset(uint32_t Index) {
if (Optional<uint64_t> Off = llvm::DWARFListTableHeader::getOffsetEntry(
LocTable->getData(), LocSectionBase, getFormat(), Index))
return *Off + LocSectionBase;
return None;
}
230 changes: 230 additions & 0 deletions llvm/test/tools/llvm-dwarfdump/X86/debug_loclists_unused_invalid.s
View file
@@ -0,0 +1,230 @@
# REQUIRES: x86-registered-target

# RUN: rm -rf %t
# RUN: mkdir %t
# RUN: cd %t
# RUN: llvm-mc %s -dwarf-version=5 -filetype obj -triple x86_64-pc-linux -o main.o
# RUN: llvm-dwarfdump main.o 2>&1 | FileCheck %s

# CHECK: .debug_info.dwo contents:
# CHECK-NEXT: Compile Unit:
# CHECK-EMPTY:
# CHECK-NEXT: compile_unit

.text
.file "main.cpp"
.globl main # -- Begin function main
.p2align 4, 0x90
.type main,@function
main: # @main
.Lfunc_begin0:
.file 0 "/usr/local/google/home/blaikie/dev/scratch" "main.cpp" md5 0x277b2d67900f5d0f46c9638ad2528ff1
.loc 0 1 0 # main.cpp:1:0
.cfi_startproc
# %bb.0: # %entry
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset %rbp, -16
movq %rsp, %rbp
.cfi_def_cfa_register %rbp
xorl %eax, %eax
.Ltmp0:
.loc 0 2 1 prologue_end # main.cpp:2:1
popq %rbp
.cfi_def_cfa %rsp, 8
retq
.Ltmp1:
.Lfunc_end0:
.size main, .Lfunc_end0-main
.cfi_endproc
# -- End function
.section .debug_abbrev,"",@progbits
.byte 1 # Abbreviation Code
.byte 74 # DW_TAG_skeleton_unit
.byte 0 # DW_CHILDREN_no
.byte 16 # DW_AT_stmt_list
.byte 23 # DW_FORM_sec_offset
.byte 114 # DW_AT_str_offsets_base
.byte 23 # DW_FORM_sec_offset
.byte 27 # DW_AT_comp_dir
.byte 37 # DW_FORM_strx1
.ascii "\264B" # DW_AT_GNU_pubnames
.byte 25 # DW_FORM_flag_present
.byte 118 # DW_AT_dwo_name
.byte 37 # DW_FORM_strx1
.byte 17 # DW_AT_low_pc
.byte 27 # DW_FORM_addrx
.byte 18 # DW_AT_high_pc
.byte 6 # DW_FORM_data4
.byte 115 # DW_AT_addr_base
.byte 23 # DW_FORM_sec_offset
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 0 # EOM(3)
.section .debug_info,"",@progbits
.Lcu_begin0:
.long .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
.Ldebug_info_start0:
.short 5 # DWARF version number
.byte 4 # DWARF Unit Type
.byte 8 # Address Size (in bytes)
.long .debug_abbrev # Offset Into Abbrev. Section
.quad 6318074710904753300
.byte 1 # Abbrev [1] 0x14:0x14 DW_TAG_skeleton_unit
.long .Lline_table_start0 # DW_AT_stmt_list
.long .Lstr_offsets_base0 # DW_AT_str_offsets_base
.byte 0 # DW_AT_comp_dir
# DW_AT_GNU_pubnames
.byte 1 # DW_AT_dwo_name
.byte 0 # DW_AT_low_pc
.long .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
.long .Laddr_table_base0 # DW_AT_addr_base
.Ldebug_info_end0:
.section .debug_str_offsets,"",@progbits
.long 12 # Length of String Offsets Set
.short 5
.short 0
.Lstr_offsets_base0:
.section .debug_str,"MS",@progbits,1
.Lskel_string0:
.asciz "" # string offset=0
.Lskel_string1:
.asciz "main.o" # string offset=43
.section .debug_str_offsets,"",@progbits
.long .Lskel_string0
.long .Lskel_string1
.section .debug_str_offsets.dwo,"e",@progbits
.long 24 # Length of String Offsets Set
.short 5
.short 0
.section .debug_str.dwo,"eMS",@progbits,1
.Linfo_string0:
.asciz "main" # string offset=0
.Linfo_string1:
.asciz "int" # string offset=5
.Linfo_string2:
.asciz "clang version 12.0.0 (git@github.com:llvm/llvm-project.git 9a33f027ac7d73e14ae287e78ab554142d1cbc8f)" # string offset=9
.Linfo_string3:
.asciz "main.cpp" # string offset=110
.Linfo_string4:
.asciz "main.s" # string offset=119
.section .debug_str_offsets.dwo,"e",@progbits
.long 0
.long 5
.long 9
.long 110
.long 119
.section .debug_info.dwo,"e",@progbits
.long .Ldebug_info_dwo_end0-.Ldebug_info_dwo_start0 # Length of Unit
.Ldebug_info_dwo_start0:
.short 5 # DWARF version number
.byte 5 # DWARF Unit Type
.byte 8 # Address Size (in bytes)
.long 0 # Offset Into Abbrev. Section
.quad 6318074710904753300
.byte 1 # Abbrev [1] 0x14:0x1a DW_TAG_compile_unit
.byte 2 # DW_AT_producer
.short 33 # DW_AT_language
.byte 3 # DW_AT_name
.byte 4 # DW_AT_dwo_name
.byte 2 # Abbrev [2] 0x1a:0xf DW_TAG_subprogram
.byte 0 # DW_AT_low_pc
.long .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
.byte 1 # DW_AT_frame_base
.byte 86
.byte 0 # DW_AT_name
.byte 0 # DW_AT_decl_file
.byte 1 # DW_AT_decl_line
.long 41 # DW_AT_type
# DW_AT_external
.byte 3 # Abbrev [3] 0x29:0x4 DW_TAG_base_type
.byte 1 # DW_AT_name
.byte 5 # DW_AT_encoding
.byte 4 # DW_AT_byte_size
.byte 0 # End Of Children Mark
.Ldebug_info_dwo_end0:
.section .debug_abbrev.dwo,"e",@progbits
.byte 1 # Abbreviation Code
.byte 17 # DW_TAG_compile_unit
.byte 1 # DW_CHILDREN_yes
.byte 37 # DW_AT_producer
.byte 37 # DW_FORM_strx1
.byte 19 # DW_AT_language
.byte 5 # DW_FORM_data2
.byte 3 # DW_AT_name
.byte 37 # DW_FORM_strx1
.byte 118 # DW_AT_dwo_name
.byte 37 # DW_FORM_strx1
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 2 # Abbreviation Code
.byte 46 # DW_TAG_subprogram
.byte 0 # DW_CHILDREN_no
.byte 17 # DW_AT_low_pc
.byte 27 # DW_FORM_addrx
.byte 18 # DW_AT_high_pc
.byte 6 # DW_FORM_data4
.byte 64 # DW_AT_frame_base
.byte 24 # DW_FORM_exprloc
.byte 3 # DW_AT_name
.byte 37 # DW_FORM_strx1
.byte 58 # DW_AT_decl_file
.byte 11 # DW_FORM_data1
.byte 59 # DW_AT_decl_line
.byte 11 # DW_FORM_data1
.byte 73 # DW_AT_type
.byte 19 # DW_FORM_ref4
.byte 63 # DW_AT_external
.byte 25 # DW_FORM_flag_present
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 3 # Abbreviation Code
.byte 36 # DW_TAG_base_type
.byte 0 # DW_CHILDREN_no
.byte 3 # DW_AT_name
.byte 37 # DW_FORM_strx1
.byte 62 # DW_AT_encoding
.byte 11 # DW_FORM_data1
.byte 11 # DW_AT_byte_size
.byte 11 # DW_FORM_data1
.byte 0 # EOM(1)
.byte 0 # EOM(2)
.byte 0 # EOM(3)
.section .debug_addr,"",@progbits
.long .Ldebug_addr_end0-.Ldebug_addr_start0 # Length of contribution
.Ldebug_addr_start0:
.short 5 # DWARF version number
.byte 8 # Address size
.byte 0 # Segment selector size
.Laddr_table_base0:
.quad .Lfunc_begin0
.Ldebug_addr_end0:
.section .debug_gnu_pubnames,"",@progbits
.long .LpubNames_end0-.LpubNames_begin0 # Length of Public Names Info
.LpubNames_begin0:
.short 2 # DWARF Version
.long .Lcu_begin0 # Offset of Compilation Unit Info
.long 40 # Compilation Unit Length
.long 26 # DIE offset
.byte 48 # Attributes: FUNCTION, EXTERNAL
.asciz "main" # External Name
.long 0 # End Mark
.LpubNames_end0:
.section .debug_gnu_pubtypes,"",@progbits
.long .LpubTypes_end0-.LpubTypes_begin0 # Length of Public Types Info
.LpubTypes_begin0:
.short 2 # DWARF Version
.long .Lcu_begin0 # Offset of Compilation Unit Info
.long 40 # Compilation Unit Length
.long 41 # DIE offset
.byte 144 # Attributes: TYPE, STATIC
.asciz "int" # External Name
.long 0 # End Mark
.LpubTypes_end0:
.ident "clang version 12.0.0 (git@github.com:llvm/llvm-project.git 9a33f027ac7d73e14ae287e78ab554142d1cbc8f)"
.section ".note.GNU-stack","",@progbits
.addrsig
.section .debug_line,"",@progbits
.Lline_table_start0:
.section .debug_loclists.dwo,"e",@progbits
.byte 0

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