[lld] r346747 - [ELF] .gdb_index: fix CuOff when a .debug_info section contains more than 1 DW_TAG_compile_unit
Fangrui Song via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 13 00:43:08 PST 2018
Author: maskray
Date: Tue Nov 13 00:43:07 2018
New Revision: 346747
URL: http://llvm.org/viewvc/llvm-project?rev=346747&view=rev
Log:
[ELF] .gdb_index: fix CuOff when a .debug_info section contains more than 1 DW_TAG_compile_unit
Summary:
Idx passed to readPubNamesAndTypes was an index into Chunks, not an
index into the CU list. This would be incorrect if some .debug_info
section contained more than 1 DW_TAG_compile_unit.
In real world, glibc Scrt1.o is a partial link of start.os abi-note.o init.o and contains 2 CUs in debug builds.
Without this patch, any application linking such Scrt1.o would have invalid .gdb_index
The issue could be demonstrated by:
(gdb) py print(gdb.lookup_global_symbol('main'))
None
Reviewers: espindola, ruiu
Reviewed By: ruiu
Subscribers: Higuoxing, grimar, dblaikie, emaste, aprantl, arichardson, JDevlieghere, arphaman, llvm-commits
Differential Revision: https://reviews.llvm.org/D54361
Added:
lld/trunk/test/ELF/gdb-index-multiple-cu.s
Modified:
lld/trunk/ELF/SyntheticSections.cpp
Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=346747&r1=346746&r2=346747&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Tue Nov 13 00:43:07 2018
@@ -2414,18 +2414,28 @@ readAddressAreas(DWARFContext &Dwarf, In
template <class ELFT>
static std::vector<GdbIndexSection::NameTypeEntry>
-readPubNamesAndTypes(DWARFContext &Dwarf, uint32_t Idx) {
- auto &Obj = static_cast<const LLDDwarfObj<ELFT> &>(Dwarf.getDWARFObj());
+readPubNamesAndTypes(const LLDDwarfObj<ELFT> &Obj,
+ const std::vector<GdbIndexSection::CuEntry> &CUs) {
const DWARFSection &PubNames = Obj.getGnuPubNamesSection();
const DWARFSection &PubTypes = Obj.getGnuPubTypesSection();
std::vector<GdbIndexSection::NameTypeEntry> Ret;
for (const DWARFSection *Pub : {&PubNames, &PubTypes}) {
DWARFDebugPubTable Table(Obj, *Pub, Config->IsLE, true);
- for (const DWARFDebugPubTable::Set &Set : Table.getData())
+ uint32_t I = 0;
+ for (const DWARFDebugPubTable::Set &Set : Table.getData()) {
+ // The value written into the constant pool is Kind << 24 | CuIndex. As we
+ // don't know how many compilation units precede this object to compute
+ // CuIndex, we compute (Kind << 24 | CuIndexInThisObject) instead, and add
+ // the number of preceding compilation units later.
+ //
+ // We assume both CUs[*].CuOff and Set.Offset are increasing.
+ while (I < CUs.size() && CUs[I].CuOffset < Set.Offset)
+ ++I;
for (const DWARFDebugPubTable::Entry &Ent : Set.Entries)
Ret.push_back({{Ent.Name, computeGdbHash(Ent.Name)},
- (Ent.Descriptor.toBits() << 24) | Idx});
+ (Ent.Descriptor.toBits() << 24) | I});
+ }
}
return Ret;
}
@@ -2433,10 +2443,19 @@ readPubNamesAndTypes(DWARFContext &Dwarf
// Create a list of symbols from a given list of symbol names and types
// by uniquifying them by name.
static std::vector<GdbIndexSection::GdbSymbol>
-createSymbols(ArrayRef<std::vector<GdbIndexSection::NameTypeEntry>> NameTypes) {
+createSymbols(ArrayRef<std::vector<GdbIndexSection::NameTypeEntry>> NameTypes,
+ const std::vector<GdbIndexSection::GdbChunk> &Chunks) {
typedef GdbIndexSection::GdbSymbol GdbSymbol;
typedef GdbIndexSection::NameTypeEntry NameTypeEntry;
+ // For each chunk, compute the number of compilation units preceding it.
+ uint32_t CuIdx = 0;
+ std::vector<uint32_t> CuIdxs(Chunks.size());
+ for (uint32_t I = 0, E = Chunks.size(); I != E; ++I) {
+ CuIdxs[I] = CuIdx;
+ CuIdx += Chunks[I].CompilationUnits.size();
+ }
+
// The number of symbols we will handle in this function is of the order
// of millions for very large executables, so we use multi-threading to
// speed it up.
@@ -2453,21 +2472,24 @@ createSymbols(ArrayRef<std::vector<GdbIn
// Instantiate GdbSymbols while uniqufying them by name.
std::vector<std::vector<GdbSymbol>> Symbols(NumShards);
parallelForEachN(0, Concurrency, [&](size_t ThreadId) {
+ uint32_t I = 0;
for (ArrayRef<NameTypeEntry> Entries : NameTypes) {
for (const NameTypeEntry &Ent : Entries) {
size_t ShardId = Ent.Name.hash() >> Shift;
if ((ShardId & (Concurrency - 1)) != ThreadId)
continue;
+ uint32_t V = Ent.Type + CuIdxs[I];
size_t &Idx = Map[ShardId][Ent.Name];
if (Idx) {
- Symbols[ShardId][Idx - 1].CuVector.push_back(Ent.Type);
+ Symbols[ShardId][Idx - 1].CuVector.push_back(V);
continue;
}
Idx = Symbols[ShardId].size() + 1;
- Symbols[ShardId].push_back({Ent.Name, {Ent.Type}, 0, 0});
+ Symbols[ShardId].push_back({Ent.Name, {V}, 0, 0});
}
+ ++I;
}
});
@@ -2519,12 +2541,14 @@ template <class ELFT> GdbIndexSection *G
Chunks[I].Sec = Sections[I];
Chunks[I].CompilationUnits = readCuList(Dwarf);
Chunks[I].AddressAreas = readAddressAreas(Dwarf, Sections[I]);
- NameTypes[I] = readPubNamesAndTypes<ELFT>(Dwarf, I);
+ NameTypes[I] = readPubNamesAndTypes<ELFT>(
+ static_cast<const LLDDwarfObj<ELFT> &>(Dwarf.getDWARFObj()),
+ Chunks[I].CompilationUnits);
});
auto *Ret = make<GdbIndexSection>();
Ret->Chunks = std::move(Chunks);
- Ret->Symbols = createSymbols(NameTypes);
+ Ret->Symbols = createSymbols(NameTypes, Ret->Chunks);
Ret->initOutputSize();
return Ret;
}
Added: lld/trunk/test/ELF/gdb-index-multiple-cu.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gdb-index-multiple-cu.s?rev=346747&view=auto
==============================================================================
--- lld/trunk/test/ELF/gdb-index-multiple-cu.s (added)
+++ lld/trunk/test/ELF/gdb-index-multiple-cu.s Tue Nov 13 00:43:07 2018
@@ -0,0 +1,64 @@
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: ld.lld --gdb-index %t.o -o %t
+# RUN: llvm-dwarfdump -gdb-index %t | FileCheck %s
+
+# Kind << 24 | CuIndex = 48 << 24 | 1 = 0x30000001
+# CHECK: Constant pool
+# CHECK-NEXT: 0(0x0): 0x30000001
+
+.globl _start
+_start:
+ ret
+
+.section .debug_abbrev,"", at progbits
+ .byte 1 # Abbreviation Code
+ .byte 17 # DW_TAG_compile_unit
+ .byte 1 # DW_CHILDREN_yes
+ .ascii "\264B" # DW_AT_GNU_pubnames
+ .byte 12 # DW_FORM_flag
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 2 # Abbreviation Code
+ .byte 46 # DW_TAG_subprogram
+ .byte 0 # DW_CHILDREN_no
+ .byte 3 # DW_AT_name
+ .byte 8 # DW_FORM_string
+ .byte 0 # EOM(1)
+ .byte 0 # EOM(2)
+ .byte 0
+
+.section .debug_info,"", at progbits
+.Lcu_begin0:
+ .long .Lcu_end0 - .Lcu_begin0 - 4
+ .short 4 # DWARF version number
+ .long 0 # Offset Into Abbrev. Section
+ .byte 4 # Address Size
+ .byte 1 # Abbrev [1] DW_TAG_compile_unit
+ .byte 0 # DW_AT_GNU_pubnames
+ .byte 0
+.Lcu_end0:
+.Lcu_begin1:
+ .long .Lcu_end1 - .Lcu_begin1 - 4
+ .short 4 # DWARF version number
+ .long 0 # Offset Into Abbrev. Section
+ .byte 4 # Address Size
+.Ldie:
+ .byte 1 # Abbrev [1] DW_TAG_compile_unit
+ .byte 1 # DW_AT_GNU_pubnames
+ .byte 2 # Abbrev [2] DW_TAG_subprogram
+ .asciz "_start" # DW_AT_name
+ .byte 0
+.Lcu_end1:
+
+# .debug_gnu_pubnames has just one set, associated with .Lcu_begin1 (CuIndex: 1)
+.section .debug_gnu_pubnames,"", at progbits
+ .long .LpubNames_end1-.LpubNames_begin1
+.LpubNames_begin1:
+ .short 2 # Version
+ .long .Lcu_begin1 # CU Offset
+ .long .Lcu_end1 - .Lcu_begin1
+ .long .Ldie - .Lcu_begin1
+ .byte 48 # Kind: FUNCTION, EXTERNAL
+ .asciz "_start" # External Name
+ .long 0
+.LpubNames_end1:
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