94 lines
4.0 KiB
C++
94 lines
4.0 KiB
C++
//===- GdbIndex.cpp -------------------------------------------------------===//
|
|
//
|
|
// The LLVM Linker
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// File contains classes for implementation of --gdb-index command line option.
|
|
//
|
|
// If that option is used, linker should emit a .gdb_index section that allows
|
|
// debugger to locate and read .dwo files, containing neccessary debug
|
|
// information.
|
|
// More information about implementation can be found in DWARF specification,
|
|
// latest version is available at http://dwarfstd.org.
|
|
//
|
|
// .gdb_index section format:
|
|
// (Information is based on/taken from
|
|
// https://sourceware.org/gdb/onlinedocs/gdb/Index-Section-Format.html (*))
|
|
//
|
|
// A mapped index consists of several areas, laid out in order:
|
|
// 1) The file header.
|
|
// 2) "The CU (compilation unit) list. This is a sequence of pairs of 64-bit
|
|
// little-endian values, sorted by the CU offset. The first element in each
|
|
// pair is the offset of a CU in the .debug_info section. The second element
|
|
// in each pair is the length of that CU. References to a CU elsewhere in the
|
|
// map are done using a CU index, which is just the 0-based index into this
|
|
// table. Note that if there are type CUs, then conceptually CUs and type CUs
|
|
// form a single list for the purposes of CU indices."(*)
|
|
// 3) The types CU list. Depricated as .debug_types does not appear in the DWARF
|
|
// v5 specification.
|
|
// 4) The address area. The address area is a sequence of address
|
|
// entries, where each entrie contains low address, high address and CU
|
|
// index.
|
|
// 5) "The symbol table. This is an open-addressed hash table. The size of the
|
|
// hash table is always a power of 2. Each slot in the hash table consists of
|
|
// a pair of offset_type values. The first value is the offset of the
|
|
// symbol's name in the constant pool. The second value is the offset of the
|
|
// CU vector in the constant pool."(*)
|
|
// 6) "The constant pool. This is simply a bunch of bytes. It is organized so
|
|
// that alignment is correct: CU vectors are stored first, followed by
|
|
// strings." (*)
|
|
//
|
|
// For constructing the .gdb_index section following steps should be performed:
|
|
// 1) For file header nothing special should be done. It contains the offsets to
|
|
// the areas below.
|
|
// 2) Scan the compilation unit headers of the .debug_info sections to build a
|
|
// list of compilation units.
|
|
// 3) CU Types are no longer needed as DWARF skeleton type units never made it
|
|
// into the standard. lld does nothing to support parsing of .debug_types
|
|
// and generates empty types CU area in .gdb_index section.
|
|
// 4) Address area entries are extracted from DW_TAG_compile_unit DIEs of
|
|
// .debug_info sections.
|
|
// 5) For building the symbol table linker extracts the public names from the
|
|
// .debug_gnu_pubnames and .debug_gnu_pubtypes sections. Then it builds the
|
|
// hashtable in according to .gdb_index format specification.
|
|
// 6) Constant pool is populated at the same time as symbol table.
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "GdbIndex.h"
|
|
#include "Memory.h"
|
|
#include "llvm/DebugInfo/DWARF/DWARFDebugPubTable.h"
|
|
#include "llvm/Object/ELFObjectFile.h"
|
|
|
|
using namespace llvm;
|
|
using namespace llvm::object;
|
|
using namespace lld;
|
|
using namespace lld::elf;
|
|
|
|
std::pair<bool, GdbSymbol *> GdbHashTab::add(uint32_t Hash, size_t Offset) {
|
|
GdbSymbol *&Sym = Map[Offset];
|
|
if (Sym)
|
|
return {false, Sym};
|
|
Sym = make<GdbSymbol>(Hash, Offset);
|
|
return {true, Sym};
|
|
}
|
|
|
|
void GdbHashTab::finalizeContents() {
|
|
uint32_t Size = std::max<uint32_t>(1024, NextPowerOf2(Map.size() * 4 / 3));
|
|
uint32_t Mask = Size - 1;
|
|
Table.resize(Size);
|
|
|
|
for (auto &P : Map) {
|
|
GdbSymbol *Sym = P.second;
|
|
uint32_t I = Sym->NameHash & Mask;
|
|
uint32_t Step = ((Sym->NameHash * 17) & Mask) | 1;
|
|
|
|
while (Table[I])
|
|
I = (I + Step) & Mask;
|
|
Table[I] = Sym;
|
|
}
|
|
}
|