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llvm-mirror/lib/DebugInfo/DWARF/DWARFListTable.cpp
David Blaikie 01ab206194 [WIP][DebugInfo] Lazily parse debug_loclist offsets
Parsing DWARFv5 debug_loclist offsets when a CU is parsed is weighing
down memory usage of symbolizers that don't need to parse this data at
all. There's not much benefit to caching these anyway - since they are
O(1) lookup and reading once you know where the offset list starts (and
can do bounds checking with the offset list size too).

In general, I think it might be time to start paying down some of the
technical debt of loc/loclist/range/rnglist parsing to try to unify it a
bit more.

eg:

* Currently DWARFUnit has: RangeSection, RangeSectionBase, LocSection,
  LocSectionBase, LocTable, RngListTable, LoclistTableHeader (be nice if
  these were all wrapped up in two variables - one for loclists, one for
  rnglists)

* rnglists and loclists are handled differently (see:
  LoclistTableHeader, but no RnglistTableHeader)

* maybe all these types could be less stateful - lazily parse what they
  need to, even reparsing rather than caching because it doesn't seem
  too expensive, for instance. (though admittedly so long as it's
  constantcost/overead per compilatiton that's probably adequate)

* Maybe implementing and using a DWARFDataExtractor that can be
  sub-ranged (so we could slice it up to just the single contribution) -
  though maybe that's not so useful because loc/ranges need to refer to
  it by absolute, not contribution-relative mechanisms

Differential Revision: https://reviews.llvm.org/D86110
2020-08-18 10:49:39 -07:00

110 lines
4.8 KiB
C++

//===- DWARFListTable.cpp ---------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/DebugInfo/DWARF/DWARFListTable.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
Error DWARFListTableHeader::extract(DWARFDataExtractor Data,
uint64_t *OffsetPtr) {
HeaderOffset = *OffsetPtr;
Error Err = Error::success();
std::tie(HeaderData.Length, Format) = Data.getInitialLength(OffsetPtr, &Err);
if (Err)
return createStringError(
errc::invalid_argument, "parsing %s table at offset 0x%" PRIx64 ": %s",
SectionName.data(), HeaderOffset, toString(std::move(Err)).c_str());
uint8_t OffsetByteSize = Format == dwarf::DWARF64 ? 8 : 4;
uint64_t FullLength =
HeaderData.Length + dwarf::getUnitLengthFieldByteSize(Format);
if (FullLength < getHeaderSize(Format))
return createStringError(errc::invalid_argument,
"%s table at offset 0x%" PRIx64
" has too small length (0x%" PRIx64
") to contain a complete header",
SectionName.data(), HeaderOffset, FullLength);
assert(FullLength == length() && "Inconsistent calculation of length.");
uint64_t End = HeaderOffset + FullLength;
if (!Data.isValidOffsetForDataOfSize(HeaderOffset, FullLength))
return createStringError(errc::invalid_argument,
"section is not large enough to contain a %s table "
"of length 0x%" PRIx64 " at offset 0x%" PRIx64,
SectionName.data(), FullLength, HeaderOffset);
HeaderData.Version = Data.getU16(OffsetPtr);
HeaderData.AddrSize = Data.getU8(OffsetPtr);
HeaderData.SegSize = Data.getU8(OffsetPtr);
HeaderData.OffsetEntryCount = Data.getU32(OffsetPtr);
// Perform basic validation of the remaining header fields.
if (HeaderData.Version != 5)
return createStringError(errc::invalid_argument,
"unrecognised %s table version %" PRIu16
" in table at offset 0x%" PRIx64,
SectionName.data(), HeaderData.Version, HeaderOffset);
if (HeaderData.AddrSize != 4 && HeaderData.AddrSize != 8)
return createStringError(errc::not_supported,
"%s table at offset 0x%" PRIx64
" has unsupported address size %" PRIu8,
SectionName.data(), HeaderOffset, HeaderData.AddrSize);
if (HeaderData.SegSize != 0)
return createStringError(errc::not_supported,
"%s table at offset 0x%" PRIx64
" has unsupported segment selector size %" PRIu8,
SectionName.data(), HeaderOffset, HeaderData.SegSize);
if (End < HeaderOffset + getHeaderSize(Format) +
HeaderData.OffsetEntryCount * OffsetByteSize)
return createStringError(errc::invalid_argument,
"%s table at offset 0x%" PRIx64 " has more offset entries (%" PRIu32
") than there is space for",
SectionName.data(), HeaderOffset, HeaderData.OffsetEntryCount);
Data.setAddressSize(HeaderData.AddrSize);
*OffsetPtr += HeaderData.OffsetEntryCount * OffsetByteSize;
return Error::success();
}
void DWARFListTableHeader::dump(DataExtractor Data, raw_ostream &OS,
DIDumpOptions DumpOpts) const {
if (DumpOpts.Verbose)
OS << format("0x%8.8" PRIx64 ": ", HeaderOffset);
int OffsetDumpWidth = 2 * dwarf::getDwarfOffsetByteSize(Format);
OS << format("%s list header: length = 0x%0*" PRIx64, ListTypeString.data(),
OffsetDumpWidth, HeaderData.Length)
<< ", format = " << dwarf::FormatString(Format)
<< format(", version = 0x%4.4" PRIx16 ", addr_size = 0x%2.2" PRIx8
", seg_size = 0x%2.2" PRIx8
", offset_entry_count = 0x%8.8" PRIx32 "\n",
HeaderData.Version, HeaderData.AddrSize, HeaderData.SegSize,
HeaderData.OffsetEntryCount);
if (HeaderData.OffsetEntryCount > 0) {
OS << "offsets: [";
for (uint32_t I = 0; I < HeaderData.OffsetEntryCount; ++I) {
auto Off = *getOffsetEntry(Data, I);
OS << format("\n0x%0*" PRIx64, OffsetDumpWidth, Off);
if (DumpOpts.Verbose)
OS << format(" => 0x%08" PRIx64,
Off + HeaderOffset + getHeaderSize(Format));
}
OS << "\n]\n";
}
}
uint64_t DWARFListTableHeader::length() const {
if (HeaderData.Length == 0)
return 0;
return HeaderData.Length + dwarf::getUnitLengthFieldByteSize(Format);
}