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49276e2904
Summary:
This is motivated by D63591, where we realized that there isn't a really
good way of telling whether a DataExtractor is reading actual data, or
is it just returning default values because it reached the end of the
buffer.
This patch resolves that by providing a new "Cursor" class. A Cursor
object encapsulates two things:
- the current position/offset in the DataExtractor
- an error object
Storing the error object inside the Cursor enables one to use the same
pattern as the std::{io}stream API, where one can blindly perform a
sequence of reads and only check for errors once at the end of the
operation. Similarly to the stream API, as soon as we encounter one
error, all of the subsequent operations are skipped (return default
values) too, even if the would suceed with clear error state. Unlike the
std::stream API (but in line with other llvm APIs), we force the error
state to be checked through usage of llvm::Error.
Reviewers: probinson, dblaikie, JDevlieghere, aprantl, echristo
Subscribers: kristina, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D63713
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@370042 91177308-0d34-0410-b5e6-96231b3b80d8
101 lines
2.7 KiB
C++
101 lines
2.7 KiB
C++
//===- DWARFDataExtractor.cpp ---------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
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#include "llvm/BinaryFormat/Dwarf.h"
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#include "llvm/DebugInfo/DWARF/DWARFContext.h"
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using namespace llvm;
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uint64_t DWARFDataExtractor::getRelocatedValue(uint32_t Size, uint64_t *Off,
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uint64_t *SecNdx,
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Error *Err) const {
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if (SecNdx)
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*SecNdx = object::SectionedAddress::UndefSection;
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if (!Section)
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return getUnsigned(Off, Size, Err);
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Optional<RelocAddrEntry> E = Obj->find(*Section, *Off);
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uint64_t A = getUnsigned(Off, Size, Err);
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if (!E)
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return A;
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if (SecNdx)
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*SecNdx = E->SectionIndex;
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uint64_t R = E->Resolver(E->Reloc, E->SymbolValue, A);
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if (E->Reloc2)
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R = E->Resolver(*E->Reloc2, E->SymbolValue2, R);
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return R;
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}
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Optional<uint64_t>
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DWARFDataExtractor::getEncodedPointer(uint64_t *Offset, uint8_t Encoding,
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uint64_t PCRelOffset) const {
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if (Encoding == dwarf::DW_EH_PE_omit)
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return None;
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uint64_t Result = 0;
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uint64_t OldOffset = *Offset;
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// First get value
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switch (Encoding & 0x0F) {
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case dwarf::DW_EH_PE_absptr:
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switch (getAddressSize()) {
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case 2:
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case 4:
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case 8:
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Result = getUnsigned(Offset, getAddressSize());
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break;
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default:
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return None;
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}
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break;
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case dwarf::DW_EH_PE_uleb128:
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Result = getULEB128(Offset);
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break;
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case dwarf::DW_EH_PE_sleb128:
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Result = getSLEB128(Offset);
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break;
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case dwarf::DW_EH_PE_udata2:
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Result = getUnsigned(Offset, 2);
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break;
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case dwarf::DW_EH_PE_udata4:
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Result = getUnsigned(Offset, 4);
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break;
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case dwarf::DW_EH_PE_udata8:
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Result = getUnsigned(Offset, 8);
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break;
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case dwarf::DW_EH_PE_sdata2:
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Result = getSigned(Offset, 2);
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break;
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case dwarf::DW_EH_PE_sdata4:
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Result = getSigned(Offset, 4);
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break;
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case dwarf::DW_EH_PE_sdata8:
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Result = getSigned(Offset, 8);
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break;
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default:
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return None;
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}
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// Then add relative offset, if required
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switch (Encoding & 0x70) {
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case dwarf::DW_EH_PE_absptr:
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// do nothing
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break;
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case dwarf::DW_EH_PE_pcrel:
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Result += PCRelOffset;
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break;
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case dwarf::DW_EH_PE_datarel:
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case dwarf::DW_EH_PE_textrel:
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case dwarf::DW_EH_PE_funcrel:
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case dwarf::DW_EH_PE_aligned:
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default:
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*Offset = OldOffset;
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return None;
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}
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return Result;
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}
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