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[LLD] Check too large offsets into merge sections earlier

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This patch moves the checking for too large offsets into merge sections
earlier.

Without this change the large offset generated in the added test-case
will cause an assert (as it happens to be a value reserved as a
"tombstone" in the DenseMap implementation) when OffsetMap is queried in
getSectionPiece().

To simplify the code and avoid future mistakes I have refactored so that
there is only one function that looks up offsets in the OffsetMap.

Differential Revision: https://reviews.llvm.org/D51180

llvm-svn: 341206
This commit is contained in:
Ben Dunbobbin 2018-08-31 11:51:51 +00:00
parent fc774e29d2
commit df6f0ad210
3 changed files with 12 additions and 23 deletions
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31
lld/ELF/InputSection.cpp
View File

@ -1149,43 +1149,32 @@ static It fastUpperBound(It First, It Last, const T &Value, Compare Comp) {
return Comp(Value, *First) ? First : First + 1;
}
// Do binary search to get a section piece at a given input offset.
static SectionPiece *findSectionPiece(MergeInputSection *Sec, uint64_t Offset) {
if (Sec->Data.size() <= Offset)
fatal(toString(Sec) + ": entry is past the end of the section");
// Find the element this offset points to.
auto I = fastUpperBound(
Sec->Pieces.begin(), Sec->Pieces.end(), Offset,
[](const uint64_t &A, const SectionPiece &B) { return A < B.InputOff; });
--I;
return &*I;
}
SectionPiece *MergeInputSection::getSectionPiece(uint64_t Offset) {
if (this->Data.size() <= Offset)
fatal(toString(this) + ": offset is outside the section");
// Find a piece starting at a given offset.
auto It = OffsetMap.find(Offset);
if (It != OffsetMap.end())
return &Pieces[It->second];
// If Offset is not at beginning of a section piece, it is not in the map.
// In that case we need to search from the original section piece vector.
return findSectionPiece(this, Offset);
// In that case we need to do a binary search of the original section piece vector.
auto I = fastUpperBound(
Pieces.begin(), Pieces.end(), Offset,
[](const uint64_t &A, const SectionPiece &B) { return A < B.InputOff; });
--I;
return &*I;
}
// Returns the offset in an output section for a given input offset.
// Because contents of a mergeable section is not contiguous in output,
// it is not just an addition to a base output offset.
uint64_t MergeInputSection::getParentOffset(uint64_t Offset) const {
// Find a string starting at a given offset.
auto It = OffsetMap.find(Offset);
if (It != OffsetMap.end())
return Pieces[It->second].OutputOff;
// If Offset is not at beginning of a section piece, it is not in the map.
// In that case we need to search from the original section piece vector.
const SectionPiece &Piece =
*findSectionPiece(const_cast<MergeInputSection *>(this), Offset);
*(const_cast<MergeInputSection *>(this)->getSectionPiece (Offset));
uint64_t Addend = Offset - Piece.InputOff;
return Piece.OutputOff + Addend;
}

2
lld/test/ELF/merge-string-error.s
View File

@ -8,4 +8,4 @@
.data
.long .rodata.str1.1 + 4
// CHECK: merge-string-error.s.tmp.o:(.rodata.str1.1): entry is past the end of the section
// CHECK: merge-string-error.s.tmp.o:(.rodata.str1.1): offset is outside the section

2
lld/test/ELF/relocation-past-merge-end.s
View File

@ -1,7 +1,7 @@
// REQUIRES: x86
// RUN: llvm-mc %s -o %t.o -filetype=obj -triple=x86_64-pc-linux
// RUN: not ld.lld %t.o -o /dev/null -shared 2>&1 | FileCheck %s
// CHECK: relocation-past-merge-end.s.tmp.o:(.foo): entry is past the end of the section
// CHECK: relocation-past-merge-end.s.tmp.o:(.foo): offset is outside the section
.data
.long .foo + 10