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[ELF] Error on relocations to local undefined symbols 

For a reference to a local symbol, ld.bfd and gold error if the symbol
is defined in a discarded section but accept it if the symbol is
undefined. This inconsistent behavior seems unnecessary for us (it
probably makes sense for them as they differentiate local/global
symbols, the error would mean more code).

Catch such errors. Symbol index 0 may be used by marker relocations,
e.g. R_*_NONE R_ARM_V4BX. Don't error on them.

The difference from D61563 (which caused msan failure) is we don't call
Sym.computeBinding() on local symbols - VersionId is uninitialized.

llvm-svn: 361213
This commit is contained in:
Fangrui Song 2019-05-21 02:38:11 +00:00
parent 67510fac36
commit 547e3e930c
2 changed files with 11 additions and 11 deletions
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14
lld/ELF/Relocations.cpp
View File

@ -675,11 +675,11 @@ static int64_t computeAddend(const RelTy &Rel, const RelTy *End,
// Returns true if this function printed out an error message. // Returns true if this function printed out an error message.
static bool maybeReportUndefined(Symbol &Sym, InputSectionBase &Sec, static bool maybeReportUndefined(Symbol &Sym, InputSectionBase &Sec,
uint64_t Offset) { uint64_t Offset) {
if (Sym.isLocal() || !Sym.isUndefined() || Sym.isWeak()) if (!Sym.isUndefined() || Sym.isWeak())
return false; return false;
bool CanBeExternal = bool CanBeExternal = !Sym.isLocal() && Sym.computeBinding() != STB_LOCAL &&
Sym.computeBinding() != STB_LOCAL && Sym.Visibility == STV_DEFAULT; Sym.Visibility == STV_DEFAULT;
if (Config->UnresolvedSymbols == UnresolvedPolicy::Ignore && CanBeExternal) if (Config->UnresolvedSymbols == UnresolvedPolicy::Ignore && CanBeExternal)
return false; return false;
@ -1012,7 +1012,8 @@ template <class ELFT, class RelTy>
static void scanReloc(InputSectionBase &Sec, OffsetGetter &GetOffset, RelTy *&I, static void scanReloc(InputSectionBase &Sec, OffsetGetter &GetOffset, RelTy *&I,
RelTy *End) { RelTy *End) {
const RelTy &Rel = *I; const RelTy &Rel = *I;
Symbol &Sym = Sec.getFile<ELFT>()->getRelocTargetSym(Rel); uint32_t SymIndex = Rel.getSymbol(Config->IsMips64EL);
Symbol &Sym = Sec.getFile<ELFT>()->getSymbol(SymIndex);
RelType Type; RelType Type;
// Deal with MIPS oddity. // Deal with MIPS oddity.
@ -1028,8 +1029,9 @@ static void scanReloc(InputSectionBase &Sec, OffsetGetter &GetOffset, RelTy *&I,
if (Offset == uint64_t(-1)) if (Offset == uint64_t(-1))
return; return;
// Skip if the target symbol is an erroneous undefined symbol. // Error if the target symbol is undefined. Symbol index 0 may be used by
if (maybeReportUndefined(Sym, Sec, Rel.r_offset)) // marker relocations, e.g. R_*_NONE and R_ARM_V4BX. Don't error on them.
if (SymIndex != 0 && maybeReportUndefined(Sym, Sec, Rel.r_offset))
return; return;
const uint8_t *RelocatedAddr = Sec.data().begin() + Rel.r_offset; const uint8_t *RelocatedAddr = Sec.data().begin() + Rel.r_offset;

8
lld/test/ELF/local-undefined-symbol.s
View File

@ -1,10 +1,8 @@
# REQUIRES: x86 # REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
# RUN: ld.lld %t -o %t1 # RUN: not ld.lld %t.o -o %t 2>&1 | FileCheck %s
# RUN: llvm-readobj --symbols %t1 | FileCheck %s
# CHECK: Symbols [ # CHECK: error: undefined symbol: foo
# CHECK-NOT: Name: foo
.global _start .global _start
_start: _start: