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[BOLT] Better handling of address references

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Summary:
We used to handle PC-relative address references differently from direct
address references. As a result, some cases, such as escaped function
label address, were not handled when dealing with absolute (non-PIC)
code. This diff moves processing of an address reference into
BinaryContext::handleAddressRef() which is called for both PIC and
non-PIC code.

(cherry picked from FBD15643535)
This commit is contained in:
Maksim Panchenko
2019-06-04 15:30:22 -07:00
parent d3c1821f5f
commit fac6a89c23
10 changed files with 142 additions and 122 deletions
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62
bolt/src/BinaryContext.cpp
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@@ -224,6 +224,68 @@ BinaryContext::getSubBinaryData(BinaryData *BD) {
return make_range(Start, End);
}
std::pair<MCSymbol *, uint64_t>
BinaryContext::handleAddressRef(uint64_t Address, BinaryFunction &BF) {
uint64_t Addend{0};
if (isAArch64()) {
// Check if this is an access to a constant island and create bookkeeping
// to keep track of it and emit it later as part of this function.
if (MCSymbol *IslandSym = BF.getOrCreateIslandAccess(Address)) {
return std::make_pair(IslandSym, Addend);
} else {
// Detect custom code written in assembly that refers to arbitrary
// constant islands from other functions. Write this reference so we
// can pull this constant island and emit it as part of this function
// too.
auto IslandIter = AddressToConstantIslandMap.lower_bound(Address);
if (IslandIter != AddressToConstantIslandMap.end()) {
if (auto *IslandSym =
IslandIter->second->getOrCreateProxyIslandAccess(Address, BF)) {
/// Make this function depend on IslandIter->second because we have
/// a reference to its constant island. When emitting this function,
/// we will also emit IslandIter->second's constants. This only
/// happens in custom AArch64 assembly code.
BF.IslandDependency.insert(IslandIter->second);
BF.ProxyIslandSymbols[IslandSym] = IslandIter->second;
return std::make_pair(IslandSym, Addend);
}
}
}
}
// Note that the address does not necessarily have to reside inside
// a section, it could be an absolute address too.
auto Section = getSectionForAddress(Address);
if (Section && Section->isText()) {
if (BF.containsAddress(Address, /*UseMaxSize=*/ isAArch64())) {
if (Address != BF.getAddress()) {
// The address could potentially escape. Mark it as another entry
// point into the function.
if (opts::Verbosity >= 1) {
outs() << "BOLT-INFO: potentially escaped address 0x"
<< Twine::utohexstr(Address) << " in function "
<< BF << '\n';
}
return std::make_pair(
BF.addEntryPointAtOffset(Address - BF.getAddress()),
Addend);
}
} else {
InterproceduralReferences.insert(std::make_pair(&BF, Address));
}
}
if (auto *BD = getBinaryDataContainingAddress(Address)) {
return std::make_pair(BD->getSymbol(), Address - BD->getAddress());
}
// TODO: use DWARF info to get size/alignment here?
auto *TargetSymbol = getOrCreateGlobalSymbol(Address, "DATAat");
DEBUG(dbgs() << "Created symbol " << TargetSymbol->getName());
return std::make_pair(TargetSymbol, Addend);
}
MCSymbol *BinaryContext::getOrCreateGlobalSymbol(uint64_t Address,
Twine Prefix,
uint64_t Size,