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//===- bolt/Passes/MarkRAStates.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
//
//===----------------------------------------------------------------------===//
//
// This file implements the MarkRAStates class.
// Three CFIs have an influence on the RA State of an instruction:
// - NegateRAState flips the RA State,
// - RememberState pushes the RA State to a stack,
// - RestoreState pops the RA State from the stack.
// These are saved as MCAnnotations on instructions they refer to at CFI
// reading (in CFIReaderWriter::fillCFIInfoFor). In this pass, we can work out
// the RA State of each instruction, and save it as new MCAnnotations. The new
// annotations are Signing, Signed, Authenticating and Unsigned. After
// optimizations, .cfi_negate_ra_state CFIs are added to the places where the
// state changes in InsertNegateRAStatePass.
//
//===----------------------------------------------------------------------===//
#include "bolt/Passes/MarkRAStates.h"
#include "bolt/Core/BinaryFunction.h"
#include "bolt/Core/ParallelUtilities.h"
#include <cstdlib>
#include <optional>
#include <stack>
using namespace llvm;
namespace llvm {
namespace bolt {
bool MarkRAStates::runOnFunction(BinaryFunction &BF) {
BinaryContext &BC = BF.getBinaryContext();
for (const BinaryBasicBlock &BB : BF) {
for (const MCInst &Inst : BB) {
if ((BC.MIB->isPSignOnLR(Inst) ||
(BC.MIB->isPAuthOnLR(Inst) && !BC.MIB->isPAuthAndRet(Inst))) &&
!BC.MIB->hasNegateRAState(Inst)) {
// Not all functions have .cfi_negate_ra_state in them. But if one does,
// we expect psign/pauth instructions to have the hasNegateRAState
// annotation.
BC.outs() << "BOLT-INFO: inconsistent RAStates in function "
<< BF.getPrintName()
<< ": ptr sign/auth inst without .cfi_negate_ra_state\n";
std::lock_guard<std::mutex> Lock(IgnoreMutex);
BF.setIgnored();
return false;
}
}
}
bool RAState = BF.getInitialRAState();
std::stack<bool> RAStateStack;
RAStateStack.push(RAState);
for (BinaryBasicBlock &BB : BF) {
for (MCInst &Inst : BB) {
if (BC.MIB->isCFI(Inst))
continue;
if (BC.MIB->isPSignOnLR(Inst)) {
if (RAState) {
// RA signing instructions should only follow unsigned RA state.
BC.outs() << "BOLT-INFO: inconsistent RAStates in function "
<< BF.getPrintName()
<< ": ptr signing inst encountered in Signed RA state\n";
std::lock_guard<std::mutex> Lock(IgnoreMutex);
BF.setIgnored();
return false;
}
} else if (BC.MIB->isPAuthOnLR(Inst)) {
if (!RAState) {
// RA authenticating instructions should only follow signed RA state.
BC.outs() << "BOLT-INFO: inconsistent RAStates in function "
<< BF.getPrintName()
<< ": ptr authenticating inst encountered in Unsigned RA "
"state\n";
std::lock_guard<std::mutex> Lock(IgnoreMutex);
BF.setIgnored();
return false;
}
}
BC.MIB->setRAState(Inst, RAState);
// Updating RAState. All updates are valid from the next instruction.
// Because the same instruction can have remember and restore, the order
// here is relevant. This is the reason to loop over Annotations instead
// of just checking each in a predefined order.
for (unsigned int Idx = 0; Idx < Inst.getNumOperands(); Idx++) {
std::optional<int64_t> Annotation =
BC.MIB->getAnnotationAtOpIndex(Inst, Idx);
if (!Annotation)
continue;
if (Annotation == MCPlus::MCAnnotation::kNegateState)
RAState = !RAState;
else if (Annotation == MCPlus::MCAnnotation::kRememberState)
RAStateStack.push(RAState);
else if (Annotation == MCPlus::MCAnnotation::kRestoreState) {
RAState = RAStateStack.top();
RAStateStack.pop();
}
}
}
}
return true;
}
Error MarkRAStates::runOnFunctions(BinaryContext &BC) {
std::atomic<uint64_t> FunctionsIgnored{0};
ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
if (!runOnFunction(BF)) {
FunctionsIgnored++;
}
};
ParallelUtilities::PredicateTy SkipPredicate = [&](const BinaryFunction &BF) {
// We can skip functions which did not include negate-ra-state CFIs. This
// includes code using pac-ret hardening as well, if the binary is
// compiled with `-fno-exceptions -fno-unwind-tables
// -fno-asynchronous-unwind-tables`
return !BF.containedNegateRAState() || BF.isIgnored();
};
int Total = llvm::count_if(BC.getBinaryFunctions(), [&](auto &P) {
return P.second.containedNegateRAState() && !P.second.isIgnored();
});
ParallelUtilities::runOnEachFunction(
BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, WorkFun,
SkipPredicate, "MarkRAStates");
BC.outs() << "BOLT-INFO: MarkRAStates ran on " << Total
<< " functions. Ignored " << FunctionsIgnored << " functions "
<< format("(%.2lf%%)", (100.0 * FunctionsIgnored) / Total)
<< " because of CFI inconsistencies\n";
return Error::success();
}
} // end namespace bolt
} // end namespace llvm
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