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[StackProtector] Introduce stack-protect-refinement pass to remove unnecessary protections.
This pass uses StackSafetyGlobalAnalysis to reduce number of functions that require stack protector.
1 parent 531cf82 commit 7a7ced9

30 files changed

+208
-18
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‎llvm/include/llvm/Transforms/Scalar/StackProtectRefinement.h

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//===- StackProtectRefinement.h - Stack Protect Refinement ----------------===//
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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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//
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// Remove ssp attributes from functions where we can prove it is safe.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_SCALAR_STACKPROTECTREFINEMENT_H
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#define LLVM_TRANSFORMS_SCALAR_STACKPROTECTREFINEMENT_H
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#include "llvm/Analysis/StackSafetyAnalysis.h"
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#include "llvm/IR/PassManager.h"
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namespace llvm {
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class BasicBlock;
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class Function;
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class Instruction;
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class StackProtectRefinementPass
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: public PassInfoMixin<StackProtectRefinementPass> {
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public:
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PreservedAnalyses run(Module &M, ModuleAnalysisManager &MAM);
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private:
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void processFunction(Function &F) const;
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const StackSafetyGlobalInfo *SSI;
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_SCALAR_STACKPROTECTREFINEMENT_H

‎llvm/lib/Passes/PassBuilder.cpp

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#include "llvm/Transforms/Scalar/SimplifyCFG.h"
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#include "llvm/Transforms/Scalar/Sink.h"
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#include "llvm/Transforms/Scalar/SpeculativeExecution.h"
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#include "llvm/Transforms/Scalar/StackProtectRefinement.h"
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#include "llvm/Transforms/Scalar/StraightLineStrengthReduce.h"
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#include "llvm/Transforms/Scalar/StructurizeCFG.h"
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#include "llvm/Transforms/Scalar/TailRecursionElimination.h"

‎llvm/lib/Passes/PassBuilderPipelines.cpp

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#include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h"
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#include "llvm/Transforms/Scalar/SimplifyCFG.h"
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#include "llvm/Transforms/Scalar/SpeculativeExecution.h"
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#include "llvm/Transforms/Scalar/StackProtectRefinement.h"
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#include "llvm/Transforms/Scalar/TailRecursionElimination.h"
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#include "llvm/Transforms/Scalar/WarnMissedTransforms.h"
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#include "llvm/Transforms/Utils/AddDiscriminators.h"
@@ -1278,6 +1279,9 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
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else
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MPM.addPass(buildInlinerPipeline(Level, Phase));
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if (Level != OptimizationLevel::O0)
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MPM.addPass(StackProtectRefinementPass());
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// Remove any dead arguments exposed by cleanups, constant folding globals,
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// and argument promotion.
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MPM.addPass(DeadArgumentEliminationPass());
@@ -1944,6 +1948,8 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
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// is fixed.
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MPM.addPass(WholeProgramDevirtPass(ExportSummary, nullptr));
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MPM.addPass(StackProtectRefinementPass());
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// Stop here at -O1.
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if (Level == OptimizationLevel::O1) {
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// The LowerTypeTestsPass needs to run to lower type metadata and the

‎llvm/lib/Passes/PassRegistry.def

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@@ -160,6 +160,7 @@ MODULE_PASS("scc-oz-module-inliner",
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buildInlinerPipeline(OptimizationLevel::Oz,
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ThinOrFullLTOPhase::None))
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MODULE_PASS("shadow-stack-gc-lowering", ShadowStackGCLoweringPass())
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MODULE_PASS("stack-protect-refinement", StackProtectRefinementPass())
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MODULE_PASS("strip", StripSymbolsPass())
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MODULE_PASS("strip-dead-debug-info", StripDeadDebugInfoPass())
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MODULE_PASS("strip-dead-prototypes", StripDeadPrototypesPass())

‎llvm/lib/Transforms/Scalar/CMakeLists.txt

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SimplifyCFGPass.cpp
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Sink.cpp
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SpeculativeExecution.cpp
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StackProtectRefinement.cpp
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StraightLineStrengthReduce.cpp
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StructurizeCFG.cpp
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TailRecursionElimination.cpp

‎llvm/lib/Transforms/Scalar/StackProtectRefinement.cpp

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//===- StackProtectRefinement.cpp - Stack Protect Refinement --------------===//
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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/Transforms/Scalar/StackProtectRefinement.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/Support/CommandLine.h"
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using namespace llvm;
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#define DEBUG_TYPE "stack-protect-refinement"
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STATISTIC(
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NumFuncsWithAllocaInst,
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"Number of functions with an instruction to allocate memory on the stack");
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STATISTIC(NumFuncsWithRemovedStackProtectAttr,
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"Number of functions with alloca and removed stack protect attr");
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static cl::opt<bool>
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UseStackSafety("optimize-ssp", cl::init(true), cl::Hidden,
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cl::desc("Use Stack Safety analysis results"));
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void StackProtectRefinementPass::processFunction(Function &F) const {
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bool hasAlloca = false;
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for (auto &I : instructions(&F)) {
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if (auto *AI = dyn_cast<AllocaInst>(&I)) {
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hasAlloca = true;
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if (!SSI->isSafe(*AI)) {
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NumFuncsWithAllocaInst++;
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return;
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}
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}
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}
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if (hasAlloca) {
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NumFuncsWithAllocaInst++;
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NumFuncsWithRemovedStackProtectAttr++;
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}
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F.removeFnAttr(Attribute::StackProtect);
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F.removeFnAttr(Attribute::StackProtectStrong);
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}
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PreservedAnalyses StackProtectRefinementPass::run(Module &M,
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ModuleAnalysisManager &MAM) {
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if (!UseStackSafety)
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return PreservedAnalyses::all();
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SSI = &MAM.getResult<StackSafetyGlobalAnalysis>(M);
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for (Function &F : M)
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if (F.hasFnAttribute(Attribute::StackProtect) ||
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F.hasFnAttribute(Attribute::StackProtectStrong))
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processFunction(F);
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return PreservedAnalyses::all();
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}

‎llvm/test/CodeGen/AArch64/GlobalISel/dynamic-alloca-lifetime.ll

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; RUN: llc -mtriple aarch64-unknown-unknown -global-isel \
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; RUN: llc -optimize-ssp=false -mtriple aarch64-unknown-unknown -global-isel \
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; RUN: -no-stack-coloring=false -pass-remarks-missed=gisel* < %s \
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; RUN: 2>&1 | FileCheck %s
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‎llvm/test/CodeGen/ARM/ifcvt-regmask-noreturn.ll

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; RUN: llc %s -o - -verify-machineinstrs | FileCheck %s
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; RUN: llc %s -o - -optimize-ssp=false -verify-machineinstrs | FileCheck %s
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target datalayout = "e-m:o-p:32:32-f64:32:64-v64:32:64-v128:32:128-a:0:32-n32-S32"
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target triple = "thumbv7s-apple-ios8.0.0"

‎llvm/test/CodeGen/ARM/ssp-data-layout.ll

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; RUN: llc < %s -frame-pointer=all -mcpu=cortex-a8 -mtriple arm-linux-gnu -target-abi=apcs -o - | FileCheck %s
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; RUN: llc < %s -optimize-ssp=false -frame-pointer=all -mcpu=cortex-a8 -mtriple arm-linux-gnu -target-abi=apcs -o - | FileCheck %s
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; This test is fairly fragile. The goal is to ensure that "large" stack
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; objects are allocated closest to the stack protector (i.e., farthest away
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; from the Stack Pointer.) In standard SSP mode this means that large (>=

‎llvm/test/CodeGen/X86/2009-04-14-IllegalRegs.ll

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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc < %s -mtriple=i386-apple-darwin -O0 -regalloc=fast | FileCheck %s
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; RUN: llc < %s -optimize-ssp=false -mtriple=i386-apple-darwin -O0 -regalloc=fast | FileCheck %s
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; rdar://6787136
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%struct.X = type { i8, [32 x i8] }

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