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[LLVM][rtsan] Add module pass to initialize rtsan #118989

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Dec 6, 2024
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[LLVM][rtsan] Add module pass to initialize rtsan #118989

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[LLVM][rtsan] Add module pass to initialize rtsan
cjappl Dec 6, 2024
7cfc1b7
[PR] fmayer - Add check that init happens in global ctor
cjappl Dec 6, 2024
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4 changes: 3 additions & 1 deletion clang/lib/CodeGen/BackendUtil.cpp
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Expand Up @@ -1024,12 +1024,14 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
FPM.addPass(BoundsCheckingPass());
});

if (LangOpts.Sanitize.has(SanitizerKind::Realtime))
if (LangOpts.Sanitize.has(SanitizerKind::Realtime)) {
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@cjappl
@why do we use this location and not addSanitizers? In particular registerOptimizerLastEPCallback?

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I'll investigate if moving it is possible! Off the top of my head I don't know if there is a reason.

I'll report back with PRs on either/both of these soon.

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You need to consider performance vs quality.

For other sanitizers it's essentially:

  1. If it's early - better precision - in sense we detect issues in C/C++ program which can be optimized out. (can Realtime related issue be optimized out, and do you care about them at all)
  2. If it's late - better performance, but we may miss bugs
    I believe performance is ~2x difference, so we can't afford that e.g. in Asan.

PB.registerScalarOptimizerLateEPCallback(
[](FunctionPassManager &FPM, OptimizationLevel Level) {
RealtimeSanitizerOptions Opts;
FPM.addPass(RealtimeSanitizerPass(Opts));
});
MPM.addPass(ModuleRealtimeSanitizerPass());
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Also we converted all but tsan from function+module to just module pass. Easier to maintain.

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Sounds good, I'll work on swapping rtsan over.

}

// Don't add sanitizers if we are here from ThinLTO PostLink. That already
// done on PreLink stage.
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7 changes: 7 additions & 0 deletions llvm/include/llvm/Transforms/Instrumentation/RealtimeSanitizer.h
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Expand Up @@ -33,6 +33,13 @@ class RealtimeSanitizerPass : public PassInfoMixin<RealtimeSanitizerPass> {
static bool isRequired() { return true; }
};

/// Create ctor and init functions.
struct ModuleRealtimeSanitizerPass
: public PassInfoMixin<ModuleRealtimeSanitizerPass> {
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
static bool isRequired() { return true; }
};

} // namespace llvm

#endif // LLVM_TRANSFORMS_INSTRUMENTATION_REALTIMESANITIZER_H
1 change: 1 addition & 0 deletions llvm/lib/Passes/PassRegistry.def
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Expand Up @@ -138,6 +138,7 @@ MODULE_PASS("rel-lookup-table-converter", RelLookupTableConverterPass())
MODULE_PASS("rewrite-statepoints-for-gc", RewriteStatepointsForGC())
MODULE_PASS("rewrite-symbols", RewriteSymbolPass())
MODULE_PASS("rpo-function-attrs", ReversePostOrderFunctionAttrsPass())
MODULE_PASS("rtsan-module", ModuleRealtimeSanitizerPass())
MODULE_PASS("sample-profile", SampleProfileLoaderPass())
MODULE_PASS("sancov-module", SanitizerCoveragePass())
MODULE_PASS("sanmd-module", SanitizerBinaryMetadataPass())
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15 changes: 15 additions & 0 deletions llvm/lib/Transforms/Instrumentation/RealtimeSanitizer.cpp
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Expand Up @@ -17,12 +17,16 @@
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Module.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"

#include "llvm/Demangle/Demangle.h"
#include "llvm/Transforms/Instrumentation/RealtimeSanitizer.h"

using namespace llvm;

const char kRtsanModuleCtorName[] = "rtsan.module_ctor";
const char kRtsanInitName[] = "__rtsan_ensure_initialized";

static SmallVector<Type *> getArgTypes(ArrayRef<Value *> FunctionArgs) {
SmallVector<Type *> Types;
for (Value *Arg : FunctionArgs)
Expand Down Expand Up @@ -89,3 +93,14 @@ PreservedAnalyses RealtimeSanitizerPass::run(Function &Fn,

return PreservedAnalyses::all();
}

PreservedAnalyses ModuleRealtimeSanitizerPass::run(Module &M,
ModuleAnalysisManager &MAM) {
getOrCreateSanitizerCtorAndInitFunctions(
M, kRtsanModuleCtorName, kRtsanInitName, /*InitArgTypes=*/{},
/*InitArgs=*/{},
// This callback is invoked when the functions are created the first
// time. Hook them into the global ctors list in that case:
[&](Function *Ctor, FunctionCallee) { appendToGlobalCtors(M, Ctor, 0); });
return PreservedAnalyses::none();
}
9 changes: 8 additions & 1 deletion llvm/test/Instrumentation/RealtimeSanitizer/rtsan.ll
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@@ -1,4 +1,4 @@
; RUN: opt < %s -passes=rtsan -S | FileCheck %s
; RUN: opt < %s -passes='function(rtsan),module(rtsan-module)' -S | FileCheck %s

define void @violation() #0 {
%1 = alloca ptr, align 8
Expand All @@ -18,10 +18,17 @@ define noundef i32 @main() #2 {

attributes #0 = { mustprogress noinline sanitize_realtime optnone ssp uwtable(sync) }

; RealtimeSanitizer pass should insert call to initialize the runtime
; CHECK: @llvm.used = appending global [1 x ptr] [ptr @rtsan.module_ctor]
; CHECK: @llvm.global_ctors = {{.*}}@rtsan.module_ctor

; RealtimeSanitizer pass should insert __rtsan_realtime_enter right after function definition
; CHECK-LABEL: @violation()
; CHECK-NEXT: call{{.*}}@__rtsan_realtime_enter

; RealtimeSanitizer pass should insert __rtsan_realtime_exit right before function return
; CHECK: call{{.*}}@__rtsan_realtime_exit
; CHECK-NEXT: ret{{.*}}void

; CHECK-LABEL: define internal void @rtsan.module_ctor()
; CHECK-NEXT: call void @__rtsan_ensure_initialized()
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