[sancov] Introduce optional callback for stack-depth tracking #138323
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@llvm/pr-subscribers-llvm-transforms @llvm/pr-subscribers-clang-codegen Author: Kees Cook (kees) ChangesNormally -fsanitize-coverage=stack-depth inserts inline arithmetic to update thread_local __sancov_lowest_stack. To support stack depth tracking in the Linux kernel, which does not implement traditional thread_local storage, provide the option to call a function instead. This matches the existing "stackleak" implementation that is supported in Linux via a GCC plugin. To make this coverage more performant, a minimum estimated stack depth can be chosen to enable the callback mode, skipping instrumentation of functions with smaller stacks. With -fsanitize-coverage-stack-depth-callback-min set greater than 0, the __sanitize_cov_stack_depth() callback will be injected when the estimated stack depth is greater than or equal to the given minimum. Full diff: https://github.com/llvm/llvm-project/pull/138323.diff 7 Files Affected:
diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index 927972015c3dc..452b1e325afb2 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -305,6 +305,7 @@ CODEGENOPT(SanitizeCoveragePCTable, 1, 0) ///< Create a PC Table.
CODEGENOPT(SanitizeCoverageControlFlow, 1, 0) ///< Collect control flow
CODEGENOPT(SanitizeCoverageNoPrune, 1, 0) ///< Disable coverage pruning.
CODEGENOPT(SanitizeCoverageStackDepth, 1, 0) ///< Enable max stack depth tracing
+VALUE_CODEGENOPT(SanitizeCoverageStackDepthCallbackMin , 32, 0) ///< Enable stack depth tracing callbacks.
CODEGENOPT(SanitizeCoverageTraceLoads, 1, 0) ///< Enable tracing of loads.
CODEGENOPT(SanitizeCoverageTraceStores, 1, 0) ///< Enable tracing of stores.
CODEGENOPT(SanitizeBinaryMetadataCovered, 1, 0) ///< Emit PCs for covered functions.
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 561b0498c549c..5823899bdb558 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2361,6 +2361,11 @@ def fsanitize_coverage_ignorelist : Joined<["-"], "fsanitize-coverage-ignorelist
HelpText<"Disable sanitizer coverage instrumentation for modules and functions "
"that match the provided special case list, even the allowed ones">,
MarshallingInfoStringVector<CodeGenOpts<"SanitizeCoverageIgnorelistFiles">>;
+def fsanitize_coverage_stack_depth_callback_min_EQ :
+ Joined<["-"], "fsanitize-coverage-stack-depth-callback-min=">,
+ Group<f_clang_Group>, MetaVarName<"<M>">,
+ HelpText<"Use callback for max stack depth tracing with minimum stack depth M">,
+ MarshallingInfoInt<CodeGenOpts<"SanitizeCoverageStackDepthCallbackMin">>;
def fexperimental_sanitize_metadata_EQ : CommaJoined<["-"], "fexperimental-sanitize-metadata=">,
Group<f_Group>,
HelpText<"Specify the type of metadata to emit for binary analysis sanitizers">;
diff --git a/clang/include/clang/Driver/SanitizerArgs.h b/clang/include/clang/Driver/SanitizerArgs.h
index 528e3b400f3dc..1213cd8dcd3b6 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -34,6 +34,7 @@ class SanitizerArgs {
std::vector<std::string> CoverageIgnorelistFiles;
std::vector<std::string> BinaryMetadataIgnorelistFiles;
int CoverageFeatures = 0;
+ int StackDepthCallbackMin = 0;
int BinaryMetadataFeatures = 0;
int OverflowPatternExclusions = 0;
int MsanTrackOrigins = 0;
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index c9ceb49ce5ceb..42c59377688b2 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -255,6 +255,7 @@ getSancovOptsFromCGOpts(const CodeGenOptions &CGOpts) {
Opts.InlineBoolFlag = CGOpts.SanitizeCoverageInlineBoolFlag;
Opts.PCTable = CGOpts.SanitizeCoveragePCTable;
Opts.StackDepth = CGOpts.SanitizeCoverageStackDepth;
+ Opts.StackDepthCallbackMin = CGOpts.SanitizeCoverageStackDepthCallbackMin;
Opts.TraceLoads = CGOpts.SanitizeCoverageTraceLoads;
Opts.TraceStores = CGOpts.SanitizeCoverageTraceStores;
Opts.CollectControlFlow = CGOpts.SanitizeCoverageControlFlow;
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index ff08bffdbde1f..414f68e4423e8 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -751,6 +751,16 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
options::OPT_fno_sanitize_ignorelist,
clang::diag::err_drv_malformed_sanitizer_ignorelist, DiagnoseErrors);
+ // Verify that -fsanitize-coverage-stack-depth-callback-min is >= 0.
+ if (Arg *A = Args.getLastArg(options::OPT_fsanitize_coverage_stack_depth_callback_min_EQ)) {
+ StringRef S = A->getValue();
+ if (S.getAsInteger(0, StackDepthCallbackMin) || StackDepthCallbackMin < 0) {
+ if (DiagnoseErrors)
+ D.Diag(clang::diag::err_drv_invalid_value)
+ << A->getAsString(Args) << S;
+ }
+ }
+
// Parse -f[no-]sanitize-memory-track-origins[=level] options.
if (AllAddedKinds & SanitizerKind::Memory) {
if (Arg *A =
@@ -1269,6 +1279,10 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
addSpecialCaseListOpt(Args, CmdArgs, "-fsanitize-coverage-ignorelist=",
CoverageIgnorelistFiles);
+ if (StackDepthCallbackMin)
+ CmdArgs.push_back(Args.MakeArgString("-fsanitize-coverage-stack-depth-callback-min=" +
+ Twine(StackDepthCallbackMin)));
+
if (!GPUSanitize) {
// Translate available BinaryMetadataFeatures to corresponding clang-cc1
// flags. Does not depend on any other sanitizers. Unsupported on GPUs.
diff --git a/llvm/include/llvm/Transforms/Utils/Instrumentation.h b/llvm/include/llvm/Transforms/Utils/Instrumentation.h
index 0e2c0d9bfa605..0b2ccf6180e1c 100644
--- a/llvm/include/llvm/Transforms/Utils/Instrumentation.h
+++ b/llvm/include/llvm/Transforms/Utils/Instrumentation.h
@@ -158,6 +158,7 @@ struct SanitizerCoverageOptions {
bool PCTable = false;
bool NoPrune = false;
bool StackDepth = false;
+ int StackDepthCallbackMin = 0;
bool TraceLoads = false;
bool TraceStores = false;
bool CollectControlFlow = false;
diff --git a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
index e52269637b92d..b8212b42b9d0c 100644
--- a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -33,6 +33,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/SpecialCaseList.h"
#include "llvm/Support/VirtualFileSystem.h"
+#include "llvm/Support/raw_ostream.h"
#include "llvm/TargetParser/Triple.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
@@ -86,6 +87,7 @@ const char SanCovPCsSectionName[] = "sancov_pcs";
const char SanCovCFsSectionName[] = "sancov_cfs";
const char SanCovCallbackGateSectionName[] = "sancov_gate";
+const char SanCovStackDepthCallbackName[] = "__sanitizer_cov_stack_depth";
const char SanCovLowestStackName[] = "__sancov_lowest_stack";
const char SanCovCallbackGateName[] = "__sancov_should_track";
@@ -152,6 +154,12 @@ static cl::opt<bool> ClStackDepth("sanitizer-coverage-stack-depth",
cl::desc("max stack depth tracing"),
cl::Hidden);
+static cl::opt<int> ClStackDepthCallbackMin(
+ "sanitizer-coverage-stack-depth-callback-min",
+ cl::desc("max stack depth tracing should use callback and only when "
+ "stack depth more than specified"),
+ cl::Hidden);
+
static cl::opt<bool>
ClCollectCF("sanitizer-coverage-control-flow",
cl::desc("collect control flow for each function"), cl::Hidden);
@@ -202,6 +210,8 @@ SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
Options.PCTable |= ClCreatePCTable;
Options.NoPrune |= !ClPruneBlocks;
Options.StackDepth |= ClStackDepth;
+ Options.StackDepthCallbackMin = std::max(Options.StackDepthCallbackMin,
+ ClStackDepthCallbackMin.getValue());
Options.TraceLoads |= ClLoadTracing;
Options.TraceStores |= ClStoreTracing;
Options.GatedCallbacks |= ClGatedCallbacks;
@@ -271,6 +281,7 @@ class ModuleSanitizerCoverage {
DomTreeCallback DTCallback;
PostDomTreeCallback PDTCallback;
+ FunctionCallee SanCovStackDepthCallback;
FunctionCallee SanCovTracePCIndir;
FunctionCallee SanCovTracePC, SanCovTracePCGuard;
std::array<FunctionCallee, 4> SanCovTraceCmpFunction;
@@ -514,6 +525,8 @@ bool ModuleSanitizerCoverage::instrumentModule() {
SanCovTracePCGuard =
M.getOrInsertFunction(SanCovTracePCGuardName, VoidTy, PtrTy);
+ SanCovStackDepthCallback = M.getOrInsertFunction(SanCovStackDepthCallbackName, VoidTy);
+
for (auto &F : M)
instrumentFunction(F);
@@ -1078,22 +1091,44 @@ void ModuleSanitizerCoverage::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
Store->setNoSanitizeMetadata();
}
if (Options.StackDepth && IsEntryBB && !IsLeafFunc) {
- // Check stack depth. If it's the deepest so far, record it.
Module *M = F.getParent();
- auto FrameAddrPtr = IRB.CreateIntrinsic(
- Intrinsic::frameaddress,
- IRB.getPtrTy(M->getDataLayout().getAllocaAddrSpace()),
- {Constant::getNullValue(Int32Ty)});
- auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
- auto LowestStack = IRB.CreateLoad(IntptrTy, SanCovLowestStack);
- auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
- auto ThenTerm = SplitBlockAndInsertIfThen(
- IsStackLower, &*IP, false,
- MDBuilder(IRB.getContext()).createUnlikelyBranchWeights());
- IRBuilder<> ThenIRB(ThenTerm);
- auto Store = ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
- LowestStack->setNoSanitizeMetadata();
- Store->setNoSanitizeMetadata();
+ if (Options.StackDepthCallbackMin) {
+ // In callback mode, only add call when stack depth reaches minimum.
+ const DataLayout &DL = M->getDataLayout();
+ uint32_t EstimatedStackSize = 0;
+
+ // Make an estimate on the stack usage.
+ for (auto &I : F.getEntryBlock()) {
+ if (auto *AI = dyn_cast<AllocaInst>(&I)) {
+ if (AI->isStaticAlloca()) {
+ uint32_t TypeSize = DL.getTypeAllocSize(AI->getAllocatedType());
+ EstimatedStackSize += TypeSize;
+ } else {
+ // Over-estimate dynamic sizes.
+ EstimatedStackSize += 4096;
+ }
+ }
+ }
+
+ if (EstimatedStackSize >= Options.StackDepthCallbackMin)
+ IRB.CreateCall(SanCovStackDepthCallback)->setCannotMerge();
+ } else {
+ // Check stack depth. If it's the deepest so far, record it.
+ auto FrameAddrPtr = IRB.CreateIntrinsic(
+ Intrinsic::frameaddress,
+ IRB.getPtrTy(M->getDataLayout().getAllocaAddrSpace()),
+ {Constant::getNullValue(Int32Ty)});
+ auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
+ auto LowestStack = IRB.CreateLoad(IntptrTy, SanCovLowestStack);
+ auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
+ auto ThenTerm = SplitBlockAndInsertIfThen(
+ IsStackLower, &*IP, false,
+ MDBuilder(IRB.getContext()).createUnlikelyBranchWeights());
+ IRBuilder<> ThenIRB(ThenTerm);
+ auto Store = ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
+ LowestStack->setNoSanitizeMetadata();
+ Store->setNoSanitizeMetadata();
+ }
}
}
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✅ With the latest revision this PR passed the C/C++ code formatter. |
Whoops, yes, I've fixed these now. |
intel-lab-lkp
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May 2, 2025
Wire up stackleak to Clang's proposed[1] stack depth tracking callback option. While __noinstr already contained __no_sanitize_coverage, it was still needed for __init and __head section markings. This is needed to make sure the callback is not executed in unsupported contexts. Link: llvm/llvm-project#138323 [1] Signed-off-by: Kees Cook <[email protected]>
lougovsk
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May 2, 2025
Wire up stackleak to Clang's proposed[1] stack depth tracking callback option. While __noinstr already contained __no_sanitize_coverage, it was still needed for __init and __head section markings. This is needed to make sure the callback is not executed in unsupported contexts. Link: llvm/llvm-project#138323 [1] Signed-off-by: Kees Cook <[email protected]> Message-Id: <[email protected]>
linux-riscv-bot
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May 2, 2025
Wire up stackleak to Clang's proposed[1] stack depth tracking callback option. While __noinstr already contained __no_sanitize_coverage, it was still needed for __init and __head section markings. This is needed to make sure the callback is not executed in unsupported contexts. Link: llvm/llvm-project#138323 [1] Signed-off-by: Kees Cook <[email protected]> Signed-off-by: Linux RISC-V bot <[email protected]>
melver
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May 4, 2025
Oh, yes, I will add those. Thanks! |
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Generally LGTM - but let's also wait for others to comment.
Documentation of this feature is lacking (and afaik also wasn't added in https://reviews.llvm.org/D36839). Given this will be used in the kernel, some kind of official documentation might be good to have.
Btw, if you want a runtime test, it's possible to add one similar to the one in compiler-rt/trunk/test/sanitizer_common/TestCases/sanitizer_coverage_stack_depth.cc.
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Okay, a couple small clean-ups, and I've also solved the lack of dynamic stack size tracking. |
vitalybuka
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bwendling
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Normally -fsanitize-coverage=stack-depth inserts inline arithmetic to update thread_local __sancov_lowest_stack. To support stack depth tracking in the Linux kernel, which does not implement traditional thread_local storage, provide the option to call a function instead. This matches the existing "stackleak" implementation that is supported in Linux via a GCC plugin. To make this coverage more performant, a minimum estimated stack depth can be chosen to enable the callback mode, skipping instrumentation of functions with smaller stacks. With -fsanitize-coverage-stack-depth-callback-min set greater than 0, the __sanitize_cov_stack_depth() callback will be injected when the estimated stack depth is greater than or equal to the given minimum.
Add documentation to detail the behaviors of the stack-depth tracer, including the new -fsanitize-coverage-stack-depth-callback-min=N argument.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/17269 Here is the relevant piece of the build log for the reference |
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Normally -fsanitize-coverage=stack-depth inserts inline arithmetic to update thread_local __sancov_lowest_stack. To support stack depth tracking in the Linux kernel, which does not implement traditional thread_local storage, provide the option to call a function instead.
This matches the existing "stackleak" implementation that is supported in Linux via a GCC plugin. To make this coverage more performant, a minimum estimated stack depth can be chosen to enable the callback mode, skipping instrumentation of functions with smaller stacks.
With -fsanitize-coverage-stack-depth-callback-min set greater than 0, the __sanitize_cov_stack_depth() callback will be injected when the estimated stack depth is greater than or equal to the given minimum.