[safestack] Add option for non-TLS unsafe stack pointer.
This patch adds an option, -safe-stack-no-tls, for using normal
storage instead of thread-local storage for the unsafe stack pointer.
This can be useful when SafeStack is applied to an operating system
kernel.
http://reviews.llvm.org/D15673
Patch by Michael LeMay.
llvm-svn: 256221
diff --git a/llvm/lib/Transforms/Instrumentation/SafeStack.cpp b/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
index 4441663..abed465 100644
--- a/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SafeStack.cpp
@@ -47,6 +47,17 @@
#define DEBUG_TYPE "safestack"
+enum UnsafeStackPtrStorageVal { ThreadLocalUSP, SingleThreadUSP };
+
+static cl::opt<UnsafeStackPtrStorageVal> USPStorage("safe-stack-usp-storage",
+ cl::Hidden, cl::init(ThreadLocalUSP),
+ cl::desc("Type of storage for the unsafe stack pointer"),
+ cl::values(clEnumValN(ThreadLocalUSP, "thread-local",
+ "Thread-local storage"),
+ clEnumValN(SingleThreadUSP, "single-thread",
+ "Non-thread-local storage"),
+ clEnumValEnd));
+
namespace llvm {
STATISTIC(NumFunctions, "Total number of functions");
@@ -344,19 +355,25 @@
auto UnsafeStackPtr =
dyn_cast_or_null<GlobalVariable>(M.getNamedValue(UnsafeStackPtrVar));
+ bool UseTLS = USPStorage == ThreadLocalUSP;
+
if (!UnsafeStackPtr) {
+ auto TLSModel = UseTLS ?
+ GlobalValue::InitialExecTLSModel :
+ GlobalValue::NotThreadLocal;
// The global variable is not defined yet, define it ourselves.
// We use the initial-exec TLS model because we do not support the
// variable living anywhere other than in the main executable.
UnsafeStackPtr = new GlobalVariable(
M, StackPtrTy, false, GlobalValue::ExternalLinkage, nullptr,
- UnsafeStackPtrVar, nullptr, GlobalValue::InitialExecTLSModel);
+ UnsafeStackPtrVar, nullptr, TLSModel);
} else {
// The variable exists, check its type and attributes.
if (UnsafeStackPtr->getValueType() != StackPtrTy)
report_fatal_error(Twine(UnsafeStackPtrVar) + " must have void* type");
- if (!UnsafeStackPtr->isThreadLocal())
- report_fatal_error(Twine(UnsafeStackPtrVar) + " must be thread-local");
+ if (UseTLS != UnsafeStackPtr->isThreadLocal())
+ report_fatal_error(Twine(UnsafeStackPtrVar) + " must " +
+ (UseTLS ? "" : "not ") + "be thread-local");
}
return UnsafeStackPtr;
}