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[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
This commit is contained in:
Evgeniy Stepanov 2015-12-22 00:13:11 +00:00
parent 5fe0455563
commit 8827f2db85
2 changed files with 25 additions and 3 deletions
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23
llvm/lib/Transforms/Instrumentation/SafeStack.cpp
View File

@ -47,6 +47,17 @@ using namespace llvm;
#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 @@ Value *SafeStack::getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F) {
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;
}

5
llvm/test/Transforms/SafeStack/array.ll
View File

@ -1,9 +1,14 @@
; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck %s
; RUN: opt -safe-stack -safe-stack-usp-storage=single-thread -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck -check-prefix=SINGLE-THREAD %s
; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck %s
; RUN: opt -safe-stack -safe-stack-usp-storage=single-thread -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck -check-prefix=SINGLE-THREAD %s
; array [4 x i8]
; Requires protector.
; CHECK: @__safestack_unsafe_stack_ptr = external thread_local(initialexec) global i8*
; SINGLE-THREAD: @__safestack_unsafe_stack_ptr = external global i8*
define void @foo(i8* %a) nounwind uwtable safestack {
entry:
; CHECK: %[[USP:.*]] = load i8*, i8** @__safestack_unsafe_stack_ptr