weimingz created this revision.
weimingz added reviewers: olista01, jmolloy.
weimingz added a subscriber: cfe-commits.
Herald added subscribers: rengolin, aemerson.
This patch adds diagnoses when initializing a global variable using the address
of another global variable that uses ROPI/RWPI relocation model.
For example,
int a;
extern void foo();
int *x = &a; // we cannot statically initialize x with -frwpi
void *y = &foo(); // we can't statically initialize y with -fropi
The above code will trigger diagnoses like:
error: 'x' cannot be initialized using address of 'a' with 'rwpi' relocation
https://reviews.llvm.org/D28526
Files:
include/clang/Basic/DiagnosticSemaKinds.td
lib/CodeGen/CGDecl.cpp
lib/CodeGen/CodeGenModule.cpp
lib/CodeGen/CodeGenModule.h
test/CodeGen/arm-ropi-rwpi.c
Index: test/CodeGen/arm-ropi-rwpi.c
===================================================================
--- /dev/null
+++ test/CodeGen/arm-ropi-rwpi.c
@@ -0,0 +1,56 @@
+// REQUIRES: arm-registered-target
+
+// OK with local initialization, rwpi with const gv and ropi with non-const gv.
+// RUN: %clang_cc1 -triple armv7 -mrelocation-model ropi-rwpi %s -S -o /dev/null
+// RUN: %clang_cc1 -triple armv7 -mrelocation-model rwpi -DTEST_RO_1 -DTEST_RO_2 -DTEST_RO_STATIC %s -S -o /dev/null
+// RUN: %clang_cc1 -triple armv7 -mrelocation-model ropi -DTEST_RW_1 -DTEST_RW_STATIC %s -S -o /dev/null
+
+// RUN: not %clang_cc1 -triple armv7 -mrelocation-model ropi -DTEST_RO_1 %s -S -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-RO-1
+// RUN: not %clang_cc1 -triple armv7 -mrelocation-model ropi -DTEST_RO_2 %s -S -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-RO-2
+// RUN: not %clang_cc1 -triple armv7 -mrelocation-model ropi -DTEST_RO_STATIC %s -S -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-RO-STATIC
+
+// RUN: not %clang_cc1 -triple armv7 -mrelocation-model rwpi -DTEST_RW_1 %s -S -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-RW-1
+
+// RUN: not %clang_cc1 -triple armv7 -mrelocation-model ropi-rwpi -DTEST_RW_STATIC %s -S -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-RW-STATIC
+
+extern int func(void);
+
+extern int gv;
+
+extern const int c_gv;
+
+#ifdef TEST_RO_1
+void *p1 = &func;
+#endif
+// CHECK-RO-1: error: 'p1' cannot be initilized using address of 'func' with 'ropi' relocation
+
+#ifdef TEST_RO_2
+const void *p2 = &c_gv;
+#endif
+// CHECK-RO-2: error: 'p2' cannot be initilized using address of 'c_gv' with 'ropi' relocation
+
+#ifdef TEST_RO_STATIC
+void bar() {
+ static void *sp = &func;
+}
+#endif
+// CHECK-RO-STATIC: error: 'bar.sp' cannot be initilized using address of 'func' with 'ropi' relocation
+
+#ifdef TEST_RW_1
+void *p3 = &gv;
+#endif
+// CHECK-RW-1: error: 'p3' cannot be initilized using address of 'gv' with 'rwpi' relocation
+
+#ifdef TEST_RW_STATIC
+void bar2() {
+ static void *sp = &gv;
+}
+#endif
+// CHECK-RW-STATIC: error: 'bar2.sp' cannot be initilized using address of 'gv' with 'ropi-rwpi' relocation
+
+unsigned test() {
+ unsigned a = (unsigned)&func;
+ unsigned b = (unsigned)&gv;
+ unsigned c = (unsigned)&c_gv;
+ return a + b + c;
+}
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -500,6 +500,9 @@
/// MDNodes.
llvm::DenseMap<QualType, llvm::Metadata *> MetadataIdMap;
+ /// The relocaton model for ARM.
+ bool IsROPI, IsRWPI;
+
public:
CodeGenModule(ASTContext &C, const HeaderSearchOptions &headersearchopts,
const PreprocessorOptions &ppopts,
@@ -1189,6 +1192,10 @@
/// \param QT is the clang QualType of the null pointer.
llvm::Constant *getNullPointer(llvm::PointerType *T, QualType QT);
+ /// Check if a static initialization is valid for ROPI/RWPI.
+ bool isValidInitForPI(const llvm::Constant *Init, StringRef GVName,
+ SourceLocation Loc);
+
private:
llvm::Constant *
GetOrCreateLLVMFunction(StringRef MangledName, llvm::Type *Ty, GlobalDecl D,
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -159,6 +159,9 @@
// CoverageMappingModuleGen object.
if (CodeGenOpts.CoverageMapping)
CoverageMapping.reset(new CoverageMappingModuleGen(*this, *CoverageInfo));
+
+ IsROPI = StringRef(CodeGenOpts.RelocationModel).startswith("ropi");
+ IsRWPI = StringRef(CodeGenOpts.RelocationModel).endswith("rwpi");
}
CodeGenModule::~CodeGenModule() {}
@@ -2505,6 +2508,49 @@
GO.setComdat(TheModule.getOrInsertComdat(GO.getName()));
}
+/// Check if the address of a GV is used in the Init expr and the consntness
+/// matches with IsROPI. If such a GV is used, returns it.
+static const llvm::Constant *UseAddrOfGlobalVar(const llvm::Constant *Init,
+ bool IsROPI) {
+ if (!Init)
+ return nullptr;
+ if (isa<llvm::GlobalValue>(Init)) {
+ bool IsConstGV = isa<llvm::Function>(Init);
+ if (!IsConstGV) {
+ if (isa<llvm::GlobalVariable>(Init))
+ IsConstGV = dyn_cast<llvm::GlobalVariable>(Init)->isConstant();
+ else
+ IsConstGV = UseAddrOfGlobalVar(
+ dyn_cast<llvm::GlobalAlias>(Init)->getAliasee(), IsROPI);
+ }
+ return IsConstGV == IsROPI ? Init : nullptr;
+ }
+ if (isa<llvm::ConstantExpr>(Init)) {
+ for (auto &Op : Init->operands()) {
+ const llvm::Constant *C = dyn_cast<llvm::Constant>(Op);
+ if (auto UsedGV = UseAddrOfGlobalVar(C, IsROPI))
+ return UsedGV;
+ }
+ return nullptr;
+ }
+ return nullptr;
+}
+
+bool CodeGenModule::isValidInitForPI(const llvm::Constant *Init,
+ StringRef GVName, SourceLocation Loc) {
+ // when RelocationModel is "ropi", "rwpi" or "ropi-rwpi", we cannot
+ // statically initialize a GV with the absolute address of another GV that has
+ // ropi/rwpi relocation type.
+ auto UsedGV = IsROPI ? UseAddrOfGlobalVar(Init, true) : nullptr;
+ UsedGV = IsRWPI ? UseAddrOfGlobalVar(Init, false) : UsedGV;
+ if (UsedGV) {
+ Diags.Report(Loc, diag::err_gv_initilized_with_address)
+ << GVName << UsedGV->getName() << CodeGenOpts.RelocationModel;
+ return false;
+ }
+ return true;
+}
+
/// Pass IsTentative as true if you want to create a tentative definition.
void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
bool IsTentative) {
@@ -2543,7 +2589,6 @@
} else {
initializedGlobalDecl = GlobalDecl(D);
Init = EmitConstantInit(*InitDecl);
-
if (!Init) {
QualType T = InitExpr->getType();
if (D->getType()->isReferenceType())
@@ -2656,6 +2701,10 @@
Linkage = llvm::GlobalValue::InternalLinkage;
}
}
+
+ if (!isValidInitForPI(Init, GV->getName(), D->getLocation()))
+ return;
+
GV->setInitializer(Init);
// If it is safe to mark the global 'constant', do so now.
Index: lib/CodeGen/CGDecl.cpp
===================================================================
--- lib/CodeGen/CGDecl.cpp
+++ lib/CodeGen/CGDecl.cpp
@@ -350,6 +350,8 @@
}
GV->setConstant(CGM.isTypeConstant(D.getType(), true));
+ if (!CGM.isValidInitForPI(Init, GV->getName(), D.getLocation()))
+ return nullptr;
GV->setInitializer(Init);
if (hasNontrivialDestruction(D.getType())) {
@@ -395,6 +397,8 @@
// If this value has an initializer, emit it.
if (D.getInit() && !isCudaSharedVar)
var = AddInitializerToStaticVarDecl(D, var);
+ if (!var)
+ return;
var->setAlignment(alignment.getQuantity());
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -187,6 +187,10 @@
def ext_flexible_array_init : Extension<
"flexible array initialization is a GNU extension">, InGroup<GNUFlexibleArrayInitializer>;
+// GV Initilizer for ROPI/RWPI
+def err_gv_initilized_with_address: Error<
+ "'%0' cannot be initilized using address of '%1' with '%2' relocation">;
+
// Declarations.
def ext_duplicate_declspec : ExtWarn<"duplicate '%0' declaration specifier">,
InGroup<DuplicateDeclSpecifier>;
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