Author: manojgupta
Date: Wed May 9 14:41:18 2018
New Revision: 331925
URL: http://llvm.org/viewvc/llvm-project?rev=331925&view=rev
Log:
[Clang] Implement function attribute no_stack_protector.
Summary:
This attribute tells clang to skip this function from stack protector
when -stack-protector option is passed.
GCC option for this is:
__attribute__((__optimize__("no-stack-protector"))) and the
equivalent clang syntax would be: __attribute__((no_stack_protector))
This is used in Linux kernel to selectively disable stack protector
in certain functions.
Reviewers: aaron.ballman, rsmith, rnk, probinson
Reviewed By: aaron.ballman
Subscribers: probinson, srhines, cfe-commits
Differential Revision: https://reviews.llvm.org/D46300
Added:
cfe/trunk/test/Sema/no_stack_protector.c
Modified:
cfe/trunk/include/clang/Basic/Attr.td
cfe/trunk/include/clang/Basic/AttrDocs.td
cfe/trunk/lib/CodeGen/CodeGenModule.cpp
cfe/trunk/lib/Sema/SemaDeclAttr.cpp
cfe/trunk/test/CodeGen/stack-protector.c
Modified: cfe/trunk/include/clang/Basic/Attr.td
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Attr.td?rev=331925&r1=331924&r2=331925&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/Attr.td (original)
+++ cfe/trunk/include/clang/Basic/Attr.td Wed May 9 14:41:18 2018
@@ -1495,6 +1495,12 @@ def NotTailCalled : InheritableAttr {
let Documentation = [NotTailCalledDocs];
}
+def NoStackProtector : InheritableAttr {
+ let Spellings = [Clang<"no_stack_protector">];
+ let Subjects = SubjectList<[Function]>;
+ let Documentation = [NoStackProtectorDocs];
+}
+
def NoThrow : InheritableAttr {
let Spellings = [GCC<"nothrow">, Declspec<"nothrow">];
let Subjects = SubjectList<[Function]>;
Modified: cfe/trunk/include/clang/Basic/AttrDocs.td
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/AttrDocs.td?rev=331925&r1=331924&r2=331925&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/AttrDocs.td (original)
+++ cfe/trunk/include/clang/Basic/AttrDocs.td Wed May 9 14:41:18 2018
@@ -2740,6 +2740,28 @@ The syntax of the declare target directi
}];
}
+def NoStackProtectorDocs : Documentation {
+ let Category = DocCatFunction;
+ let Content = [{
+Clang supports the ``__attribute__((no_stack_protector))`` attribute which
disables
+the stack protector on the specified function. This attribute is useful for
+selectively disabling the stack protector on some functions when building with
+``-fstack-protector`` compiler option.
+
+For example, it disables the stack protector for the function ``foo`` but
function
+``bar`` will still be built with the stack protector with the
``-fstack-protector``
+option.
+
+.. code-block:: c
+
+ int __attribute__((no_stack_protector))
+ foo (int x); // stack protection will be disabled for foo.
+
+ int bar(int y); // bar can be built with the stack protector.
+
+ }];
+}
+
def NotTailCalledDocs : Documentation {
let Category = DocCatFunction;
let Content = [{
Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=331925&r1=331924&r2=331925&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Wed May 9 14:41:18 2018
@@ -1142,12 +1142,14 @@ void CodeGenModule::SetLLVMFunctionAttri
if (!hasUnwindExceptions(LangOpts))
B.addAttribute(llvm::Attribute::NoUnwind);
- if (LangOpts.getStackProtector() == LangOptions::SSPOn)
- B.addAttribute(llvm::Attribute::StackProtect);
- else if (LangOpts.getStackProtector() == LangOptions::SSPStrong)
- B.addAttribute(llvm::Attribute::StackProtectStrong);
- else if (LangOpts.getStackProtector() == LangOptions::SSPReq)
- B.addAttribute(llvm::Attribute::StackProtectReq);
+ if (!D || !D->hasAttr<NoStackProtectorAttr>()) {
+ if (LangOpts.getStackProtector() == LangOptions::SSPOn)
+ B.addAttribute(llvm::Attribute::StackProtect);
+ else if (LangOpts.getStackProtector() == LangOptions::SSPStrong)
+ B.addAttribute(llvm::Attribute::StackProtectStrong);
+ else if (LangOpts.getStackProtector() == LangOptions::SSPReq)
+ B.addAttribute(llvm::Attribute::StackProtectReq);
+ }
if (!D) {
// If we don't have a declaration to control inlining, the function isn't
Modified: cfe/trunk/lib/Sema/SemaDeclAttr.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclAttr.cpp?rev=331925&r1=331924&r2=331925&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDeclAttr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDeclAttr.cpp Wed May 9 14:41:18 2018
@@ -6230,6 +6230,10 @@ static void ProcessDeclAttribute(Sema &S
case AttributeList::AT_NoInstrumentFunction: // Interacts with -pg.
handleSimpleAttribute<NoInstrumentFunctionAttr>(S, D, AL);
break;
+ case AttributeList::AT_NoStackProtector:
+ // Interacts with -fstack-protector options.
+ handleSimpleAttribute<NoStackProtectorAttr>(S, D, AL);
+ break;
case AttributeList::AT_StdCall:
case AttributeList::AT_CDecl:
case AttributeList::AT_FastCall:
Modified: cfe/trunk/test/CodeGen/stack-protector.c
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/stack-protector.c?rev=331925&r1=331924&r2=331925&view=diff
==============================================================================
--- cfe/trunk/test/CodeGen/stack-protector.c (original)
+++ cfe/trunk/test/CodeGen/stack-protector.c Wed May 9 14:41:18 2018
@@ -22,6 +22,14 @@ void test1(const char *msg) {
printf("%s\n", a);
}
+// DEF: define {{.*}}void @test2(i8* %msg) #[[B:.*]] {
+__attribute__((no_stack_protector))
+void test2(const char *msg) {
+ char a[strlen(msg) + 1];
+ strcpy(a, msg);
+ printf("%s\n", a);
+}
+
// NOSSP-NOT: attributes #[[A]] = {{.*}} ssp
// SSP: attributes #[[A]] = {{.*}} ssp{{ }}
// SSPSTRONG: attributes #[[A]] = {{.*}} sspstrong
@@ -33,3 +41,15 @@ void test1(const char *msg) {
// SAFESTACK-SSP: attributes #[[A]] = {{.*}} safestack ssp{{ }}
// SAFESTACK-SSPSTRONG: attributes #[[A]] = {{.*}} safestack sspstrong
// SAFESTACK-SSPREQ: attributes #[[A]] = {{.*}} safestack sspreq
+
+// NOSSP-NOT: attributes #[[B]] = {{.*}} ssp
+// SSP-NOT: attributes #[[B]] = {{.*}} ssp{{ }}
+// SSPSTRONG-NOT: attributes #[[B]] = {{.*}} sspstrong
+// SSPREQ-NOT: attributes #[[B]] = {{.*}} sspreq
+
+// SAFESTACK-SSP: attributes #[[B]] = {{.*}} safestack
+// SAFESTACK-SSP-NOT: attributes #[[B]] = {{.*}} safestack ssp{{ }}
+// SAFESTACK-SSPSTRONG: attributes #[[B]] = {{.*}} safestack
+// SAFESTACK-SSPSTRONG-NOT: attributes #[[B]] = {{.*}} safestack sspstrong
+// SAFESTACK-SSPREQ: attributes #[[B]] = {{.*}} safestack
+// SAFESTACK-SSPREQ-NOT: attributes #[[B]] = {{.*}} safestack sspreq
Added: cfe/trunk/test/Sema/no_stack_protector.c
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/no_stack_protector.c?rev=331925&view=auto
==============================================================================
--- cfe/trunk/test/Sema/no_stack_protector.c (added)
+++ cfe/trunk/test/Sema/no_stack_protector.c Wed May 9 14:41:18 2018
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void __attribute__((no_stack_protector)) foo() {}
+int __attribute__((no_stack_protector)) var; // expected-warning
{{'no_stack_protector' attribute only applies to functions}}
+void __attribute__((no_stack_protector(2))) bar() {} // expected-error
{{'no_stack_protector' attribute takes no arguments}}
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
