From 732444d28901785aa22c5c58624c1e7ce2d74160 Mon Sep 17 00:00:00 2001 From: Zola Bridges Date: Tue, 27 Nov 2018 19:56:46 +0000 Subject: [PATCH] [clang][slh] add attribute for speculative load hardening Summary: Resubmit this with no changes because I think the build was broken by a different diff. ----- The prior diff had to be reverted because there were two tests that failed. I updated the two tests in this diff clang/test/Misc/pragma-attribute-supported-attributes-list.test clang/test/SemaCXX/attr-speculative-load-hardening.cpp ----- Summary from Previous Diff (Still Accurate) ----- LLVM IR already has an attribute for speculative_load_hardening. Before this commit, when a user passed the -mspeculative-load-hardening flag to Clang, every function would have this attribute added to it. This Clang attribute will allow users to opt into SLH on a function by function basis. This can be applied to functions and Objective C methods. Reviewers: chandlerc, echristo, kristof.beyls, aaron.ballman Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D54915 git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@347701 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/clang/Basic/Attr.td | 6 ++++ include/clang/Basic/AttrDocs.td | 24 +++++++++++++ lib/CodeGen/CGCall.cpp | 4 +++ lib/Sema/SemaDeclAttr.cpp | 3 ++ .../attr-speculative-load-hardening.cpp | 18 ++++++++++ .../CodeGen/attr-speculative-load-hardening.m | 9 +++++ ...a-attribute-supported-attributes-list.test | 3 +- .../attr-speculative-load-hardening.cpp | 34 +++++++++++++++++++ 8 files changed, 100 insertions(+), 1 deletion(-) create mode 100644 test/CodeGen/attr-speculative-load-hardening.cpp create mode 100644 test/CodeGen/attr-speculative-load-hardening.m create mode 100644 test/SemaCXX/attr-speculative-load-hardening.cpp diff --git a/include/clang/Basic/Attr.td b/include/clang/Basic/Attr.td index a6be48c234..5b52ba4f64 100644 --- a/include/clang/Basic/Attr.td +++ b/include/clang/Basic/Attr.td @@ -3091,3 +3091,9 @@ def AlwaysDestroy : InheritableAttr { let Subjects = SubjectList<[Var]>; let Documentation = [AlwaysDestroyDocs]; } + +def SpeculativeLoadHardening : InheritableAttr { + let Spellings = [Clang<"speculative_load_hardening">]; + let Subjects = SubjectList<[Function, ObjCMethod], ErrorDiag>; + let Documentation = [SpeculativeLoadHardeningDocs]; +} diff --git a/include/clang/Basic/AttrDocs.td b/include/clang/Basic/AttrDocs.td index e38c557f14..203ae82719 100644 --- a/include/clang/Basic/AttrDocs.td +++ b/include/clang/Basic/AttrDocs.td @@ -3629,3 +3629,27 @@ GNU inline semantics are the default behavior with ``-std=gnu89``, ``-std=c89``, ``-std=c94``, or ``-fgnu89-inline``. }]; } + +def SpeculativeLoadHardeningDocs : Documentation { + let Category = DocCatFunction; + let Content = [{ + This attribute can be applied to a function declaration in order to indicate + that `Speculative Load Hardening `_ + should be enabled for the function body. This can also be applied to a method + in Objective C. + + Speculative Load Hardening is a best-effort mitigation against + information leak attacks that make use of control flow + miss-speculation - specifically miss-speculation of whether a branch + is taken or not. Typically vulnerabilities enabling such attacks are + classified as "Spectre variant #1". Notably, this does not attempt to + mitigate against miss-speculation of branch target, classified as + "Spectre variant #2" vulnerabilities. + + When inlining, the attribute is sticky. Inlining a function that + carries this attribute will cause the caller to gain the + attribute. This is intended to provide a maximally conservative model + where the code in a function annotated with this attribute will always + (even after inlining) end up hardened. + }]; +} diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp index 0ec5c7fb45..6d89f3919f 100644 --- a/lib/CodeGen/CGCall.cpp +++ b/lib/CodeGen/CGCall.cpp @@ -1791,6 +1791,8 @@ void CodeGenModule::ConstructDefaultFnAttrList(StringRef Name, bool HasOptnone, if (CodeGenOpts.Backchain) FuncAttrs.addAttribute("backchain"); + // FIXME: The interaction of this attribute with the SLH command line flag + // has not been determined. if (CodeGenOpts.SpeculativeLoadHardening) FuncAttrs.addAttribute(llvm::Attribute::SpeculativeLoadHardening); } @@ -1854,6 +1856,8 @@ void CodeGenModule::ConstructAttributeList( FuncAttrs.addAttribute(llvm::Attribute::NoDuplicate); if (TargetDecl->hasAttr()) FuncAttrs.addAttribute(llvm::Attribute::Convergent); + if (TargetDecl->hasAttr()) + FuncAttrs.addAttribute(llvm::Attribute::SpeculativeLoadHardening); if (const FunctionDecl *Fn = dyn_cast(TargetDecl)) { AddAttributesFromFunctionProtoType( diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp index 9f5325d109..be662b9b91 100644 --- a/lib/Sema/SemaDeclAttr.cpp +++ b/lib/Sema/SemaDeclAttr.cpp @@ -6373,6 +6373,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, case ParsedAttr::AT_Section: handleSectionAttr(S, D, AL); break; + case ParsedAttr::AT_SpeculativeLoadHardening: + handleSimpleAttribute(S, D, AL); + break; case ParsedAttr::AT_CodeSeg: handleCodeSegAttr(S, D, AL); break; diff --git a/test/CodeGen/attr-speculative-load-hardening.cpp b/test/CodeGen/attr-speculative-load-hardening.cpp new file mode 100644 index 0000000000..e2eb805cbb --- /dev/null +++ b/test/CodeGen/attr-speculative-load-hardening.cpp @@ -0,0 +1,18 @@ +// RUN: %clang_cc1 -std=c++11 -disable-llvm-passes -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK1 +// RUN: %clang_cc1 -std=c++11 -disable-llvm-passes -emit-llvm %s -o - | FileCheck %s --check-prefix=CHECK2 +// +// Check that we set the attribute on each function. + +[[clang::speculative_load_hardening]] +int test1() { + return 42; +} + +int __attribute__((speculative_load_hardening)) test2() { + return 42; +} +// CHECK1: @{{.*}}test1{{.*}}[[SLH1:#[0-9]+]] +// CHECK1: attributes [[SLH1]] = { {{.*}}speculative_load_hardening{{.*}} } + +// CHECK2: @{{.*}}test2{{.*}}[[SLH2:#[0-9]+]] +// CHECK2: attributes [[SLH2]] = { {{.*}}speculative_load_hardening{{.*}} } diff --git a/test/CodeGen/attr-speculative-load-hardening.m b/test/CodeGen/attr-speculative-load-hardening.m new file mode 100644 index 0000000000..2de945b974 --- /dev/null +++ b/test/CodeGen/attr-speculative-load-hardening.m @@ -0,0 +1,9 @@ +// RUN: %clang -emit-llvm %s -o - -S | FileCheck %s -check-prefix=SLH + +int main() __attribute__((speculative_load_hardening)) { + return 0; +} + +// SLH: @{{.*}}main{{.*}}[[SLH:#[0-9]+]] + +// SLH: attributes [[SLH]] = { {{.*}}speculative_load_hardening{{.*}} } diff --git a/test/Misc/pragma-attribute-supported-attributes-list.test b/test/Misc/pragma-attribute-supported-attributes-list.test index 0a54c6c05a..0aa923de7d 100644 --- a/test/Misc/pragma-attribute-supported-attributes-list.test +++ b/test/Misc/pragma-attribute-supported-attributes-list.test @@ -2,7 +2,7 @@ // The number of supported attributes should never go down! -// CHECK: #pragma clang attribute supports 129 attributes: +// CHECK: #pragma clang attribute supports 130 attributes: // CHECK-NEXT: AMDGPUFlatWorkGroupSize (SubjectMatchRule_function) // CHECK-NEXT: AMDGPUNumSGPR (SubjectMatchRule_function) // CHECK-NEXT: AMDGPUNumVGPR (SubjectMatchRule_function) @@ -116,6 +116,7 @@ // CHECK-NEXT: ScopedLockable (SubjectMatchRule_record) // CHECK-NEXT: Section (SubjectMatchRule_function, SubjectMatchRule_variable_is_global, SubjectMatchRule_objc_method, SubjectMatchRule_objc_property) // CHECK-NEXT: SetTypestate (SubjectMatchRule_function_is_member) +// CHECK-NEXT: SpeculativeLoadHardening (SubjectMatchRule_function, SubjectMatchRule_objc_method) // CHECK-NEXT: SwiftContext (SubjectMatchRule_variable_is_parameter) // CHECK-NEXT: SwiftErrorResult (SubjectMatchRule_variable_is_parameter) // CHECK-NEXT: SwiftIndirectResult (SubjectMatchRule_variable_is_parameter) diff --git a/test/SemaCXX/attr-speculative-load-hardening.cpp b/test/SemaCXX/attr-speculative-load-hardening.cpp new file mode 100644 index 0000000000..bba3b6921e --- /dev/null +++ b/test/SemaCXX/attr-speculative-load-hardening.cpp @@ -0,0 +1,34 @@ +// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s + +int i __attribute__((speculative_load_hardening)); // expected-error {{'speculative_load_hardening' attribute only applies to functions}} + +void f1() __attribute__((speculative_load_hardening)); +void f2() __attribute__((speculative_load_hardening(1))); // expected-error {{'speculative_load_hardening' attribute takes no arguments}} + +template +void tf1() __attribute__((speculative_load_hardening)); + +int f3(int __attribute__((speculative_load_hardening)), int); // expected-error {{'speculative_load_hardening' attribute only applies to functions}} + +struct A { + int f __attribute__((speculative_load_hardening)); // expected-error {{'speculative_load_hardening' attribute only applies to functions}} + void mf1() __attribute__((speculative_load_hardening)); + static void mf2() __attribute__((speculative_load_hardening)); +}; + +int ci [[clang::speculative_load_hardening]]; // expected-error {{'speculative_load_hardening' attribute only applies to functions}} + +[[clang::speculative_load_hardening]] void cf1(); +[[clang::speculative_load_hardening(1)]] void cf2(); // expected-error {{'speculative_load_hardening' attribute takes no arguments}} + +template +[[clang::speculative_load_hardening]] +void ctf1(); + +int cf3(int c[[clang::speculative_load_hardening]], int); // expected-error {{'speculative_load_hardening' attribute only applies to functions}} + +struct CA { + int f [[clang::speculative_load_hardening]]; // expected-error {{'speculative_load_hardening' attribute only applies to functions}} + [[clang::speculative_load_hardening]] void mf1(); + [[clang::speculative_load_hardening]] static void mf2(); +}; -- 2.40.0