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Revert "[clang][slh] add attribute for speculative load hardening" 

until I figure out why the build is failing or timing out

***************************

Summary:
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

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

This reverts commit a5b3c232d1e3613f23efbc3960f8e23ea70f2a79.
(r347617)

llvm-svn: 347628
This commit is contained in:
Zola Bridges 2018-11-27 02:22:00 +00:00
parent 5cec19dc1a
commit 0b35afd79d
9 changed files with 14 additions and 109 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
clang/include/clang/Basic/Attr.td
View File

@ -3091,9 +3091,3 @@ 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];
}

24
clang/include/clang/Basic/AttrDocs.td
View File

@ -3629,27 +3629,3 @@ 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 <https://llvm.org/docs/SpeculativeLoadHardening.html>`_
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.
}];
}

4
clang/lib/CodeGen/CGCall.cpp
View File

@ -1791,8 +1791,6 @@ 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);
}
@ -1856,8 +1854,6 @@ void CodeGenModule::ConstructAttributeList(
FuncAttrs.addAttribute(llvm::Attribute::NoDuplicate);
if (TargetDecl->hasAttr<ConvergentAttr>())
FuncAttrs.addAttribute(llvm::Attribute::Convergent);
if (TargetDecl->hasAttr<SpeculativeLoadHardeningAttr>())
FuncAttrs.addAttribute(llvm::Attribute::SpeculativeLoadHardening);
if (const FunctionDecl *Fn = dyn_cast<FunctionDecl>(TargetDecl)) {
AddAttributesFromFunctionProtoType(

3
clang/lib/Sema/SemaDeclAttr.cpp
View File

@ -6373,9 +6373,6 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
case ParsedAttr::AT_Section:
handleSectionAttr(S, D, AL);
break;
case ParsedAttr::AT_SpeculativeLoadHardening:
handleSimpleAttribute<SpeculativeLoadHardeningAttr>(S, D, AL);
break;
case ParsedAttr::AT_CodeSeg:
handleCodeSegAttr(S, D, AL);
break;

18
clang/test/CodeGen/attr-speculative-load-hardening.cpp
View File

@ -1,18 +0,0 @@
// 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{{.*}} }

9
clang/test/CodeGen/attr-speculative-load-hardening.m
View File

@ -1,9 +0,0 @@
// 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{{.*}} }

3
clang/test/Misc/pragma-attribute-supported-attributes-list.test
View File

@ -2,7 +2,7 @@
// The number of supported attributes should never go down!
// CHECK: #pragma clang attribute supports 130 attributes:
// CHECK: #pragma clang attribute supports 129 attributes:
// CHECK-NEXT: AMDGPUFlatWorkGroupSize (SubjectMatchRule_function)
// CHECK-NEXT: AMDGPUNumSGPR (SubjectMatchRule_function)
// CHECK-NEXT: AMDGPUNumVGPR (SubjectMatchRule_function)
@ -116,7 +116,6 @@
// 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)

34
clang/test/SemaCXX/attr-speculative-load-hardening.cpp
View File

@ -1,34 +0,0 @@
// 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 <typename T>
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 <typename T>
[[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();
};

22
llvm/docs/LangRef.rst
View File

@ -1643,15 +1643,19 @@ example:
``speculative_load_hardening``
This attribute indicates that
`Speculative Load Hardening <https://llvm.org/docs/SpeculativeLoadHardening.html>`_
should be enabled for the function body.
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.
should be enabled for the function body. This is a best-effort attempt to
mitigate all known speculative execution information leak vulnerabilities
that are based on the fundamental principles of modern processors'
speculative execution. These vulnerabilities are classified as "Spectre
variant #1" vulnerabilities typically. Notably, this does not attempt to
mitigate any vulnerabilities where the speculative execution and/or
prediction devices of specific processors can be *completely* undermined
(such as "Branch Target Injection", a.k.a, "Spectre variant #2"). Instead,
this is a target-independent request to harden against the completely
generic risk posed by speculative execution to incorrectly load secret data,
making it available to some micro-architectural side-channel for information
leak. For a processor without any speculative execution or predictors, this
is expected to be a no-op.
When inlining, the attribute is sticky. Inlining a function that carries
this attribute will cause the caller to gain the attribute. This is intended