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[x86/SLH] Add a real Clang flag and LLVM IR attribute for Speculative

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Load Hardening.

Wires up the existing pass to work with a proper IR attribute rather
than just a hidden/internal flag. The internal flag continues to work
for now, but I'll likely remove it soon.

Most of the churn here is adding the IR attribute. I talked about this
Kristof Beyls and he seemed at least initially OK with this direction.
The idea of using a full attribute here is that we *do* expect at least
some forms of this for other architectures. There isn't anything
*inherently* x86-specific about this technique, just that we only have
an implementation for x86 at the moment.

While we could potentially expose this as a Clang-level attribute as
well, that seems like a good question to defer for the moment as it
isn't 100% clear whether that or some other programmer interface (or
both?) would be best. We'll defer the programmer interface side of this
for now, but at least get to the point where the feature can be enabled
without relying on implementation details.

This also allows us to do something that was really hard before: we can
enable *just* the indirect call retpolines when using SLH. For x86, we
don't have any other way to mitigate indirect calls. Other architectures
may take a different approach of course, and none of this is surfaced to
user-level flags.

Differential Revision: https://reviews.llvm.org/D51157

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341363 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2018-09-04 12:38:00 +00:00
parent 24a8df2c42
commit d2b1fb11d3
19 changed files with 105 additions and 21 deletions
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22
docs/LangRef.rst
View File

@ -1636,6 +1636,28 @@ example:
This attribute indicates that HWAddressSanitizer checks
(dynamic address safety analysis based on tagged pointers) are enabled for
this function.
``speculative_load_hardening``
This attribute indicates that
`Speculative Load Hardening <https://llvm.org/docs/SpeculativeLoadHardening.html>`_
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
to provide a maximally conservative model where the code in a function
annotated with this attribute will always (even after inlining) end up
hardened.
``speculatable``
This function attribute indicates that the function does not have any
effects besides calculating its result and does not have undefined behavior.

1
include/llvm/Bitcode/LLVMBitCodes.h
View File

@ -591,6 +591,7 @@ enum AttributeKindCodes {
ATTR_KIND_NOCF_CHECK = 56,
ATTR_KIND_OPT_FOR_FUZZING = 57,
ATTR_KIND_SHADOWCALLSTACK = 58,
ATTR_KIND_SPECULATIVE_LOAD_HARDENING = 59,
};
enum ComdatSelectionKindCodes {

9
include/llvm/IR/Attributes.td
View File

@ -176,6 +176,14 @@ def SanitizeMemory : EnumAttr<"sanitize_memory">;
/// HWAddressSanitizer is on.
def SanitizeHWAddress : EnumAttr<"sanitize_hwaddress">;
/// Speculative Load Hardening is enabled.
///
/// Note that this uses the default compatibility (always compatible during
/// inlining) and a conservative merge strategy where inlining an attributed
/// body will add the attribute to the caller. This ensures that code carrying
/// this attribute will always be lowered with hardening enabled.
def SpeculativeLoadHardening : EnumAttr<"speculative_load_hardening">;
/// Argument is swift error.
def SwiftError : EnumAttr<"swifterror">;
@ -232,6 +240,7 @@ def : MergeRule<"setAND<UnsafeFPMathAttr>">;
def : MergeRule<"setOR<NoImplicitFloatAttr>">;
def : MergeRule<"setOR<NoJumpTablesAttr>">;
def : MergeRule<"setOR<ProfileSampleAccurateAttr>">;
def : MergeRule<"setOR<SpeculativeLoadHardeningAttr>">;
def : MergeRule<"adjustCallerSSPLevel">;
def : MergeRule<"adjustCallerStackProbes">;
def : MergeRule<"adjustCallerStackProbeSize">;

1
lib/AsmParser/LLLexer.cpp
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@ -678,6 +678,7 @@ lltok::Kind LLLexer::LexIdentifier() {
KEYWORD(sanitize_hwaddress);
KEYWORD(sanitize_thread);
KEYWORD(sanitize_memory);
KEYWORD(speculative_load_hardening);
KEYWORD(swifterror);
KEYWORD(swiftself);
KEYWORD(uwtable);

5
lib/AsmParser/LLParser.cpp
View File

@ -1276,6 +1276,9 @@ bool LLParser::ParseFnAttributeValuePairs(AttrBuilder &B,
B.addAttribute(Attribute::SanitizeThread); break;
case lltok::kw_sanitize_memory:
B.addAttribute(Attribute::SanitizeMemory); break;
case lltok::kw_speculative_load_hardening:
B.addAttribute(Attribute::SpeculativeLoadHardening);
break;
case lltok::kw_strictfp: B.addAttribute(Attribute::StrictFP); break;
case lltok::kw_uwtable: B.addAttribute(Attribute::UWTable); break;
case lltok::kw_writeonly: B.addAttribute(Attribute::WriteOnly); break;
@ -1619,6 +1622,7 @@ bool LLParser::ParseOptionalParamAttrs(AttrBuilder &B) {
case lltok::kw_sanitize_hwaddress:
case lltok::kw_sanitize_memory:
case lltok::kw_sanitize_thread:
case lltok::kw_speculative_load_hardening:
case lltok::kw_ssp:
case lltok::kw_sspreq:
case lltok::kw_sspstrong:
@ -1715,6 +1719,7 @@ bool LLParser::ParseOptionalReturnAttrs(AttrBuilder &B) {
case lltok::kw_sanitize_hwaddress:
case lltok::kw_sanitize_memory:
case lltok::kw_sanitize_thread:
case lltok::kw_speculative_load_hardening:
case lltok::kw_ssp:
case lltok::kw_sspreq:
case lltok::kw_sspstrong:

1
lib/AsmParser/LLToken.h
View File

@ -219,6 +219,7 @@ enum Kind {
kw_sret,
kw_sanitize_thread,
kw_sanitize_memory,
kw_speculative_load_hardening,
kw_strictfp,
kw_swifterror,
kw_swiftself,

4
lib/Bitcode/Reader/BitcodeReader.cpp
View File

@ -1165,6 +1165,8 @@ static uint64_t getRawAttributeMask(Attribute::AttrKind Val) {
case Attribute::NoCfCheck: return 1ULL << 57;
case Attribute::OptForFuzzing: return 1ULL << 58;
case Attribute::ShadowCallStack: return 1ULL << 59;
case Attribute::SpeculativeLoadHardening:
return 1ULL << 60;
case Attribute::Dereferenceable:
llvm_unreachable("dereferenceable attribute not supported in raw format");
break;
@ -1389,6 +1391,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
return Attribute::SanitizeThread;
case bitc::ATTR_KIND_SANITIZE_MEMORY:
return Attribute::SanitizeMemory;
case bitc::ATTR_KIND_SPECULATIVE_LOAD_HARDENING:
return Attribute::SpeculativeLoadHardening;
case bitc::ATTR_KIND_SWIFT_ERROR:
return Attribute::SwiftError;
case bitc::ATTR_KIND_SWIFT_SELF:

2
lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -690,6 +690,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
return bitc::ATTR_KIND_SANITIZE_THREAD;
case Attribute::SanitizeMemory:
return bitc::ATTR_KIND_SANITIZE_MEMORY;
case Attribute::SpeculativeLoadHardening:
return bitc::ATTR_KIND_SPECULATIVE_LOAD_HARDENING;
case Attribute::SwiftError:
return bitc::ATTR_KIND_SWIFT_ERROR;
case Attribute::SwiftSelf:

2
lib/IR/Attributes.cpp
View File

@ -323,6 +323,8 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
return "returns_twice";
if (hasAttribute(Attribute::SExt))
return "signext";
if (hasAttribute(Attribute::SpeculativeLoadHardening))
return "speculative_load_hardening";
if (hasAttribute(Attribute::Speculatable))
return "speculatable";
if (hasAttribute(Attribute::StackProtect))

1
lib/IR/Verifier.cpp
View File

@ -1478,6 +1478,7 @@ static bool isFuncOnlyAttr(Attribute::AttrKind Kind) {
case Attribute::InaccessibleMemOnly:
case Attribute::InaccessibleMemOrArgMemOnly:
case Attribute::AllocSize:
case Attribute::SpeculativeLoadHardening:
case Attribute::Speculatable:
case Attribute::StrictFP:
return true;

11
lib/Target/X86/X86SpeculativeLoadHardening.cpp
View File

@ -75,6 +75,11 @@ STATISTIC(NumCallsOrJumpsHardened,
STATISTIC(NumInstsInserted, "Number of instructions inserted");
STATISTIC(NumLFENCEsInserted, "Number of lfence instructions inserted");
static cl::opt<bool> EnableSpeculativeLoadHardening(
"x86-speculative-load-hardening",
cl::desc("Force enable speculative load hardening"), cl::init(false),
cl::Hidden);
static cl::opt<bool> HardenEdgesWithLFENCE(
PASS_KEY "-lfence",
cl::desc(
@ -404,6 +409,12 @@ bool X86SpeculativeLoadHardeningPass::runOnMachineFunction(
LLVM_DEBUG(dbgs() << "********** " << getPassName() << " : " << MF.getName()
<< " **********\n");
// Only run if this pass is forced enabled or we detect the relevant function
// attribute requesting SLH.
if (!EnableSpeculativeLoadHardening &&
!MF.getFunction().hasFnAttribute(Attribute::SpeculativeLoadHardening))
return false;
Subtarget = &MF.getSubtarget<X86Subtarget>();
MRI = &MF.getRegInfo();
TII = Subtarget->getInstrInfo();

8
lib/Target/X86/X86TargetMachine.cpp
View File

@ -54,10 +54,6 @@ static cl::opt<bool> EnableMachineCombinerPass("x86-machine-combiner",
cl::desc("Enable the machine combiner pass"),
cl::init(true), cl::Hidden);
static cl::opt<bool> EnableSpeculativeLoadHardening(
"x86-speculative-load-hardening",
cl::desc("Enable speculative load hardening"), cl::init(false), cl::Hidden);
namespace llvm {
void initializeWinEHStatePassPass(PassRegistry &);
@ -475,9 +471,7 @@ void X86PassConfig::addPreRegAlloc() {
addPass(createX86AvoidStoreForwardingBlocks());
}
if (EnableSpeculativeLoadHardening)
addPass(createX86SpeculativeLoadHardeningPass());
addPass(createX86SpeculativeLoadHardeningPass());
addPass(createX86FlagsCopyLoweringPass());
addPass(createX86WinAllocaExpander());
}

1
lib/Transforms/IPO/ForceFunctionAttrs.cpp
View File

@ -58,6 +58,7 @@ static Attribute::AttrKind parseAttrKind(StringRef Kind) {
.Case("sanitize_hwaddress", Attribute::SanitizeHWAddress)
.Case("sanitize_memory", Attribute::SanitizeMemory)
.Case("sanitize_thread", Attribute::SanitizeThread)
.Case("speculative_load_hardening", Attribute::SpeculativeLoadHardening)
.Case("ssp", Attribute::StackProtect)
.Case("sspreq", Attribute::StackProtectReq)
.Case("sspstrong", Attribute::StackProtectStrong)

1
lib/Transforms/Utils/CodeExtractor.cpp
View File

@ -753,6 +753,7 @@ Function *CodeExtractor::constructFunction(const ValueSet &inputs,
case Attribute::SanitizeMemory:
case Attribute::SanitizeThread:
case Attribute::SanitizeHWAddress:
case Attribute::SpeculativeLoadHardening:
case Attribute::StackProtect:
case Attribute::StackProtectReq:
case Attribute::StackProtectStrong:

1
test/CodeGen/X86/O0-pipeline.ll
View File

@ -37,6 +37,7 @@
; CHECK-NEXT: X86 PIC Global Base Reg Initialization
; CHECK-NEXT: Expand ISel Pseudo-instructions
; CHECK-NEXT: Local Stack Slot Allocation
; CHECK-NEXT: X86 speculative load hardening
; CHECK-NEXT: MachineDominator Tree Construction
; CHECK-NEXT: X86 EFLAGS copy lowering
; CHECK-NEXT: X86 WinAlloca Expander

1
test/CodeGen/X86/O3-pipeline.ll
View File

@ -90,6 +90,7 @@
; CHECK-NEXT: X86 LEA Optimize
; CHECK-NEXT: X86 Optimize Call Frame
; CHECK-NEXT: X86 Avoid Store Forwarding Block
; CHECK-NEXT: X86 speculative load hardening
; CHECK-NEXT: MachineDominator Tree Construction
; CHECK-NEXT: X86 EFLAGS copy lowering
; CHECK-NEXT: X86 WinAlloca Expander

8
test/CodeGen/X86/speculative-load-hardening-gather.ll
View File

@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -x86-speculative-load-hardening | FileCheck %s
; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
declare <4 x float> @llvm.x86.avx2.gather.d.ps(<4 x float>, i8*, <4 x i32>, <4 x float>, i8)
@ -950,6 +950,6 @@ entry:
ret <4 x i64> %v
}
attributes #0 = { nounwind "target-features"="+avx2" }
attributes #1 = { nounwind "target-features"="+avx512f" }
attributes #2 = { nounwind "target-features"="+avx512vl" }
attributes #0 = { nounwind speculative_load_hardening "target-features"="+avx2" }
attributes #1 = { nounwind speculative_load_hardening "target-features"="+avx512f" }
attributes #2 = { nounwind speculative_load_hardening "target-features"="+avx512vl" }

20
test/CodeGen/X86/speculative-load-hardening.ll
View File

@ -1,6 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -x86-speculative-load-hardening | FileCheck %s --check-prefix=X64
; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -x86-speculative-load-hardening -x86-slh-lfence | FileCheck %s --check-prefix=X64-LFENCE
; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s --check-prefix=X64
; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -x86-slh-lfence | FileCheck %s --check-prefix=X64-LFENCE
;
; FIXME: Add support for 32-bit and other EH ABIs.
@ -8,7 +8,7 @@ declare void @leak(i32 %v1, i32 %v2)
declare void @sink(i32)
define i32 @test_trivial_entry_load(i32* %ptr) {
define i32 @test_trivial_entry_load(i32* %ptr) speculative_load_hardening {
; X64-LABEL: test_trivial_entry_load:
; X64: # %bb.0: # %entry
; X64-NEXT: movq %rsp, %rcx
@ -29,7 +29,7 @@ entry:
ret i32 %v
}
define void @test_basic_conditions(i32 %a, i32 %b, i32 %c, i32* %ptr1, i32* %ptr2, i32** %ptr3) {
define void @test_basic_conditions(i32 %a, i32 %b, i32 %c, i32* %ptr1, i32* %ptr2, i32** %ptr3) speculative_load_hardening {
; X64-LABEL: test_basic_conditions:
; X64: # %bb.0: # %entry
; X64-NEXT: pushq %r15
@ -193,7 +193,7 @@ exit:
ret void
}
define void @test_basic_loop(i32 %a, i32 %b, i32* %ptr1, i32* %ptr2) nounwind {
define void @test_basic_loop(i32 %a, i32 %b, i32* %ptr1, i32* %ptr2) nounwind speculative_load_hardening {
; X64-LABEL: test_basic_loop:
; X64: # %bb.0: # %entry
; X64-NEXT: pushq %rbp
@ -301,7 +301,7 @@ exit:
ret void
}
define void @test_basic_nested_loop(i32 %a, i32 %b, i32 %c, i32* %ptr1, i32* %ptr2) nounwind {
define void @test_basic_nested_loop(i32 %a, i32 %b, i32 %c, i32* %ptr1, i32* %ptr2) nounwind speculative_load_hardening {
; X64-LABEL: test_basic_nested_loop:
; X64: # %bb.0: # %entry
; X64-NEXT: pushq %rbp
@ -497,7 +497,7 @@ declare i8* @__cxa_allocate_exception(i64) local_unnamed_addr
declare void @__cxa_throw(i8*, i8*, i8*) local_unnamed_addr
define void @test_basic_eh(i32 %a, i32* %ptr1, i32* %ptr2) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
define void @test_basic_eh(i32 %a, i32* %ptr1, i32* %ptr2) speculative_load_hardening personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
; X64-LABEL: test_basic_eh:
; X64: # %bb.0: # %entry
; X64-NEXT: pushq %rbp
@ -668,7 +668,7 @@ declare void @sink_float(float)
declare void @sink_double(double)
; Test direct and converting loads of floating point values.
define void @test_fp_loads(float* %fptr, double* %dptr, i32* %i32ptr, i64* %i64ptr) nounwind {
define void @test_fp_loads(float* %fptr, double* %dptr, i32* %i32ptr, i64* %i64ptr) nounwind speculative_load_hardening {
; X64-LABEL: test_fp_loads:
; X64: # %bb.0: # %entry
; X64-NEXT: pushq %r15
@ -855,7 +855,7 @@ declare void @sink_v4i32(<4 x i32>)
declare void @sink_v2i64(<2 x i64>)
; Test loads of vectors.
define void @test_vec_loads(<4 x float>* %v4f32ptr, <2 x double>* %v2f64ptr, <16 x i8>* %v16i8ptr, <8 x i16>* %v8i16ptr, <4 x i32>* %v4i32ptr, <2 x i64>* %v2i64ptr) nounwind {
define void @test_vec_loads(<4 x float>* %v4f32ptr, <2 x double>* %v2f64ptr, <16 x i8>* %v16i8ptr, <8 x i16>* %v8i16ptr, <4 x i32>* %v4i32ptr, <2 x i64>* %v2i64ptr) nounwind speculative_load_hardening {
; X64-LABEL: test_vec_loads:
; X64: # %bb.0: # %entry
; X64-NEXT: pushq %rbp
@ -996,7 +996,7 @@ entry:
ret void
}
define void @test_deferred_hardening(i32* %ptr1, i32* %ptr2, i32 %x) nounwind {
define void @test_deferred_hardening(i32* %ptr1, i32* %ptr2, i32 %x) nounwind speculative_load_hardening {
; X64-LABEL: test_deferred_hardening:
; X64: # %bb.0: # %entry
; X64-NEXT: pushq %r15

27
test/Transforms/Inline/attributes.ll
View File

@ -26,6 +26,10 @@ define i32 @safestack_callee(i32 %i) safestack {
ret i32 %i
}
define i32 @slh_callee(i32 %i) speculative_load_hardening {
ret i32 %i
}
define i32 @alwaysinline_callee(i32 %i) alwaysinline {
ret i32 %i
}
@ -161,6 +165,28 @@ define i32 @test_safestack(i32 %arg) safestack {
; CHECK-NEXT: ret i32
}
; Can inline a normal function into an SLH'ed function.
define i32 @test_caller_slh(i32 %i) speculative_load_hardening {
; CHECK-LABEL: @test_caller_slh(
; CHECK-SAME: ) [[SLH:.*]] {
; CHECK-NOT: call
; CHECK: ret i32
entry:
%callee = call i32 @noattr_callee(i32 %i)
ret i32 %callee
}
; Can inline a SLH'ed function into a normal one, propagating SLH.
define i32 @test_callee_slh(i32 %i) {
; CHECK-LABEL: @test_callee_slh(
; CHECK-SAME: ) [[SLH:.*]] {
; CHECK-NOT: call
; CHECK: ret i32
entry:
%callee = call i32 @slh_callee(i32 %i)
ret i32 %callee
}
; Check that a function doesn't get inlined if target-cpu strings don't match
; exactly.
define i32 @test_target_cpu_callee0(i32 %i) "target-cpu"="corei7" {
@ -384,6 +410,7 @@ define i32 @test_null-pointer-is-valid2(i32 %i) "null-pointer-is-valid"="true" {
; CHECK-NEXT: ret i32
}
; CHECK: attributes [[SLH]] = { speculative_load_hardening }
; CHECK: attributes [[FPMAD_FALSE]] = { "less-precise-fpmad"="false" }
; CHECK: attributes [[FPMAD_TRUE]] = { "less-precise-fpmad"="true" }
; CHECK: attributes [[NOIMPLICITFLOAT]] = { noimplicitfloat }