r313096 - [ubsan] Function Sanitizer: Don't require writable text segments
Eric Christopher via cfe-commits
cfe-commits at lists.llvm.org
Fri Oct 13 13:44:43 PDT 2017
On Fri, Oct 13, 2017 at 1:42 PM Vedant Kumar <vsk at apple.com> wrote:
> On Oct 13, 2017, at 1:39 PM, Vedant Kumar <vsk at apple.com> wrote:
>
> Hey Eric,
>
> I'm sorry for the breakage. I made sure to check the run-time tests in
> compiler-rt but we could have missing coverage there.
>
> The original version of this patch restricted the prologue data changes to
> Darwin only. We can switch back to that easily, just let me know.
>
>
> Actually I'll go ahead and work a patch up.
>
>
Appreciated :)
Basically we were getting an error of:
error: Cannot represent a difference across sections
trying to compile things with the current code.
Thanks!
-eric
> vedant
>
>
> vedant
>
>
> On Oct 13, 2017, at 1:33 PM, Eric Christopher <echristo at gmail.com> wrote:
>
> Hi Vedant,
>
> So this actually broke -fsanitize=function on linux. Han is working up a
> testcase for it, but letting you know for now that we'll probably need some
> change here.
>
> -eric
>
> On Tue, Sep 12, 2017 at 5:05 PM Vedant Kumar via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> Author: vedantk
>> Date: Tue Sep 12 17:04:35 2017
>> New Revision: 313096
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=313096&view=rev
>> Log:
>> [ubsan] Function Sanitizer: Don't require writable text segments
>>
>> This change will make it possible to use -fsanitize=function on Darwin and
>> possibly on other platforms. It fixes an issue with the way RTTI is
>> stored into
>> function prologue data.
>>
>> On Darwin, addresses stored in prologue data can't require run-time
>> fixups and
>> must be PC-relative. Run-time fixups are undesirable because they
>> necessitate
>> writable text segments, which can lead to security issues. And absolute
>> addresses are undesirable because they break PIE mode.
>>
>> The fix is to create a private global which points to the RTTI, and then
>> to
>> encode a PC-relative reference to the global into prologue data.
>>
>> Differential Revision: https://reviews.llvm.org/D37597
>>
>> Modified:
>> cfe/trunk/lib/CodeGen/CGExpr.cpp
>> cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
>> cfe/trunk/lib/CodeGen/CodeGenFunction.h
>> cfe/trunk/lib/CodeGen/TargetInfo.cpp
>> cfe/trunk/test/CodeGenCXX/catch-undef-behavior.cpp
>>
>> Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=313096&r1=313095&r2=313096&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/CodeGen/CGExpr.cpp (original)
>> +++ cfe/trunk/lib/CodeGen/CGExpr.cpp Tue Sep 12 17:04:35 2017
>> @@ -4409,10 +4409,7 @@ RValue CodeGenFunction::EmitCall(QualTyp
>> SanitizerScope SanScope(this);
>> llvm::Constant *FTRTTIConst =
>> CGM.GetAddrOfRTTIDescriptor(QualType(FnType, 0),
>> /*ForEH=*/true);
>> - llvm::Type *PrefixStructTyElems[] = {
>> - PrefixSig->getType(),
>> - FTRTTIConst->getType()
>> - };
>> + llvm::Type *PrefixStructTyElems[] = {PrefixSig->getType(),
>> Int32Ty};
>> llvm::StructType *PrefixStructTy = llvm::StructType::get(
>> CGM.getLLVMContext(), PrefixStructTyElems, /*isPacked=*/true);
>>
>> @@ -4433,8 +4430,10 @@ RValue CodeGenFunction::EmitCall(QualTyp
>> EmitBlock(TypeCheck);
>> llvm::Value *CalleeRTTIPtr =
>> Builder.CreateConstGEP2_32(PrefixStructTy, CalleePrefixStruct,
>> 0, 1);
>> - llvm::Value *CalleeRTTI =
>> + llvm::Value *CalleeRTTIEncoded =
>> Builder.CreateAlignedLoad(CalleeRTTIPtr, getPointerAlign());
>> + llvm::Value *CalleeRTTI =
>> + DecodeAddrUsedInPrologue(CalleePtr, CalleeRTTIEncoded);
>> llvm::Value *CalleeRTTIMatch =
>> Builder.CreateICmpEQ(CalleeRTTI, FTRTTIConst);
>> llvm::Constant *StaticData[] = {
>>
>> Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.cpp?rev=313096&r1=313095&r2=313096&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/CodeGen/CodeGenFunction.cpp (original)
>> +++ cfe/trunk/lib/CodeGen/CodeGenFunction.cpp Tue Sep 12 17:04:35 2017
>> @@ -429,6 +429,43 @@ bool CodeGenFunction::ShouldXRayInstrume
>> return CGM.getCodeGenOpts().XRayInstrumentFunctions;
>> }
>>
>> +llvm::Constant *
>> +CodeGenFunction::EncodeAddrForUseInPrologue(llvm::Function *F,
>> + llvm::Constant *Addr) {
>> + // Addresses stored in prologue data can't require run-time fixups and
>> must
>> + // be PC-relative. Run-time fixups are undesirable because they
>> necessitate
>> + // writable text segments, which are unsafe. And absolute addresses are
>> + // undesirable because they break PIE mode.
>> +
>> + // Add a layer of indirection through a private global. Taking its
>> address
>> + // won't result in a run-time fixup, even if Addr has linkonce_odr
>> linkage.
>> + auto *GV = new llvm::GlobalVariable(CGM.getModule(), Addr->getType(),
>> + /*isConstant=*/true,
>> + llvm::GlobalValue::PrivateLinkage,
>> Addr);
>> +
>> + // Create a PC-relative address.
>> + auto *GOTAsInt = llvm::ConstantExpr::getPtrToInt(GV, IntPtrTy);
>> + auto *FuncAsInt = llvm::ConstantExpr::getPtrToInt(F, IntPtrTy);
>> + auto *PCRelAsInt = llvm::ConstantExpr::getSub(GOTAsInt, FuncAsInt);
>> + return (IntPtrTy == Int32Ty)
>> + ? PCRelAsInt
>> + : llvm::ConstantExpr::getTrunc(PCRelAsInt, Int32Ty);
>> +}
>> +
>> +llvm::Value *
>> +CodeGenFunction::DecodeAddrUsedInPrologue(llvm::Value *F,
>> + llvm::Value *EncodedAddr) {
>> + // Reconstruct the address of the global.
>> + auto *PCRelAsInt = Builder.CreateSExt(EncodedAddr, IntPtrTy);
>> + auto *FuncAsInt = Builder.CreatePtrToInt(F, IntPtrTy, "func_addr.int
>> ");
>> + auto *GOTAsInt = Builder.CreateAdd(PCRelAsInt, FuncAsInt, "
>> global_addr.int");
>> + auto *GOTAddr = Builder.CreateIntToPtr(GOTAsInt, Int8PtrPtrTy,
>> "global_addr");
>> +
>> + // Load the original pointer through the global.
>> + return Builder.CreateLoad(Address(GOTAddr, getPointerAlign()),
>> + "decoded_addr");
>> +}
>> +
>> /// EmitFunctionInstrumentation - Emit LLVM code to call the specified
>> /// instrumentation function with the current function and the call
>> site, if
>> /// function instrumentation is enabled.
>> @@ -856,7 +893,10 @@ void CodeGenFunction::StartFunction(Glob
>> CGM.getTargetCodeGenInfo().getUBSanFunctionSignature(CGM))
>> {
>> llvm::Constant *FTRTTIConst =
>> CGM.GetAddrOfRTTIDescriptor(FD->getType(), /*ForEH=*/true);
>> - llvm::Constant *PrologueStructElems[] = { PrologueSig,
>> FTRTTIConst };
>> + llvm::Constant *FTRTTIConstEncoded =
>> + EncodeAddrForUseInPrologue(Fn, FTRTTIConst);
>> + llvm::Constant *PrologueStructElems[] = {PrologueSig,
>> + FTRTTIConstEncoded};
>> llvm::Constant *PrologueStructConst =
>> llvm::ConstantStruct::getAnon(PrologueStructElems,
>> /*Packed=*/true);
>> Fn->setPrologueData(PrologueStructConst);
>>
>> Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=313096&r1=313095&r2=313096&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
>> +++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Tue Sep 12 17:04:35 2017
>> @@ -1776,6 +1776,15 @@ public:
>> /// EmitMCountInstrumentation - Emit call to .mcount.
>> void EmitMCountInstrumentation();
>>
>> + /// Encode an address into a form suitable for use in a function
>> prologue.
>> + llvm::Constant *EncodeAddrForUseInPrologue(llvm::Function *F,
>> + llvm::Constant *Addr);
>> +
>> + /// Decode an address used in a function prologue, encoded by \c
>> + /// EncodeAddrForUseInPrologue.
>> + llvm::Value *DecodeAddrUsedInPrologue(llvm::Value *F,
>> + llvm::Value *EncodedAddr);
>> +
>> /// EmitFunctionProlog - Emit the target specific LLVM code to load the
>> /// arguments for the given function. This is also responsible for
>> naming the
>> /// LLVM function arguments.
>>
>> Modified: cfe/trunk/lib/CodeGen/TargetInfo.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/TargetInfo.cpp?rev=313096&r1=313095&r2=313096&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/CodeGen/TargetInfo.cpp (original)
>> +++ cfe/trunk/lib/CodeGen/TargetInfo.cpp Tue Sep 12 17:04:35 2017
>> @@ -1086,8 +1086,8 @@ public:
>> getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const override {
>> unsigned Sig = (0xeb << 0) | // jmp rel8
>> (0x06 << 8) | // .+0x08
>> - ('F' << 16) |
>> - ('T' << 24);
>> + ('v' << 16) |
>> + ('2' << 24);
>> return llvm::ConstantInt::get(CGM.Int32Ty, Sig);
>> }
>>
>> @@ -2277,17 +2277,10 @@ public:
>>
>> llvm::Constant *
>> getUBSanFunctionSignature(CodeGen::CodeGenModule &CGM) const override {
>> - unsigned Sig;
>> - if (getABIInfo().has64BitPointers())
>> - Sig = (0xeb << 0) | // jmp rel8
>> - (0x0a << 8) | // .+0x0c
>> - ('F' << 16) |
>> - ('T' << 24);
>> - else
>> - Sig = (0xeb << 0) | // jmp rel8
>> - (0x06 << 8) | // .+0x08
>> - ('F' << 16) |
>> - ('T' << 24);
>> + unsigned Sig = (0xeb << 0) | // jmp rel8
>> + (0x06 << 8) | // .+0x08
>> + ('v' << 16) |
>> + ('2' << 24);
>> return llvm::ConstantInt::get(CGM.Int32Ty, Sig);
>> }
>>
>>
>> Modified: cfe/trunk/test/CodeGenCXX/catch-undef-behavior.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/catch-undef-behavior.cpp?rev=313096&r1=313095&r2=313096&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/test/CodeGenCXX/catch-undef-behavior.cpp (original)
>> +++ cfe/trunk/test/CodeGenCXX/catch-undef-behavior.cpp Tue Sep 12
>> 17:04:35 2017
>> @@ -16,6 +16,10 @@ struct S {
>> // Check that type mismatch handler is not modified by ASan.
>> // CHECK-ASAN: private unnamed_addr global { { [{{.*}} x i8]*, i32, i32
>> }, { i16, i16, [4 x i8] }*, i8*, i8 } { {{.*}}, { i16, i16, [4 x i8] }*
>> [[TYPE_DESCR]], {{.*}} }
>>
>> +// CHECK: [[IndirectRTTI_ZTIFvPFviEE:@.+]] = private constant i8*
>> bitcast ({ i8*, i8* }* @_ZTIFvPFviEE to i8*)
>> +// CHECK-X86: [[IndirectRTTI_ZTIFvPFviEE:@.+]] = private constant i8*
>> bitcast ({ i8*, i8* }* @_ZTIFvPFviEE to i8*)
>> +// CHECK-X32: [[IndirectRTTI_ZTIFvPFviEE:@.+]] = private constant i8*
>> bitcast ({ i8*, i8* }* @_ZTIFvPFviEE to i8*)
>> +
>> struct T : S {};
>>
>> // CHECK-LABEL: @_Z17reference_binding
>> @@ -395,23 +399,30 @@ void downcast_reference(B &b) {
>> // CHECK-NEXT: br i1 [[AND]]
>> }
>>
>> -// CHECK-LABEL: @_Z22indirect_function_callPFviE({{.*}} prologue <{ i32,
>> i8* }> <{ i32 1413876459, i8* bitcast ({ i8*, i8* }* @_ZTIFvPFviEE to i8*)
>> }>
>> -// CHECK-X32: @_Z22indirect_function_callPFviE({{.*}} prologue <{ i32,
>> i8* }> <{ i32 1413875435, i8* bitcast ({ i8*, i8* }* @_ZTIFvPFviEE to i8*)
>> }>
>> -// CHECK-X86: @_Z22indirect_function_callPFviE({{.*}} prologue <{ i32,
>> i8* }> <{ i32 1413875435, i8* bitcast ({ i8*, i8* }* @_ZTIFvPFviEE to i8*)
>> }>
>> +//
>> +// CHECK-LABEL: @_Z22indirect_function_callPFviE({{.*}} prologue <{ i32,
>> i32 }> <{ i32 846595819, i32 trunc (i64 sub (i64 ptrtoint (i8** {{.*}} to
>> i64), i64 ptrtoint (void (void (i32)*)* @_Z22indirect_function_callPFviE to
>> i64)) to i32) }>
>> +// CHECK-X32: @_Z22indirect_function_callPFviE({{.*}} prologue <{ i32,
>> i32 }> <{ i32 846595819, i32 sub (i32 ptrtoint (i8**
>> [[IndirectRTTI_ZTIFvPFviEE]] to i32), i32 ptrtoint (void (void (i32)*)*
>> @_Z22indirect_function_callPFviE to i32)) }>
>> +// CHECK-X86: @_Z22indirect_function_callPFviE({{.*}} prologue <{ i32,
>> i32 }> <{ i32 846595819, i32 sub (i32 ptrtoint (i8**
>> [[IndirectRTTI_ZTIFvPFviEE]] to i32), i32 ptrtoint (void (void (i32)*)*
>> @_Z22indirect_function_callPFviE to i32)) }>
>> void indirect_function_call(void (*p)(int)) {
>> - // CHECK: [[PTR:%.+]] = bitcast void (i32)* {{.*}} to <{ i32, i8* }>*
>> + // CHECK: [[PTR:%.+]] = bitcast void (i32)* {{.*}} to <{ i32, i32 }>*
>>
>> // Signature check
>> - // CHECK-NEXT: [[SIGPTR:%.+]] = getelementptr <{ i32, i8* }>, <{ i32,
>> i8* }>* [[PTR]], i32 0, i32 0
>> + // CHECK-NEXT: [[SIGPTR:%.+]] = getelementptr <{ i32, i32 }>, <{ i32,
>> i32 }>* [[PTR]], i32 0, i32 0
>> // CHECK-NEXT: [[SIG:%.+]] = load i32, i32* [[SIGPTR]]
>> - // CHECK-NEXT: [[SIGCMP:%.+]] = icmp eq i32 [[SIG]], 1413876459
>> + // CHECK-NEXT: [[SIGCMP:%.+]] = icmp eq i32 [[SIG]], 846595819
>> // CHECK-NEXT: br i1 [[SIGCMP]]
>>
>> // RTTI pointer check
>> - // CHECK: [[RTTIPTR:%.+]] = getelementptr <{ i32, i8* }>, <{ i32, i8*
>> }>* [[PTR]], i32 0, i32 1
>> - // CHECK-NEXT: [[RTTI:%.+]] = load i8*, i8** [[RTTIPTR]]
>> + // CHECK: [[RTTIPTR:%.+]] = getelementptr <{ i32, i32 }>, <{ i32, i32
>> }>* [[PTR]], i32 0, i32 1
>> + // CHECK-NEXT: [[RTTIEncIntTrunc:%.+]] = load i32, i32* [[RTTIPTR]]
>> + // CHECK-NEXT: [[RTTIEncInt:%.+]] = sext i32 [[RTTIEncIntTrunc]] to i64
>> + // CHECK-NEXT: [[FuncAddrInt:%.+]] = ptrtoint void (i32)* {{.*}} to i64
>> + // CHECK-NEXT: [[IndirectGVInt:%.+]] = add i64 [[RTTIEncInt]],
>> [[FuncAddrInt]]
>> + // CHECK-NEXT: [[IndirectGV:%.+]] = inttoptr i64 [[IndirectGVInt]] to
>> i8**
>> + // CHECK-NEXT: [[RTTI:%.+]] = load i8*, i8** [[IndirectGV]], align 8
>> // CHECK-NEXT: [[RTTICMP:%.+]] = icmp eq i8* [[RTTI]], bitcast ({ i8*,
>> i8* }* @_ZTIFviE to i8*)
>> // CHECK-NEXT: br i1 [[RTTICMP]]
>> +
>> p(42);
>> }
>>
>>
>>
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