r243206 - [CodeGen] Don't UBSan-ize the argument to __builtin_frame_address

[Hans Wennborg]

Sure. Richard, what say you?

On Tue, Jul 28, 2015 at 3:54 PM, Pieb, Wolfgang
<Wolfgang_Pieb at playstation.sony.com> wrote:
> Hi, would it be possible to put this fix into the 3.7 branch?
>
> Thanks
>
>> -----Original Message-----
>> From: cfe-commits-bounces at cs.uiuc.edu [mailto:cfe-commits-
>> bounces at cs.uiuc.edu] On Behalf Of David Majnemer
>> Sent: Friday, July 24, 2015 10:57 PM
>> To: cfe-commits at cs.uiuc.edu
>> Subject: r243206 - [CodeGen] Don't UBSan-ize the argument to
>> __builtin_frame_address
>>
>> Author: majnemer
>> Date: Sat Jul 25 00:57:24 2015
>> New Revision: 243206
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=243206&view=rev
>> Log:
>> [CodeGen] Don't UBSan-ize the argument to __builtin_frame_address
>>
>> __builtin_frame_address requires its argument to be a constant
>> expression which already implies that it cannot have undefined
>> behavior.
>> However, we used EmitScalarExpr to emit the argument causing UBSan to
>> try to check for overflow.
>>
>> Instead, use the constant expression emission system.
>>
>> This fixes PR24256.
>>
>> Modified:
>>     cfe/trunk/lib/CodeGen/CGBuiltin.cpp
>>     cfe/trunk/test/CodeGen/integer-overflow.c
>>
>> Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
>> URL: http://llvm.org/viewvc/llvm-
>> project/cfe/trunk/lib/CodeGen/CGBuiltin.cpp?rev=243206&r1=243205&r2=243
>> 206&view=diff
>> =======================================================================
>> =======
>> --- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original)
>> +++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Sat Jul 25 00:57:24 2015
>> @@ -866,14 +866,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(
>>                                        llvm::ConstantInt::get(Int32Ty,
>> Offset)));
>>    }
>>    case Builtin::BI__builtin_return_address: {
>> -    Value *Depth = EmitScalarExpr(E->getArg(0));
>> -    Depth = Builder.CreateIntCast(Depth, Int32Ty, false);
>> +    Value *Depth =
>> +        CGM.EmitConstantExpr(E->getArg(0), getContext().UnsignedIntTy,
>> + this);
>>      Value *F = CGM.getIntrinsic(Intrinsic::returnaddress);
>>      return RValue::get(Builder.CreateCall(F, Depth));
>>    }
>>    case Builtin::BI__builtin_frame_address: {
>> -    Value *Depth = EmitScalarExpr(E->getArg(0));
>> -    Depth = Builder.CreateIntCast(Depth, Int32Ty, false);
>> +    Value *Depth =
>> +        CGM.EmitConstantExpr(E->getArg(0), getContext().UnsignedIntTy,
>> + this);
>>      Value *F = CGM.getIntrinsic(Intrinsic::frameaddress);
>>      return RValue::get(Builder.CreateCall(F, Depth));
>>    }
>>
>> Modified: cfe/trunk/test/CodeGen/integer-overflow.c
>> URL: http://llvm.org/viewvc/llvm-
>> project/cfe/trunk/test/CodeGen/integer-
>> overflow.c?rev=243206&r1=243205&r2=243206&view=diff
>> =======================================================================
>> =======
>> --- cfe/trunk/test/CodeGen/integer-overflow.c (original)
>> +++ cfe/trunk/test/CodeGen/integer-overflow.c Sat Jul 25 00:57:24 2015
>> @@ -72,4 +72,11 @@ void test1() {
>>    // TRAPV: add i8 {{.*}}, 1
>>    // CATCH_UB: add i8 {{.*}}, 1
>>    ++PR9350;
>> +
>> +  // PR24256: don't instrument __builtin_frame_address.
>> +  __builtin_frame_address(0 + 0);
>> +  // DEFAULT:  call i8* @llvm.frameaddress(i32 0)
>> +  // WRAPV:    call i8* @llvm.frameaddress(i32 0)
>> +  // TRAPV:    call i8* @llvm.frameaddress(i32 0)
>> +  // CATCH_UB: call i8* @llvm.frameaddress(i32 0)
>>  }
>>
>>
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