[ubsan] Minimize size of data for type_mismatch

[filcab]

Summary

This patch makes the type_mismatch static data 7 bytes smaller (and it ends up
being 16 bytes smaller due to alignment restrictions, at least on some x86-64
environments).

Currently, I have no binary compatibility for using an older object file
(compiled before this change) with a newer clang. Depending on the compiler-rt
code review, this patch might be updated to better signal to the library that
this object has this new binary format.

[bcraig]

Is there an associated patch on the consuming side for this data?

[filcab]

http://reviews.llvm.org/D19668 is the compiler-rt side of the patch.

[filcab]

Update catch-undef-behavior.c

[filcab]

Hi Richard. Just want to double-check something. If we have no alignment value, for this check, can we assume 1?
It seems to me that that shouldn't be a problem, but wanted to double-check.

lib/CodeGen/CGExpr.cpp

587

Would it be acceptable to set AlignVal to 1 if it's 0?

[rsmith]

lib/CodeGen/CGExpr.cpp

587

Yes, that seems fine. The alignment check will never fire if AlignVal is zero (that only happens if the type in question is incomplete, and we don't emit a check for it in that case). Setting it to 1 should prevent the runtime library from thinking that we detected an alignment problem.

It looks like the current patch will emit 255 as the alignment in that case; that also seems fine as a way of indicating "no alignment check". I doubt we'll ever need to deal with a real alignment value of 2^255 :)

[filcab]

Minor update which never sets an AlignVal to 0.

[filcab]

Added a version field.

[filcab]

I will post a new patch, using the features from rL289444.

lib/CodeGen/CGExpr.cpp

if (AlignVal) {
                             llvm::ConstantInt::get(IntPtrTy, AlignVal - 1));
       llvm::Value *Aligned =
         Builder.CreateICmpEQ(Align, llvm::ConstantInt::get(IntPtrTy, 0));
       Checks.push_back(std::make_pair(Aligned, SanitizerKind::Alignment));
     }
   }
 
   if (Checks.size() > 0) {
+    // Make sure we're not losing information. Alignment needs to be a power of
+    // 2
+    assert(!AlignVal || (uint64_t)1 << llvm::Log2_64(AlignVal) == AlignVal);
+    const unsigned TypeMismatchDataVersion = 2;
     llvm::Constant *StaticData[] = {
-     EmitCheckSourceLocation(Loc),
-      EmitCheckTypeDescriptor(Ty),
-      llvm::ConstantInt::get(SizeTy, AlignVal),
-      llvm::ConstantInt::get(Int8Ty, TCK)
-    };
+        EmitCheckSourceLocation(Loc), EmitCheckTypeDescriptor(Ty),
+        llvm::ConstantInt::get(Int8Ty, TypeMismatchDataVersion),
+        llvm::ConstantInt::get(Int8Ty, AlignVal ? llvm::Log2_64(AlignVal) : 1),
+        llvm::ConstantInt::get(Int8Ty, TCK)};
     EmitCheck(Checks, "type_mismatch", StaticData, Ptr);
   }
 
   // If possible, check that the vptr indicates that there is a subobject of
   // type Ty at offset zero within this object.
   //
   // C++11 [basic.life]p5,6:
   //   [For storage which does not refer to an object within its lifetime]

test/CodeGen/catch-undef-behavior.c

 // RUN: %clang_cc1 -fsanitize=alignment,null,object-size,shift-base,shift-exponent,return,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize-recover=alignment,null,object-size,shift-base,shift-exponent,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -emit-llvm %s -o - -triple x86_64-linux-gnu | opt -instnamer -S | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-UBSAN
 // RUN: %clang_cc1 -fsanitize-trap=alignment,null,object-size,shift-base,shift-exponent,return,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize-recover=alignment,null,object-size,shift-base,shift-exponent,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize=alignment,null,object-size,shift-base,shift-exponent,return,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -fsanitize-recover=alignment,null,object-size,shift-base,shift-exponent,signed-integer-overflow,vla-bound,float-cast-overflow,integer-divide-by-zero,bool,returns-nonnull-attribute,nonnull-attribute -emit-llvm %s -o - -triple x86_64-linux-gnu | opt -instnamer -S | FileCheck %s --check-prefix=CHECK-COMMON --check-prefix=CHECK-TRAP
 // RUN: %clang_cc1 -fsanitize=null -fsanitize-recover=null -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK-NULL
 // RUN: %clang_cc1 -fsanitize=signed-integer-overflow -emit-llvm %s -o - -triple x86_64-linux-gnu | FileCheck %s --check-prefix=CHECK-OVERFLOW
 
 // CHECK-UBSAN: @[[INT:.*]] = private unnamed_addr constant { i16, i16, [6 x i8] } { i16 0, i16 11, [6 x i8] c"'int'\00" }
 
 // FIXME: When we only emit each type once, use [[INT]] more below.
-// CHECK-UBSAN: @[[LINE_100:.*]] = private unnamed_addr global {{.*}}, i32 100, i32 5 {{.*}} @[[INT]], i64 4, i8 1
-// CHECK-UBSAN: @[[LINE_200:.*]] = {{.*}}, i32 200, i32 10 {{.*}}, i64 4, i8 0
+// CHECK-UBSAN: @[[LINE_100:.*]] = private unnamed_addr global {{.*}}, i32 100, i32 5 {{.*}} @[[INT]], i8 2, i8 2, i8 1
+// CHECK-UBSAN: @[[LINE_200:.*]] = {{.*}}, i32 200, i32 10 {{.*}}, i8 2, i8 2, i8 0
 // CHECK-UBSAN: @[[LINE_300:.*]] = {{.*}}, i32 300, i32 12 {{.*}} @{{.*}}, {{.*}} @{{.*}}
 // CHECK-UBSAN: @[[LINE_400:.*]] = {{.*}}, i32 400, i32 12 {{.*}} @{{.*}}, {{.*}} @{{.*}}
-// CHECK-UBSAN: @[[LINE_500:.*]] = {{.*}}, i32 500, i32 10 {{.*}} @{{.*}}, i64 4, i8 0 }
-// CHECK-UBSAN: @[[LINE_600:.*]] = {{.*}}, i32 600, i32 3 {{.*}} @{{.*}}, i64 4, i8 1 }
+// CHECK-UBSAN: @[[LINE_500:.*]] = {{.*}}, i32 500, i32 10 {{.*}} @{{.*}}, i8 2, i8 2, i8 0 }
+// CHECK-UBSAN: @[[LINE_600:.*]] = {{.*}}, i32 600, i32 3 {{.*}} @{{.*}}, i8 2, i8 2, i8 1 }
 
 // CHECK-UBSAN: @[[STRUCT_S:.*]] = private unnamed_addr constant { i16, i16, [11 x i8] } { i16 -1, i16 0, [11 x i8] c"'struct S'\00" }
 
-// CHECK-UBSAN: @[[LINE_700:.*]] = {{.*}}, i32 700, i32 14 {{.*}} @[[STRUCT_S]], i64 4, i8 3 }
+// CHECK-UBSAN: @[[LINE_700:.*]] = {{.*}}, i32 700, i32 14 {{.*}} @[[STRUCT_S]], i8 2, i8 2, i8 3 }
 // CHECK-UBSAN: @[[LINE_800:.*]] = {{.*}}, i32 800, i32 12 {{.*}} @{{.*}} }
 // CHECK-UBSAN: @[[LINE_900:.*]] = {{.*}}, i32 900, i32 11 {{.*}} @{{.*}} }
 // CHECK-UBSAN: @[[LINE_1000:.*]] = {{.*}}, i32 1000, i32 10 {{.*}} @{{.*}} }
 // CHECK-UBSAN: @[[FP16:.*]] = private unnamed_addr constant { i16, i16, [9 x i8] } { i16 1, i16 16, [9 x i8] c"'__fp16'\00" }
 // CHECK-UBSAN: @[[LINE_1100:.*]] = {{.*}}, i32 1100, i32 8 {{.*}} @{{.*}} }
 // CHECK-UBSAN: @[[LINE_1200:.*]] = {{.*}}, i32 1200, i32 10 {{.*}} @{{.*}} }
 // CHECK-UBSAN: @[[LINE_1300:.*]] = {{.*}}, i32 1300, i32 10 {{.*}} @{{.*}} }
 // CHECK-UBSAN: @[[LINE_1400:.*]] = {{.*}}, i32 1400, i32 10 {{.*}} @{{.*}} }