Ignore blacklist when generating __cfi_check_fail.

[eugenis]

Summary

Fixes PR37898.

[eugenis]

Another option is to add a special case to blacklist logic to make it not apply to __cfi_check_fail.

Yet another option is to make blacklist not apply to functions without a source location, but that seems to be done intentionally here:
http://llvm-cs.pcc.me.uk/tools/clang/lib/CodeGen/CodeGenModule.cpp#1827

[pcc]

__cfi_check_fail certainly seems like a special case in that its behaviour is controlled only by flags and not the blacklist.

Maybe a simpler fix would be to add this to the top of EmitCfiCheckFail?

SanOpts = CGM.getLangOpts().Sanitize;

[eugenis]

Simplify code.

[eugenis]

Yes, that's better.

[pcc]

LGTM

clang/lib/CodeGen/CGExpr.cpp

const std::pair<int, SanitizerMask> CheckKinds[] = {
       {CFITCK_ICall, SanitizerKind::CFIICall}};
 
   SmallVector<std::pair<llvm::Value *, SanitizerMask>, 5> Checks;
   for (auto CheckKindMaskPair : CheckKinds) {
     int Kind = CheckKindMaskPair.first;
     SanitizerMask Mask = CheckKindMaskPair.second;
     llvm::Value *Cond =
         Builder.CreateICmpNE(CheckKind, llvm::ConstantInt::get(Int8Ty, Kind));
-    if (CGM.getLangOpts().Sanitize.has(Mask))
+    if (CGM.getLangOpts().Sanitize.has(Mask)) {
+      // This sanitizer may have been disabled in blacklist. This function does
+      // not have a source location, but "src:*" would still apply. Enable it
+      // back.
+      SanOpts.Mask |= Mask;
       EmitCheck(std::make_pair(Cond, Mask), SanitizerHandler::CFICheckFail, {},
                 {Data, Addr, ValidVtable});
-    else
+    } else {
       EmitTrapCheck(Cond);
     }
+  }
 
   FinishFunction();
   // The only reference to this function will be created during LTO link.
   // Make sure it survives until then.
   CGM.addUsedGlobal(F);
 }
 
 void CodeGenFunction::EmitUnreachable(SourceLocation Loc) {

clang/test/CodeGen/cfi-check-fail2.c

 // __cfi_check_fail codegen when not all CFI checkers are enabled.
 // RUN: %clang_cc1 -triple x86_64-unknown-linux -O0 -fsanitize-cfi-cross-dso \
 // RUN:     -fsanitize=cfi-vcall \
 // RUN:     -emit-llvm -o - %s | FileCheck %s
 
+// Check that blacklist does not affect generated code.
+// RUN: echo "src:*" > %t-all.blacklist
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -O0 -fsanitize-cfi-cross-dso \
+// RUN:     -fsanitize=cfi-vcall -fsanitize-blacklist=%t-all.blacklist \
+// RUN:     -emit-llvm -o - %s | FileCheck %s
+
 void caller(void (*f)()) {
   f();
 }
 
 // CHECK: define weak_odr hidden void @__cfi_check_fail(i8*, i8*)
 // CHECK: store i8* %0, i8** %[[ALLOCA0:.*]], align 8
 // CHECK: store i8* %1, i8** %[[ALLOCA1:.*]], align 8
 // CHECK: %[[DATA:.*]] = load i8*, i8** %[[ALLOCA0]], align 8