[llvm-branch-commits] [llvm][fatlto] Drop any CFI related instrumentation after emitting bitcode (PR #112788)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Paul Kirth (ilovepi)

<details>
<summary>Changes</summary>

We want to support CFI instrumentation for the bitcode section, without
miscompiling the object code portion of a FatLTO object. We can reuse
the existing mechanisms in the LowerTypeTestsPass to do that, by just
adding the pass to the FatLTO pipeline after the EmbedBitcodePass with
the correct options set.

Fixes #<!-- -->112053


---
Full diff: https://github.com/llvm/llvm-project/pull/112788.diff


2 Files Affected:

- (added) clang/test/CodeGen/fat-lto-objects-cfi.cpp (+46) 
- (modified) llvm/lib/Passes/PassBuilderPipelines.cpp (+4) 


``````````diff
diff --git a/clang/test/CodeGen/fat-lto-objects-cfi.cpp b/clang/test/CodeGen/fat-lto-objects-cfi.cpp
new file mode 100644
index 00000000000000..022e74fd9b6f22
--- /dev/null
+++ b/clang/test/CodeGen/fat-lto-objects-cfi.cpp
@@ -0,0 +1,46 @@
+// REQUIRES: x86-registered-target
+
+// RUN: %clangxx --target=x86_64-unknown-fuchsia -O2 -flto -ffat-lto-objects \
+// RUN:          -fsanitize=cfi -fvisibility=hidden -S -emit-llvm -o - %s \
+// RUN:   | FileCheck %s
+
+// CHECK: llvm.embedded.object
+// CHECK-SAME: section ".llvm.lto"
+
+// CHECK-LABEL: define hidden void @foo
+//      CHECK: entry:
+// CHECK-NEXT:   %cmp14.not = icmp eq i64 %len, 0
+// CHECK-NEXT:   br i1 %cmp14.not, label %for.end7, label %for.cond1.preheader.preheader
+//      CHECK: for.cond1.preheader.preheader:                    ; preds = %entry
+// CHECK-NEXT:   %arrayidx.1 = getelementptr inbounds nuw i8, ptr %ptr, i64 4
+// CHECK-NEXT:   br label %for.cond1.preheader
+
+// CHECK-NOT: @llvm.type.test
+
+// The code below is a reduced case from https://github.com/llvm/llvm-project/issues/112053
+#define __PRINTFLIKE(__fmt, __varargs) __attribute__((__format__(__printf__, __fmt, __varargs)))
+typedef void func(void* arg, const char* fmt, ...) __PRINTFLIKE(2, 3);
+typedef __SIZE_TYPE__ size_t;
+typedef unsigned long uintptr_t;
+
+extern "C"
+void foo(const void* ptr, size_t len, long disp_addr,
+                     func* printf_func, void* printf_arg) {
+  uintptr_t address = (uintptr_t)ptr;
+  size_t count;
+
+  for (count = 0; count < len; count += 16) {
+    union {
+      unsigned int buf[4];
+      unsigned char cbuf[16];
+    } u;
+    size_t s = 10;
+    size_t i;
+
+    for (i = 0; i < s / 4; i++) {
+      u.buf[i] = ((const unsigned int*)address)[i];
+      printf_func(printf_arg, "%08x ", static_cast<unsigned int>(u.buf[i]));
+    }
+  }
+}
+
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 17710eb94b6ded..81ea6ac7dcdf18 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1629,6 +1629,10 @@ PassBuilder::buildFatLTODefaultPipeline(OptimizationLevel Level, bool ThinLTO,
     MPM.addPass(buildLTOPreLinkDefaultPipeline(Level));
   MPM.addPass(EmbedBitcodePass(ThinLTO, EmitSummary));
 
+  // If we're doing FatLTO w/ CFI enabled, we don't want the type tests in the
+  // object file.
+  MPM.addPass(LowerTypeTestsPass(nullptr, nullptr, true, true));
+
   // Use the ThinLTO post-link pipeline with sample profiling
   if (ThinLTO && PGOOpt && PGOOpt->Action == PGOOptions::SampleUse)
     MPM.addPass(buildThinLTODefaultPipeline(Level, /*ImportSummary=*/nullptr));

``````````

</details>


https://github.com/llvm/llvm-project/pull/112788