[BOLT] Skip functions with unsupported Linux kernel features (#86345)

Do not overwrite functions with alternative and paravirtual instructions
until a proper update support is implemented.

bolt/lib/Rewrite/LinuxKernelRewriter.cpp

@@ -252,11 +252,17 @@ class LinuxKernelRewriter final : public MetadataRewriter {
 
   /// Paravirtual instruction patch sites.
   Error readParaInstructions();
+  Error rewriteParaInstructions();
 
   Error readBugTable();
 
-  /// Read alternative instruction info from .altinstructions.
+  /// Do no process functions containing instruction annotated with
+  /// \p Annotation.
+  void skipFunctionsWithAnnotation(StringRef Annotation) const;
+
+  /// Handle alternative instruction info from .altinstructions.
   Error readAltInstructions();
+  Error rewriteAltInstructions();
 
   /// Read .pci_fixup
   Error readPCIFixupTable();
@@ -318,6 +324,12 @@ public:
     if (Error E = rewriteExceptionTable())
       return E;
 
+    if (Error E = rewriteAltInstructions())
+      return E;
+
+    if (Error E = rewriteParaInstructions())
+      return E;
+
     if (Error E = rewriteORCTables())
       return E;
 
@@ -1126,6 +1138,31 @@ Error LinuxKernelRewriter::readParaInstructions() {
   return Error::success();
 }
 
+void LinuxKernelRewriter::skipFunctionsWithAnnotation(
+    StringRef Annotation) const {
+  for (BinaryFunction &BF : llvm::make_second_range(BC.getBinaryFunctions())) {
+    if (!BC.shouldEmit(BF))
+      continue;
+    for (const BinaryBasicBlock &BB : BF) {
+      const bool HasAnnotation = llvm::any_of(BB, [&](const MCInst &Inst) {
+        return BC.MIB->hasAnnotation(Inst, Annotation);
+      });
+      if (HasAnnotation) {
+        BF.setSimple(false);
+        break;
+      }
+    }
+  }
+}
+
+Error LinuxKernelRewriter::rewriteParaInstructions() {
+  // Disable output of functions with paravirtual instructions before the
+  // rewrite support is complete.
+  skipFunctionsWithAnnotation("ParaSite");
+
+  return Error::success();
+}
+
 /// Process __bug_table section.
 /// This section contains information useful for kernel debugging.
 /// Each entry in the section is a struct bug_entry that contains a pointer to
@@ -1305,6 +1342,14 @@ Error LinuxKernelRewriter::readAltInstructions() {
   return Error::success();
 }
 
+Error LinuxKernelRewriter::rewriteAltInstructions() {
+  // Disable output of functions with alt instructions before the rewrite
+  // support is complete.
+  skipFunctionsWithAnnotation("AltInst");
+
+  return Error::success();
+}
+
 /// When the Linux kernel needs to handle an error associated with a given PCI
 /// device, it uses a table stored in .pci_fixup section to locate a fixup code
 /// specific to the vendor and the problematic device. The section contains a