1 files changed, 72 insertions, 0 deletions
diff --git a/bolt/lib/Rewrite/RSeqRewriter.cpp b/bolt/lib/Rewrite/RSeqRewriter.cpp
new file mode 100644
index 000000000000..46bce66d13dd
--- /dev/null
+++ b/bolt/lib/Rewrite/RSeqRewriter.cpp
@@ -0,0 +1,72 @@
+//===- bolt/Rewrite/RSeqRewriter.cpp --------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Basic support for restartable sequences used by tcmalloc. Prevent critical
+// section overrides by ignoring optimizations in containing functions.
+//
+// References:
+//   * https://google.github.io/tcmalloc/rseq.html
+//   * tcmalloc/internal/percpu_rseq_x86_64.S
+//
+//===----------------------------------------------------------------------===//
+
+#include "bolt/Core/BinaryFunction.h"
+#include "bolt/Rewrite/MetadataRewriter.h"
+#include "bolt/Rewrite/MetadataRewriters.h"
+#include "llvm/Support/Errc.h"
+
+using namespace llvm;
+using namespace bolt;
+
+namespace {
+
+class RSeqRewriter final : public MetadataRewriter {
+public:
+  RSeqRewriter(StringRef Name, BinaryContext &BC)
+      : MetadataRewriter(Name, BC) {}
+
+  Error preCFGInitializer() override {
+    for (const BinarySection &Section : BC.allocatableSections()) {
+      if (Section.getName() != "__rseq_cs")
+        continue;
+
+      auto handleRelocation = [&](const Relocation &Rel, bool IsDynamic) {
+        BinaryFunction *BF = nullptr;
+        if (Rel.Symbol)
+          BF = BC.getFunctionForSymbol(Rel.Symbol);
+        else if (Relocation::isRelative(Rel.Type))
+          BF = BC.getBinaryFunctionContainingAddress(Rel.Addend);
+
+        if (!BF) {
+          BC.errs() << "BOLT-WARNING: no function found matching "
+                    << (IsDynamic ? "dynamic " : "")
+                    << "relocation in __rseq_cs\n";
+        } else if (!BF->isIgnored()) {
+          BC.outs() << "BOLT-INFO: restartable sequence reference detected in "
+                    << *BF << ". Function will not be optimized\n";
+          BF->setIgnored();
+        }
+      };
+
+      for (const Relocation &Rel : Section.dynamicRelocations())
+        handleRelocation(Rel, /*IsDynamic*/ true);
+
+      for (const Relocation &Rel : Section.relocations())
+        handleRelocation(Rel, /*IsDynamic*/ false);
+    }
+
+    return Error::success();
+  }
+};
+
+} // namespace
+
+std::unique_ptr<MetadataRewriter>
+llvm::bolt::createRSeqRewriter(BinaryContext &BC) {
+  return std::make_unique<RSeqRewriter>("rseq-cs-rewriter", BC);
+}