diff --git a/cmd/symbol_inject/macho.go b/cmd/symbol_inject/macho.go
new file mode 100644
index 0000000..0945293
--- /dev/null
+++ b/cmd/symbol_inject/macho.go
@@ -0,0 +1,65 @@
+// Copyright 2018 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"debug/macho"
+	"fmt"
+	"io"
+)
+
+func findMachoSymbol(r io.ReaderAt, symbolName string) (uint64, uint64, error) {
+	machoFile, err := macho.NewFile(r)
+	if err != nil {
+		return maxUint64, maxUint64, cantParseError{err}
+	}
+
+	// TODO(ccross): why?
+	symbolName = "_" + symbolName
+
+	for i, symbol := range machoFile.Symtab.Syms {
+		if symbol.Sect == 0 {
+			continue
+		}
+		if symbol.Name == symbolName {
+			var nextSymbol *macho.Symbol
+			if i+1 < len(machoFile.Symtab.Syms) {
+				nextSymbol = &machoFile.Symtab.Syms[i+1]
+			}
+			return calculateMachoSymbolOffset(machoFile, symbol, nextSymbol)
+		}
+	}
+
+	return maxUint64, maxUint64, fmt.Errorf("symbol not found")
+}
+
+func calculateMachoSymbolOffset(file *macho.File, symbol macho.Symbol, nextSymbol *macho.Symbol) (uint64, uint64, error) {
+	section := file.Sections[symbol.Sect-1]
+
+	var end uint64
+	if nextSymbol != nil && nextSymbol.Sect != symbol.Sect {
+		nextSymbol = nil
+	}
+	if nextSymbol != nil {
+		end = nextSymbol.Value
+	} else {
+		end = section.Addr + section.Size
+	}
+
+	size := end - symbol.Value - 1
+	offset := uint64(section.Offset) + (symbol.Value - section.Addr)
+
+	return offset, size, nil
+}