Add a tool to inject data into an elf, macho, or PE symbol
Test: symbol_inject -i a.out -o a.out2 -s symbol -v value
Change-Id: I16cd8facbae754f679bef07ab0ba23638286e1d7
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
+}