Make dt_runpath work for libraries opened from apk

This patch also fixes realpath for libraries opened directly
from apks.

Bug: http://b/21960914
Bug: http://b/21961857
Change-Id: I35ade661c87f1d448191f385811f6e9fd3cacf11

linker/linker_utils.cpp

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "linker_utils.h"
+#include "linker_debug.h"
+
+bool normalize_path(const char* path, std::string* normalized_path) {
+  // Input should be an absolute path
+  if (path[0] != '/') {
+    PRINT("canonize_path - invalid input: '%s', the input path should be absolute", path);
+    return false;
+  }
+
+  const size_t len = strlen(path) + 1;
+  char buf[len];
+
+  const char* in_ptr = path;
+  char* out_ptr = buf;
+
+  while (*in_ptr != 0) {
+    if (*in_ptr == '/') {
+      char c1 = in_ptr[1];
+      if (c1 == '.') {
+        char c2 = in_ptr[2];
+        if (c2 == '/') {
+          in_ptr += 2;
+          continue;
+        } else if (c2 == '.' && (in_ptr[3] == '/' || in_ptr[3] == 0)) {
+          in_ptr += 3;
+          while (out_ptr > buf && *--out_ptr != '/') {
+          }
+          if (in_ptr[0] == 0) {
+            // retain '/'
+            out_ptr++;
+          }
+          continue;
+        }
+      } else if (c1 == '/') {
+        ++in_ptr;
+        continue;
+      }
+    }
+    *out_ptr++ = *in_ptr++;
+  }
+
+  *out_ptr = 0;
+  *normalized_path = buf;
+  return true;
+}
+