Elf interface for new unwinder.

This cl includes the code to read arm unwind information from a shared
library.

Bug: 23762183

Test: Passes all unit tests. I can dump the arm unwind information
Test: for an arm shared library.
Change-Id: I43501ea2eab843b81de8bd5128401dd1971af8d3
diff --git a/libunwindstack/unwind_info.cpp b/libunwindstack/unwind_info.cpp
new file mode 100644
index 0000000..6f158b0
--- /dev/null
+++ b/libunwindstack/unwind_info.cpp
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2016 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 <elf.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "ArmExidx.h"
+#include "Elf.h"
+#include "ElfInterface.h"
+#include "ElfInterfaceArm.h"
+#include "Log.h"
+
+void DumpArm(ElfInterfaceArm* interface) {
+  if (interface == nullptr) {
+    printf("No ARM Unwind Information.\n\n");
+    return;
+  }
+
+  printf("ARM Unwind Information:\n");
+  for (const auto& entry : interface->pt_loads()) {
+    uint64_t load_bias = entry.second.table_offset;
+    printf(" PC Range 0x%" PRIx64 " - 0x%" PRIx64 "\n", entry.second.offset + load_bias,
+           entry.second.table_size + load_bias);
+    for (auto addr : *interface) {
+      std::string name;
+      printf("  PC 0x%" PRIx64, addr + load_bias);
+      uint64_t func_offset;
+      if (interface->GetFunctionName(addr + load_bias + 1, &name, &func_offset) && !name.empty()) {
+        printf(" <%s>", name.c_str());
+      }
+      printf("\n");
+      uint64_t entry;
+      if (!interface->FindEntry(addr + load_bias, &entry)) {
+        printf("    Cannot find entry for address.\n");
+        continue;
+      }
+      ArmExidx arm(nullptr, interface->memory(), nullptr);
+      arm.set_log(true);
+      arm.set_log_skip_execution(true);
+      arm.set_log_indent(2);
+      if (!arm.ExtractEntryData(entry)) {
+        if (arm.status() != ARM_STATUS_NO_UNWIND) {
+          printf("    Error trying to extract data.\n");
+        }
+        continue;
+      }
+      if (arm.data()->size() > 0) {
+        if (!arm.Eval() && arm.status() != ARM_STATUS_NO_UNWIND) {
+          printf("      Error trying to evaluate dwarf data.\n");
+        }
+      }
+    }
+  }
+  printf("\n");
+}
+
+int main(int argc, char** argv) {
+  if (argc != 2) {
+    printf("Need to pass the name of an elf file to the program.\n");
+    return 1;
+  }
+
+  struct stat st;
+  if (stat(argv[1], &st) == -1) {
+    printf("Cannot stat %s: %s\n", argv[1], strerror(errno));
+    return 1;
+  }
+  if (!S_ISREG(st.st_mode)) {
+    printf("%s is not a regular file.\n", argv[1]);
+    return 1;
+  }
+  if (S_ISDIR(st.st_mode)) {
+    printf("%s is a directory.\n", argv[1]);
+    return 1;
+  }
+
+  // Send all log messages to stdout.
+  log_to_stdout(true);
+
+  MemoryFileAtOffset* memory = new MemoryFileAtOffset;
+  if (!memory->Init(argv[1], 0)) {
+    // Initializatation failed.
+    printf("Failed to init\n");
+    return 1;
+  }
+
+  Elf elf(memory);
+  if (!elf.Init() || !elf.valid()) {
+    printf("%s is not a valid elf file.\n", argv[1]);
+    return 1;
+  }
+
+  ElfInterface* interface = elf.interface();
+  if (elf.machine_type() == EM_ARM) {
+    DumpArm(reinterpret_cast<ElfInterfaceArm*>(interface));
+    printf("\n");
+  }
+
+  return 0;
+}