Rewrite libbacktrace using C++.

The old code was essentially trying to be C++ in C and was awkward. This
change makes it all objects with a thin layer that C code can use.

There is a C++ backtrace object that is not very useful, this code will
replace it.

This change also includes moving the backtrace test to a gtest, and adding
coverage of all major functionality.

Bug: 8410085
Change-Id: Iae0f1b09b3dd60395f71ed66010c1ea5cdd37841

1 files changed, 136 insertions, 0 deletions

diff --git a/libbacktrace/UnwindPtrace.cpp b/libbacktrace/UnwindPtrace.cpp
new file mode 100644
index 000000000..628caa04b
--- /dev/null
+++ b/libbacktrace/UnwindPtrace.cpp
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2013 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.
+ */
+
+#define LOG_TAG "libbacktrace"
+
+#include <backtrace/backtrace.h>
+
+#include <sys/types.h>
+#include <string.h>
+
+#include <cutils/log.h>
+
+#include <libunwind.h>
+#include <libunwind-ptrace.h>
+
+#include "UnwindPtrace.h"
+
+UnwindPtrace::UnwindPtrace() : addr_space_(NULL), upt_info_(NULL) {
+}
+
+UnwindPtrace::~UnwindPtrace() {
+  if (upt_info_) {
+    _UPT_destroy(upt_info_);
+    upt_info_ = NULL;
+  }
+  if (addr_space_) {
+    unw_destroy_addr_space(addr_space_);
+    addr_space_ = NULL;
+  }
+}
+
+bool UnwindPtrace::Unwind(size_t num_ignore_frames) {
+  addr_space_ = unw_create_addr_space(&_UPT_accessors, 0);
+  if (!addr_space_) {
+    ALOGW("UnwindPtrace::Unwind: unw_create_addr_space failed.\n");
+    return false;
+  }
+
+  upt_info_ = reinterpret_cast<struct UPT_info*>(_UPT_create(backtrace_obj_->Tid()));
+  if (!upt_info_) {
+    ALOGW("UnwindPtrace::Unwind: Failed to create upt info.\n");
+    return false;
+  }
+
+  backtrace_t* backtrace = GetBacktraceData();
+  backtrace->num_frames = 0;
+
+  unw_cursor_t cursor;
+  int ret = unw_init_remote(&cursor, addr_space_, upt_info_);
+  if (ret < 0) {
+    ALOGW("UnwindPtrace::Unwind: unw_init_remote failed %d\n", ret);
+    return false;
+  }
+
+  do {
+    unw_word_t pc;
+    ret = unw_get_reg(&cursor, UNW_REG_IP, &pc);
+    if (ret < 0) {
+      ALOGW("UnwindPtrace::Unwind: Failed to read IP %d\n", ret);
+      break;
+    }
+    unw_word_t sp;
+    ret = unw_get_reg(&cursor, UNW_REG_SP, &sp);
+    if (ret < 0) {
+      ALOGW("UnwindPtrace::Unwind: Failed to read SP %d\n", ret);
+      break;
+    }
+
+    if (num_ignore_frames == 0) {
+      size_t num_frames = backtrace->num_frames;
+      backtrace_frame_data_t* frame = &backtrace->frames[num_frames];
+      frame->pc = static_cast<uintptr_t>(pc);
+      frame->sp = static_cast<uintptr_t>(sp);
+      frame->stack_size = 0;
+      frame->map_name = NULL;
+      frame->map_offset = 0;
+      frame->func_name = NULL;
+      frame->func_offset = 0;
+
+      if (num_frames > 0) {
+        backtrace_frame_data_t* prev = &backtrace->frames[num_frames-1];
+        prev->stack_size = frame->sp - prev->sp;
+      }
+
+      std::string func_name = backtrace_obj_->GetFunctionName(frame->pc, &frame->func_offset);
+      if (!func_name.empty()) {
+        frame->func_name = strdup(func_name.c_str());
+      }
+
+      uintptr_t map_start;
+      frame->map_name = backtrace_obj_->GetMapName(frame->pc, &map_start);
+      if (frame->map_name) {
+        frame->map_offset = frame->pc - map_start;
+      }
+
+      backtrace->num_frames++;
+    } else {
+      num_ignore_frames--;
+    }
+    ret = unw_step (&cursor);
+  } while (ret > 0 && backtrace->num_frames < MAX_BACKTRACE_FRAMES);
+
+  return true;
+}
+
+std::string UnwindPtrace::GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) {
+  *offset = 0;
+  char buf[512];
+  unw_word_t value;
+  if (unw_get_proc_name_by_ip(addr_space_, pc, buf, sizeof(buf), &value,
+                              upt_info_) >= 0 && buf[0] != '\0') {
+    *offset = static_cast<uintptr_t>(value);
+    return buf;
+  }
+  return "";
+}
+
+//-------------------------------------------------------------------------
+// C++ object creation function.
+//-------------------------------------------------------------------------
+Backtrace* CreatePtraceObj(pid_t pid, pid_t tid) {
+  return new BacktracePtrace(new UnwindPtrace(), pid, tid);
+}