Add Symbols parsing.

Bug: 23762183

Test: New unit tests pass.
Change-Id: Ib67fee879120b5e82889076a0f7221dc429ac140

1 files changed, 110 insertions, 0 deletions

diff --git a/libunwindstack/Symbols.cpp b/libunwindstack/Symbols.cpp
new file mode 100644
index 0000000..86c1233
--- /dev/null
+++ b/libunwindstack/Symbols.cpp
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2017 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 <assert.h>
+#include <elf.h>
+#include <stdint.h>
+
+#include <string>
+
+#include "Memory.h"
+#include "Symbols.h"
+
+Symbols::Symbols(uint64_t offset, uint64_t size, uint64_t entry_size, uint64_t str_offset,
+                 uint64_t str_size)
+    : cur_offset_(offset),
+      offset_(offset),
+      end_(offset + size),
+      entry_size_(entry_size),
+      str_offset_(str_offset),
+      str_end_(str_offset_ + str_size) {}
+
+const Symbols::Info* Symbols::GetInfoFromCache(uint64_t addr) {
+  // Binary search the table.
+  size_t first = 0;
+  size_t last = symbols_.size();
+  while (first < last) {
+    size_t current = first + (last - first) / 2;
+    const Info* info = &symbols_[current];
+    if (addr < info->start_offset) {
+      last = current;
+    } else if (addr < info->end_offset) {
+      return info;
+    } else {
+      first = current + 1;
+    }
+  }
+  return nullptr;
+}
+
+template <typename SymType>
+bool Symbols::GetName(uint64_t addr, uint64_t load_bias, Memory* elf_memory, std::string* name,
+                      uint64_t* func_offset) {
+  addr += load_bias;
+
+  if (symbols_.size() != 0) {
+    const Info* info = GetInfoFromCache(addr);
+    if (info) {
+      assert(addr >= info->start_offset && addr <= info->end_offset);
+      *func_offset = addr - info->start_offset;
+      return elf_memory->ReadString(info->str_offset, name, str_end_ - info->str_offset);
+    }
+  }
+
+  bool symbol_added = false;
+  bool return_value = false;
+  while (cur_offset_ + entry_size_ <= end_) {
+    SymType entry;
+    if (!elf_memory->Read(cur_offset_, &entry, sizeof(entry))) {
+      // Stop all processing, something looks like it is corrupted.
+      cur_offset_ = UINT64_MAX;
+      return false;
+    }
+    cur_offset_ += entry_size_;
+
+    if (entry.st_shndx != SHN_UNDEF && ELF32_ST_TYPE(entry.st_info) == STT_FUNC) {
+      // Treat st_value as virtual address.
+      uint64_t start_offset = entry.st_value;
+      if (entry.st_shndx != SHN_ABS) {
+        start_offset += load_bias;
+      }
+      uint64_t end_offset = start_offset + entry.st_size;
+
+      // Cache the value.
+      symbols_.emplace_back(start_offset, end_offset, str_offset_ + entry.st_name);
+      symbol_added = true;
+
+      if (addr >= start_offset && addr < end_offset) {
+        *func_offset = addr - start_offset;
+        uint64_t offset = str_offset_ + entry.st_name;
+        if (offset < str_end_) {
+          return_value = elf_memory->ReadString(offset, name, str_end_ - offset);
+        }
+        break;
+      }
+    }
+  }
+
+  if (symbol_added) {
+    std::sort(symbols_.begin(), symbols_.end(),
+              [](const Info& a, const Info& b) { return a.start_offset < b.start_offset; });
+  }
+  return return_value;
+}
+
+// Instantiate all of the needed template functions.
+template bool Symbols::GetName<Elf32_Sym>(uint64_t, uint64_t, Memory*, std::string*, uint64_t*);
+template bool Symbols::GetName<Elf64_Sym>(uint64_t, uint64_t, Memory*, std::string*, uint64_t*);