1 files changed, 119 insertions, 0 deletions
diff --git a/debuggerd/elf_utils.cpp b/debuggerd/elf_utils.cpp
new file mode 100644
index 0000000..764b9db
--- /dev/null
+++ b/debuggerd/elf_utils.cpp
@@ -0,0 +1,119 @@
+/*
+ * 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.
+ */
+
+#define LOG_TAG "DEBUG"
+
+#include <elf.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <string>
+
+#include <backtrace/Backtrace.h>
+#include <base/stringprintf.h>
+#include <log/log.h>
+
+#include "elf_utils.h"
+
+template <typename HdrType, typename PhdrType, typename NhdrType>
+static bool get_build_id(
+    Backtrace* backtrace, uintptr_t base_addr, uint8_t* e_ident, std::string* build_id) {
+  HdrType hdr;
+
+  memcpy(&hdr.e_ident[0], e_ident, EI_NIDENT);
+
+  // First read the rest of the header.
+  if (backtrace->Read(base_addr + EI_NIDENT, reinterpret_cast<uint8_t*>(&hdr) + EI_NIDENT,
+                      sizeof(HdrType) - EI_NIDENT) != sizeof(HdrType) - EI_NIDENT) {
+    return false;
+  }
+
+  for (size_t i = 0; i < hdr.e_phnum; i++) {
+    PhdrType phdr;
+    if (backtrace->Read(base_addr + hdr.e_phoff + i * hdr.e_phentsize,
+                        reinterpret_cast<uint8_t*>(&phdr), sizeof(phdr)) != sizeof(phdr)) {
+      return false;
+    }
+    // Looking for the .note.gnu.build-id note.
+    if (phdr.p_type == PT_NOTE) {
+      size_t hdr_size = phdr.p_filesz;
+      uintptr_t addr = base_addr + phdr.p_offset;
+      while (hdr_size >= sizeof(NhdrType)) {
+        NhdrType nhdr;
+        if (backtrace->Read(addr, reinterpret_cast<uint8_t*>(&nhdr), sizeof(nhdr)) != sizeof(nhdr)) {
+          return false;
+        }
+        addr += sizeof(nhdr);
+        if (nhdr.n_type == NT_GNU_BUILD_ID) {
+          // Skip the name (which is the owner and should be "GNU").
+          addr += nhdr.n_namesz;
+          uint8_t build_id_data[128];
+          if (nhdr.n_namesz > sizeof(build_id_data)) {
+            ALOGE("Possible corrupted note, name size value is too large: %u",
+                  nhdr.n_namesz);
+            return false;
+          }
+          if (backtrace->Read(addr, build_id_data, nhdr.n_descsz) != nhdr.n_descsz) {
+            return false;
+          }
+
+          build_id->clear();
+          for (size_t bytes = 0; bytes < nhdr.n_descsz; bytes++) {
+            *build_id += android::base::StringPrintf("%02x", build_id_data[bytes]);
+          }
+
+          return true;
+        } else {
+          // Move past the extra note data.
+          hdr_size -= sizeof(nhdr);
+          size_t skip_bytes = nhdr.n_namesz + nhdr.n_descsz;
+          addr += skip_bytes;
+          if (hdr_size < skip_bytes) {
+            break;
+          }
+          hdr_size -= skip_bytes;
+        }
+      }
+    }
+  }
+  return false;
+}
+
+bool elf_get_build_id(Backtrace* backtrace, uintptr_t addr, std::string* build_id) {
+  // Read and verify the elf magic number first.
+  uint8_t e_ident[EI_NIDENT];
+  if (backtrace->Read(addr, e_ident, SELFMAG) != SELFMAG) {
+    return false;
+  }
+
+  if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
+    return false;
+  }
+
+  // Read the rest of EI_NIDENT.
+  if (backtrace->Read(addr + SELFMAG, e_ident + SELFMAG, EI_NIDENT - SELFMAG) != EI_NIDENT - SELFMAG) {
+    return false;
+  }
+
+  if (e_ident[EI_CLASS] == ELFCLASS32) {
+    return get_build_id<Elf32_Ehdr, Elf32_Phdr, Elf32_Nhdr>(backtrace, addr, e_ident, build_id);
+  } else if (e_ident[EI_CLASS] == ELFCLASS64) {
+    return get_build_id<Elf64_Ehdr, Elf64_Phdr, Elf64_Nhdr>(backtrace, addr, e_ident, build_id);
+  }
+
+  return false;
+}