stack: Adjust Pre-M Android incorrect debuggerd addresses.

third_party/android_platform/development/scripts/stack_libs.py

+#!/usr/bin/env python
+#
+# Copyright (C) 2015 The Android Open Source Project

[rmcilroy, 2015/10/23 16:25:10]

Was this taken straight from the Android project with no modifications? If so,
can we add a git hash reference in the README.chromium. Otherwise, could we land
unmodified as a seperate CL (with git reference) then do the modifications in
this CL. This will make it obvious what has changed if we need to cherry-pick
upstream fixes.

[simonb (inactive), 2015/10/26 12:38:31]

No, the file is brand new and only in here. Local 'modification', then. Just a
bit too chunky for me to feel comfortable shoe-horning it into stack-core.py or
stack itself.

I've changed the copyright to Chromium style. Sorry for the wrong steer.

[rmcilroy, 2015/10/26 16:42:17]

Acknowledged.

+#
+# 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.
+
+"""Identifies address adjustments required for native crash dumps."""
+
+import glob
+import os.path
+import subprocess
+
+
+def _HasElfHeader(path):
+  """Return True if the file at the given path has an ELF magic header.
+
+  Minimal check only, for 'ELF' in bytes 1 to 3 of the file. Filters out
+  the zero-byte false-positives such as libchromeview.so returned by glob.
+
+  Args:
+    path: Path to file to check.
+  Returns:
+    True or False
+  """
+  with open(path) as stream:
+    elf_header = stream.read(4)
+    return len(elf_header) == 4 and elf_header[1:4] == 'ELF'
+
+
+def _ReadElfProgramHeaders(lib):
+  """Return an iterable of program headers, from 'readelf -l ...'.
+
+  Uses the platform readelf in all cases. This is somewhat lazy, but suffices
+  in practice because program headers in ELF files are architecture-agnostic.
+
+  Args:
+    lib: Library file to read.
+  Returns:
+    [readelf -l output line, ...]
+  """
+  string = subprocess.check_output(['readelf', '-l', lib])
+  return string.split('\n')
+
+
+def _FindMinLoadVaddr(lib):
+  """Return the minimum VirtAddr field of all library LOAD segments.
+
+  Args:
+    lib: Library file to read.
+  Returns:
+    Min VirtAddr field for all LOAD segments, or 0 if none found.
+  """
+  vaddrs = []
+  # Locate LOAD lines and find the smallest VirtAddr field, eg:
+  #   Type       Offset    VirtAddr   PhysAddr   FileSiz   MemSiz    Flg Align
+  #   LOAD       0x000000  0x001d6000 0x001d6000 0x20f63fc 0x20f63fc R E 0x1000
+  #   LOAD       0x20f6970 0x022cd970 0x022cd970 0x182df8  0x1b4490  RW  0x1000
+  # would return 0x1d6000. Ignores all non-LOAD lines.
+  for line in _ReadElfProgramHeaders(lib):
+    elements = line.split()
+    if elements and elements[0] == 'LOAD':
+      vaddrs.append(int(elements[2], 16))
+  if vaddrs:
+    return min(vaddrs)
+  return 0
+
+
+def GetLoadVaddrs(apk_dir):
+  """Return a dictionary of minimum VirtAddr fields for libraries in apk_dir.
+
+  The dictionary returned may be passed to stack_core.ConvertTrace(). In
+  pre-M Android releases the addresses printed by debuggerd into tombstones
+  do not take account of non-zero vaddrs. Here we collect this information,
+  so that we can use it later to correct such debuggerd tombstones.
+
+  Args:
+    apk_dir: Path to APK staging directory.
+  Returns:
+    {'libchrome.so': 12345, ...}
+  """
+  pathname = apk_dir + '/libs/*/*.so'
+  libs = [lib for lib in glob.glob(pathname) if _HasElfHeader(lib)]
+
+  load_vaddrs = {}
+  for lib in libs:
+    min_vaddr = _FindMinLoadVaddr(lib)
+    if min_vaddr:
+      # Store with the library basename as the key. This is because once on
+      # the device its path may not fully match its place in the APK staging
+      # directory
+      load_vaddrs[os.path.basename(lib)] = min_vaddr
+
+  # Direct load from APK causes debuggerd to tag trace lines as if from the
+  # file .../base.apk. So if we encounter a libchrome.so with packed
+  # relocations, replicate this as base.apk so that later adjustment code
+  # finds the appropriate adjustment.
+  if 'libchrome.so' in load_vaddrs:
+    load_vaddrs['base.apk'] = load_vaddrs['libchrome.so']
+
+  return load_vaddrs