blob: af38c4d1c4fcefbc50bde730ad9e563fe034cc2e [file] [log] [blame]
Name: libunwindstack
Revision: a7b4c5d25aebc2c7e6156473dae98238c029e630
Date: March 31, 2020
License: Apache 2.0
License File: LICENSE
Security Critical: yes
Canonical library to unwind Android call stacks.
libunwindstack (and its relevant dependencies) are copied from Android's
system/core. libunwindstack handles many of the details of unwinding on Android,
which is inherently more difficult than on other platforms due to the wider
variety of frame types that occur on Android. These include Java frames, JITted
Java frames, Chrome C++ frames, and system library C++ frames. Different frame
types can have different call frame information (CFI) formats that the unwinder
must parse to know how to move up the stack. These formats include DWARF,
MiniDebugInfo, and EHABI. libunwindstack handles much of this complexity.
libunwindstack is copied from the Android tree and utilizes common Android
libraries from that tree. This is analagous to how a static library that is
built within the Chromium tree might utilize //base and //threading. For
libunwindstack, we copy its Android tree dependencies into this directory.
Further complicating matters, Chrome is built against a much older version of
the Android NDK than this version of libunwindstack, which targets Android tip
of tree. The local modifications made allow libunwindstack to compile against
Chrome's older version of the NDK.
Steps to update libunwindstack:
1. Update the contents to the upstream revision.
git checkout master && git pull -q
git checkout -b update && git cl upstream master
rm -rf src
tools/ <upstream_git_tag>
# ... manually update the revision info in README.chromium ...
git add --all
git commit -m 'step 1'
2. Build and apply/update/add patches until the code compiles. Update existing
patches so that they apply cleanly. Remove any patches that are no longer
required. Assumes out/Debug is configured for an Android component build.
(cd ../.. && autoninja -C out/Debug
patch -p1 < patches/... # etc.
# Remove remnants of failed patch attempts.
find src -name \*.orig -o -name \*.rej | xargs rm
git add --all
git commit -m 'step 2'
3. Prune to the subset of libunwindstack sources that should be compiled and
checked in.
tools/ out/Debug > required_sources
# Replace 'public' files with these:
grep src/libunwindstack/include required_sources | sed 's/.*/ "&",/'
# Replace 'sources' files with these:
grep -v 'src/libunwindstack/include\|\.S$' required_sources | \
sed 's/.*/ "&",/'
# Remove unused files.
find src -type f | sort | comm -2 -3 - required_sources | xargs rm
find src -depth -type d -empty -exec rmdir \{\} \;
rm required_sources
git add -u src
git commit -m 'step 3'
4. Prepare CLs to land the changes. Using `git rebase -i master` reorder the
commits as
step 1
step 3
step 2
and squash the step 3 commit into step 1.
Land a CL with step1, which contains the upstream libunwindstack changes to
the files we need. After landing `master` will be in a noncompiling state.
Land a CL with step2, which contains the Chrome-specific changes required to
build libunwindstack.
Local modifications:
- Android's base/ directory is renamed android-base/.
- 0001-lzma-interface.patch:
Chromium uses an older version of LZMA (15.14, released 2015/12/31) than
platform/system/core (18.06, released 2018/12/30). libunwindstack uses the 8
parameter XzUnpacker_Code call, which wasn't available until 18.03
The 7 parameter XzUnpacker_Code call is equivalent to the new
XzUnpacker_CodeFull call (, which is in turn equivalent
to XzUnpacker_Code with the new `srcFinished` parameter set to `true`
( Because of this, we can safely delete the `true`
`srcFinished` parameter used by libunwindstack and have our 15.14-compliant
code be the same as upstream libunwindstack's 18.06-compliant code.
We also add a missing typedef.
- 0002-disable-ftw.patch:
The `TemporaryDir` destructor uses the `nftw` function, which isn't available
in Android NDK version 16 (it was first made available in 17, as per `TemporaryDir` is unused by libunwindstack, though,
so we safely disable the call.
- 0003-remove-file-logging.patch:
Stubs out PLOG() in android-base/file.cpp, which allows us to remove the
dependency on android-base/logging.cpp. logging.cpp is problematic because it
attempts to use BSD's getprogname(), which isn't available in Android NDK
version 16 (it was first made available in 21, as per
- 0004-gnu-basename.patch:
Adds a short implementation of the non-modifying GNU basename() function
which isn't available in Android NDK version 16 (it was first made available
in 23, as per We call this function `compat_basename`.
Although there's a POSIX basename() available via <libgen.h>, that function
has different behavior with regards to trailing slashes and can also modify
its argument under some circumstances.
- 0005-disable-fdsan.patch:
Disables fdsan on unique_fd.h. fdsan isn't available in Android NDK version 16
(it was first made available in 29, as per
- 0006-memory-process-vm-readv.patch:
Uses syscall() to call process_vm_readv instead of the process_vm_readv()
function, which isn't available in Android NDK 16 (it was first made available
in 23, as per The syscall() version was already
available, as per
- 0007-create-local-process-memory.patch:
Exposes an interface to create and return a Memory subclass for reading local
process memory, as a unique_ptr.