Fix various ftw/nftw "shall fail"s from POSIX.
POSIX says ftw/nftw "shall fail" in various cases where BSD's fts_open doesn't. Since our ftw/nftw are written in terms of fts_open, add a back door so we can hint to ourselves when we should have the POSIX semantics. Also pull several O_CLOEXEC and don't-null-check-before-free cleanups from upstream, and add a couple of tests. Bug: http://b/31152735 Test: ran bionic tests and LTP "nftw01" test Change-Id: Ib05facacc1da4c8b2ab48e9ecce88f11a5406630 Signed-off-by: Simao Gomes Viana <firstname.lastname@example.org>
|8 months ago|
|benchmarks||1 year ago|
|build||2 years ago|
|libc||7 months ago|
|libdl||1 year ago|
|libm||1 year ago|
|libstdc++||2 years ago|
|linker||1 year ago|
|tests||7 months ago|
|tools||1 year ago|
|.clang-format||2 years ago|
|.gitignore||9 years ago|
|Android.bp||2 years ago|
|Android.mk||2 years ago|
|CPPLINT.cfg||4 years ago|
|CleanSpec.mk||3 years ago|
|PREUPLOAD.cfg||1 year ago|
|README.md||1 year ago|
|android-changes-for-ndk-developers.md||1 year ago|
The C library. Stuff like
The math library. Traditionally Unix systems kept stuff like
cos(3) in a separate library to save space in the days before shared
The dynamic linker interface library. This is actually just a bunch of stubs
that the dynamic linker replaces with pointers to its own implementation at
runtime. This is where stuff like
The C++ ABI support functions. The C++ compiler doesn’t know how to implement
thread-safe static initialization and the like, so it just calls functions that
are supplied by the system. Stuff like
__cxa_pure_virtual live here.
The dynamic linker. When you run a dynamically-linked executable, its ELF file
DT_INTERP entry that says “use the following program to start me”. On
Android, that’s either
linker64 (depending on whether it’s a
32-bit or 64-bit executable). It’s responsible for loading the ELF executable
into memory and resolving references to symbols (so that when your code tries to
fopen(3), say, it lands in the right place).
tests/ directory contains unit tests. Roughly arranged as one file per
publicly-exported header file.
benchmarks/ directory contains benchmarks.
libc/ arch-arm/ arch-arm64/ arch-common/ arch-mips/ arch-mips64/ arch-x86/ arch-x86_64/ # Each architecture has its own subdirectory for stuff that isn't shared # because it's architecture-specific. There will be a .mk file in here that # drags in all the architecture-specific files. bionic/ # Every architecture needs a handful of machine-specific assembler files. # They live here. include/ machine/ # The majority of header files are actually in libc/include/, but many # of them pull in a for things like limits, # endianness, and how floating point numbers are represented. Those # headers live here. string/ # Most architectures have a handful of optional assembler files # implementing optimized versions of various routines. The # functions are particular favorites. syscalls/ # The syscalls directories contain script-generated assembler files. # See 'Adding system calls' later. include/ # The public header files on everyone's include path. These are a mixture of # files written by us and files taken from BSD. kernel/ # The kernel uapi header files. These are scrubbed copies of the originals # in external/kernel-headers/. These files must not be edited directly. The # generate_uapi_headers.sh script should be used to go from a kernel tree to # external/kernel-headers/ --- this takes care of the architecture-specific # details. The update_all.py script should be used to regenerate bionic's # scrubbed headers from external/kernel-headers/. private/ # These are private header files meant for use within bionic itself. dns/ # Contains the DNS resolver (originates from NetBSD code). upstream-freebsd/ upstream-netbsd/ upstream-openbsd/ # These directories contain unmolested upstream source. Any time we can # just use a BSD implementation of something unmodified, we should. # The structure under these directories mimics the upstream tree, # but there's also... android/ include/ # This is where we keep the hacks necessary to build BSD source # in our world. The *-compat.h files are automatically included # using -include, but we also provide equivalents for missing # header/source files needed by the BSD implementation. bionic/ # This is the biggest mess. The C++ files are files we own, typically # because the Linux kernel interface is sufficiently different that we # can't use any of the BSD implementations. The C files are usually # legacy mess that needs to be sorted out, either by replacing it with # current upstream source in one of the upstream directories or by # switching the file to C++ and cleaning it up. malloc_debug/ # The code that implements the functionality to enable debugging of # native allocation problems. stdio/ # These are legacy files of dubious provenance. We're working to clean # this mess up, and this directory should disappear. tools/ # Various tools used to maintain bionic. tzcode/ # A modified superset of the IANA tzcode. Most of the modifications relate # to Android's use of a single file (with corresponding index) to contain # time zone data. zoneinfo/ # Android-format time zone data. # See 'Updating tzdata' later.
Adding a system call usually involves:
As mentioned above, this is currently a two-step process:
This is fully automated (and these days handled by the libcore team, because they own icu, and that needs to be updated in sync with bionic):
If you make a change that is likely to have a wide effect on the tree (such as a
libc header change), you should run
make checkbuild. A regular
not build the entire tree; just the minimum number of projects that are
required for the device. Tests, additional developer tools, and various other
modules will not be built. Note that
make checkbuild will not be complete
make tests covers a few additional modules, but generally speaking
make checkbuild is enough.
The tests are all built from the tests/ directory.
$ mma # In $ANDROID_ROOT/bionic. $ adb root && adb remount && adb sync $ adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests32 $ adb shell \ /data/nativetest/bionic-unit-tests-static/bionic-unit-tests-static32 # Only for 64-bit targets $ adb shell /data/nativetest64/bionic-unit-tests/bionic-unit-tests64 $ adb shell \ /data/nativetest64/bionic-unit-tests-static/bionic-unit-tests-static64
Note that we use our own custom gtest runner that offers a superset of the options documented at https://github.com/google/googletest/blob/master/googletest/docs/AdvancedGuide.md#running-test-programs-advanced-options, in particular for test isolation and parallelism (both on by default).
Most of the unit tests are executed by CTS. By default, CTS runs as
a non-root user, so the unit tests must also pass when not run as root.
Some tests cannot do any useful work unless run as root. In this case,
the test should check
getuid() == 0 and do nothing otherwise (typically
we log in this case to prevent accidents!). Obviously, if the test can be
rewritten to not require root, that’s an even better solution.
Currently, the list of bionic CTS tests is generated at build time by running a host version of the test executable and dumping the list of all tests. In order for this to continue to work, all architectures must have the same number of tests, and the host version of the executable must also have the same number of tests.
Running the gtests directly is orders of magnitude faster than using CTS, but in cases where you really have to run CTS:
$ make cts # In $ANDROID_ROOT. $ adb unroot # Because real CTS doesn't run as root. # This will sync any *test* changes, but not *code* changes: $ cts-tradefed \ run singleCommand cts --skip-preconditions -m CtsBionicTestCases
The host tests require that you have
lunched either an x86 or x86_64 target.
Note that due to ABI limitations (specifically, the size of pthread_mutex_t),
32-bit bionic requires PIDs less than 65536. To enforce this, set /proc/sys/kernel/pid_max
$ ./tests/run-on-host.sh 32 $ ./tests/run-on-host.sh 64 # For x86_64-bit *targets* only.
You can supply gtest flags as extra arguments to this script.
As a way to check that our tests do in fact test the correct behavior (and not just the behavior we think is correct), it is possible to run the tests against the host’s glibc.
$ ./tests/run-on-host.sh glibc
For either host or target coverage, you must first:
$ export NATIVE_COVERAGE=true
$ mma $ adb sync $ adb shell \ GCOV_PREFIX=/data/local/tmp/gcov \ GCOV_PREFIX_STRIP=`echo $ANDROID_BUILD_TOP | grep -o / | wc -l` \ /data/nativetest/bionic-unit-tests/bionic-unit-tests32 $ acov
acov will pull all coverage information from the device, push it to the right
lcov, and open the coverage report in your browser.
First, build and run the host tests as usual (see above).
$ croot $ lcov -c -d $ANDROID_PRODUCT_OUT -o coverage.info $ genhtml -o covreport coverage.info # or lcov --list coverage.info
The coverage report is now available at
$ mma $ adb remount $ adb sync $ adb shell /data/nativetest/bionic-benchmarks/bionic-benchmarks $ adb shell /data/nativetest64/bionic-benchmarks/bionic-benchmarks
You can use
--benchmark_filter=getpid to just run benchmarks with “getpid”
in their name.
See the “Host tests” section of “Running the tests” above.
Bionic’s test runner will run each test in its own process by default to prevent tests failures from impacting other tests. This also has the added benefit of running them in parallel, so they are much faster.
However, this also makes it difficult to run the tests under GDB. To prevent
each test from being forked, run the tests with the flag
On 32-bit Android,
off_t is a signed 32-bit integer. This limits functions
off_t to working on files no larger than 2GiB.
Android does not require the
_LARGEFILE_SOURCE macro to be used to make
ftello available. Instead they’re always available from API
level 24 where they were introduced, and never available before then.
Android also does not require the
_LARGEFILE64_SOURCE macro to be used
off64_t and corresponding functions such as
Instead, whatever subset of those functions was available at your target API
level will be visible.
There are a couple of exceptions to note. Firstly,
off64_t and the single
lseek64 were available right from the beginning in API 3. Secondly,
Android has always silently inserted
O_LARGEFILE into any open call, so if
all you need are functions like
read that don’t take/return
files have always worked.
Android support for
_FILE_OFFSET_BITS=64 (which turns
and replaces each
off_t function with its
off64_t counterpart, such as
lseek in the source becoming
lseek64 at runtime) was added late. Even when
it became available for the platform, it wasn’t available from the NDK until
r15. Before NDK r15,
_FILE_OFFSET_BITS=64 silently did nothing: all code
compiled with that was actually using a 32-bit
off_t. With a new enough NDK,
the situation becomes complicated. If you’re targeting an API before 21, almost
all functions that take an
off_t become unavailable. You’ve asked for their
64-bit equivalents, and none of them (except
lseek64) exist. As you
increase your target API level, you’ll have more and more of the functions
available. API 12 adds some of the
<unistd.h> functions, API 21 adds
and by API 24 you have everything including
<stdio.h>. See the
linker map for full details.
In the 64-bit ABI,
off_t is always 64-bit.
sigset_tis too small for real-time signals.
On 32-bit Android,
sigset_t is too small for ARM and x86 (but correct for
MIPS). This means that there is no support for real-time signals in 32-bit
In the 64-bit ABI,
sigset_t is the correct size for every architecture.
On 32-bit Android,
time_t is 32-bit. The header
<time64.h> and type
time64_t exist as a workaround, but the kernel interfaces exposed on 32-bit
Android all use the 32-bit
In the 64-bit ABI,
time_t is 64-bit.