Name: android_bionic
Owner: PAC-ROM
Description: null
Created: 2015-10-20 01:31:28.0
Updated: 2016-06-18 17:48:23.0
Pushed: 2016-05-02 00:58:38.0
Homepage: null
Size: 21052
Language: C
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The C library. Stuff like fopen(3)
and kill(2)
.
The math library. Traditionally Unix systems kept stuff like sin(3)
and
cos(3)
in a separate library to save space in the days before shared
libraries.
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 dlopen(3)
lives.
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_guard_acquire
and
__cxa_pure_virtual
live here.
The dynamic linker. When you run a dynamically-linked executable, its ELF file
has a DT_INTERP
entry that says “use the following program to start me”. On
Android, that's either linker
or 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
jump to fopen(3)
, say, it lands in the right place).
The tests/
directory contains unit tests. Roughly arranged as one file per
publicly-exported header file.
The 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 afor 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-dlmalloc/ 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. 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:
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 make
will
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
either, as make tests
covers a few additional modules, but generally speaking
make checkbuild
is enough.
The tests are all built from the tests/ directory.
$ mma
$ 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/nativetest/bionic-unit-tests/bionic-unit-tests64
$ adb shell \
/data/nativetest/bionic-unit-tests-static/bionic-unit-tests-static64
The host tests require that you have lunch
ed either an x86 or x86_64 target.
$ mma
$ mm bionic-unit-tests-run-on-host32
$ mm bionic-unit-tests-run-on-host64 # For 64-bit *targets* only.
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. The executables are already in your path.
$ mma
$ bionic-unit-tests-glibc32
$ bionic-unit-tests-glibc64
For either host or target coverage, you must first:
$ export NATIVE_COVERAGE=true
bionic_coverage=true
in libc/Android.mk
and libm/Android.mk
.$ 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
directories, run 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 covreport/index.html
.
This probably belongs in the NDK documentation rather than here, but these are the known ABI bugs in LP32:
time_t
is 32-bit. http://b/5819737
off_t
is 32-bit. There is off64_t
, but no _FILE_OFFSET_BITS
support.
Many of the off64_t
functions are missing in older releases, and
stdio uses 32-bit offsets, so there's no way to fully implement
_FILE_OFFSET_BITS
.
sigset_t
is too small on ARM and x86 (but correct on MIPS), so support
for real-time signals is broken. http://b/5828899