| commit | c3a61c8e76110831e7b3bf3af05af1f3d647cced | [log] [tgz] |
|---|---|---|
| author | Kevin Brodsky <kevin.brodsky@linaro.org> | Thu Dec 31 10:38:38 2015 +0000 |
| committer | Meninblack007 <sanyam.53jain@gmail.com> | Wed Mar 29 20:43:48 2017 +0530 |
| tree | b20924718148d4146f3cd5113fc03b0889ad7187 | |
| parent | ac8a0d13a47fbd5ba458d9fd24933292675a34e7 [diff] |
linker: try remaining locations on library load failure This commit modifies the behavior of the linker when trying to load a library. Until now, the linker stopped on the first file it could open in the path search order (starting with LD_LIBRARY_PATH); if loading the file failed for any reason, then linking would fail. Now, the linker tries to load the file immediately after opening it; if either opening or loading the file fails, then it moves on to the next location. If all attempts fail, they are all reported in the same order, otherwise nothing is reported. Some error messages have been modified in order to always show the full path to the file that could not be loaded. This new behavior matches that of ld-linux.so. It is particularly useful in that it allows to support search paths with mixed bitness (libraries with the wrong bitness are merely ignored). More specifically, it enables 64b executables to execute 32b files (or the other way around) with LD_LIBRARY_PATH containing both 32b and 64b paths, which is impossible with the old behavior. AOSPA Ticket: NOUGAT-35 Change-Id: Ieedd08e4f5bfb3b17bcd07af2d091ed03210ba81 Signed-off-by: Alex Naidis <alex.naidis@linux.com> Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
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.
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 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 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
The host tests require that you have lunched 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=truebionic_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.
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 --no-isolate.
This probably belongs in the NDK documentation rather than here, but these are the known ABI bugs in the 32-bit ABI:
time_t is 32-bit. http://b/5819737. In the 64-bit ABI, time_t is 64-bit.
off_t is 32-bit. There is off64_t, and in newer releases there is almost-complete support for _FILE_OFFSET_BITS. Unfortunately our stdio implementation uses 32-bit offsets and -- worse -- function pointers to functions that use 32-bit offsets, so there's no good way to implement the last few pieces http://b/24807045. In the 64-bit ABI, off_t is off64_t.
sigset_t is too small on ARM and x86 (but correct on MIPS), so support for real-time signals is broken. http://b/5828899 In the 64-bit ABI, sigset_t is the correct size for every architecture.