145 lines
5.6 KiB
Python
Executable File
145 lines
5.6 KiB
Python
Executable File
#!/usr/bin/python
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'''
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/* This file generates libgcc_compat.c file that contains dummy
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* references to libgcc.a functions to force the dynamic linker
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* to copy their definition into the final libc.so binary.
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*
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* They are required to ensure backwards binary compatibility with
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* libc.so provided by the platform and binaries built with the NDK or
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* different versions/configurations of toolchains.
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*
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* Now, for a more elaborate description of the issue:
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*
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* libgcc.a is a compiler-specific library containing various helper
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* functions used to implement certain operations that are not necessarily
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* supported by the target CPU. For example, integer division doesn't have a
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* corresponding CPU instruction on ARMv5, and is instead implemented in the
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* compiler-generated machine code as a call to an __idiv helper function.
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*
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* Normally, one has to place libgcc.a in the link command used to generate
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* target binaries (shared libraries and executables) after all objects and
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* static libraries, but before dependent shared libraries, i.e. something
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* like:
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* gcc <options> -o libfoo.so foo.a libgcc.a -lc -lm
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*
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* This ensures that any helper function needed by the code in foo.a is copied
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* into the final libfoo.so. However, doing so will link a bunch of other __cxa
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* functions from libgcc.a into each .so and executable, causing 4k+ increase
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* in every binary. Therefore the Android platform build system has been
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* using this instead:
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*
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* gcc <options> -o libfoo.so foo.a -lc -lm libgcc.a
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*
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* The problem with this is that if one helper function needed by foo.a has
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* already been copied into libc.so or libm.so, then nothing will be copied
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* into libfoo.so. Instead, a symbol import definition will be added to it
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* so libfoo.so can directly call the one in libc.so at runtime.
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*
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* When refreshing toolchains for new versions or using different architecture
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* flags, the set of helper functions copied to libc.so may change, which
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* resulted in some native shared libraries generated with the NDK or prebuilts
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* from vendors to fail to load properly.
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*
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* The NDK has been fixed after 1.6_r1 to use the correct link command, so
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* any native shared library generated with it should now be safe from that
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* problem. On the other hand, existing shared libraries distributed with
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* applications that were generated with a previous version of the NDK
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* still need all 1.5/1.6 helper functions in libc.so and libm.so
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*
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* After 3.2, the toolchain was updated again, adding __aeabi_f2uiz to the
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* list of requirements. Technically, this is due to mis-linked NDK libraries
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* but it is easier to add a single function here than asking several app
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* developers to fix their build.
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*
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* The __aeabi_idiv function is added to the list since cortex-a15 supports
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* HW idiv instructions so the system libc.so doesn't pull in the reference to
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* __aeabi_idiv but legacy libraries built against cortex-a9 targets still need
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* it.
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*
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* Final note: some of the functions below should really be in libm.so to
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* completely reflect the state of 1.5/1.6 system images. However,
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* since libm.so depends on libc.so, it's easier to put all of
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* these in libc.so instead, since the dynamic linker will always
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* search in libc.so before libm.so for dependencies.
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*/
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'''
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import os
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import sys
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import subprocess
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import tempfile
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import re
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libgcc_compat_header = "/* Generated by genlibgcc_compat.py */\n" + \
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"""
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#define COMPAT_FUNCTIONS_LIST \\
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"""
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libgcc_compat_footer = """
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#define XX(f) extern void f(void);
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COMPAT_FUNCTIONS_LIST
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#undef XX
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void __bionic_libgcc_compat_hooks(void) {
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#define XX(f) f();
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COMPAT_FUNCTIONS_LIST
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#undef XX
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}
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"""
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class Generator:
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def process(self):
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android_build_top_path = os.environ["ANDROID_BUILD_TOP"]
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build_path = android_build_top_path + "/bionic/libc"
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file_name = "libgcc_compat.c"
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file_path = build_path + "/arch-arm/bionic/" + file_name
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print "* ANDROID_BUILD_TOP=" + android_build_top_path
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# Check TARGET_ARCH
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arch = subprocess.check_output(["CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core make --no-print-directory -f build/core/config.mk dumpvar-TARGET_ARCH"],
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cwd=android_build_top_path, shell=True).strip()
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if arch != 'arm':
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sys.exit("Error: Invalid TARGET_ARCH='" + arch + "' expecting 'arm'")
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build_output_file_path = tempfile.mkstemp()[1]
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p = subprocess.Popen(["ONE_SHOT_MAKEFILE=bionic/libc/Android.mk make -C " + android_build_top_path
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+ " -f build/core/main.mk all_modules TARGET_LIBGCC= -j20 -B 2>&1 | tee " + build_output_file_path],
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cwd=build_path, shell=True)
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p.wait()
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print "* Build complete, logfile: " + build_output_file_path
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func_set = set()
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prog=re.compile("(?<=undefined reference to ')\w+")
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fd = open(build_output_file_path, 'r')
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for line in fd:
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m = prog.search(line)
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if m:
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func_set.add(m.group(0))
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fd.close()
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func_list = sorted(func_set)
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print "* Found " + repr(len(func_list)) + " referenced functions: " + repr(func_list)
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if 0 == len(func_list):
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sys.exit("Error: function list is empty, please check the build log: " + build_output_file_path)
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print "* Generating " + file_path
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fres = open(file_path, 'w')
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fres.write(libgcc_compat_header)
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for func_name in func_list:
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fres.write(" XX("+func_name+") \\\n")
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fres.write(libgcc_compat_footer)
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fres.close()
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generator = Generator()
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generator.process()
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