1 Welcome to Bionic, Android's small and custom C library for the Android 2 platform. 3 4 Bionic is mainly a port of the BSD C library to our Linux kernel with the 5 following additions/changes: 6 7 - no support for locales 8 - no support for wide chars (i.e. multi-byte characters) 9 - its own smallish implementation of pthreads based on Linux futexes 10 - support for x86, ARM and ARM thumb CPU instruction sets and kernel interfaces 11 12 Bionic is released under the standard 3-clause BSD License 13 14 Bionic doesn't want to implement all features of a traditional C library, we only 15 add features to it as we need them, and we try to keep things as simple and small 16 as possible. Our goal is not to support scaling to thousands of concurrent threads 17 on multi-processors machines; we're running this on cell-phones, damnit !! 18 19 Note that Bionic doesn't provide a libthread_db or a libm implementation. 20 21 22 Adding new syscalls: 23 ==================== 24 25 Bionic provides the gensyscalls.py Python script to automatically generate syscall 26 stubs from the list defined in the file SYSCALLS.TXT. You can thus add a new syscall 27 by doing the following: 28 29 - edit SYSCALLS.TXT 30 - add a new line describing your syscall, it should look like: 31 32 return_type syscall_name(parameters) syscall_number 33 34 - in the event where you want to differentiate the syscall function from its entry name, 35 use the alternate: 36 37 return_type funcname:syscall_name(parameters) syscall_number 38 39 - additionally, if the syscall number is different between ARM and x86, use: 40 41 return_type funcname[:syscall_name](parameters) arm_number,x86_number 42 43 - a syscall number can be -1 to indicate that the syscall is not implemented on 44 a given platform, for example: 45 46 void __set_tls(void*) arm_number,-1 47 48 49 the comments in SYSCALLS.TXT contain more information about the line format 50 51 You can also use the 'checksyscalls.py' script to check that all the syscall 52 numbers you entered are correct. It does so by looking at the values defined in 53 your Linux kernel headers. The script indicates where the values are incorrect 54 and what is expected instead. 55
