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| -rw-r--r-- | README.md | 22 |
1 files changed, 19 insertions, 3 deletions
@@ -144,8 +144,23 @@ libc/ </pre> -Adding system calls -------------------- +Adding libc wrappers for system calls +------------------------------------- + +The first question you should ask is "should I add a libc wrapper for +this system call?". The answer is usually "no". + +The answer is "yes" if the system call is part of the POSIX standard. + +The answer is probably "yes" if the system call has a wrapper in at +least one other C library. + +The answer may be "yes" if the system call has three/four distinct +users in different projects, and there isn't a more specific library +that would make more sense as the place to add the wrapper. + +In all other cases, you should use +[syscall(3)](http://man7.org/linux/man-pages/man2/syscall.2.html) instead. Adding a system call usually involves: @@ -157,7 +172,8 @@ Adding a system call usually involves: kernel uapi header files, in which case you just need to make sure that the appropriate POSIX header file in libc/include/ includes the relevant file or files. - 4. Add function declarations to the appropriate header file. + 4. Add function declarations to the appropriate header file. Don't forget + to include the appropriate `__INTRODUCED_IN()`. 5. Add the function name to the correct section in libc/libc.map.txt and run `./libc/tools/genversion-scripts.py`. 6. Add at least basic tests. Even a test that deliberately supplies |