On Tue, Jul 28, 2015 at 3:19 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Tue, Jul 28, 2015 at 07:59:16AM -0600, Shuah Khan wrote: >> On 07/28/2015 05:41 AM, David Drysdale wrote: >> > Given that I've gotten some of the details wrong in the past (and I've >> > seen others do likewise), I thought it might be helpful to collate the >> > best practices for adding a new system call to the kernel. >> > >> > Apologies for the wide circulation -- I've tried to include folk who've >> > recently added or proposed a system call, as they're most likely to >> > have opinions on: >> > - whether this a useful addition to Documentation/ >> > - whether the details of the advice are correct and complete. >> > >> > Shuah, is there anything more that should be added for the Testing >> > section in particular? >> > >> >> David, >> >> Looks good. You could add a one liner on in some cases, it might be >> necessary to install headers before test compiles. Other than that, >> the information looks good. > > For perf we still use the syscall() wrapper and we have hardcoded > (fallback) syscall numbers in there in case they've not yet reached > unistd.h. > > People update their kernels far more often than their userspace headers. How about: diff --git a/Documentation/adding-syscalls.txt b/Documentation/adding-syscalls.txt index 5f52edda8951..b274c3d01edb 100644 --- a/Documentation/adding-syscalls.txt +++ b/Documentation/adding-syscalls.txt @@ -389,6 +389,11 @@ reviewers with a demonstration of how user space programs will use the system call. A good way to combine these aims is to include a simple self-test program in a new directory under tools/testing/selftests/. +For a new system call, there will obviously be no libc wrapper function and so +the test will need to invoke it using syscall(); also, if the system call +involves a new userspace-visible structure, the corresponding header will need +to be installed to compile the test. + Make sure the selftest runs successfully on all supported architectures. For example, check that it works when compiled as an x86_64 (-m64), x86_32 (-m32) and x32 (-mx32) ABI program. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
