[klibc] [PATCH] Add syscall wrappers required by libkeyutils

[Christian Eggers]

On Tuesday, 28 July 2020, 05:11:03 CEST, H. Peter Anvin wrote:
> On 2020-07-27 19:20, hpa at zytor.com wrote:
> > ...
> > Now, thinking about it, it *might* be possible to implement some of this
> > using varadic macros. Let me play around with it a little bit.
> This might actually work:
>
> /*
>  * Not prototyped on purpose, as (...) isn't a valid prototype.
>  * __extension__ prevents erroring out due to lack of prototype.
>  */
> __extension__ extern long long ___syscall();
> extern long ___syscall_num;
>
> #define syscall(n, ...)                                       \
>   (___syscall_num = (n), ___syscall(__VA_ARGS__))
>
> ... then have ___syscall() get the system call number from the memory
> variable ___syscall_num (If klibc were multithreaded it would have to be a
> thread-local variable, of course) and call the common syscall handler code.
>

If you could provide a patch for ARM, I would test it with libkeyutils. I have
no special knowledge about the various calling conventions, but in case of
problems I have access to a JTAG debugger...

regards
Christian



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