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H A D | sys.h | 3ec38af6 Tue Aug 01 10:39:54 CDT 2023 Yuan Tan <tanyuan@tinylab.org> tools/nolibc: add pipe() and pipe2() support
According to manual page [1], posix spec [2] and source code like arch/mips/kernel/syscall.c, for historic reasons, the sys_pipe() syscall on some architectures has an unusual calling convention. It returns results in two registers which means there is no need for it to do verify the validity of a userspace pointer argument. Historically that used to be expensive in Linux. These days the performance advantage is negligible.
Nolibc doesn't support the unusual calling convention above, luckily Linux provides a generic sys_pipe2() with an additional flags argument from 2.6.27. If flags is 0, then pipe2() is the same as pipe(). So here we use sys_pipe2() to implement the pipe().
pipe2() is also provided to allow users to use flags argument on demand.
[1]: https://man7.org/linux/man-pages/man2/pipe.2.html [2]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html
Suggested-by: Zhangjin Wu <falcon@tinylab.org> Link: https://lore.kernel.org/all/20230729100401.GA4577@1wt.eu/ Signed-off-by: Yuan Tan <tanyuan@tinylab.org> Reviewed-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Willy Tarreau <w@1wt.eu>
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