linux-kernel - Re: [PATCH 1/2] tools/nolibc: add pipe() support

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Date:   Sat, 29 Jul 2023 12:04:01 +0200
From:   Willy Tarreau <w@....eu>
To:     Zhangjin Wu <falcon@...ylab.org>
Cc:     linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        tanyuan@...ylab.org
Subject: Re: [PATCH 1/2] tools/nolibc: add pipe() support

On Sat, Jul 29, 2023 at 04:37:00PM +0800, Zhangjin Wu wrote:
> > This one does not have the correct prototype for the function exposed
> > to the user, pipe really is "int pipe(int pipefd[2])". Maybe you were
> > thinking about sys_pipe() instead ? But since MIPS also has pipe2() now,
> > there's no reason to make an exception.
> >
> 
> Yes, pipe2() should be a better choice, but I have seen this sentence in
> syscall manpage [1]:
> 
>        /* On Alpha, IA-64, MIPS, SuperH, and SPARC/SPARC64, pipe() has the
>           following prototype; see NOTES */
> 
>        #include <unistd.h>
> 
>        struct fd_pair {
>            long fd[2];
>        };
>        struct fd_pair pipe(void);
> 
> If it is about syscall, then we are ok to align all of the architectures
> together to use "int pipe(int pipefd[2])"

Yes it's OK, that's how applications expect it to be used:

  https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html

For the archs you mention above, it's the libc that wraps the call,
exactly what we ought to do as well (using pipe2() since it will be
easier).

Willy