linux-kernel - Re: [PATCH 3/4] rcutorture/nolibc: add a bit of documentation to explain how to use nolibc

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Message-ID: <20181230070846.GA17139@1wt.eu>
Date:   Sun, 30 Dec 2018 08:08:46 +0100
From:   Willy Tarreau <w@....eu>
To:     Joey Pabalinas <joeypabalinas@...il.com>, mingo@...nel.org,
        paulmck@...ux.vnet.ibm.com, rdunlap@...radead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] rcutorture/nolibc: add a bit of documentation to
 explain how to use nolibc

On Sat, Dec 29, 2018 at 12:33:24PM -1000, Joey Pabalinas wrote:
> On Sat, Dec 29, 2018 at 07:02:18PM +0100, Willy Tarreau wrote:
> > + *   - the lower level is the arch-specific syscall() definition, consisting in
> > + *     assembly code in compound expressions. These are called my_syscall0() to
> > + *     my_syscall6() depending on the number of arguments. The MIPS
> > + *     implementation is limited to 5 arguments. All input arguments are cast
> > + *     to a long stored in a register. These expressions always return the
> > + *     syscall's return value as a signed long value which is often either a
> > + *     pointer or the negated errno value.
> > + *
> > + *   - the second level is mostly architecture-independent. It is made of
> > + *     static functions called sys_<name>() which rely on my_syscallN()
> > + *     depending on the syscall definition. These functions are responsible
> > + *     for exposing the appropriate types for the syscall arguments (int,
> > + *     pointers, etc) and for setting the appropriate return type (often int).
> > + *     A few of them are architecture-specific because the syscalls are not all
> > + *     mapped exactly the same among architectures. For example, some archs do
> > + *     not implement select() and need pselect6() instead, so the sys_select()
> > + *     function will have to abstract this.
> > + *
> > + *   - the third level is the libc call definition. It exposes the lower raw
> > + *     sys_<name>() calls in a way that looks like what a libc usually does,
> > + *     takes care of specific input values, and of setting errno upon error.
> > + *     There can be minor variations compared to standard libc calls. For
> > + *     example the open() call always takes 3 args here.
> 
> Shouldn't these sentences begin with a capitalized "The" for
> consistency?

Not sure since they're just list items. But probably as such they should
end with a semi-colon and not a dot. Anyway, this is minor and likely for
a later update to the file.

> >  /* some archs (at least aarch64) don't expose the regular syscalls anymore by
> >   * default, either because they have an "_at" replacement, or because there are
> >   * more modern alternatives. For now we'd rather still use them.
> 
> Also here. Shouldn't this begin with a capitalized "Some"?

Definitely! Same, I won't emit a patch just for this, Paul already queued it.

Thanks!
Willy