linux-kernel - Re: [PATCH v5 07/14] tools/nolibc: arch-loongarch.h: shrink with SYSCALL

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Date:   Mon,  3 Jul 2023 19:28:46 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     w@....eu
Cc:     arnd@...db.de, david.laight@...lab.com, falcon@...ylab.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-riscv@...ts.infradead.org, thomas@...ch.de
Subject: Re: [PATCH v5 07/14] tools/nolibc: arch-loongarch.h: shrink with SYSCALL_CLOBBERLIST

> On Wed, Jun 28, 2023 at 09:22:21PM +0800, Zhangjin Wu wrote:
> > my_syscall<N> share a same long clobber list, define a macro for them.
> > 
> > Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
> > ---
> >  tools/include/nolibc/arch-loongarch.h | 25 +++++++++++--------------
> >  1 file changed, 11 insertions(+), 14 deletions(-)
> > 
> > diff --git a/tools/include/nolibc/arch-loongarch.h b/tools/include/nolibc/arch-loongarch.h
> > index 292d6a58dc87..fbb4844f7993 100644
> > --- a/tools/include/nolibc/arch-loongarch.h
> > +++ b/tools/include/nolibc/arch-loongarch.h
> > @@ -23,6 +23,10 @@
> >   */
> >  #define __ARCH_WANT_SYS_PSELECT6
> >  
> > +#define SYSCALL_CLOBBERLIST			\
> > +	"memory", "$t0", "$t1", "$t2", "$t3",	\
> > +	"$t4", "$t5", "$t6", "$t7", "$t8"
> > +
> 
> That's a good idea, but please be careful when adding macro definitions,
> we're in code that is used by user space we have no control on, and we're
> polluting the end user's macro namespace with plenty of names. While one
> could argue that it's unlikely that some program already defines and uses
> SYSCALL_CLOBBERLIST, actually with low-level code it's fairly possible.
> 
> Till now most of the definitions were for stuff that user-space really
> needs (e.g. STDIN_FILENO, various integer limits). If we start to declare
> random macros for internal use, at least we should probably prefix them
> with _NOLIBC_ or something like this to avoid the risk of collision.
>

Ok, _NOLIBC_ prefix will be applied, Thanks.

Best regards,
Zhangjin

> Willy