linux-kernel - Re: [PATCH v1 1/8] tools/nolibc: add support for powerpc

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Message-ID: <ZL/gAORYFijgjfvH@biznet-home.integral.gnuweeb.org>
Date:   Tue, 25 Jul 2023 21:45:20 +0700
From:   Ammar Faizi <ammarfaizi2@...weeb.org>
To:     Zhangjin Wu <falcon@...ylab.org>
Cc:     Willy Tarreau <w@....eu>, Arnd Bergmann <arnd@...db.de>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Weißschuh <thomas@...ch.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kselftest Mailing List 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v1 1/8] tools/nolibc: add support for powerpc

Hi Zhangjin, 

On Tue, Jul 25, 2023 at 07:02:55PM +0800, Zhangjin Wu wrote:
> Btw, have checked "=r" instead of "=a" works on i386 too for we already
> bind the _ret variable with "RET" register, but still need to check if
> "=a" is necessary?

I need to tell you that syscall6() for i386 can't use "r" and "=r"
because there was a historical bug that made GCC stuck in a loop forever
when compiling the nolibc code. It's already fixed in the latest version
of GCC, but we should still support older compilers.

Ref: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105032

I discovered that bug in 2022 in the latest version of GCC at that time,
so it's pretty new, and those buggy versions are very likely still in
the wild today.

-- 
Ammar Faizi