From: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
To: Erwin Rol <mailinglists@erwinrol.com>
Cc: barebox@lists.infradead.org
Subject: Re: x86 weirdness
Date: Tue, 31 Jul 2012 17:51:25 +0200 [thread overview]
Message-ID: <20120731155125.GJ19759@game.jcrosoft.org> (raw)
In-Reply-To: <5017F6CA.1040308@erwinrol.com>
On 17:16 Tue 31 Jul , Erwin Rol wrote:
> Hey Sascha,
>
> On 31-7-2012 15:13, Sascha Hauer wrote:
> >Hi Erwin,
> >
> >On Tue, Jul 31, 2012 at 12:49:29PM +0200, Erwin Rol wrote:
> >>Hey x86-asm-experts,
> >
> >Surely you do not mean me ;)
> >
> >>
> >>On 31-7-2012 0:36, Erwin Rol wrote:
> >>
> >>So when I use the memset code the asm looks like this below. As you
> >>can see the memset gets its 3 parameters from the stack (see
> >>comments below in the asm src). But when you look at the location
> >>when memset is called it looks like the caller tries to pass the
> >>parameters in registers. After looking into the Makefile I noticed
> >>the arch/x86/boot/* sources get compiled with -mregparm=3, but the
> >>other sources use normal calling convention. This means code from
> >>arch/x86/boot/* can not call any other barebox functions when they
> >>are not of type void f(void). The file arch/x86/boot/regs.c also
> >>calls memset but it seems the compiler notices that regs.c is 16bit
> >>code and so it inlines a 16bit memset version (I at least don't see
> >>a call function).
> >>
> >>Is there any GCC or LD magic we can use to prevent error like this?
> >>Wouldn't it be better to _not_ change the calling convention in the
> >>Makefile, but mark the functions that need it with __attribute__ ?
> >
> >Maybe it's easier and more straight forward to just use a for-loop here
> >instead of playing magic games with attributes and or flags? Are there
> >more functions affected or is it just memset?
>
> There seem to be two memset calls, that could be problematic. Both
> should be easily replaceable with for-loops (like I already did by
> the first).
>
> We just have to be very careful to not call any functions from
> outside the boot dir (expect for the main barebox entry point).
>
> Don't you love the weird x86 world :-)
so I guess we should update the x86 to use the pbl so we can have two explicit
part of binary and we can avoid those issue
Best Regards,
J.
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next prev parent reply other threads:[~2012-07-31 15:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-30 22:36 Erwin Rol
2012-07-31 10:49 ` Erwin Rol
2012-07-31 13:13 ` Sascha Hauer
2012-07-31 15:16 ` Erwin Rol
2012-07-31 15:51 ` Jean-Christophe PLAGNIOL-VILLARD [this message]
2012-07-31 16:16 ` Erwin Rol
2012-07-31 17:07 ` Sascha Hauer
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