linux-kernel - Re: [PATCH 16/28] nios2: System calls handling

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Date:	Sat, 19 Apr 2014 22:12:28 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Ley Foon Tan <lftan@...era.com>
Cc:	Linux-Arch <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	lftan.linux@...il.com, cltang@...esourcery.com,
	Pavel Machek <pavel@...x.de>
Subject: Re: [PATCH 16/28] nios2: System calls handling

On Fri, Apr 18, 2014 at 2:26 PM, Ley Foon Tan <lftan@...era.com> wrote:
> +/* sys_cacheflush -- flush the processor cache. */
> +asmlinkage int sys_cacheflush(unsigned long addr, unsigned long len,
> +                               unsigned int op)
> +{
> +       struct vm_area_struct *vma;
> +
> +       if (len == 0)
> +               return 0;
> +
> +       /* Check for overflow */
> +       if (addr + len < addr)
> +               return -EFAULT;
> +
> +       /*
> +        * Verify that the specified address region actually belongs
> +        * to this process.
> +        */
> +       vma = find_vma(current->mm, addr);
> +       if (vma == NULL || addr < vma->vm_start || addr + len > vma->vm_end)
> +               return -EFAULT;
> +
> +       /* Ignore the scope and cache arguments. */

This function doesn't have scope and cache arguments
(sys_cacheflush() on m68k does have them ;-)

On Sat, Apr 19, 2014 at 6:09 PM, Pavel Machek <pavel@...x.de> wrote:
> Also... explanation why you need this syscall while other
> architectures live happily without it would be nice.

12 our of 28 architectures provide such a syscall...

Is flushing the cache a privileged operation on nios2?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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