Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 14 Jan 2020 16:08:15 -0800
From:   Paul Burton <paulburton@kernel.org>
To:     Guoyun Sun <sunguoyun@loongson.cn>
Cc:     Ralf Baechle <ralf@linux-mips.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Allison Randal <allison@lohutok.net>,
        linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH]  mips/vdso: Support mremap() for vDSO
Message-ID: <20200115000815.narpydp4unkkuboj@pburton-laptop>
References: <1578978808-18633-1-git-send-email-sunguoyun@loongson.cn>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1578978808-18633-1-git-send-email-sunguoyun@loongson.cn>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Guoyun,

On Tue, Jan 14, 2020 at 01:13:28PM +0800, Guoyun Sun wrote:
> diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
> index bc35f84..eac3982 100644
> --- a/arch/mips/kernel/vdso.c
> +++ b/arch/mips/kernel/vdso.c
> @@ -38,6 +38,28 @@ static struct vm_special_mapping vdso_vvar_mapping = {
>  	.pages = no_pages,
>  };
>  
> +int vdso_mremap(const struct vm_special_mapping *sm,
> +		       struct vm_area_struct *new_vma)
> +{
> +	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
> +
> +#ifdef CONFIG_MIPS32_O32
> +	if (vdso_image_o32.size != new_size)
> +		return -EINVAL;
> +#endif
> +
> +#ifdef CONFIG_MIPS32_N32
> +	if (vdso_image_n32.size != new_size)
> +		return -EINVAL;
> +#endif
> +
> +	if (vdso_image.size != new_size)
> +		return -EINVAL;
> +
> +	current->mm->context.vdso = (void __user *)(new_vma->vm_start);
> +	return 0;
> +}
> +

Thanks for the patch; this bit doesn't seem right though. It requires
that all the VDSOs be the same size, which seems questionable. I think
we probably need separate mremap callbacks for each VDSO, so that we can
check the appropriate VDSO size.

Thanks,
    Paul