linux-kernel - Re: [PATCH 4/4] drm/tegra: Use u64_to_user

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Date:   Sat, 19 Aug 2017 01:05:14 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mikko Perttunen <mperttunen@...dia.com>, thierry.reding@...il.com,
        jonathanh@...dia.com
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] drm/tegra: Use u64_to_user_ptr helper

On 18.08.2017 19:15, Mikko Perttunen wrote:
> Use the u64_to_user_ptr helper macro to cast IOCTL argument u64 values
> to user pointers instead of writing out the cast manually.
> 
> Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
> ---
>  drivers/gpu/drm/tegra/drm.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> index e3331a2bc082..78c98736b0a5 100644
> --- a/drivers/gpu/drm/tegra/drm.c
> +++ b/drivers/gpu/drm/tegra/drm.c
> @@ -389,11 +389,10 @@ int tegra_drm_submit(struct tegra_drm_context *context,
>  	unsigned int num_relocs = args->num_relocs;
>  	unsigned int num_waitchks = args->num_waitchks;
>  	struct drm_tegra_cmdbuf __user *cmdbufs =
> -		(void __user *)(uintptr_t)args->cmdbufs;
> -	struct drm_tegra_reloc __user *relocs =
> -		(void __user *)(uintptr_t)args->relocs;
> +		u64_to_user_ptr(args->cmdbufs);
> +	struct drm_tegra_reloc __user *relocs = u64_to_user_ptr(args->relocs);
>  	struct drm_tegra_waitchk __user *waitchks =
> -		(void __user *)(uintptr_t)args->waitchks;
> +		u64_to_user_ptr(args->waitchks);

What about to factor out 'u64_to_user_ptr()' assignments to reduce messiness a
tad? Like this:

	struct drm_tegra_waitchk __user *waitchks;
	struct drm_tegra_cmdbuf __user *cmdbufs;
	struct drm_tegra_reloc __user *relocs;
...
	waitchks = u64_to_user_ptr(args->waitchks);
	cmdbufs = u64_to_user_ptr(args->cmdbufs);
	relocs = u64_to_user_ptr(args->relocs);


>  	struct drm_tegra_syncpt syncpt;
>  	struct host1x *host1x = dev_get_drvdata(drm->dev->parent);
>  	struct host1x_syncpt *sp;
> @@ -520,7 +519,7 @@ int tegra_drm_submit(struct tegra_drm_context *context,
>  		}
>  	}
>  
> -	if (copy_from_user(&syncpt, (void __user *)(uintptr_t)args->syncpts,
> +	if (copy_from_user(&syncpt, u64_to_user_ptr(args->syncpts),

What about to define and use 'struct drm_tegra_reloc __user *syncpts' for
consistency with other '__user' definitions?

>  			   sizeof(syncpt))) {
>  		err = -EFAULT;
>  		goto fail;
> 

-- 
Dmitry