[LTP] [PATCH] device-drivers/uaccess: add a workaround for Intel's SMAP feature

[Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>]

hello,

Sorry, I do not have a machine with this SMAP feature, anybody can
help to test this patch, thanks very much.

Regards,
Xiaoguang Wang

On 03/15/2016 05:25 PM, Xiaoguang Wang wrote:
> When Intel's new "Supervisor Mode Access Prevention" (SMAP) feature is
> enabled, kernel will be forbidden to visit user space memory, please
> see url: https://lwn.net/Articles/517475/ for detailed infomation.
> 
> Here, we explicitly call stac()/clac() to enable/disable SMAP feature.
> 
> Signed-off-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
> ---
>  testcases/kernel/device-drivers/uaccess/ltp_uaccess.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/testcases/kernel/device-drivers/uaccess/ltp_uaccess.c b/testcases/kernel/device-drivers/uaccess/ltp_uaccess.c
> index a9a06e9..35a9aa0 100644
> --- a/testcases/kernel/device-drivers/uaccess/ltp_uaccess.c
> +++ b/testcases/kernel/device-drivers/uaccess/ltp_uaccess.c
> @@ -68,6 +68,9 @@ static ssize_t sys_tcase(struct device *dev,
>  	str = (char *) ptr;
>  	test_result = 0;
>  
> +#ifdef CONFIG_X86_SMAP
> +	stac();
> +#endif
>  	switch (tc) {
>  	case TC_READ_USER:
>  		if (copy_from_user(buffer, str, str_size))
> @@ -90,6 +93,11 @@ static ssize_t sys_tcase(struct device *dev,
>  	break;
>  	}
>  
> +#ifdef CONFIG_X86_SMAP
> +	clac();
> +#endif
> +
> +
>  	return count;
>  }
>  static DEVICE_ATTR(tcase, S_IWUSR, NULL, sys_tcase);
>