linux-kernel - Re: [PATCH v10 05/33] counter: 104-quad-8: Annotate hardware config module parameter

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Date:   Thu, 15 Apr 2021 20:45:28 +0530
From:   Syed Nayyar Waris <syednwaris@...il.com>
To:     William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     jic23@...nel.org, kernel@...gutronix.de,
        linux-stm32@...md-mailman.stormreply.com, a.fatoum@...gutronix.de,
        kamel.bouhara@...tlin.com, gwendal@...omium.org,
        alexandre.belloni@...tlin.com, david@...hnology.com,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        patrick.havelange@...ensium.com, fabrice.gasnier@...com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        o.rempel@...gutronix.de
Subject: Re: [PATCH v10 05/33] counter: 104-quad-8: Annotate hardware config
 module parameter

On Fri, Mar 19, 2021 at 08:00:24PM +0900, William Breathitt Gray wrote:
> When the kernel is running in secure boot mode, we lock down the kernel to
> prevent userspace from modifying the running kernel image.  Whilst this
> includes prohibiting access to things like /dev/mem, it must also prevent
> access by means of configuring driver modules in such a way as to cause a
> device to access or modify the kernel image.
> 
> To this end, annotate module_param* statements that refer to hardware
> configuration and indicate for future reference what type of parameter they
> specify.  The parameter parser in the core sees this information and can
> skip such parameters with an error message if the kernel is locked down.
> The module initialisation then runs as normal, but just sees whatever the
> default values for those parameters is.
> 
> Note that we do still need to do the module initialisation because some
> drivers have viable defaults set in case parameters aren't specified and
> some drivers support automatic configuration (e.g. PNP or PCI) in addition
> to manually coded parameters.
> 
> This patch annotates the 104-QUAD-8 driver.
> 
> Cc: Syed Nayyar Waris <syednwaris@...il.com>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@...il.com>
> ---
>  drivers/counter/104-quad-8.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
> index 233a3acc1377..0fd61cc82d30 100644
> --- a/drivers/counter/104-quad-8.c
> +++ b/drivers/counter/104-quad-8.c
> @@ -21,7 +21,7 @@
>  
>  static unsigned int base[max_num_isa_dev(QUAD8_EXTENT)];
>  static unsigned int num_quad8;
> -module_param_array(base, uint, &num_quad8, 0);
> +module_param_hw_array(base, uint, ioport, &num_quad8, 0);
>  MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");
>  
>  #define QUAD8_NUM_COUNTERS 8
> -- 
> 2.30.2
>

Acked-by: Syed Nayyar Waris <syednwaris@...il.com>