linux-kernel - Re: [PATCH 2/7] stm class: Replace uuid

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Date:   Wed, 14 Apr 2021 22:16:01 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] stm class: Replace uuid_t with plain u8 uuid[16]

On Wed, Apr 14, 2021 at 10:14:34PM +0300, Alexander Shishkin wrote:
> Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:
> 
> >> Using raw buffer APIs against uuid_t / guid_t.
> >
> > So you want to do that, or you do not want to do that?  Totally
> > confused,
> 
> My understanding is that:
> 1) generate_random_uuid() use is allegedly bad even though it's in their
> header,
> 2) poking directly at the byte array inside uuid_t is bad, even though,
> again, header.
> 
> It is, indeed, not ideal.
> 
> If agreeable, I'll update this patch to the below and respin the whole
> series.

Below patch looks good to me, thanks!

> From 02340f8c7c17ace028040a35553c33cce8f3bce4 Mon Sep 17 00:00:00 2001
> From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Date: Wed, 22 Apr 2020 16:02:20 +0300
> Subject: [PATCH] stm class: Use correct UUID APIs
> 
> It appears that the STM code didn't manage to accurately decypher the
> delicate inner workings of an alternative thought process behind the
> UUID API and directly called generate_random_uuid() that clearly needs
> to be a static function in lib/uuid.c.
> 
> At the same time, said STM code is poking directly at the byte array
> inside the uuid_t when it uses the UUID for its internal purposes.
> 
> Fix these two transgressions by using intended APIs instead.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> [ash: changed back to uuid_t and updated the commit message]
> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> ---
>  drivers/hwtracing/stm/p_sys-t.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/stm/p_sys-t.c b/drivers/hwtracing/stm/p_sys-t.c
> index 360b5c03df95..8254971c02e7 100644
> --- a/drivers/hwtracing/stm/p_sys-t.c
> +++ b/drivers/hwtracing/stm/p_sys-t.c
> @@ -92,7 +92,7 @@ static void sys_t_policy_node_init(void *priv)
>  {
>  	struct sys_t_policy_node *pn = priv;
>  
> -	generate_random_uuid(pn->uuid.b);
> +	uuid_gen(&pn->uuid);
>  }
>  
>  static int sys_t_output_open(void *priv, struct stm_output *output)
> @@ -292,6 +292,7 @@ static ssize_t sys_t_write(struct stm_data *data, struct stm_output *output,
>  	unsigned int m = output->master;
>  	const unsigned char nil = 0;
>  	u32 header = DATA_HEADER;
> +	u8 uuid[UUID_SIZE];
>  	ssize_t sz;
>  
>  	/* We require an existing policy node to proceed */
> @@ -322,7 +323,8 @@ static ssize_t sys_t_write(struct stm_data *data, struct stm_output *output,
>  		return sz;
>  
>  	/* GUID */
> -	sz = stm_data_write(data, m, c, false, op->node.uuid.b, UUID_SIZE);
> +	export_uuid(uuid, &op->node.uuid);
> +	sz = stm_data_write(data, m, c, false, uuid, sizeof(op->node.uuid));
>  	if (sz <= 0)
>  		return sz;
>  
> -- 
> 2.30.2
> 

-- 
With Best Regards,
Andy Shevchenko