Re: [PATCH] rcuscale: Constify struct rcu_scale_ops

[Joel Fernandes <joelagnelf@nvidia.com>]

On Sat, Nov 07, 2026 at 10:02:25PM +0100, Christophe JAILLET wrote:
> 'struct rcu_scale_ops' is not modified in this driver.
> 
> Constifying these structures moves some data to a read-only section, so
> increases overall security, especially when the structure holds some
> function pointers.
> 
> On a x86_64, with allmodconfig:
> Before:
> ======
>    text	   data	    bss	    dec	    hex	filename
>   45585	  24946	   2816	  73347	  11e83	kernel/rcu/rcuscale.o
> 
> After:
> =====
>    text	   data	    bss	    dec	    hex	filename
>   46545	  23986	   2816	  73347	  11e83	kernel/rcu/rcuscale.o
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> Compile tested only.

rcuscale is a test kernel module, is it worth adding boilerplate for
non-production code sighting security reasons?

Do you mind runtime testing it too if you still feel we should do it (and
provide reasons why)?

thanks,

Joel Fernandes


> ---
>  kernel/rcu/rcuscale.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
> index 1097ec15879c..522f7bc2e693 100644
> --- a/kernel/rcu/rcuscale.c
> +++ b/kernel/rcu/rcuscale.c
> @@ -159,7 +159,7 @@ struct rcu_scale_ops {
>  	const char *name;
>  };
>  
> -static struct rcu_scale_ops *cur_ops;
> +static const struct rcu_scale_ops *cur_ops;
>  
>  /*
>   * Definitions for rcu scalability testing.
> @@ -185,7 +185,7 @@ static void rcu_sync_scale_init(void)
>  {
>  }
>  
> -static struct rcu_scale_ops rcu_ops = {
> +static const struct rcu_scale_ops rcu_ops = {
>  	.ptype		= RCU_FLAVOR,
>  	.init		= rcu_sync_scale_init,
>  	.readlock	= rcu_scale_read_lock,
> @@ -247,7 +247,7 @@ static void srcu_scale_synchronize_expedited(void)
>  	synchronize_srcu_expedited(srcu_ctlp);
>  }
>  
> -static struct rcu_scale_ops srcu_ops = {
> +static const struct rcu_scale_ops srcu_ops = {
>  	.ptype		= SRCU_FLAVOR,
>  	.init		= rcu_sync_scale_init,
>  	.readlock	= srcu_scale_read_lock,
> @@ -276,7 +276,7 @@ static void srcu_sync_scale_cleanup(void)
>  	cleanup_srcu_struct(srcu_ctlp);
>  }
>  
> -static struct rcu_scale_ops srcud_ops = {
> +static const struct rcu_scale_ops srcud_ops = {
>  	.ptype		= SRCU_FLAVOR,
>  	.init		= srcu_sync_scale_init,
>  	.cleanup	= srcu_sync_scale_cleanup,
> @@ -313,7 +313,7 @@ static void rcu_tasks_scale_stats(void)
>  	rcu_tasks_torture_stats_print(scale_type, SCALE_FLAG);
>  }
>  
> -static struct rcu_scale_ops tasks_ops = {
> +static const struct rcu_scale_ops tasks_ops = {
>  	.ptype		= RCU_TASKS_FLAVOR,
>  	.init		= rcu_sync_scale_init,
>  	.readlock	= tasks_scale_read_lock,
> @@ -357,7 +357,7 @@ static void rcu_tasks_rude_scale_stats(void)
>  	rcu_tasks_rude_torture_stats_print(scale_type, SCALE_FLAG);
>  }
>  
> -static struct rcu_scale_ops tasks_rude_ops = {
> +static const struct rcu_scale_ops tasks_rude_ops = {
>  	.ptype		= RCU_TASKS_RUDE_FLAVOR,
>  	.init		= rcu_sync_scale_init,
>  	.readlock	= tasks_rude_scale_read_lock,
> @@ -396,7 +396,7 @@ static void tasks_trace_scale_read_unlock(int idx)
>  	rcu_read_unlock_trace();
>  }
>  
> -static struct rcu_scale_ops tasks_tracing_ops = {
> +static const struct rcu_scale_ops tasks_tracing_ops = {
>  	.ptype		= RCU_TASKS_FLAVOR,
>  	.init		= rcu_sync_scale_init,
>  	.readlock	= tasks_trace_scale_read_lock,
> @@ -693,7 +693,7 @@ rcu_scale_writer(void *arg)
>  }
>  
>  static void
> -rcu_scale_print_module_parms(struct rcu_scale_ops *cur_ops, const char *tag)
> +rcu_scale_print_module_parms(const struct rcu_scale_ops *cur_ops, const char *tag)
>  {
>  	pr_alert("%s" SCALE_FLAG
>  		 "--- %s: gp_async=%d gp_async_max=%d gp_exp=%d holdoff=%d minruntime=%d nreaders=%d nwriters=%d nexp=%d exp_interval=%d writer_holdoff=%d writer_holdoff_jiffies=%d verbose=%d shutdown_secs=%d\n",
> @@ -1109,7 +1109,7 @@ rcu_scale_init(void)
>  	int firsterr = 0;
>  	long i;
>  	long j;
> -	static struct rcu_scale_ops *scale_ops[] = {
> +	static const struct rcu_scale_ops *scale_ops[] = {
>  		&rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
>  	};
>  
> -- 
> 2.56.0
>