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Message-ID: <86dbcaa7-db16-4a90-9022-eb7b6e736ed7@paulmck-laptop>
Date: Tue, 6 Aug 2024 11:10:59 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Davidlohr Bueso <dave@...olabs.net>,
	Josh Triplett <josh@...htriplett.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, rcu@...r.kernel.org
Subject: Re: [PATCH] refscale: Constify struct ref_scale_ops

On Tue, Aug 06, 2024 at 03:30:16PM +0200, Christophe JAILLET wrote:
> 'struct ref_scale_ops' are not modified in these drivers.
> 
> Constifying this structure moves some data to a read-only section, so
> increase overall security.
> 
> On a x86_64, with allmodconfig:
> Before:
> ======
>    text	   data	    bss	    dec	    hex	filename
>   34231	   4167	    736	  39134	   98de	kernel/rcu/refscale.o
> 
> After:
> =====
>    text	   data	    bss	    dec	    hex	filename
>   35175	   3239	    736	  39150	   98ee	kernel/rcu/refscale.o
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> Compile tested-only.

Tested-by: Paul E. McKenney <paulmck@...nel.org>

> ---
>  kernel/rcu/refscale.c | 42 +++++++++++++++++++++---------------------
>  1 file changed, 21 insertions(+), 21 deletions(-)
> 
> diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
> index cfec0648e141..0db9db73f57f 100644
> --- a/kernel/rcu/refscale.c
> +++ b/kernel/rcu/refscale.c
> @@ -135,7 +135,7 @@ struct ref_scale_ops {
>  	const char *name;
>  };
>  
> -static struct ref_scale_ops *cur_ops;
> +static const struct ref_scale_ops *cur_ops;
>  
>  static void un_delay(const int udl, const int ndl)
>  {
> @@ -171,7 +171,7 @@ static bool rcu_sync_scale_init(void)
>  	return true;
>  }
>  
> -static struct ref_scale_ops rcu_ops = {
> +static const struct ref_scale_ops rcu_ops = {
>  	.init		= rcu_sync_scale_init,
>  	.readsection	= ref_rcu_read_section,
>  	.delaysection	= ref_rcu_delay_section,
> @@ -205,7 +205,7 @@ static void srcu_ref_scale_delay_section(const int nloops, const int udl, const
>  	}
>  }
>  
> -static struct ref_scale_ops srcu_ops = {
> +static const struct ref_scale_ops srcu_ops = {
>  	.init		= rcu_sync_scale_init,
>  	.readsection	= srcu_ref_scale_read_section,
>  	.delaysection	= srcu_ref_scale_delay_section,
> @@ -232,7 +232,7 @@ static void rcu_tasks_ref_scale_delay_section(const int nloops, const int udl, c
>  		un_delay(udl, ndl);
>  }
>  
> -static struct ref_scale_ops rcu_tasks_ops = {
> +static const struct ref_scale_ops rcu_tasks_ops = {
>  	.init		= rcu_sync_scale_init,
>  	.readsection	= rcu_tasks_ref_scale_read_section,
>  	.delaysection	= rcu_tasks_ref_scale_delay_section,
> @@ -271,7 +271,7 @@ static void rcu_trace_ref_scale_delay_section(const int nloops, const int udl, c
>  	}
>  }
>  
> -static struct ref_scale_ops rcu_trace_ops = {
> +static const struct ref_scale_ops rcu_trace_ops = {
>  	.init		= rcu_sync_scale_init,
>  	.readsection	= rcu_trace_ref_scale_read_section,
>  	.delaysection	= rcu_trace_ref_scale_delay_section,
> @@ -310,7 +310,7 @@ static void ref_refcnt_delay_section(const int nloops, const int udl, const int
>  	}
>  }
>  
> -static struct ref_scale_ops refcnt_ops = {
> +static const struct ref_scale_ops refcnt_ops = {
>  	.init		= rcu_sync_scale_init,
>  	.readsection	= ref_refcnt_section,
>  	.delaysection	= ref_refcnt_delay_section,
> @@ -347,7 +347,7 @@ static void ref_rwlock_delay_section(const int nloops, const int udl, const int
>  	}
>  }
>  
> -static struct ref_scale_ops rwlock_ops = {
> +static const struct ref_scale_ops rwlock_ops = {
>  	.init		= ref_rwlock_init,
>  	.readsection	= ref_rwlock_section,
>  	.delaysection	= ref_rwlock_delay_section,
> @@ -384,7 +384,7 @@ static void ref_rwsem_delay_section(const int nloops, const int udl, const int n
>  	}
>  }
>  
> -static struct ref_scale_ops rwsem_ops = {
> +static const struct ref_scale_ops rwsem_ops = {
>  	.init		= ref_rwsem_init,
>  	.readsection	= ref_rwsem_section,
>  	.delaysection	= ref_rwsem_delay_section,
> @@ -419,7 +419,7 @@ static void ref_lock_delay_section(const int nloops, const int udl, const int nd
>  	preempt_enable();
>  }
>  
> -static struct ref_scale_ops lock_ops = {
> +static const struct ref_scale_ops lock_ops = {
>  	.readsection	= ref_lock_section,
>  	.delaysection	= ref_lock_delay_section,
>  	.name		= "lock"
> @@ -454,7 +454,7 @@ static void ref_lock_irq_delay_section(const int nloops, const int udl, const in
>  	preempt_enable();
>  }
>  
> -static struct ref_scale_ops lock_irq_ops = {
> +static const struct ref_scale_ops lock_irq_ops = {
>  	.readsection	= ref_lock_irq_section,
>  	.delaysection	= ref_lock_irq_delay_section,
>  	.name		= "lock-irq"
> @@ -490,7 +490,7 @@ static void ref_acqrel_delay_section(const int nloops, const int udl, const int
>  	preempt_enable();
>  }
>  
> -static struct ref_scale_ops acqrel_ops = {
> +static const struct ref_scale_ops acqrel_ops = {
>  	.readsection	= ref_acqrel_section,
>  	.delaysection	= ref_acqrel_delay_section,
>  	.name		= "acqrel"
> @@ -524,7 +524,7 @@ static void ref_clock_delay_section(const int nloops, const int udl, const int n
>  	stopopts = x;
>  }
>  
> -static struct ref_scale_ops clock_ops = {
> +static const struct ref_scale_ops clock_ops = {
>  	.readsection	= ref_clock_section,
>  	.delaysection	= ref_clock_delay_section,
>  	.name		= "clock"
> @@ -556,7 +556,7 @@ static void ref_jiffies_delay_section(const int nloops, const int udl, const int
>  	stopopts = x;
>  }
>  
> -static struct ref_scale_ops jiffies_ops = {
> +static const struct ref_scale_ops jiffies_ops = {
>  	.readsection	= ref_jiffies_section,
>  	.delaysection	= ref_jiffies_delay_section,
>  	.name		= "jiffies"
> @@ -706,9 +706,9 @@ static void refscale_typesafe_ctor(void *rtsp_in)
>  	preempt_enable();
>  }
>  
> -static struct ref_scale_ops typesafe_ref_ops;
> -static struct ref_scale_ops typesafe_lock_ops;
> -static struct ref_scale_ops typesafe_seqlock_ops;
> +static const struct ref_scale_ops typesafe_ref_ops;
> +static const struct ref_scale_ops typesafe_lock_ops;
> +static const struct ref_scale_ops typesafe_seqlock_ops;
>  
>  // Initialize for a typesafe test.
>  static bool typesafe_init(void)
> @@ -769,7 +769,7 @@ static void typesafe_cleanup(void)
>  }
>  
>  // The typesafe_init() function distinguishes these structures by address.
> -static struct ref_scale_ops typesafe_ref_ops = {
> +static const struct ref_scale_ops typesafe_ref_ops = {
>  	.init		= typesafe_init,
>  	.cleanup	= typesafe_cleanup,
>  	.readsection	= typesafe_read_section,
> @@ -777,7 +777,7 @@ static struct ref_scale_ops typesafe_ref_ops = {
>  	.name		= "typesafe_ref"
>  };
>  
> -static struct ref_scale_ops typesafe_lock_ops = {
> +static const struct ref_scale_ops typesafe_lock_ops = {
>  	.init		= typesafe_init,
>  	.cleanup	= typesafe_cleanup,
>  	.readsection	= typesafe_read_section,
> @@ -785,7 +785,7 @@ static struct ref_scale_ops typesafe_lock_ops = {
>  	.name		= "typesafe_lock"
>  };
>  
> -static struct ref_scale_ops typesafe_seqlock_ops = {
> +static const struct ref_scale_ops typesafe_seqlock_ops = {
>  	.init		= typesafe_init,
>  	.cleanup	= typesafe_cleanup,
>  	.readsection	= typesafe_read_section,
> @@ -1026,7 +1026,7 @@ static int main_func(void *arg)
>  }
>  
>  static void
> -ref_scale_print_module_parms(struct ref_scale_ops *cur_ops, const char *tag)
> +ref_scale_print_module_parms(const struct ref_scale_ops *cur_ops, const char *tag)
>  {
>  	pr_alert("%s" SCALE_FLAG
>  		 "--- %s:  verbose=%d verbose_batched=%d shutdown=%d holdoff=%d lookup_instances=%ld loops=%ld nreaders=%d nruns=%d readdelay=%d\n", scale_type, tag,
> @@ -1081,7 +1081,7 @@ ref_scale_init(void)
>  {
>  	long i;
>  	int firsterr = 0;
> -	static struct ref_scale_ops *scale_ops[] = {
> +	static const struct ref_scale_ops *scale_ops[] = {
>  		&rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops,
>  		&rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, &jiffies_ops,
>  		&typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
> -- 
> 2.45.2
> 

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