Re: Re: [PATCH v2] treewide: const qualify ctl_tables where applicable

[Joel Granados <joel.granados@kernel.org>]

On Tue, Jan 21, 2025 at 02:40:16PM +0100, Alexander Gordeev wrote:
> On Fri, Jan 10, 2025 at 03:16:08PM +0100, Joel Granados wrote:
> 
> Hi Joel,
> 
> > Add the const qualifier to all the ctl_tables in the tree except for
> > watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls,
> > loadpin_sysctl_table and the ones calling register_net_sysctl (./net,
> > drivers/inifiniband dirs). These are special cases as they use a
> > registration function with a non-const qualified ctl_table argument or
> > modify the arrays before passing them on to the registration function.
> > 
> > Constifying ctl_table structs will prevent the modification of
> > proc_handler function pointers as the arrays would reside in .rodata.
> > This is made possible after commit 78eb4ea25cd5 ("sysctl: treewide:
> > constify the ctl_table argument of proc_handlers") constified all the
> > proc_handlers.
> 
> I could identify at least these occurences in s390 code as well:
Hey Alexander

Thx for bringing these to my attention. I had completely missed them as
the spatch only deals with ctl_tables outside functions.

Short answer:
These should not be included in the current patch because they are a
different pattern from how sysctl tables are usually used. So I will not
include them.

With that said, I think it might be interesting to look closer at them
as they seem to be complicating the proc_handler (I have to look at them
closer).

I see that they are defining a ctl_table struct within the functions and
just using the data (from the incoming ctl_table) to forward things down
to proc_do{u,}intvec_* functions. This is very odd and I have only seen
it done in order to change the incoming ctl_table (which is not what is
being done here).

I will take a closer look after the merge window and circle back with
more info. Might take me a while as I'm not very familiar with s390
code; any additional information on why those are being used inside the
functions would be helpfull.

Best


> 
> diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
> index dd7ba7587dd5..9b83c318f919 100644
> --- a/arch/s390/appldata/appldata_base.c
> +++ b/arch/s390/appldata/appldata_base.c
> @@ -204,7 +204,7 @@ appldata_timer_handler(const struct ctl_table *ctl, int write,
>  {
>  	int timer_active = appldata_timer_active;
>  	int rc;
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.procname	= ctl->procname,
>  		.data		= &timer_active,
>  		.maxlen		= sizeof(int),
> @@ -237,7 +237,7 @@ appldata_interval_handler(const struct ctl_table *ctl, int write,
>  {
>  	int interval = appldata_interval;
>  	int rc;
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.procname	= ctl->procname,
>  		.data		= &interval,
>  		.maxlen		= sizeof(int),
> @@ -269,7 +269,7 @@ appldata_generic_handler(const struct ctl_table *ctl, int write,
>  	struct list_head *lh;
>  	int rc, found;
>  	int active;
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.data		= &active,
>  		.maxlen		= sizeof(int),
>  		.extra1		= SYSCTL_ZERO,
> diff --git a/arch/s390/kernel/hiperdispatch.c b/arch/s390/kernel/hiperdispatch.c
> index 7857a7e8e56c..7d0ba16085c1 100644
> --- a/arch/s390/kernel/hiperdispatch.c
> +++ b/arch/s390/kernel/hiperdispatch.c
> @@ -273,7 +273,7 @@ static int hiperdispatch_ctl_handler(const struct ctl_table *ctl, int write,
>  {
>  	int hiperdispatch;
>  	int rc;
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.procname	= ctl->procname,
>  		.data		= &hiperdispatch,
>  		.maxlen		= sizeof(int),
> diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
> index 6691808bf50a..26e50de83d80 100644
> --- a/arch/s390/kernel/topology.c
> +++ b/arch/s390/kernel/topology.c
> @@ -629,7 +629,7 @@ static int topology_ctl_handler(const struct ctl_table *ctl, int write,
>  	int enabled = topology_is_enabled();
>  	int new_mode;
>  	int rc;
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.procname	= ctl->procname,
>  		.data		= &enabled,
>  		.maxlen		= sizeof(int),
> @@ -658,7 +658,7 @@ static int polarization_ctl_handler(const struct ctl_table *ctl, int write,
>  {
>  	int polarization;
>  	int rc;
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.procname	= ctl->procname,
>  		.data		= &polarization,
>  		.maxlen		= sizeof(int),
> diff --git a/arch/s390/mm/cmm.c b/arch/s390/mm/cmm.c
> index 939e3bec2db7..8e354c90a3dd 100644
> --- a/arch/s390/mm/cmm.c
> +++ b/arch/s390/mm/cmm.c
> @@ -263,7 +263,7 @@ static int cmm_pages_handler(const struct ctl_table *ctl, int write,
>  			     void *buffer, size_t *lenp, loff_t *ppos)
>  {
>  	long nr = cmm_get_pages();
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.procname	= ctl->procname,
>  		.data		= &nr,
>  		.maxlen		= sizeof(long),
> @@ -283,7 +283,7 @@ static int cmm_timed_pages_handler(const struct ctl_table *ctl, int write,
>  				   loff_t *ppos)
>  {
>  	long nr = cmm_get_timed_pages();
> -	struct ctl_table ctl_entry = {
> +	const struct ctl_table ctl_entry = {
>  		.procname	= ctl->procname,
>  		.data		= &nr,
>  		.maxlen		= sizeof(long),
> 
> 
> > Best regards,
> > -- 
> > Joel Granados <joel.granados@kernel.org>
> 
> Thanks!

-- 

Joel Granados