[PATCH] i2c: virtio: Constify struct i2c_algorithm and struct virtio_device_id

[PATCH] i2c: virtio: Constify struct i2c_algorithm and struct virtio_device_id

[Christophe JAILLET]

'struct i2c_algorithm' and 'struct virtio_device_id' are not modified in
this driver.

Constifying this structure moves some data to a read-only section, so
increase overall security, especially when the structure holds some
function pointers, which is the case for struct i2c_algorithm.

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
   6663	    568	     16	   7247	   1c4f	drivers/i2c/busses/i2c-virtio.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
   6735	    472	     16	   7223	   1c37	drivers/i2c/busses/i2c-virtio.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
--
Compile tested only
---
 drivers/i2c/busses/i2c-virtio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
index 52ba1e0845ca..2a351f961b89 100644
--- a/drivers/i2c/busses/i2c-virtio.c
+++ b/drivers/i2c/busses/i2c-virtio.c
@@ -182,7 +182,7 @@ static u32 virtio_i2c_func(struct i2c_adapter *adap)
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 }
 
-static struct i2c_algorithm virtio_algorithm = {
+static const struct i2c_algorithm virtio_algorithm = {
 	.xfer = virtio_i2c_xfer,
 	.functionality = virtio_i2c_func,
 };
@@ -237,7 +237,7 @@ static void virtio_i2c_remove(struct virtio_device *vdev)
 	virtio_i2c_del_vqs(vdev);
 }
 
-static struct virtio_device_id id_table[] = {
+static const struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_I2C_ADAPTER, VIRTIO_DEV_ANY_ID },
 	{}
 };
-- 
2.46.0

Re: [PATCH] i2c: virtio: Constify struct i2c_algorithm and struct virtio_device_id

[Andi Shyti]

Hi Christophe,

On Sun, Sep 08, 2024 at 08:52:07AM GMT, Christophe JAILLET wrote:
> 'struct i2c_algorithm' and 'struct virtio_device_id' are not modified in
> this driver.
> 
> Constifying this structure moves some data to a read-only section, so
> increase overall security, especially when the structure holds some
> function pointers, which is the case for struct i2c_algorithm.
> 
> On a x86_64, with allmodconfig:
> Before:
> ======
>    text	   data	    bss	    dec	    hex	filename
>    6663	    568	     16	   7247	   1c4f	drivers/i2c/busses/i2c-virtio.o
> 
> After:
> =====
>    text	   data	    bss	    dec	    hex	filename
>    6735	    472	     16	   7223	   1c37	drivers/i2c/busses/i2c-virtio.o
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> --
> Compile tested only

Makes sense to me... if this works, you could pioneer a sequence
of simiar changes :-)

Merged to i2c/i2c-host.

Thanks,
Andi

Re: [PATCH] i2c: virtio: Constify struct i2c_algorithm and struct virtio_device_id

[Christophe JAILLET]

Le 09/09/2024 à 20:54, Andi Shyti a écrit :
> Hi Christophe,
> 
> On Sun, Sep 08, 2024 at 08:52:07AM GMT, Christophe JAILLET wrote:
>> 'struct i2c_algorithm' and 'struct virtio_device_id' are not modified in
>> this driver.
>>
>> Constifying this structure moves some data to a read-only section, so
>> increase overall security, especially when the structure holds some
>> function pointers, which is the case for struct i2c_algorithm.
>>
>> On a x86_64, with allmodconfig:
>> Before:
>> ======
>>     text	   data	    bss	    dec	    hex	filename
>>     6663	    568	     16	   7247	   1c4f	drivers/i2c/busses/i2c-virtio.o
>>
>> After:
>> =====
>>     text	   data	    bss	    dec	    hex	filename
>>     6735	    472	     16	   7223	   1c37	drivers/i2c/busses/i2c-virtio.o
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> --
>> Compile tested only
> 
> Makes sense to me... if this works, you could pioneer a sequence
> of simiar changes :-)

Hi,

I already did some other ones [1]. A few more still need to be checked.

I'll finish it after ending struct regulator_desc that I'm currently 
looking at. [2]


[1]: https://lore.kernel.org/all/?q=%22Constify+struct+i2c_algorithm%22
[2]: https://lore.kernel.org/all/?q=%22Constify+struct+regulator_desc%22

> 
> Merged to i2c/i2c-host.

Thanks.
CJ

> 
> Thanks,
> Andi
> 
>