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From:   Oscar Carter <oscar.carter@gmx.com>
To:     Forest Bond <forest@alittletooquiet.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Oscar Carter <oscar.carter@gmx.com>,
        Malcolm Priestley <tvboxspy@gmail.com>,
        Quentin Deslandes <quentin.deslandes@itdev.co.uk>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Colin Ian King <colin.king@canonical.com>,
        Benjamin Sherman <benjamin@bensherman.io>,
        devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org,
        Amir Mahdi Ghorbanian <indigoomega021@gmail.com>
Subject: [PATCH] staging: vt6656: Use const for read only data
Date:   Mon,  4 May 2020 19:14:14 +0200
Message-Id: <20200504171414.11307-1-oscar.carter@gmx.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Use const for the arrays that are used as "read only". Also, modify the
prototype of vnt_control_out_blocks() function to use a pointer to a
const type.

The vnt_vt3184_al2230 array can't be converted to const as it's modified
later.

Then in the vnt_vt3184_init() function use two types of pointers (to
const type and to no const type) to avoid the compiler warning:

assignment discards 'const' qualifiers from pointer target type

This way decrease the .data section and increase the .rodata section
limiting the surface attack.

Before this change:
=2D------------------

drivers/staging/vt6656/baseband.o  :
section              size   addr
.text                1278      0
.data                 576      0
.bss                    0      0
.rodata               319      0
.comment               45      0
.note.GNU-stack         0      0
.note.gnu.property     32      0
Total                2250

After this change:
=2D-----------------

drivers/staging/vt6656/baseband.o  :
section              size   addr
.text                1278      0
.data                 256      0
.bss                    0      0
.rodata               640      0
.comment               45      0
.note.GNU-stack         0      0
.note.gnu.property     32      0
Total                2251

Signed-off-by: Oscar Carter <oscar.carter@gmx.com>
=2D--
 drivers/staging/vt6656/baseband.c | 14 +++++++++-----
 drivers/staging/vt6656/usbpipe.c  |  2 +-
 drivers/staging/vt6656/usbpipe.h  |  2 +-
 3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/vt6656/baseband.c b/drivers/staging/vt6656/ba=
seband.c
index 1d75acaec8f3..41ae779ec61f 100644
=2D-- a/drivers/staging/vt6656/baseband.c
+++ b/drivers/staging/vt6656/baseband.c
@@ -31,7 +31,7 @@
 #include "rf.h"
 #include "usbpipe.h"

-static u8 vnt_vt3184_agc[] =3D {
+static const u8 vnt_vt3184_agc[] =3D {
 	0x00, 0x00, 0x02, 0x02, 0x04, 0x04, 0x06, 0x06,
 	0x08, 0x08, 0x0a, 0x0a, 0x0c, 0x0c, 0x0e, 0x0e, /* 0x0f */
 	0x10, 0x10, 0x12, 0x12, 0x14, 0x14, 0x16, 0x16,
@@ -78,7 +78,7 @@ static u8 vnt_vt3184_al2230[] =3D {
 };

 /* {{RobertYu:20060515, new BB setting for VT3226D0 */
-static u8 vnt_vt3184_vt3226d0[] =3D {
+static const u8 vnt_vt3184_vt3226d0[] =3D {
 	0x31, 0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00,
 	0x70, 0x45, 0x2a, 0x76, 0x00, 0x00, 0x80, 0x00, /* 0x0f */
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -243,7 +243,8 @@ int vnt_vt3184_init(struct vnt_private *priv)
 {
 	int ret;
 	u16 length;
-	u8 *addr;
+	u8 *addr =3D NULL;
+	const u8 *c_addr;
 	u8 data;

 	ret =3D vnt_control_in(priv, MESSAGE_TYPE_READ, 0, MESSAGE_REQUEST_EEPRO=
M,
@@ -275,7 +276,7 @@ int vnt_vt3184_init(struct vnt_private *priv)
 		   (priv->rf_type =3D=3D RF_VT3342A0)) {
 		priv->bb_rx_conf =3D vnt_vt3184_vt3226d0[10];
 		length =3D sizeof(vnt_vt3184_vt3226d0);
-		addr =3D vnt_vt3184_vt3226d0;
+		c_addr =3D vnt_vt3184_vt3226d0;

 		priv->bb_vga[0] =3D 0x20;
 		priv->bb_vga[1] =3D 0x10;
@@ -291,8 +292,11 @@ int vnt_vt3184_init(struct vnt_private *priv)
 		goto end;
 	}

+	if (addr)
+		c_addr =3D addr;
+
 	ret =3D vnt_control_out_blocks(priv, VNT_REG_BLOCK_SIZE,
-				     MESSAGE_REQUEST_BBREG, length, addr);
+				     MESSAGE_REQUEST_BBREG, length, c_addr);
 	if (ret)
 		goto end;

diff --git a/drivers/staging/vt6656/usbpipe.c b/drivers/staging/vt6656/usb=
pipe.c
index 91b62c3dff7b..fb5e1b0dce6b 100644
=2D-- a/drivers/staging/vt6656/usbpipe.c
+++ b/drivers/staging/vt6656/usbpipe.c
@@ -77,7 +77,7 @@ int vnt_control_out_u8(struct vnt_private *priv, u8 reg,=
 u8 reg_off, u8 data)
 }

 int vnt_control_out_blocks(struct vnt_private *priv,
-			   u16 block, u8 reg, u16 length, u8 *data)
+			   u16 block, u8 reg, u16 length, const u8 *data)
 {
 	int ret =3D 0, i;

diff --git a/drivers/staging/vt6656/usbpipe.h b/drivers/staging/vt6656/usb=
pipe.h
index 35697b58d748..1f0b2566c288 100644
=2D-- a/drivers/staging/vt6656/usbpipe.h
+++ b/drivers/staging/vt6656/usbpipe.h
@@ -52,7 +52,7 @@ int vnt_control_out_u8(struct vnt_private *priv, u8 reg,=
 u8 ref_off, u8 data);
 int vnt_control_in_u8(struct vnt_private *priv, u8 reg, u8 reg_off, u8 *d=
ata);

 int vnt_control_out_blocks(struct vnt_private *priv,
-			   u16 block, u8 reg, u16 len, u8 *data);
+			   u16 block, u8 reg, u16 len, const u8 *data);

 int vnt_start_interrupt_urb(struct vnt_private *priv);
 int vnt_submit_rx_urb(struct vnt_private *priv, struct vnt_rcb *rcb);
=2D-
2.20.1