From: Arnd Bergmann <arnd@arndb.de>
To: Michael Krufky <mkrufky@linuxtv.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] tuners: tda8290: reduce stack usage with kasan
Date: Mon, 11 Dec 2017 13:06:04 +0100
Message-Id: <20171211120612.3775893-1-arnd@arndb.de>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 6620
Lines: 153

With CONFIG_KASAN enabled, we get a relatively large stack frame in one function

drivers/media/tuners/tda8290.c: In function 'tda8290_set_params':
drivers/media/tuners/tda8290.c:310:1: warning: the frame size of 1520 bytes is larger than 1024 bytes [-Wframe-larger-than=]

With CONFIG_KASAN_EXTRA this goes up to

drivers/media/tuners/tda8290.c: In function 'tda8290_set_params':
drivers/media/tuners/tda8290.c:310:1: error: the frame size of 3200 bytes is larger than 3072 bytes [-Werror=frame-larger-than=]

We can significantly reduce this by marking local arrays as 'static const', and
this should result in better compiled code for everyone.

I have another patch for the same symptom to patch tuner_i2c_xfer_*, and we
actually want both of them.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/media/tuners/tda8290.c | 76 ++++++++++++++++++++++--------------------
 1 file changed, 39 insertions(+), 37 deletions(-)

diff --git a/drivers/media/tuners/tda8290.c b/drivers/media/tuners/tda8290.c
index a59c567c55d6..19854221b72d 100644
--- a/drivers/media/tuners/tda8290.c
+++ b/drivers/media/tuners/tda8290.c
@@ -63,8 +63,8 @@ static int tda8290_i2c_bridge(struct dvb_frontend *fe, int close)
 {
 	struct tda8290_priv *priv = fe->analog_demod_priv;
 
-	unsigned char  enable[2] = { 0x21, 0xC0 };
-	unsigned char disable[2] = { 0x21, 0x00 };
+	static unsigned char  enable[2] = { 0x21, 0xC0 };
+	static unsigned char disable[2] = { 0x21, 0x00 };
 	unsigned char *msg;
 
 	if (close) {
@@ -84,9 +84,9 @@ static int tda8295_i2c_bridge(struct dvb_frontend *fe, int close)
 {
 	struct tda8290_priv *priv = fe->analog_demod_priv;
 
-	unsigned char  enable[2] = { 0x45, 0xc1 };
-	unsigned char disable[2] = { 0x46, 0x00 };
-	unsigned char buf[3] = { 0x45, 0x01, 0x00 };
+	static unsigned char  enable[2] = { 0x45, 0xc1 };
+	static unsigned char disable[2] = { 0x46, 0x00 };
+	static unsigned char buf[3] = { 0x45, 0x01, 0x00 };
 	unsigned char *msg;
 
 	if (close) {
@@ -178,24 +178,24 @@ static void tda8290_set_params(struct dvb_frontend *fe,
 {
 	struct tda8290_priv *priv = fe->analog_demod_priv;
 
-	unsigned char soft_reset[]  = { 0x00, 0x00 };
+	static unsigned char soft_reset[]  = { 0x00, 0x00 };
 	unsigned char easy_mode[]   = { 0x01, priv->tda8290_easy_mode };
-	unsigned char expert_mode[] = { 0x01, 0x80 };
-	unsigned char agc_out_on[]  = { 0x02, 0x00 };
-	unsigned char gainset_off[] = { 0x28, 0x14 };
-	unsigned char if_agc_spd[]  = { 0x0f, 0x88 };
-	unsigned char adc_head_6[]  = { 0x05, 0x04 };
-	unsigned char adc_head_9[]  = { 0x05, 0x02 };
-	unsigned char adc_head_12[] = { 0x05, 0x01 };
-	unsigned char pll_bw_nom[]  = { 0x0d, 0x47 };
-	unsigned char pll_bw_low[]  = { 0x0d, 0x27 };
-	unsigned char gainset_2[]   = { 0x28, 0x64 };
-	unsigned char agc_rst_on[]  = { 0x0e, 0x0b };
-	unsigned char agc_rst_off[] = { 0x0e, 0x09 };
-	unsigned char if_agc_set[]  = { 0x0f, 0x81 };
-	unsigned char addr_adc_sat  = 0x1a;
-	unsigned char addr_agc_stat = 0x1d;
-	unsigned char addr_pll_stat = 0x1b;
+	static unsigned char expert_mode[] = { 0x01, 0x80 };
+	static unsigned char agc_out_on[]  = { 0x02, 0x00 };
+	static unsigned char gainset_off[] = { 0x28, 0x14 };
+	static unsigned char if_agc_spd[]  = { 0x0f, 0x88 };
+	static unsigned char adc_head_6[]  = { 0x05, 0x04 };
+	static unsigned char adc_head_9[]  = { 0x05, 0x02 };
+	static unsigned char adc_head_12[] = { 0x05, 0x01 };
+	static unsigned char pll_bw_nom[]  = { 0x0d, 0x47 };
+	static unsigned char pll_bw_low[]  = { 0x0d, 0x27 };
+	static unsigned char gainset_2[]   = { 0x28, 0x64 };
+	static unsigned char agc_rst_on[]  = { 0x0e, 0x0b };
+	static unsigned char agc_rst_off[] = { 0x0e, 0x09 };
+	static unsigned char if_agc_set[]  = { 0x0f, 0x81 };
+	static unsigned char addr_adc_sat  = 0x1a;
+	static unsigned char addr_agc_stat = 0x1d;
+	static unsigned char addr_pll_stat = 0x1b;
 	unsigned char adc_sat, agc_stat,
 		      pll_stat;
 	int i;
@@ -468,9 +468,9 @@ static void tda8290_standby(struct dvb_frontend *fe)
 {
 	struct tda8290_priv *priv = fe->analog_demod_priv;
 
-	unsigned char cb1[] = { 0x30, 0xD0 };
-	unsigned char tda8290_standby[] = { 0x00, 0x02 };
-	unsigned char tda8290_agc_tri[] = { 0x02, 0x20 };
+	static unsigned char cb1[] = { 0x30, 0xD0 };
+	static unsigned char tda8290_standby[] = { 0x00, 0x02 };
+	static unsigned char tda8290_agc_tri[] = { 0x02, 0x20 };
 	struct i2c_msg msg = {.addr = priv->tda827x_addr, .flags=0, .buf=cb1, .len = 2};
 
 	if (fe->ops.analog_ops.i2c_gate_ctrl)
@@ -495,9 +495,9 @@ static void tda8290_init_if(struct dvb_frontend *fe)
 {
 	struct tda8290_priv *priv = fe->analog_demod_priv;
 
-	unsigned char set_VS[] = { 0x30, 0x6F };
-	unsigned char set_GP00_CF[] = { 0x20, 0x01 };
-	unsigned char set_GP01_CF[] = { 0x20, 0x0B };
+	static unsigned char set_VS[] = { 0x30, 0x6F };
+	static unsigned char set_GP00_CF[] = { 0x20, 0x01 };
+	static unsigned char set_GP01_CF[] = { 0x20, 0x0B };
 
 	if ((priv->cfg.config == TDA8290_LNA_GP0_HIGH_ON) ||
 	    (priv->cfg.config == TDA8290_LNA_GP0_HIGH_OFF))
@@ -539,10 +539,12 @@ static void tda8295_init_if(struct dvb_frontend *fe)
 static void tda8290_init_tuner(struct dvb_frontend *fe)
 {
 	struct tda8290_priv *priv = fe->analog_demod_priv;
-	unsigned char tda8275_init[]  = { 0x00, 0x00, 0x00, 0x40, 0xdC, 0x04, 0xAf,
-					  0x3F, 0x2A, 0x04, 0xFF, 0x00, 0x00, 0x40 };
-	unsigned char tda8275a_init[] = { 0x00, 0x00, 0x00, 0x00, 0xdC, 0x05, 0x8b,
-					  0x0c, 0x04, 0x20, 0xFF, 0x00, 0x00, 0x4b };
+	static unsigned char tda8275_init[]  =
+		{ 0x00, 0x00, 0x00, 0x40, 0xdC, 0x04, 0xAf,
+		  0x3F, 0x2A, 0x04, 0xFF, 0x00, 0x00, 0x40 };
+	static unsigned char tda8275a_init[] =
+		 { 0x00, 0x00, 0x00, 0x00, 0xdC, 0x05, 0x8b,
+		   0x0c, 0x04, 0x20, 0xFF, 0x00, 0x00, 0x4b };
 	struct i2c_msg msg = {.addr = priv->tda827x_addr, .flags=0,
 			      .buf=tda8275_init, .len = 14};
 	if (priv->ver & TDA8275A)
@@ -834,11 +836,11 @@ int tda829x_probe(struct i2c_adapter *i2c_adap, u8 i2c_addr)
 		.addr = i2c_addr,
 	};
 
-	unsigned char soft_reset[]   = { 0x00, 0x00 };
-	unsigned char easy_mode_b[]  = { 0x01, 0x02 };
-	unsigned char easy_mode_g[]  = { 0x01, 0x04 };
-	unsigned char restore_9886[] = { 0x00, 0xd6, 0x30 };
-	unsigned char addr_dto_lsb = 0x07;
+	static unsigned char soft_reset[]   = { 0x00, 0x00 };
+	static unsigned char easy_mode_b[]  = { 0x01, 0x02 };
+	static unsigned char easy_mode_g[]  = { 0x01, 0x04 };
+	static unsigned char restore_9886[] = { 0x00, 0xd6, 0x30 };
+	static unsigned char addr_dto_lsb = 0x07;
 	unsigned char data;
 #define PROBE_BUFFER_SIZE 8
 	unsigned char buf[PROBE_BUFFER_SIZE];
-- 
2.9.0