[PATCH v2 1/2] r8169: Load MAC address from device tree if present

[PATCH v2 1/2] r8169: Load MAC address from device tree if present

[Thierry Reding]

From: Thierry Reding <treding@nvidia.com>

If the system was booted using a device tree and if the device tree
contains a MAC address, use it instead of reading one from the EEPROM.
This is useful in situations where the EEPROM isn't properly programmed
or where the firmware wants to override the existing MAC address.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Applies to net-next.

Changes in v2:
- rewrite error check for readability
- initialize mac_addr array

 drivers/net/ethernet/realtek/r8169.c | 36 ++++++++++++++++++----------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index e8a112149a62..501891be7c56 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -7110,6 +7110,21 @@ static int rtl_alloc_irq(struct rtl8169_private *tp)
 	return pci_alloc_irq_vectors(tp->pci_dev, 1, 1, flags);
 }
 
+static void rtl_read_mac_address(struct rtl8169_private *tp,
+				 u8 mac_addr[ETH_ALEN])
+{
+	/* Get MAC address */
+	switch (tp->mac_version) {
+	case RTL_GIGA_MAC_VER_35 ... RTL_GIGA_MAC_VER_38:
+	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_51:
+		*(u32 *)&mac_addr[0] = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
+		*(u16 *)&mac_addr[4] = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
+		break;
+	default:
+		break;
+	}
+}
+
 DECLARE_RTL_COND(rtl_link_list_ready_cond)
 {
 	return RTL_R8(tp, MCU) & LINK_LIST_RDY;
@@ -7301,6 +7316,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
 static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
+	u8 mac_addr[ETH_ALEN] __aligned(4) = {};
 	struct rtl8169_private *tp;
 	struct net_device *dev;
 	int chipset, region, i;
@@ -7403,20 +7419,14 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	u64_stats_init(&tp->rx_stats.syncp);
 	u64_stats_init(&tp->tx_stats.syncp);
 
-	/* Get MAC address */
-	switch (tp->mac_version) {
-		u8 mac_addr[ETH_ALEN] __aligned(4);
-	case RTL_GIGA_MAC_VER_35 ... RTL_GIGA_MAC_VER_38:
-	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_51:
-		*(u32 *)&mac_addr[0] = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
-		*(u16 *)&mac_addr[4] = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
+	/* get MAC address */
+	rc = eth_platform_get_mac_address(&pdev->dev, mac_addr);
+	if (rc)
+		rtl_read_mac_address(tp, mac_addr);
+
+	if (is_valid_ether_addr(mac_addr))
+		rtl_rar_set(tp, mac_addr);
 
-		if (is_valid_ether_addr(mac_addr))
-			rtl_rar_set(tp, mac_addr);
-		break;
-	default:
-		break;
-	}
 	for (i = 0; i < ETH_ALEN; i++)
 		dev->dev_addr[i] = RTL_R8(tp, MAC0 + i);
 
-- 
2.19.1

[PATCH v2 2/2] r8169: Avoid pointer aliasing

[Thierry Reding]

From: Thierry Reding <treding@nvidia.com>

Read MAC address 32-bit at a time and manually extract the individual
bytes. This avoids pointer aliasing and gives the compiler a better
chance of optimizing the operation.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Applies to net-next.

I tested this on a Jetson TX2 with an add-in Realtek ethernet card that
has a properly programmed OTP to verify that I got the endianess right.
Seems like everything works and the device behaves the same with or
without this patch.

 drivers/net/ethernet/realtek/r8169.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 501891be7c56..192fbb36bc9f 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -7113,12 +7113,21 @@ static int rtl_alloc_irq(struct rtl8169_private *tp)
 static void rtl_read_mac_address(struct rtl8169_private *tp,
 				 u8 mac_addr[ETH_ALEN])
 {
+	u32 value;
+
 	/* Get MAC address */
 	switch (tp->mac_version) {
 	case RTL_GIGA_MAC_VER_35 ... RTL_GIGA_MAC_VER_38:
 	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_51:
-		*(u32 *)&mac_addr[0] = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
-		*(u16 *)&mac_addr[4] = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
+		value = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
+		mac_addr[0] = (value >>  0) & 0xff;
+		mac_addr[1] = (value >>  8) & 0xff;
+		mac_addr[2] = (value >> 16) & 0xff;
+		mac_addr[3] = (value >> 24) & 0xff;
+
+		value = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
+		mac_addr[4] = (value >>  0) & 0xff;
+		mac_addr[5] = (value >>  8) & 0xff;
 		break;
 	default:
 		break;
@@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
 static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
-	u8 mac_addr[ETH_ALEN] __aligned(4) = {};
+	u8 mac_addr[ETH_ALEN] = {};
 	struct rtl8169_private *tp;
 	struct net_device *dev;
 	int chipset, region, i;
-- 
2.19.1

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Andrew Lunn]

On Mon, Feb 04, 2019 at 05:42:13PM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> Read MAC address 32-bit at a time and manually extract the individual
> bytes. This avoids pointer aliasing and gives the compiler a better
> chance of optimizing the operation.
> 
> Suggested-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Thierry Reding <treding@nvidia.com>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Heiner Kallweit]

On 04.02.2019 17:42, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> Read MAC address 32-bit at a time and manually extract the individual
> bytes. This avoids pointer aliasing and gives the compiler a better
> chance of optimizing the operation.
> 
> Suggested-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
> Applies to net-next.
> 
> I tested this on a Jetson TX2 with an add-in Realtek ethernet card that
> has a properly programmed OTP to verify that I got the endianess right.
> Seems like everything works and the device behaves the same with or
> without this patch.
> 
>  drivers/net/ethernet/realtek/r8169.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
> index 501891be7c56..192fbb36bc9f 100644
> --- a/drivers/net/ethernet/realtek/r8169.c
> +++ b/drivers/net/ethernet/realtek/r8169.c
> @@ -7113,12 +7113,21 @@ static int rtl_alloc_irq(struct rtl8169_private *tp)
>  static void rtl_read_mac_address(struct rtl8169_private *tp,
>  				 u8 mac_addr[ETH_ALEN])
>  {
> +	u32 value;
> +
>  	/* Get MAC address */
>  	switch (tp->mac_version) {
>  	case RTL_GIGA_MAC_VER_35 ... RTL_GIGA_MAC_VER_38:
>  	case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_51:
> -		*(u32 *)&mac_addr[0] = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
> -		*(u16 *)&mac_addr[4] = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
> +		value = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
> +		mac_addr[0] = (value >>  0) & 0xff;
> +		mac_addr[1] = (value >>  8) & 0xff;
> +		mac_addr[2] = (value >> 16) & 0xff;
> +		mac_addr[3] = (value >> 24) & 0xff;
> +
> +		value = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
> +		mac_addr[4] = (value >>  0) & 0xff;
> +		mac_addr[5] = (value >>  8) & 0xff;
>  		break;
>  	default:
>  		break;
> @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
>  static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>  {
>  	const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
> -	u8 mac_addr[ETH_ALEN] __aligned(4) = {};
> +	u8 mac_addr[ETH_ALEN] = {};
>  	struct rtl8169_private *tp;
>  	struct net_device *dev;
>  	int chipset, region, i;
> 
I just have one concern / question:

After this there's a call to is_valid_ether_addr(mac_addr) and kernel-doc of
is_valid_ether_addr() states that argument must be u16-aligned.
AFAIK that's not guaranteed for a byte array.

Heiner

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[David Miller]

From: Thierry Reding <thierry.reding@gmail.com>
Date: Mon,  4 Feb 2019 17:42:13 +0100

> @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
>  static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>  {
>  	const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
> -	u8 mac_addr[ETH_ALEN] __aligned(4) = {};
> +	u8 mac_addr[ETH_ALEN] = {};
>  	struct rtl8169_private *tp;

I agree with Heiner, you have to provide at least 2 byte alignment for this
buffer due to the reasons he stated.

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Joe Perches]

On Mon, 2019-02-04 at 19:20 -0800, David Miller wrote:
> From: Thierry Reding <thierry.reding@gmail.com>
> Date: Mon,  4 Feb 2019 17:42:13 +0100
> 
> > @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
> >  static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
> >  {
> >       const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
> > -     u8 mac_addr[ETH_ALEN] __aligned(4) = {};
> > +     u8 mac_addr[ETH_ALEN] = {};
> >       struct rtl8169_private *tp;
> 
> I agree with Heiner, you have to provide at least 2 byte alignment for this
> buffer due to the reasons he stated.

It's declared after a pointer so it is already is 2 byte aligned.

A lot of drivers wouldn't work otherwise.

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[David Miller]

From: Joe Perches <joe@perches.com>
Date: Tue, 05 Feb 2019 10:42:54 -0800

> On Mon, 2019-02-04 at 19:20 -0800, David Miller wrote:
>> From: Thierry Reding <thierry.reding@gmail.com>
>> Date: Mon,  4 Feb 2019 17:42:13 +0100
>> 
>> > @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
>> >  static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>> >  {
>> >       const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
>> > -     u8 mac_addr[ETH_ALEN] __aligned(4) = {};
>> > +     u8 mac_addr[ETH_ALEN] = {};
>> >       struct rtl8169_private *tp;
>> 
>> I agree with Heiner, you have to provide at least 2 byte alignment for this
>> buffer due to the reasons he stated.
> 
> It's declared after a pointer so it is already is 2 byte aligned.
> 
> A lot of drivers wouldn't work otherwise.

That's assuming a lot about what the compiler will do when it allocates
local variables to the stack.

I want it _explicit_.

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Joe Perches]

On Tue, 2019-02-05 at 11:14 -0800, David Miller wrote:
> From: Joe Perches <joe@perches.com>
> Date: Tue, 05 Feb 2019 10:42:54 -0800
> 
> > On Mon, 2019-02-04 at 19:20 -0800, David Miller wrote:
> >> From: Thierry Reding <thierry.reding@gmail.com>
> >> Date: Mon,  4 Feb 2019 17:42:13 +0100
> >> 
> >> > @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
> >> >  static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
> >> >  {
> >> >       const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
> >> > -     u8 mac_addr[ETH_ALEN] __aligned(4) = {};
> >> > +     u8 mac_addr[ETH_ALEN] = {};
> >> >       struct rtl8169_private *tp;
> >> 
> >> I agree with Heiner, you have to provide at least 2 byte alignment for this
> >> buffer due to the reasons he stated.
> > 
> > It's declared after a pointer so it is already is 2 byte aligned.
> > 
> > A lot of drivers wouldn't work otherwise.
> 
> That's assuming a lot about what the compiler will do when nit allocates
> local variables to the stack.

It's also assuming what a compiler will do when
it defines a struct.

> I want it _explicit_.

Your choice, but there are a _lot_ of existing uses
and I think requiring it is as senseless as requiring
void * arithmetic to be cast to char * as gcc and
clang already do not add padding after a pointer.

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Michal Kubecek]

On Tue, Feb 05, 2019 at 11:19:04AM -0800, Joe Perches wrote:
> On Tue, 2019-02-05 at 11:14 -0800, David Miller wrote:
> > From: Joe Perches <joe@perches.com>
> > Date: Tue, 05 Feb 2019 10:42:54 -0800
> > 
> > > On Mon, 2019-02-04 at 19:20 -0800, David Miller wrote:
> > >> From: Thierry Reding <thierry.reding@gmail.com>
> > >> Date: Mon,  4 Feb 2019 17:42:13 +0100
> > >> 
> > >> > @@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
> > >> >  static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
> > >> >  {
> > >> >       const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
> > >> > -     u8 mac_addr[ETH_ALEN] __aligned(4) = {};
> > >> > +     u8 mac_addr[ETH_ALEN] = {};
> > >> >       struct rtl8169_private *tp;
> > >> 
> > >> I agree with Heiner, you have to provide at least 2 byte alignment for this
> > >> buffer due to the reasons he stated.
> > > 
> > > It's declared after a pointer so it is already is 2 byte aligned.
> > > 
> > > A lot of drivers wouldn't work otherwise.
> > 
> > That's assuming a lot about what the compiler will do when nit allocates
> > local variables to the stack.
> 
> It's also assuming what a compiler will do when
> it defines a struct.

This is not a structure member, it's a local variable. I'm not aware of
any C norm requirement for ordering of local variables on the stack.
After all, some of them might not be on the stack at all and use only
registers or be optimized out completely.

Michal Kubecek

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Eric Dumazet]

On 02/05/2019 10:42 AM, Joe Perches wrote:
> 
> It's declared after a pointer so it is already is 2 byte aligned.
> 
> A lot of drivers wouldn't work otherwise.

Maybe these drivers are only used on arches where this does not matter.

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Joe Perches]

On Tue, 2019-02-05 at 12:04 -0800, Eric Dumazet wrote:
> 
> On 02/05/2019 10:42 AM, Joe Perches wrote:
> > It's declared after a pointer so it is already is 2 byte aligned.
> > 
> > A lot of drivers wouldn't work otherwise.
> 
> Maybe these drivers are only used on arches where this does not matter.

Possible.

I had only grepped through the sources looking for
declarations using:

$ git grep -B1 '\[ETH_ALEN\];' -- '*.c' | grep -A1 '\*'

It's quite a few files in net/ too btw.

I still think adding __align(<even#>) is unnecessary here unless
it follows something like a bool or a u8.

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Eric Dumazet]

On 02/05/2019 12:18 PM, Joe Perches wrote:

> I still think adding __align(<even#>) is unnecessary here unless
> it follows something like a bool or a u8.

This would be some historical side effect, and we do not want to rely on that.

A security feature could in fact ask a compiler to perform random
shuffling of automatic variables.

( a la __randomize_layout )

Re: [PATCH v2 2/2] r8169: Avoid pointer aliasing

[Heiner Kallweit]

On 05.02.2019 21:18, Joe Perches wrote:
> On Tue, 2019-02-05 at 12:04 -0800, Eric Dumazet wrote:
>>
>> On 02/05/2019 10:42 AM, Joe Perches wrote:
>>> It's declared after a pointer so it is already is 2 byte aligned.
>>>
>>> A lot of drivers wouldn't work otherwise.
>>
>> Maybe these drivers are only used on arches where this does not matter.
> 
> Possible.
> 
> I had only grepped through the sources looking for
> declarations using:
> 
> $ git grep -B1 '\[ETH_ALEN\];' -- '*.c' | grep -A1 '\*'
> 
> It's quite a few files in net/ too btw.
> 
> I still think adding __align(<even#>) is unnecessary here unless
> it follows something like a bool or a u8.
> 
> 
I there's such a controversy, then it may be better to stay with
the current code, or?

Re: [PATCH v2 1/2] r8169: Load MAC address from device tree if present

[Heiner Kallweit]

On 04.02.2019 17:42, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> If the system was booted using a device tree and if the device tree
> contains a MAC address, use it instead of reading one from the EEPROM.
> This is useful in situations where the EEPROM isn't properly programmed
> or where the firmware wants to override the existing MAC address.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>

Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>