svn commit: r305354 - head/sys/arm/allwinner

[Jared McNeill]

Hi Oliver --

It's really just a serial number. The Allwinner A20 datasheet refers to it 
as a root key, later ones such as A83T refer to it as chip ID. U-Boot 
uses the same process to generate MAC addresses for all Allwinner boards.

Cheers,
Jared


On Sat, 3 Sep 2016, Oliver Pinter wrote:

> Hi!
>
> On 9/3/16, Jared McNeill <jmcneill at freebsd.org> wrote:
>> Author: jmcneill
>> Date: Sat Sep  3 15:28:09 2016
>> New Revision: 305354
>> URL: https://svnweb.freebsd.org/changeset/base/305354
>>
>> Log:
>>   Use the root key in the Security ID EFUSE (when valid) to generate a
>>   MAC address instead of creating a random one each boot.
>
> Could you please describe a little more about this root key? What is
> it? What's the main purpose? Is is a crypto root key?
>
>>
>> Modified:
>>   head/sys/arm/allwinner/if_awg.c
>>
>> Modified: head/sys/arm/allwinner/if_awg.c
>> ==============================================================================
>> --- head/sys/arm/allwinner/if_awg.c	Sat Sep  3 15:26:28 2016	(r305353)
>> +++ head/sys/arm/allwinner/if_awg.c	Sat Sep  3 15:28:09 2016	(r305354)
>> @@ -62,6 +62,7 @@ __FBSDID("$FreeBSD$");
>>  #include <dev/ofw/ofw_bus_subr.h>
>>
>>  #include <arm/allwinner/if_awgreg.h>
>> +#include <arm/allwinner/aw_sid.h>
>>  #include <dev/mii/mii.h>
>>  #include <dev/mii/miivar.h>
>>
>> @@ -1277,6 +1278,7 @@ awg_get_eaddr(device_t dev, uint8_t *ead
>>  {
>>  	struct awg_softc *sc;
>>  	uint32_t maclo, machi, rnd;
>> +	u_char rootkey[16];
>>
>>  	sc = device_get_softc(dev);
>>
>> @@ -1285,9 +1287,19 @@ awg_get_eaddr(device_t dev, uint8_t *ead
>>
>>  	if (maclo == 0xffffffff && machi == 0xffff) {
>>  		/* MAC address in hardware is invalid, create one */
>> -		rnd = arc4random();
>> -		maclo = 0x00f2 | (rnd & 0xffff0000);
>> -		machi = rnd & 0xffff;
>> +		if (aw_sid_get_rootkey(rootkey) == 0 &&
>> +		    (rootkey[3] | rootkey[12] | rootkey[13] | rootkey[14] |
>> +		     rootkey[15]) != 0) {
>> +			/* MAC address is derived from the root key in SID */
>> +			maclo = (rootkey[13] << 24) | (rootkey[12] << 16) |
>> +				(rootkey[3] << 8) | 0x02;
>> +			machi = (rootkey[15] << 8) | rootkey[14];
>> +		} else {
>> +			/* Create one */
>> +			rnd = arc4random();
>> +			maclo = 0x00f2 | (rnd & 0xffff0000);
>> +			machi = rnd & 0xffff;
>> +		}
>>  	}
>>
>>  	eaddr[0] = maclo & 0xff;
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>
>