Re: [PATCH 1/2] Initial support for Allwinner's Security ID fuses

[Tomasz Figa <tomasz.figa@gmail.com>]

Hi Oliver,

On Monday 17 of June 2013 22:59:37 Oliver Schinagl wrote:
> From: Oliver Schinagl <oliver@schinagl.nl>
> 
> Allwinner has electric fuses (efuse) on their line of chips. This driver
> reads those fuses, seeds the kernel entropy and exports them as a sysfs
> node.
> 
> These fuses are most likly to be programmed at the factory, encoding
> things like Chip ID, some sort of serial number etc and appear to be
> reasonable unique.
> While in theory, these should be writeable by the user, it will probably
> be inconvinient to do so. Allwinner recommends that a certain input
> pin, labeled 'efuse_vddq', be connected to GND. To write these fuses,
> 2.5 V needs to be applied to this pin.
> 
> Even so, they can still be used to generate a board-unique mac from,
> board unique RSA key and seed the kernel RNG.
> 
> Currently supported are the following known chips:
> Allwinner sun4i (A10)
> Allwinner sun5i (A10s, A13)
> 
> Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
> ---
>  drivers/misc/eeprom/Kconfig     |  17 +++++
>  drivers/misc/eeprom/Makefile    |   1 +
>  drivers/misc/eeprom/sunxi_sid.c | 147
> ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 165
> insertions(+)
>  create mode 100644 drivers/misc/eeprom/sunxi_sid.c

Looks good to me. Have my

Reviewed-by: Tomasz Figa <tomasz.figa@gmail.com>

Best regards,
Tomasz

> diff --git a/drivers/misc/eeprom/Kconfig b/drivers/misc/eeprom/Kconfig
> index 04f2e1f..c7bc6ed 100644
> --- a/drivers/misc/eeprom/Kconfig
> +++ b/drivers/misc/eeprom/Kconfig
> @@ -96,4 +96,21 @@ config EEPROM_DIGSY_MTC_CFG
> 
>  	  If unsure, say N.
> 
> +config EEPROM_SUNXI_SID
> +	tristate "Allwinner sunxi security ID support"
> +	depends on ARCH_SUNXI && SYSFS
> +	help
> +	  This is a driver for the 'security ID' available on various
> Allwinner +	  devices. Currently supported are:
> +		sun4i (A10)
> +		sun5i (A13)
> +
> +	  Due to the potential risks involved with changing e-fuses,
> +	  this driver is read-only
> +
> +	  For more information visit http://linux-sunxi.org/SID
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called sunxi_sid.
> +
>  endmenu
> diff --git a/drivers/misc/eeprom/Makefile b/drivers/misc/eeprom/Makefile
> index fc1e81d..9507aec 100644
> --- a/drivers/misc/eeprom/Makefile
> +++ b/drivers/misc/eeprom/Makefile
> @@ -4,4 +4,5 @@ obj-$(CONFIG_EEPROM_LEGACY)	+= eeprom.o
>  obj-$(CONFIG_EEPROM_MAX6875)	+= max6875.o
>  obj-$(CONFIG_EEPROM_93CX6)	+= eeprom_93cx6.o
>  obj-$(CONFIG_EEPROM_93XX46)	+= eeprom_93xx46.o
> +obj-$(CONFIG_EEPROM_SUNXI_SID)	+= sunxi_sid.o
>  obj-$(CONFIG_EEPROM_DIGSY_MTC_CFG) += digsy_mtc_eeprom.o
> diff --git a/drivers/misc/eeprom/sunxi_sid.c
> b/drivers/misc/eeprom/sunxi_sid.c new file mode 100644
> index 0000000..6a16c19
> --- /dev/null
> +++ b/drivers/misc/eeprom/sunxi_sid.c
> @@ -0,0 +1,147 @@
> +/*
> + * Copyright (c) 2013 Oliver Schinagl
> + * http://www.linux-sunxi.org
> + *
> + * Oliver Schinagl <oliver@schinagl.nl>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published
> by + * the Free Software Foundation; either version 2 of the License,
> or + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * This driver exposes the Allwinner security ID, a 128 bit eeprom, in
> byte + * sized chunks.
> + */
> +
> +#include <linux/compiler.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/export.h>
> +#include <linux/fs.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/kobject.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/random.h>
> +#include <linux/stat.h>
> +#include <linux/sysfs.h>
> +#include <linux/types.h>
> +
> +#define DRV_NAME "sunxi-sid"
> +
> +/* There are 4 32-bit keys */
> +#define SID_KEYS 4
> +/* Each key is 4 bytes long */
> +#define SID_SIZE (SID_KEYS * 4)
> +
> +/* We read the entire key, due to a 32 bit read alignment requirement.
> Since we + * want to return the requested byte, this resuls in somewhat
> slower code and + * uses 4 times more reads as needed but keeps code
> simpler. Since the SID is + * only very rarly probed, this is not
> really an issue.
> + */
> +static u8 sunxi_sid_read_byte(const void __iomem *sid_reg_base,
> +			      const unsigned int offset)
> +{
> +	u32 sid_key;
> +
> +	if (offset >= SID_SIZE)
> +		return 0;
> +
> +	sid_key = ioread32be(sid_reg_base + round_down(offset, 4));
> +	sid_key >>= (offset % 4) * 8;
> +
> +	return sid_key; /* Only return the last byte */
> +}
> +
> +static ssize_t sid_read(struct file *fd, struct kobject *kobj,
> +			struct bin_attribute *attr, char *buf,
> +			loff_t pos, size_t size)
> +{
> +	int i;
> +	struct platform_device *pdev;
> +	void __iomem *sid_reg_base;
> +
> +	pdev = to_platform_device(kobj_to_dev(kobj));
> +	sid_reg_base = (void __iomem *)platform_get_drvdata(pdev);
> +
> +	if (pos < 0 || pos >= SID_SIZE)
> +		return 0;
> +	if (size > (SID_SIZE - pos))
> +		size = SID_SIZE - pos;
> +
> +	for (i = 0; i < size; i++)
> +		buf[i] = sunxi_sid_read_byte(sid_reg_base, pos + i);
> +
> +	return i;
> +}
> +
> +static const struct of_device_id sunxi_sid_of_match[] = {
> +	{ .compatible = "allwinner,sun4i-sid", },
> +	{/* sentinel */}
> +};
> +MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);
> +
> +static const struct bin_attribute sid_bin_attr = {
> +	.attr = {
> +		.name = "eeprom",
> +		.mode = S_IRUGO,
> +	},
> +	.size = SID_SIZE,
> +	.read = sid_read,
> +};
> +
> +static int sunxi_sid_remove(struct platform_device *pdev)
> +{
> +	device_remove_bin_file(&pdev->dev, &sid_bin_attr);
> +	dev_dbg(&pdev->dev, "%s driver unloaded\n", DRV_NAME);
> +
> +	return 0;
> +}
> +
> +static int __init sunxi_sid_probe(struct platform_device *pdev)
> +{
> +	u8 entropy[SID_SIZE];
> +	unsigned int i;
> +	struct resource *res;
> +	void __iomem *sid_reg_base;
> +	int ret;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	sid_reg_base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(sid_reg_base))
> +		return PTR_ERR(sid_reg_base);
> +	platform_set_drvdata(pdev, sid_reg_base);
> +
> +	ret = device_create_bin_file(&pdev->dev, &sid_bin_attr);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < SID_SIZE; i++)
> +		entropy[i] = sunxi_sid_read_byte(sid_reg_base, i);
> +	add_device_randomness(entropy, SID_SIZE);
> +	dev_dbg(&pdev->dev, "%s loaded\n", DRV_NAME);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver sunxi_sid_driver = {
> +	.probe = sunxi_sid_probe,
> +	.remove = sunxi_sid_remove,
> +	.driver = {
> +		.name = DRV_NAME,
> +		.owner = THIS_MODULE,
> +		.of_match_table = sunxi_sid_of_match,
> +	},
> +};
> +module_platform_driver(sunxi_sid_driver);
> +
> +MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
> +MODULE_DESCRIPTION("Allwinner sunxi security id driver");
> +MODULE_LICENSE("GPL");