linux-kernel - Re: [PATCH 2/2] ARM: aspeed: Add secure boot controller support

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Message-ID: <YfjyNo5wBPs16vkz@kroah.com>
Date:   Tue, 1 Feb 2022 09:41:26 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Joel Stanley <joel@....id.au>
Cc:     Arnd Bergmann <arnd@...db.de>, Andrew Jeffery <andrew@...id.au>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, Ryan Chen <ryan_chen@...eedtech.com>
Subject: Re: [PATCH 2/2] ARM: aspeed: Add secure boot controller support

On Tue, Feb 01, 2022 at 03:35:01PM +1030, Joel Stanley wrote:
> This reads out the status of the secure boot controller and exposes it
> in sysfs using the bootinfo sysfs api.
> 
> An example on a AST2600A3 QEMU model:
> 
>  # grep -r . /sys/firmware/bootinfo/*
>  /sys/firmware/bootinfo/abr_image:0
>  /sys/firmware/bootinfo/low_security_key:0
>  /sys/firmware/bootinfo/otp_protected:0
>  /sys/firmware/bootinfo/secure_boot:1
>  /sys/firmware/bootinfo/uart_boot:0
> 
> On boot the state of the system according to the secure boot controller
> will be printed:
> 
>  [    0.037634] AST2600 secure boot enabled
> 
> or
> 
>  [    0.037935] AST2600 secure boot disabled
> 
> The initialisation is changed from early_initcall to subsys_initcall
> because we need the firmware_kobj to be initialised, and because there's
> no requirement to print this information early.
> 
> Signed-off-by: Joel Stanley <joel@....id.au>
> Reviewed-by: Ryan Chen <ryan_chen@...eedtech.com>
> ---
>  drivers/soc/aspeed/aspeed-socinfo.c | 84 ++++++++++++++++++++++++++++-
>  1 file changed, 83 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/aspeed/aspeed-socinfo.c b/drivers/soc/aspeed/aspeed-socinfo.c
> index 1ca140356a08..fe77b31e4d1d 100644
> --- a/drivers/soc/aspeed/aspeed-socinfo.c
> +++ b/drivers/soc/aspeed/aspeed-socinfo.c
> @@ -8,6 +8,9 @@
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
>  #include <linux/sys_soc.h>
> +#include <linux/firmware_bootinfo.h>
> +
> +static u32 security_status;
>  
>  static struct {
>  	const char *name;
> @@ -74,6 +77,83 @@ static const char *siliconid_to_rev(u32 siliconid)
>  	return "??";
>  }
>  
> +#define SEC_STATUS		0x14
> +#define ABR_IMAGE_SOURCE	BIT(13)
> +#define OTP_PROTECTED		BIT(8)
> +#define LOW_SEC_KEY		BIT(7)
> +#define SECURE_BOOT		BIT(6)
> +#define UART_BOOT		BIT(5)

Where do these bits come from?

> +
> +static ssize_t abr_image_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", !!(security_status & ABR_IMAGE_SOURCE));

sysfs_emit() here and everywhere else you use sprintf() please.

> +}
> +static DEVICE_ATTR_RO(abr_image);
> +
> +static ssize_t low_security_key_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", !!(security_status & LOW_SEC_KEY));
> +}
> +static DEVICE_ATTR_RO(low_security_key);
> +
> +static ssize_t otp_protected_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", !!(security_status & OTP_PROTECTED));
> +}
> +static DEVICE_ATTR_RO(otp_protected);
> +
> +static ssize_t secure_boot_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d\n", !!(security_status & SECURE_BOOT));
> +}
> +static DEVICE_ATTR_RO(secure_boot);
> +
> +static ssize_t uart_boot_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	/* Invert the bit, as 1 is boot from SPI/eMMC */
> +	return sprintf(buf, "%d\n", !(security_status & UART_BOOT));
> +}
> +static DEVICE_ATTR_RO(uart_boot);
> +
> +static struct attribute *aspeed_attrs[] = {
> +	&dev_attr_abr_image.attr,
> +	&dev_attr_low_security_key.attr,
> +	&dev_attr_otp_protected.attr,
> +	&dev_attr_secure_boot.attr,
> +	&dev_attr_uart_boot.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(aspeed);
> +
> +static int __init aspeed_bootinfo_init(void)
> +{
> +	struct device_node *np;
> +	void __iomem *base;
> +
> +	/* AST2600 only */
> +	np = of_find_compatible_node(NULL, NULL, "aspeed,ast2600-sbc");
> +	if (!of_device_is_available(np))
> +		return -ENODEV;
> +
> +	base = of_iomap(np, 0);
> +	if (!base) {
> +		of_node_put(np);
> +		return -ENODEV;
> +	}
> +
> +	security_status = readl(base + SEC_STATUS);
> +
> +	iounmap(base);
> +	of_node_put(np);
> +
> +	firmware_bootinfo_init(aspeed_groups[0]);
> +
> +	pr_info("AST2600 secure boot %s\n",
> +		(security_status & SECURE_BOOT) ? "enabled" : "disabled");

When all is good, no need to print anything out.

> +
> +	return 0;
> +}
> +
>  static int __init aspeed_socinfo_init(void)
>  {
>  	struct soc_device_attribute *attrs;
> @@ -148,6 +228,8 @@ static int __init aspeed_socinfo_init(void)
>  			attrs->revision,
>  			attrs->soc_id);
>  
> +	aspeed_bootinfo_init();

Why does this function return a value and yet you ignore it?


thanks,

greg k-h