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Date:   Mon, 18 May 2020 09:45:57 +0200
From:   =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= <mirq-linux@rere.qmqm.pl>
To:     Dmitry Osipenko <digetx@gmail.com>
Cc:     Jens Axboe <axboe@kernel.dk>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        David Heidelberg <david@ixit.cz>,
        Peter Geis <pgwipeout@gmail.com>,
        Stephen Warren <swarren@wwwdotorg.org>,
        Nicolas Chauvet <kwizart@gmail.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Billy Laws <blaws05@gmail.com>,
        Nils =?iso-8859-2?Q?=D6stlund?= <nils@naltan.com>,
        Christoph Hellwig <hch@infradead.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        linux-tegra@vger.kernel.org, linux-block@vger.kernel.org,
        Andrey Danin <danindrey@mail.ru>,
        Gilles Grandou <gilles@grandou.net>,
        Ryan Grachek <ryan@edited.us>, linux-mmc@vger.kernel.org,
        linux-kernel@vger.kernel.org, Steve McIntyre <steve@einval.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        linux-efi <linux-efi@vger.kernel.org>
Subject: Re: [PATCH v5 6/6] soc/tegra: Expose Boot Configuration Table via
 sysfs
Message-ID: <20200518074557.GA12306@qmqm.qmqm.pl>
References: <20200516153644.13748-1-digetx@gmail.com>
 <20200516153644.13748-7-digetx@gmail.com>
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On Sat, May 16, 2020 at 06:36:44PM +0300, Dmitry Osipenko wrote:
> It's quite useful to have unencrypted BCT exposed to userspace for
> debugging purposes, so let's expose it via sysfs.  The BCT data will be
> present in '/sys/tegra/boot_config_table' binary file if BCT is available.
[...]
> +/*
> + * spare_bct[] will be released once kernel is booted, hence not wasting
> + * kernel space if BCT is missing. The tegra_bct can't be allocated during
> + * of BCT setting up because it's too early for the slab allocator.
> + */
> +static u8 spare_bct[SZ_8K] __initdata;
> +static u8 *tegra_bct;
> +
> +static ssize_t boot_config_table_read(struct file *filp,
> +				      struct kobject *kobj,
> +				      struct bin_attribute *bin_attr,
> +				      char *buf, loff_t off, size_t count)
> +{
> +	memcpy(buf, tegra_bct + off, count);
> +	return count;
> +}
> +static BIN_ATTR_RO(boot_config_table, 0);
> +
> +static int __init tegra_bootdata_bct_sysfs_init(void)
> +{
> +	if (!bin_attr_boot_config_table.size)
> +		return 0;
> +
> +	tegra_bct = kmalloc(GFP_KERNEL, bin_attr_boot_config_table.size);
> +	if (!tegra_bct)
> +		return -ENOMEM;
> +
> +	memcpy(tegra_bct, spare_bct, bin_attr_boot_config_table.size);
> +
> +	return sysfs_create_bin_file(tegra_soc_kobj,
> +				     &bin_attr_boot_config_table);

Should we consider freeing the table if sysfs registration fails?

> +}
> +late_initcall(tegra_bootdata_bct_sysfs_init)
> +
> +void __init tegra_bootdata_bct_setup(void __iomem *bct_ptr, size_t bct_size)
> +{
> +	memcpy_fromio(spare_bct, bct_ptr, bct_size);
> +	bin_attr_boot_config_table.size = bct_size;
[...]

The size isn't checked anywhere. How the maximum is obtained? At least
a comment would be good if the 8k limit is guaranteed by other means.

Best Regards,
Micha? Miros?aw