linux-kernel - Re: [PATCH v4 1/2] remoteproc: Introduce deny_sysfs

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Message-ID: <20220210184802.GB3603040@p14s>
Date:   Thu, 10 Feb 2022 11:48:02 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Puranjay Mohan <p-mohan@...com>
Cc:     puranjay12@...il.com, kishon@...com, vigneshr@...com,
        s-anna@...com, bjorn.andersson@...aro.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 1/2] remoteproc: Introduce deny_sysfs_ops flag

Hi Puranjay,

On Wed, Feb 09, 2022 at 02:33:41PM +0530, Puranjay Mohan wrote:
> The remoteproc framework provides sysfs interfaces for changing
> the firmware name and for starting/stopping a remote processor
> through the sysfs files 'state' and 'firmware'. The 'recovery'
> sysfs file can also be used similarly to control the error recovery
> state machine of a remoteproc. These interfaces are currently
> allowed irrespective of how the remoteprocs were booted (like
> remoteproc self auto-boot, remoteproc client-driven boot etc).
> These interfaces can adversely affect a remoteproc and its clients
> especially when a remoteproc is being controlled by a remoteproc
> client driver(s). Also, not all remoteproc drivers may want to
> support the sysfs interfaces by default.
> 
> Add support to deny the sysfs state/firmware/recovery change by
> introducing a state flag 'deny_sysfs_ops' that the individual
> remoteproc drivers can set based on their usage needs. The default
> behavior is to allow the sysfs operations as before.
> 
> Implement attribute_group->is_visible() to hide the sysfs
> state/firmware/recovery entries when deny_sysfs_ops flag is set.
> 
> Signed-off-by: Puranjay Mohan <p-mohan@...com>
> ---
> Changes in v3->v4:
> Use mode = 0444 in rproc_is_visible() to make the sysfs entries
> read-only when the deny_sysfs_ops flag is set.
> ---
>  drivers/remoteproc/remoteproc_sysfs.c | 18 +++++++++++++++++-
>  include/linux/remoteproc.h            |  2 ++
>  2 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> index ea8b89f97d7b..da2d0eecfa44 100644
> --- a/drivers/remoteproc/remoteproc_sysfs.c
> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> @@ -230,6 +230,21 @@ static ssize_t name_show(struct device *dev, struct device_attribute *attr,
>  }
>  static DEVICE_ATTR_RO(name);
>  
> +static umode_t rproc_is_visible(struct kobject *kobj, struct attribute *attr,
> +				int n)
> +{
> +	struct device *dev = kobj_to_dev(kobj);
> +	struct rproc *rproc = to_rproc(dev);
> +	umode_t mode = attr->mode;
> +
> +	if (rproc->deny_sysfs_ops && (attr == &dev_attr_recovery.attr ||
> +				      attr == &dev_attr_firmware.attr ||
> +				      attr == &dev_attr_state.attr))

I was wondering if we should also add coredump to this group to make it an all
or nothing option (name is already read only).

> +		mode = 0444;

Much better.

> +
> +	return mode;
> +}
> +
>  static struct attribute *rproc_attrs[] = {
>  	&dev_attr_coredump.attr,
>  	&dev_attr_recovery.attr,
> @@ -240,7 +255,8 @@ static struct attribute *rproc_attrs[] = {
>  };
>  
>  static const struct attribute_group rproc_devgroup = {
> -	.attrs = rproc_attrs
> +	.attrs = rproc_attrs,
> +	.is_visible = rproc_is_visible,
>  };
>  
>  static const struct attribute_group *rproc_devgroups[] = {
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index e0600e1e5c17..3849c66ce38f 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -523,6 +523,7 @@ struct rproc_dump_segment {
>   * @table_sz: size of @cached_table
>   * @has_iommu: flag to indicate if remote processor is behind an MMU
>   * @auto_boot: flag to indicate if remote processor should be auto-started
> + * @deny_sysfs_ops: flag to not permit sysfs operations on state, firmware and recovery
>   * @dump_segments: list of segments in the firmware
>   * @nb_vdev: number of vdev currently handled by rproc
>   * @elf_class: firmware ELF class
> @@ -562,6 +563,7 @@ struct rproc {
>  	size_t table_sz;
>  	bool has_iommu;
>  	bool auto_boot;
> +	bool deny_sysfs_ops;

Wouldn't "sysfs_read_only" make more sense?


With or without the above and for this set:

Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>

>  	struct list_head dump_segments;
>  	int nb_vdev;
>  	u8 elf_class;
> -- 
> 2.17.1
>