linux-kernel - Re: [EXTERNAL] Re: [PATCH v5 1/2] remoteproc: Introduce sysfs_read

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Date:   Fri, 4 Mar 2022 09:53:46 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Puranjay Mohan <p-mohan@...com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Kishon Vijay Abraham I <kishon@...com>, vigneshr@...com,
        s-anna@...com, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [EXTERNAL] Re: [PATCH v5 1/2] remoteproc: Introduce
 sysfs_read_only flag

On Thu, Mar 03, 2022 at 01:30:08PM +0530, Puranjay Mohan wrote:
> Hi Bjorn,
> Hi Mathieu,
> 
> When is this series expected to be applied?
> 
> I am going to post another series titled "PRU Consumer API".
> One patch from that series depends on this "Introduce sysfs_read_only
> flag" patch.
> 
> Please let me know so I can rebase and post that series.

Applied and pushed.

Thanks,
Mathieu

> 
> Thanks,
> Puranjay Mohan
> 
> On 18/02/22 11:24, Bjorn Andersson wrote:
> > On Thu 17 Feb 21:00 PST 2022, Kishon Vijay Abraham I wrote:
> > 
> >>
> >>
> >> On 16/02/22 1:42 pm, 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 'coredump'
> >>> file is used to set the coredump configuration. 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 make the remoteproc sysfs files read only by
> >>> introducing a state flag 'sysfs_read_only' 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 make the sysfs
> >>> entries read only when 'sysfs_read_only' flag is set.
> >>>
> >>> Signed-off-by: Puranjay Mohan <p-mohan@...com>
> >>> Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> >>> ---
> >>> Changes in v4->v5:
> >>> Rename deny_sysfs_ops to sysfs_read_only.
> >>> Make coredump readonly with other files.
> >>>
> >>> 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 | 19 ++++++++++++++++++-
> >>>  include/linux/remoteproc.h            |  2 ++
> >>>  2 files changed, 20 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> >>> index ea8b89f97d7b..abf0cd05d5e1 100644
> >>> --- a/drivers/remoteproc/remoteproc_sysfs.c
> >>> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> >>> @@ -230,6 +230,22 @@ 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->sysfs_read_only && (attr == &dev_attr_recovery.attr ||
> >>> +				       attr == &dev_attr_firmware.attr ||
> >>> +				       attr == &dev_attr_state.attr ||
> >>> +				       attr == &dev_attr_coredump.attr))
> >>> +		mode = 0444;
> >>
> >> Nitpick: use S_IRUGO instead of 0444.
> >>
> > 
> > Thanks for the suggestion Kishon, but I like 0444, it has direct meaning
> > to me.
> > 
> > So unless there's some directive to use S_I*** throughout the kernel I
> > would prefer this.
> > 
> > Regards,
> > Bjorn
> > 
> >> Thanks,
> >> Kishon
> >>> +
> >>> +	return mode;
> >>> +}
> >>> +
> >>>  static struct attribute *rproc_attrs[] = {
> >>>  	&dev_attr_coredump.attr,
> >>>  	&dev_attr_recovery.attr,
> >>> @@ -240,7 +256,8 @@ 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..93a1d0050fbc 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
> >>> + * @sysfs_read_only: flag to make remoteproc sysfs files read only
> >>>   * @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 sysfs_read_only;
> >>>  	struct list_head dump_segments;
> >>>  	int nb_vdev;
> >>>  	u8 elf_class;
> >>>