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

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Date:   Wed, 16 Feb 2022 13:35:07 +0530
From:   Puranjay Mohan <p-mohan@...com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     <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: [EXTERNAL] Re: [PATCH v4 1/2] remoteproc: Introduce
 deny_sysfs_ops flag

Hi Mathieu,

On 11/02/22 00:18, Mathieu Poirier wrote:
> 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).

I have sent a v5 where I have added coredump to this.

> 
>> +		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?

I agree, I have renamed it to sysfs_read_only in v5 patch

> 
> 
> With or without the above and for this set:
> 
> Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>

Thanks.
Puranjay Mohan

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