linux-kernel - Re: [PATCH v4 10/14] gunyah: sysfs: Add node to describe supported features

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1f599b97-9242-3844-4372-1610948f4baf@quicinc.com>
Date:   Sun, 2 Oct 2022 16:30:30 -0700
From:   Jeff Johnson <quic_jjohnson@...cinc.com>
To:     Joe Perches <joe@...ches.com>,
        Elliot Berman <quic_eberman@...cinc.com>,
        Bjorn Andersson <quic_bjorande@...cinc.com>
CC:     Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Andy Gross <agross@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        "Mark Rutland" <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        "Marc Zyngier" <maz@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 10/14] gunyah: sysfs: Add node to describe supported
 features

On 9/29/2022 12:36 AM, Joe Perches wrote:
> On Wed, 2022-09-28 at 12:56 -0700, Elliot Berman wrote:
>> Add a sysfs node to list the features that the Gunyah hypervisor and
>> Linux supports. For now, Linux support cspace (capability IDs) and
>> message queues, so only report those..
> []
>> diff --git a/drivers/virt/gunyah/sysfs.c b/drivers/virt/gunyah/sysfs.c
> []
>> @@ -25,9 +25,24 @@ static ssize_t variant_show(struct kobject *kobj, struct kobj_attribute *attr, c
>>   }
>>   static struct kobj_attribute variant_attr = __ATTR_RO(variant);
>>   
>> +static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr, char *buffer)
>> +{
>> +	int len = 0;
>> +
>> +	if (GH_IDENTIFY_PARTITION_CSPACE(gunyah_api.flags))
>> +		len += sysfs_emit_at(buffer, len, "cspace ");
>> +	if (GH_IDENTIFY_MSGQUEUE(gunyah_api.flags))
>> +		len += sysfs_emit_at(buffer, len, "message-queue ");
>> +
>> +	len += sysfs_emit_at(buffer, len, "\n");
>> +	return len;
>> +}
> 
> It's generally nicer to avoid unnecessary output spaces.
> 
> Perhaps:
> 
> {
> 	int len = 0;
> 
> 	if (GH_IDENTIFY_PARTITION_CSPACE(gunyah_api.flags))
> 		len += sysfs_emit_at(buffer, len, "cspace");
> 	if (GH_IDENTIFY_MSGQUEUE(gunyah_api.flags)) {
> 		if (len)
> 			len += sysfs_emit_at(buffer, len, " ");
> 		len += sysfs_emit_at(buffer, len, "message-queue");
> 	}
> 
> 	len += sysfs_emit_at(buffer, len, "\n");
> 
> 	return len;
> }
> 

that approach seems ok for 2 features, but imo doesn't scale for more.
I like the original code with one exception:

	if (GH_IDENTIFY_PARTITION_CSPACE(gunyah_api.flags))
		len += sysfs_emit_at(buffer, len, "cspace ");
	if (GH_IDENTIFY_MSGQUEUE(gunyah_api.flags))
		len += sysfs_emit_at(buffer, len, "message-queue ");

	/* overwrite last trailing space */
	if (len)
		len--;

	len += sysfs_emit_at(buffer, len, "\n");
	return len;