linux-kernel - Re: [PATCH V4 01/20] rv: Add Runtime Verification (RV) interface

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Date:   Mon, 4 Jul 2022 21:49:14 +0200
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Gabriele Paoloni <gpaoloni@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH V4 01/20] rv: Add Runtime Verification (RV) interface

On 6/23/22 22:26, Steven Rostedt wrote:
> On Thu, 16 Jun 2022 10:44:43 +0200
> Daniel Bristot de Oliveira <bristot@...nel.org> wrote:

[ removing comments that I agreed and changed the code/log accordingly ]

>>
>>  "monitoring_on"
>>    - It is an on/off general switcher for monitoring. Note
>>    that it does not disable enabled monitors, but stop the per-entity
>>    monitors of monitoring the events received from the system.
>>    It resambles the "tracing_on" switcher.
> 
> You mean that the tracepoints are still attached, but the process of
> monitoring isn't doing anything?

correct, I am now mentioning it in the comment.
 
[...]

>> +static int disable_monitor(struct rv_monitor_def *mdef)
>> +{
>> +	if (mdef->monitor->enabled) {
>> +		mdef->monitor->enabled = 0;
>> +		mdef->monitor->stop();
>> +	}
>> +
>> +	mdef->enabled = 0;
> 
> What's the difference between mdef->enabled and mdef->monitor->enabled?

Ooops, the mdef->enabled is a leftover... removing mdef->enabled.

>> +	return 0;
>> +}
>> +

[...]

>> +static int create_monitor_dir(struct rv_monitor_def *mdef)
>> +{
>> +	struct dentry *root = get_monitors_root();
>> +	struct dentry *tmp;
>> +	const char *name = mdef->monitor->name;
>> +	int retval = 0;
>> +
>> +	mdef->root_d = rv_create_dir(name, root);
>> +
>> +	if (!mdef->root_d)
>> +		return -ENOMEM;
>> +
>> +	tmp = rv_create_file("enable", 0600,
> 
> I'd recommend make the modes (0600) into macros. I recently changed
> these for tracing, and having them hard coded was a pain.
> 
> #define RV_FILE_READ	0600
> 

Added:
#define RV_MODE_WRITE                   TRACE_MODE_WRITE
#define RV_MODE_READ                    TRACE_MODE_READ


>> +			     mdef->root_d, mdef,
>> +			     &interface_enable_fops);
>> +	if (!tmp) {
>> +		retval = -ENOMEM;
>> +		goto out_remove_root;
>> +	}
>> +
>> +	tmp = rv_create_file("desc", 0400,
> 
> Same here, and in all other cases.
> 
>> +			      mdef->root_d, mdef,
>> +			      &interface_desc_fops);
>> +	if (!tmp) {
>> +		retval = -ENOMEM;
>> +		goto out_remove_root;
>> +	}
>> +
>> +	return retval;
>> +
>> +out_remove_root:
>> +	rv_remove(mdef->root_d);
>> +	return retval;
>> +}

[...]
>> +static ssize_t
>> +enabled_monitors_write(struct file *filp, const char __user *user_buf,
>> +		      size_t count, loff_t *ppos)
>> +{
>> +	char buff[MAX_RV_MONITOR_NAME_SIZE+1];
>> +	struct rv_monitor_def *mdef;
>> +	int retval = -EINVAL;
>> +	bool enable = true;
>> +	char *ptr = buff;
>> +	int len;
>> +
>> +	if (count < 1 || count > MAX_RV_MONITOR_NAME_SIZE+1)
>> +		return -EINVAL;
>> +
>> +	memset(buff, 0, sizeof(buff));
>> +
>> +	retval = simple_write_to_buffer(buff, sizeof(buff)-1, ppos, user_buf,
>> +					count);
>> +	if (!retval)
>> +		return -EFAULT;
>> +
>> +	if (buff[0] == '!') {
>> +		enable = false;
>> +		ptr++;
>> +	}
>> +
>> +	len = strlen(ptr);
>> +	if (!len)
>> +		return count;
>> +	/*
>> +	 * remove \n
>> +	 */
>> +	ptr[len-1] = '\0';
> 
> Are you sure there's an '\n' here?
> 
> One could just do "write(fd, "monitor", 7)"
> 
> Perhaps use strim()

ack.

> 
>> +
>> +	mutex_lock(&rv_interface_lock);
>> +
>> +	retval = -EINVAL;
>> +
>> +	list_for_each_entry(mdef, &rv_monitors_list, list) {
>> +		if (strcmp(ptr, mdef->monitor->name) == 0) {
> 
> BTW, you could do:
> 
> 		if (strcmp(ptr, mdef->monitor->name) != 0)
> 			continue;
> 
> And then get rid of an extra indent below.
> 
>> +			/*
>> +			 * Monitor found!
>> +			 */
>> +			if (enable)
>> +				retval = enable_monitor(mdef);
>> +			else
>> +				retval = disable_monitor(mdef);
>> +
>> +			if (retval)
>> +				goto out;
> 
> Why not just break?
> 
> In fact, you could just do:
> 
> 			if (!retval)
> 				retval = count;
> 			break;

yep, it looks better.

-- Daniel