Re: [PATCH] oprofile: disable write access to oprofilefs while profiler is running

[Maynard Johnson <maynardj@us.ibm.com>]

On 10/05/2010 11:33 AM, Robert Richter wrote:
> On 05.10.10 06:36:57, Robert Richter wrote:
>> Oprofile counters are setup when profiling is disabled. Thus, writing
>> to oprofilefs has no immediate effect. Changes are updated only after
>> oprofile is reenabled.
Robert, I don't have any issue with this patch except I'm not sure what problem 
it's fixing.  From my read of oprofile userland code, I don't see where 
profiling parameters are ever written to oprofilefs when profiling is active. 
Is your patch intended to guard against potential non-intentional cases 
occurring in userland code?  Or is there some case existing right now?

-Maynard
>>
>> To keep userland and kernel states synchronized, we now allow
>> configuration of oprofile only if profiling is disabled.  In this case
>> it checks if the profiler is running and then disables write access to
>> oprofilefs by returning -EBUSY. The change should be backward
>> compatible with current oprofile userland daemon.
>>
>> Cc: Maynard Johnson<maynardj@us.ibm.com>
>> Cc: William Cohen<wcohen@redhat.com>
>> Cc: Suravee Suthikulpanit<suravee.suthikulpanit@amd.com>
>> Signed-off-by: Robert Richter<robert.richter@amd.com>
>> ---
>>   drivers/oprofile/oprof.c          |   19 +++++--------------
>>   drivers/oprofile/oprof.h          |    2 +-
>>   drivers/oprofile/oprofile_files.c |    7 +++++--
>>   drivers/oprofile/oprofilefs.c     |    8 ++++++--
>>   4 files changed, 17 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
>> index b4a6857..a7ab09e 100644
>> --- a/drivers/oprofile/oprof.c
>> +++ b/drivers/oprofile/oprof.c
>> @@ -225,26 +225,17 @@ post_sync:
>>   	mutex_unlock(&start_mutex);
>>   }
>>
>> -int oprofile_set_backtrace(unsigned long val)
>> +int oprofile_set_ulong(unsigned long *addr, unsigned long val)
>>   {
>> -	int err = 0;
>> +	int err = -EBUSY;
>>
>>   	mutex_lock(&start_mutex);
>> -
>>   	if (oprofile_started) {
>
> I did a late change which I never should do. It should be:
>
> 	if (!oprofile_started) ...
>
> The concept remains the same.
>
> Updated patch below.
>
> Sorry,
>
> -Robert
>
>> -		err = -EBUSY;
>> -		goto out;
>> -	}
>> -
>> -	if (!oprofile_ops.backtrace) {
>> -		err = -EINVAL;
>> -		goto out;
>> +		*addr = val;
>> +		err = 0;
>>   	}
>> -
>> -	oprofile_backtrace_depth = val;
>> -
>> -out:
>>   	mutex_unlock(&start_mutex);
>> +
>>   	return err;
>>   }
>
> --
>
>  From 2d5710a2850eec24c54a1338ae5986963928cf8a Mon Sep 17 00:00:00 2001
> From: Robert Richter<robert.richter@amd.com>
> Date: Mon, 4 Oct 2010 21:09:36 +0200
> Subject: [PATCH] oprofile: disable write access to oprofilefs while profiler is running
>
> Oprofile counters are setup when profiling is disabled. Thus, writing
> to oprofilefs has no immediate effect. Changes are updated only after
> oprofile is reenabled.
>
> To keep userland and kernel states synchronized, we now allow
> configuration of oprofile only if profiling is disabled.  In this case
> it checks if the profiler is running and then disables write access to
> oprofilefs by returning -EBUSY. The change should be backward
> compatible with current oprofile userland daemon.
>
> Cc: Maynard Johnson<maynardj@us.ibm.com>
> Cc: William Cohen<wcohen@redhat.com>
> Cc: Suravee Suthikulpanit<suravee.suthikulpanit@amd.com>
> Signed-off-by: Robert Richter<robert.richter@amd.com>
> ---
>   drivers/oprofile/oprof.c          |   21 ++++++---------------
>   drivers/oprofile/oprof.h          |    2 +-
>   drivers/oprofile/oprofile_files.c |    7 +++++--
>   drivers/oprofile/oprofilefs.c     |    8 ++++++--
>   4 files changed, 18 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
> index b4a6857..f9bda64 100644
> --- a/drivers/oprofile/oprof.c
> +++ b/drivers/oprofile/oprof.c
> @@ -225,26 +225,17 @@ post_sync:
>   	mutex_unlock(&start_mutex);
>   }
>
> -int oprofile_set_backtrace(unsigned long val)
> +int oprofile_set_ulong(unsigned long *addr, unsigned long val)
>   {
> -	int err = 0;
> +	int err = -EBUSY;
>
>   	mutex_lock(&start_mutex);
> -
> -	if (oprofile_started) {
> -		err = -EBUSY;
> -		goto out;
> +	if (!oprofile_started) {
> +		*addr = val;
> +		err = 0;
>   	}
> -
> -	if (!oprofile_ops.backtrace) {
> -		err = -EINVAL;
> -		goto out;
> -	}
> -
> -	oprofile_backtrace_depth = val;
> -
> -out:
>   	mutex_unlock(&start_mutex);
> +
>   	return err;
>   }
>
> diff --git a/drivers/oprofile/oprof.h b/drivers/oprofile/oprof.h
> index 47e12cb..177b73d 100644
> --- a/drivers/oprofile/oprof.h
> +++ b/drivers/oprofile/oprof.h
> @@ -37,7 +37,7 @@ void oprofile_create_files(struct super_block *sb, struct dentry *root);
>   int oprofile_timer_init(struct oprofile_operations *ops);
>   void oprofile_timer_exit(void);
>
> -int oprofile_set_backtrace(unsigned long depth);
> +int oprofile_set_ulong(unsigned long *addr, unsigned long val);
>   int oprofile_set_timeout(unsigned long time);
>
>   #endif /* OPROF_H */
> diff --git a/drivers/oprofile/oprofile_files.c b/drivers/oprofile/oprofile_files.c
> index bbd7516..ccf099e 100644
> --- a/drivers/oprofile/oprofile_files.c
> +++ b/drivers/oprofile/oprofile_files.c
> @@ -79,14 +79,17 @@ static ssize_t depth_write(struct file *file, char const __user *buf, size_t cou
>   	if (*offset)
>   		return -EINVAL;
>
> +	if (!oprofile_ops.backtrace)
> +		return -EINVAL;
> +
>   	retval = oprofilefs_ulong_from_user(&val, buf, count);
>   	if (retval)
>   		return retval;
>
> -	retval = oprofile_set_backtrace(val);
> -
> +	retval = oprofile_set_ulong(&oprofile_backtrace_depth, val);
>   	if (retval)
>   		return retval;
> +
>   	return count;
>   }
>
> diff --git a/drivers/oprofile/oprofilefs.c b/drivers/oprofile/oprofilefs.c
> index 789a1a8..1944621 100644
> --- a/drivers/oprofile/oprofilefs.c
> +++ b/drivers/oprofile/oprofilefs.c
> @@ -91,16 +91,20 @@ static ssize_t ulong_read_file(struct file *file, char __user *buf, size_t count
>
>   static ssize_t ulong_write_file(struct file *file, char const __user *buf, size_t count, loff_t *offset)
>   {
> -	unsigned long *value = file->private_data;
> +	unsigned long value;
>   	int retval;
>
>   	if (*offset)
>   		return -EINVAL;
>
> -	retval = oprofilefs_ulong_from_user(value, buf, count);
> +	retval = oprofilefs_ulong_from_user(&value, buf, count);
> +	if (retval)
> +		return retval;
>
> +	retval = oprofile_set_ulong(file->private_data, value);
>   	if (retval)
>   		return retval;
> +
>   	return count;
>   }
>