linux-kernel - Re: [PATCH v2 5/6] printk: insert newline in devkmsg

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Date:	Fri, 18 Jul 2014 09:02:18 -0500
From:	Alex Elder <elder@...aro.org>
To:	Petr Mládek <pmladek@...e.cz>
CC:	akpm@...ux-foundation.org, bp@...e.de, john.stultz@...aro.org,
	jack@...e.cz, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/6] printk: insert newline in devkmsg_read()

On 07/18/2014 06:45 AM, Petr Mládek wrote:
> On Thu 2014-07-17 09:09:10, Alex Elder wrote:
>> If a log record has LOG_PREFIX set, its predecessor record should be
>> terminated if it was marked LOG_CONT.  In devkmsg_read(), this
>> condition was being ignored, which would lead to such records
>> showing up combined when reading /dev/kmsg.  Fix this oversight.
>>
>> Reported-by: Petr Mládek <pmladek@...e.cz>
>> Signed-off-by: Alex Elder <elder@...aro.org>
>> ---
>>  kernel/printk/printk.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index e5ee1cb..3174ba9 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c
>> @@ -575,6 +575,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
>>  	char cont;
>>  	size_t len;
>>  	ssize_t ret;
>> +	bool insert_newline;
>>  
>>  	if (!user)
>>  		return -EBADF;
>> @@ -626,7 +627,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
>>  	else
>>  		cont = '-';
>>  
>> -	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
>> +	/* Insert a newline if we're terminating the previous record
>> early */
> 
> More correct description would be:
> 
> 	/* Insert a newline if the previous line was not terminated properly */

I will change it as you suggest.

> 
>> +	insert_newline = (user->prev & LOG_CONT) && (msg->flags & LOG_PREFIX);
>> +	len = sprintf(user->buf, "%s%u,%llu,%llu,%c;",
>> +		      insert_newline ? "\n" : "",
>>  		      (msg->facility << 3) | msg->level,
>>  		      user->seq, ts_usec, cont);
>>  	user->prev = msg->flags;
> 
> Please, do similar change also in msg_print_text() that would fix also
> syslog(). Note that syslog is the place where we stopped to disable
> prefix when there was continuous line before.

I will do this, as you will see in v3 which I plan to post in a
few hours.  (Note that this touches a spot where I have yet another
minor bug fix that I have not yet posted...  Oh well.)

					-Alex

> Best Regards.
> Petr
> 

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