On Thu, Aug 11, 2011 at 1:50 PM, Jeff Haran [off-list ref] wrote:

quoted

-----Original Message-----
From: kernelnewbies-bounces at kernelnewbies.org [mailto:kernelnewbies-
bounces at kernelnewbies.org] On Behalf Of william douglas
Sent: Thursday, August 11, 2011 1:23 PM
To: kernelnewbies at kernelnewbies.org
Subject: SYSLOG_ACTION_READ_ALL question

Hello all,

I'm trying to figure out why the do_syslog code in kernel/printk.c is
using put_user instead of copy_to_user.

I *THINK* this has something to do with copy_to_user not being
well-behaved in other than process context and since printk() gets
called in all contexts, it wouldn't be a safe operation.
But don't take my word for it.

Well from what I understand, copy_to_user doesn't work in interrupt
context for example as there is no user space necessarily to copy to.
In this case we have a __user buffer to copy back to and
__copy_to_user looks sane for the work load so I'm still unsure.