svn commit: r327423 - in head/sys: kern sys

[Gleb Smirnoff]

  Hi Colin,

On Sun, Dec 31, 2017 at 09:21:01AM +0000, Colin Percival wrote:
C> Author: cperciva
C> Date: Sun Dec 31 09:21:01 2017
C> New Revision: 327423
C> URL: https://svnweb.freebsd.org/changeset/base/327423
C> 
C> Log:
C>   Code for recording timestamps of events, especially function entries/exits.
C>   This is a very primitive system, intended for use in measuring performance
C>   during the early system boot, before more sophisticated tools like DTrace
C>   or infrastructure like kernel memory allocation and mutexes are available.
C>   
C>   Because this code records pointers to strings rather than copying strings
C>   (in order to keep the memory usage more manageable), if a kernel module is
C>   unloaded after logging an event, Bad Things can happen.  Users are advised
C>   to not do that.
C>   
C>   Since cycle counts from the early kernel boot are used as an initial entropy
C>   source, publishing this information to userland could result in inadequate
C>   entropy being kept private to the kernel RNG.  Users are advised to not
C>   enable this on systems with untrusted users.
C>   
C>   Discussed on:	freebsd-current

Sorry if my question is too lame and late. Why can't you use ktr(4) tracer
for that purpose? The discussion on freebsd-current also doesn't have answer.

-- 
Gleb Smirnoff