lkml.org 
[lkml]   [2010]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)
On 01/20/2010 11:57 AM, Peter Zijlstra wrote:
> On Wed, 2010-01-20 at 11:43 +0200, Avi Kivity wrote:
>
>> 1. Write a trace entry into shared memory, trap into the kernel on overflow.
>> 2. Trap if a condition is satisfied (fast watchpoint implementation).
>>
> So now you want to consume more of a process' address space to store
> trace data as well?

Yes. I know I'm bad.

> Not to mention that that process could wreck the
> trace data rendering it utterly unreliable.
>

It could, but it also might not. Are we going to deny high performance
tracing to users just because it doesn't work in all cases?

Note this applies to any kind of monitoring or debugging technology. A
process can be influenced by the debugger and render any debug info you
get out of it unreliable. One non-timing example is a process using a
checksum of its text as an input to some algorithm.

--
error compiling committee.c: too many arguments to function



\
 
 \ /
  Last update: 2010-01-20 13:25    [W:0.371 / U:0.784 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site