Re: [PATCH] tracer for sys_open() - sreadahead

[Harald Hoyer <harald@redhat.com>]

Karel Zak wrote:
> On Thu, Feb 05, 2009 at 03:44:42PM +0100, Harald Hoyer wrote:
>> Ingo Molnar wrote:
>>> * Pavel Machek <pavel@suse.cz> wrote:
>>>
>>>> On Tue 2009-01-27 12:08:04, Kok, Auke wrote:
>>>>> This tracer monitors regular file open() syscalls. This is a fast
>>>>> and low-overhead alternative to strace, and does not allow or
>>>>> require to be attached to every process.
>>>>>
>>>>> The tracer only logs succesfull calls, as those are the only ones we
>>>>> are currently interested in, and we can determine the absolute path
>>>>> of these files as we log.
>>>> Maybe fanotify() should be used instead?
>>>>
>>>> Or maybe just plain strace? One slow boot should not really hurt...
>>> ptrace is out of question for good tracing because it's not a 
>>> transparent probe. (ptrace monopolizes the traced task - if we use that 
>>> then we break regular strace usage.)
>>>
>>> 	Ingo
>> Can strace can be used on init?
>>
>> $ man strace
>> ...
>>        On Linux, exciting as it would be, tracing the init process is forbidden.
>> ...
>>
>> Any hope getting _any_ mechanism in the kernel??
> 
>  Do you remember Linux Auditing System? That's RH's baby with hooks to
>  all relevant syscalls. It would be better to fix/improve the current
>  kernel mechanisms that introduce a new one.
> 
>     Karel
> 


Yes, I do remember it, because this is how the current fedora readahead gathers 
its data. It delays the audit daemon, because there is no clean way to hook into 
the stream. I asked to add a second "channel" (auditd wants the kernel socket 
for its own)...