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SubjectRe: [PATCH] tracer for sys_open() - sreadahead
On Mon, Feb 09, 2009 at 02:23:35PM +0100, Harald Hoyer wrote:
> Karel Zak wrote:
>> On Thu, Feb 05, 2009 at 03:44:42PM +0100, Harald Hoyer wrote:
>>> Ingo Molnar wrote:
>>>> * Pavel Machek <> 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.
> 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)...

yes, it'd be nice to support arbitrary number of connections and
rules per connection. (.. or export audit stuff to userspace by a
special pseudo filesystem (see cgroups, debugfs, ...)).


Karel Zak <>

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