Xorg input thread (2)
vignatti at c3sl.ufpr.br
Tue Jul 17 18:15:48 PDT 2007
Continuing with this work...
Keith Packard escreveu:
> On Mon, 2007-07-09 at 03:38 -0300, Tiago Vignatti wrote:
>> How easily I could identify these functions? I think that I must dig
>> more this way and study these ELF tricks. Keith, could you please tell
>> more about it or point me something? Some docs would be good.
> It should be fairly easy to statically examine the code to determine
> which functions are related to mouse/cursor echoing. If you want an
> automatic mechanism, you might look at the -finstrument-functions
> compiler option.
Okay. I'm using that asm inline code to get the start and the end of the
section which is responsible for the mouse and then locking it with
mlock(). But now I'm stucked trying to know what exactly functions and
datas to lock.
It's very hard to 'automatically' examine all data and text code 
that deals with the mouse movements using -finstrument-functions just
like Keith said (just to have an idea, until arriving in the Dispatch()
we have about 240000 function calls!). What remains is try to examine
the code 'statically', which IMHO is hard. Hard because even if we
minutely trace the code, we'll forget some global data and simple
functions (like xfree, for instance). Well, my attempt to do this
statically failed. So yesterday I spent some time trying to figure out a
better way to deal with this issue.
I thought that a userspace tool that prints something when a page fault
occurs is good enough. Google tells me that 'truss' with '-m fltpage'
arg does exactly what we need [2, 3]. But the problem is that it doesn't
exists a port for Linux. Neither strace has the 'fltpage' similar
truss's option. Then I dig a little more and found Ulrich Drepper's
pagein tool . My simple tests here demonstrates that this tool does
not print a page that isn't hit a twice in memory (I already mailed him
to obtain more infos about it).
So, you guys understand where we are? I really want to avoid the kernel
traps which tells when a page fault occurs. Also, maybe someone here
could point me mailing lists or someone to give tips about this kind of
problem. And please, post your comments.
Thanks a lot!
 Just to be sure, We need to put only global data and functions
(text) inside the separate ELF sections? So it's one section for
functions and other one to data? We don't need to worry with local
variables? And the dynamic allocated variables?
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