linux-kernel - Re: create a file in kernel mode. help please!

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Date:	Mon, 21 Jan 2008 09:44:07 -0300
From:	"Rafael Sisto" <rafael.sisto@...il.com>
To:	Joe <zentrale.at.work@...il.com>
Cc:	"Linux kernel" <linux-kernel@...r.kernel.org>
Subject: Re: create a file in kernel mode. help please!

Thanks Joe for the answer! I will find another work around for my problem, then!

greetings, Rafael Sisto.

On Jan 21, 2008 5:21 AM, Joe <zentrale.at.work@...il.com> wrote:
> Hi Rafael.
>
> Probably you haven't got any answers yet because you should NEVER EVER
> (i repeat: NEVER EVER, not even in college projects) go for file I/O in
> the kernel. You might want to think the whole thing over one or two
> times, i think.
>
> If it comes to you that it is absolutely necessary (i repeat again:
> ABSOLUTELY NECESSARY, like a solution to feed the world) then you might
> google for some ancient FAQ of Greg (K-H) (i think he was) where he
> tries to give a little more details about this kind of problem, and also
> gives a possible solution, IIRC. Sorry that i don't remember the exact
> page/adress anymore, for i intend never to look at it again.
>
> Greetz
> Joe
>
> Rafael Sisto schrieb:
>
> > Hi there,
> > obviously this is a newbie question, but I couldn't find any
> > documentation on how to do it.. I tried several ways but couldnt do
> > it.
> > I designed a system call, so a user will call it, and a new file will
> > be created ('/tmp/filexx'). After that, I have another system call,
> > that will map the file into the maps of the user process. The idea is
> > the same as IPC...
> >
> > I managed to create the file with this function (in the first system call):
> >         fd = filp_open(path, O_CREAT | O_RDWR , 777);
> >
> > After that, the user will call another system call, and it will map
> > this file to the process maps.
> > something like this:
> >          filp_open(route, O_RDWR,0 );
> >          do_mmap(fp, 0, tamano, PROT_READ | PROT_WRITE | PROT_EXEC,
> > MAP_SHARED, 0);
> >
> > After I call the second system call, the user tries to access the
> > memory, but gets the message "Bus Error".
> > I tried to manually create a file with vi, and then use the second
> > system call, and worked perfectly. I could use the shared memory
> > without problems.
> >
> > The problems seems to be in the first system call (with filp_open),
> > when I try to create a new file... Can somebody suggest me something,
> > on how I could fix this issue?? It is very important because it is for
> > a college projects.
> >
> > Greetings, and thanks in advance for the answers.
> > Rafael Sisto - Uruguay.-
> > --
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> >
>
>
> --
> Sepp "ZaP" Holzmayr
>
> please reply to:
> zentrale.at.work@...il.com
>
> watch out for:
> www.rocksociety.de
>
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