Re: how do you call userspace syscalls (e.g. sys_rename) from inside kernel
From: Luke Kenneth Casson Leighton (lkcl_at_lkcl.net)
Date: 10/08/04
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Date: Fri, 8 Oct 2004 16:35:23 +0100 To: Fabiano Ramos <ramos_fabiano@yahoo.com.br>
On Fri, Oct 08, 2004 at 10:07:04AM -0300, Fabiano Ramos wrote:
> On Fri, 2004-10-08 at 14:04 +0100, Luke Kenneth Casson Leighton wrote:
> > could someone kindly advise me on the location of some example code in
> > the kernel which calls one of the userspace system calls from inside the
> > kernel?
> >
> > alternatively if this has never been considered before, please could
> > someone advise me as to how it might be achieved?
> >
>
> you cannot do that. For every sys_xx there is a do_xx, that can
> be called from inside the kernel.
so, there's a do_rename (yes i found that and ISTRC that when
i used it i can't exactly remember what the problem was:
either i got an error code -14 or i got "warning symbol
do_rename not found" when my module was linked together,
even though it says EXPORT_SYMBOL(do_rename) in fs/namei.c,
so i was forced to cut/paste sys_rename)
and there's a do_open no there isn't, there's filp_open.
and a do_pread64 no there isn't i had to cut/paste sys_pread64
which was okay because it's pretty basic, just call vfs_read.
and a do_mkdir no there isn't so i had to cut/paste that.
basically what i am doing is writing a file system "proxy"
module which re-calls back into the filesystem with a prefix
onto the front of the pathname.
> > [p.s. i found asm/unistd.h, i found the macros syscall012345
> > etc., i believe i don't quite understand what these are for, and
> > may be on the wrong track.]
>
> These are are available for you to make syscalls from user mode
> without library support (usually that brand new syscall you added).
> They are basically wrappers that expand into C code. _syscallx,
> where x is the number of arguments the syscall needs.
so, it's for use the other way round. okay, thanks for keeping me off
a broken line of enquiry.
[oh, and i'll be abandoning this line of enquiry _entirely_ if i find
that supermount-ng can do the same job - namely manage to keep
userspace programs happy when users rip out media]
-- -- Truth, honesty and respect are rare commodities that all spring from the same well: Love. If you love yourself and everyone and everything around you, funnily and coincidentally enough, life gets a lot better. -- <a href="http://lkcl.net"> lkcl.net </a> <br /> <a href="mailto:lkcl@lkcl.net"> lkcl@lkcl.net </a> <br /> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
- Previous message: Brice Goglin: "Re: how do you call userspace syscalls (e.g. sys_rename) from inside kernel"
- In reply to: Fabiano Ramos: "Re: how do you call userspace syscalls (e.g. sys_rename) from inside kernel"
- Next in thread: Brian Gerst: "Re: how do you call userspace syscalls (e.g. sys_rename) from inside kernel"
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