proper way to annotate kernel use of sys_xxx?

proper way to annotate kernel use of sys_xxx?

[Roland Dreier]

What is the correct way to annotate kernel code that calls a sys_xxx
function that expects a __user pointer as an argument?

To give a concrete example, sparse (among lots of other warnings for
do_mounts.c) says:

	init/do_mounts.c:69:16: warning: incorrect type in argument 1 (different address spaces)
	init/do_mounts.c:69:16:    expected char const [noderef] *filename<asn:1>
	init/do_mounts.c:69:16:    got char [addressable] *<noident>

The code in question is the following:

	char path[64];

	/* ... */

	sprintf(path, "/sys/block/%s/dev", name);
	fd = sys_open(path, 0, 0);                 /* LINE 69 */

This is an abuse of sys_open(), but we know it's OK.  Is the right way
to shut up sparse to just change it to:

	fd = sys_open((const char __user *) path, 0, 0);

Thanks,
  Roland

Re: proper way to annotate kernel use of sys_xxx?

[Arnd Bergmann]

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On Dienstag, 5. Oktober 2004 07:28, Roland Dreier wrote:
> This is an abuse of sys_open(), but we know it's OK.  Is the right way
> to shut up sparse to just change it to:
> 
>         fd = sys_open((const char __user *) path, 0, 0);
> 
No, that's wrong, see 
http://marc.theaimsgroup.com/?l=linux-kernel&m=108697882525067 ;-)

In this case, you can easily convert the calls to use
filp_open/vfs_read/filp_close, though I'm not sure if that's
the correct solution either.

	Arnd <><

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Re: proper way to annotate kernel use of sys_xxx?

[Roland Dreier]

    Arnd> In this case, you can easily convert the calls to use
    Arnd> filp_open/vfs_read/filp_close, though I'm not sure if that's
    Arnd> the correct solution either.

For the do_mounts.c code, I see how the call to sys_open() could be
replaced with a call to filp_open().  However, vfs_read() still takes
a __user pointer for its buffer argument -- in fact, even the
filesystem .aio_read method takes a __user pointer.  So I'm not sure
how this code should be fixed.

Thanks,
  Roland