Experimental Physics and
Industrial Control System

Vesna Samardzic-Boban <[email protected]> · Wed, 17 Apr 2013 19:56:27 +1000

Hi Tim and Andrew,

Agree with Andrew it is a vxWorks bug in creat().
But it's easier (for me) to replace the line/creat() in saveData.c
    file= creat(tmpfile, O_RDWR);
with open() e.g.
#ifdef vxWorks
    file = open (tmpfile, O_CREAT | O_RDWR, 0666);
#else
    file = creat (tmpfile, O_RDWR);       /* if this is needed by other OS's*/
#endif
That way we do not depend on Wind River and their bug/fix.

REgards Vesna

________________________________________
From: Andrew Johnson [[email protected]]
Sent: Wednesday, 17 April 2013 1:31 AM
To: [email protected]
Cc: Tim Mooney; Vesna Samardzic-Boban
Subject: Re: sscan/ saveData problem with RW permission, and not an NFS issue

Hi Tim,

On 2013-04-16 Tim Mooney wrote:
> Thanks for the information.  I haven't tested sscan on vxWorks 6.9, though
> I'm told it works on vxWorks 6.8.  I don't think creat() uses O_RDRW as a
> file-permission mask, and I don't understand why open() would work while
> creat() does not.  I'm ok with making this change, but I'd like to
> understand it better first.

I don't think there's going to be any difference in the behavior between
VxWorks 6.8 and 6.9.  This is one of those things that I believe Wind River
got wrong very early in the life of VxWorks and it has never been fixed
properly.  This is from the documentation for creat():
    The parameter mode is set to O_RDONLY (0), O_WRONLY (1), or O_RDWR (2)
    for the duration of time the file is open. On NFS and POSIX compliant
    file systems such as HRFS, mode refers instead to the UNIX style file
    permission bits.
They even say that the second argument has a different meaning on different
file-systems, which means there is /no/ way to write code using this routine
that works properly on all file-systems, because you have to know what kind of
file-system it is to give the right parameter.
I recommend that creat() not be used in code that runs on vxWorks, and that
all calls to it be replaced with the equivalent open() call instead.  The
Linux man-page for creat() says:
    creat() is equivalent to open() with flags equal to
    O_CREAT|O_WRONLY|O_TRUNC.
You will also need to add the mode parameter 0666.
- Andrew
--
It is difficult to get a man to understand something, when his salary
depends upon his not understanding it. -- Upton Sinclair

________________________________________
From: Tim Mooney [[email protected]]
Sent: Wednesday, 17 April 2013 1:18 AM
To: Vesna Samardzic-Boban
Cc: [email protected]
Subject: Re: sscan/ saveData problem with RW permission, and not an NFS issue

Hi Vesna,

Thanks for the information.  I haven't tested sscan on vxWorks 6.9, though
I'm told it works on vxWorks 6.8.  I don't think creat() uses O_RDRW as a
file-permission mask, and I don't understand why open() would work while
creat() does not.  I'm ok with making this change, but I'd like to understand
it better first.

Tim

----- Original Message -----
> From: "Vesna Samardzic-Boban" <[email protected]>
> To: [email protected]
> Sent: Monday, April 15, 2013 8:52:30 PM
> Subject: sscan/ saveData problem with RW permission, and not an NFS issue
>
> Hi All,
>
>
> Found a problem as follows:
>
> Running a scan record on a vxWorks IOC and when entering 'File
> system' in scan_saveData.adl screen, an error message in the 'Save
> status' field follows:
> "RW permission denied !!!"
>
> At first I suspected NFS but after checking it found that my problem
> was in the sscan's saveData.c and/or VxWorks is 6.9
>
> Tried two versions of sscan, 2-6-6 and 2-8-2, they gave the same
> result as above. These two versions are same regarding the
> saveData.c and its function
>     checkRWpermission(char* path)
> and specifically the line
>
>     file= creat(tmpfile, O_RDWR);
>
> that creates test file "rix_" with file permissions 002 (because
> O_RDRW = 2)
> (O_RDRW is flag "Open for reading and writing" or File Access
> Options)
>
> The file permissions 002 become
> -------w-  in   terms of    rwxrwxrwx
> and hence the error "RW permission denied !!!"
>
> Found a solution by using vxWorks function open() instead of creat().
> open() - opens a file and optionally creates a file if it does not
> exist.
> open() - also offers a parameter for "mode" i.e. file permissions,
> which i set to 0x666 in the example below
>
>      file = open (tmpfile, O_CREAT | O_RDWR, 0666);
>
> Then scan data can be saved as expected.
>
> BTW
> saveData.c uses open() for creating 'subdirectory'.
>           fd = open (local_pathname, O_RDWR | O_CREAT,
>                            FSTAT_DIR | DEFAULT_DIR_PERM | 0775);
>
>
> Has anyone had similar problems ?
> Is this an sscan/saveData.c issue or vxWorks 6.9 issue (I do not have
> any other version of vxWorks) ?
> How about sscan/saveData on OS's other than vxWorks?
>
>
> Thanks Vesna
>
> P.S.
> In my vxWorks 6.9 and its ioLib.c, creat() does not offer file
> permissions (set to 0 as below):
> int creat
>     (
>     const char *name,           /* name of the file to create */
>     int         flag            /* file permissions */
>     )
>     {
>     return (ioCreateOrOpen (name, flag, 0, TRUE));
>     }

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System