Re: [microblaze-uclinux] Loadable module support for Petalinux w/MMU?

[Rod Campbell <rod@xxxxxxxxxxxxxxxxxx>]

Hi,

This may not be related, but I ran into a problem with pointers to 
strings getting clobbered in microblaze uClinux 2.4.  I posted to the 
group about this in June.  Basically, there was an array of string 
pointers and one of them was overlaid by another pointer.  At first I 
thought it was run-time corruption, but this appears to have happened in 
the conversion process from elf to binflt.  If I dumped the .elf object, 
the array looked OK, but if I dumped the equivalent flat file 
executable, the array was corrupted.

To get around this, I tracked down the source line that the overlaying 
pointer represented and changed it from "const unsigned char MyVar = 8;" 
to "unsigned char MyVar = 8;".  I know this doesn't solve what appears 
to me to be the actual problem, but no one else seems to have reported 
problems of this type. 

Rod Campbell  

Steven Hein wrote:
> John Williams wrote:
> > Hi Steve,
> >
> > Steven Hein wrote:
> >
> > > Does anyone have loadable kernel module support working in
> > > the Petalinux w/ the Microaze MMU enabled? I tried to build
> > > the kernel with module support enabled, and I got this
> > > compile error:
> >
> > This was discussed a couple of months ago, and I posted a patch.  It 
> > will be in the archives, but let us know if you are unable to track 
> > it down.
> >
> > cheers,
> Thanks John, I found it.
>
> After applying the patch, the printk's work.....however, I am now
> having troubles with strings that are statically initialized in a
> structure.     Here's a simple example:
>
>
>
> #include <linux/module.h>
> #include <linux/types.h>
>
> static struct attribute tstattr  = { .name = "tstattr", .mode = 0654, 
> .owner = THIS_MODULE };
>
> static void __exit
> hello_exit (void)
> {
>        return;
> }
>
> static int __init
> hello_init (void)
> {
>        printk ("name=|%s| mode=0%o\n", tstattr.name, tstattr.mode);
>
>        return 0;
> }
>
> module_init (hello_init);
> module_exit (hello_exit);
>
>
> When I load this module (compiled with mb-linux-gcc), I see:
>
> # insmod 
> /tmp/hello.ko                                                         
> name=|hello| mode=0654
>
> The value of tstattr.name is printed as "hello", not as "tstattr"
> which it should be!
> (Note that the string I see within the |'s varies depending on the
> complexity of the loadable module.    The original problem I
> was trying to debug was problems creating a sysfs file.    Based
> on the output in those cases, I could see that this isn't a simple
> printk problem, but a problem with the initialization of the
> string.)
>
>
> Can anyone offer any insight into this type of problem?
>
> Thanks,
> Steve
>
>
>
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