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unexpected bahavior with module - relocation problem ?

DISCUSSION Matthias Fuchs 1 participant 2 messages May 8, 2002

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#0 lore raw

Hi all,

I got a little problem that I cannot really understand.
I wrote a little device driver for a 405 PPC board. The driver registers a miscdevice.

Normally all misc devices are listed under /proc/misc. My first attempt resulted in a /proc/misc looking like this:

# cat /proc/misc
187          <- "test" is missing here !
185 gpio

The code is attached. When I change the init stuff for the miscdevice structure a little bit (see below with WORKING defined), I got the expected bahavior.

Is this a relocation problem when loading the module ? In the two version the NAME string sits in different segments. Is there a way to fix the problem by a compiler switch ? Is this a PPC issue ? I noticed that the Linux rtc driver uses the same code as I do, but it does not have the problem. The difference is that my code is a lkm and mot compiled into the kernel.

Matthias

...

#define NAME "test"
#define MINOR 187

#ifdef WORKING
static char name[]=NAME;
#endif

static struct file_operations my_fops =
{
...
};

static struct miscdevice my_miscdev =
{
#ifdef WORKING
name: name, // results in correct bahavior
#else
name: NAME, // results in missing module name in /proc/misc
#endif
minor: MINOR,
fops: &my_fops
};

int __init my_init(void)
{
misc_register(&my_miscdev);
return 0;
}

void __exit my_exit(void)
{
misc_deregister(&my_miscdev);
}

module_init(my_init);
module_exit(my_exit);

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

#1 lore raw

Hi,

I found the problem. It seems to be a problem with the insmod tool in the busybox that I am using on my target (0.61pre from cvs).

Matthias

Quoted 60 lines · Matthias Fuchs

Hi all,

I got a little problem that I cannot really understand.
I wrote a little device driver for a 405 PPC board. The driver registers a miscdevice.

Normally all misc devices are listed under /proc/misc. My first attempt resulted in a /proc/misc looking like this:

# cat /proc/misc
187          <- "test" is missing here !
185 gpio

The code is attached. When I change the init stuff for the miscdevice structure
a little bit (see below with WORKING defined), I got the expected bahavior.

Is this a relocation problem when loading the module ? In the two version the NAME string
sits in different segments. Is there a way to fix the problem by a compiler switch ? Is this a PPC issue ?
I noticed that the Linux rtc driver uses the same code as I do, but it does not have the problem.
The difference is that my code is a lkm and mot compiled into the kernel.

Matthias

...

#define NAME "test"
#define MINOR 187

#ifdef WORKING
static char name[]=NAME;
#endif

static struct file_operations my_fops =
{
...
};

static struct miscdevice my_miscdev =
{
#ifdef WORKING
name: name, // results in correct bahavior
#else
name: NAME, // results in missing module name in /proc/misc
#endif
minor: MINOR,
fops: &my_fops
};

int __init my_init(void)
{
misc_register(&my_miscdev);
return 0;
}

Quoted 11 lines

void __exit my_exit(void)
{
misc_deregister(&my_miscdev);
}

module_init(my_init);
module_exit(my_exit);

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/