Re: Problem Installing Linux Kernel Module compiled with gcc-3.2.x

[Kendrick Hamilton]

I have been manually recompillng the module and kernel to ensure they are 
both compiled with the same version of gcc. When I do switch gcc versions, 
I cp .config to config, make mrproper, cp config .config, make dep, make 
all modules modules_install install; reboot; make clean on my driver the 
make it.

 On Fri, 30 May 2003, Bernd Jendrissek wrote:

> Not *exactly* on-topic for [e-mail] I suppose, but here goes.
> 
> [Cc'ed to [e-mail]]
> 
> On Fri, May 30, 2003 at 09:26:51AM -0600, Kendrick Hamilton wrote:
> > 	I have a module for a custom developped PCI card. The device 
> > driver is written for the Linux 2.4 series kernels. When I build the 
> > module and the Linux kernel with gcc-2.95.3, the module installs 
> > correctly. When I build the module and the Linux kernel with gcc-3.2.3 
> > (also other gcc-3.2.x), the module installs but the Linux kernel crashes 
> > in random places outside of the module. Do you have any suggestions of 
> > what to look for? I can email you the complete module source code. I have 
> > not tried gcc-3.3 because I cannot compile the current Linux kernel with 
> > it (there is a known bug that is being fixed and should be out in 
> > Linux-2.4.21).
> 
> Been there, done that, got the T-shirt.  I was lucky: while my module
> installed, it broke in a fairly harmless way.  (It just didn't work; it
> didn't screw with my system.)
> 
> If you look at linux/include/linux/spinlock.h, you'll see:
> 
> /*
>  * Your basic spinlocks, allowing only a single CPU anywhere
>  *
>  * Most gcc versions have a nasty bug with empty initializers.
>  */
> #if (__GNUC__ > 2)
>   typedef struct { } spinlock_t;
>   #define SPIN_LOCK_UNLOCKED (spinlock_t) { }
> #else
>   typedef struct { int gcc_is_buggy; } spinlock_t;
>   #define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
> #endif
> 
> There are a couple of spinlock_t's (directly or through other structs) in
> the task_struct.  So when your module accesses parts of the "current"
> task_struct beyond the first spinlock_t, you better hope it's reading and
> not writing (which was the case with my module).
> 
> I bet your module modifies "current".
> 
> Hmm, actually I thought the kernel had a mechanism to prevent a GCC 3.x
> module from being loaded into a GCC 2.x kernel and vice versa?
> 

-- 
Kendrick Hamilton E.I.T.
SED Systems, a division of Calian Ltd.
18 Innovation Blvd.
PO Box 1464
Saskatoon, Saskatchewan
Canada
S7N 3R1

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