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

Kendrick Hamilton
2003-05-30T17:19:03Z

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 gcc@gcc.gnu.org I suppose, but here goes.
>
> [Cc'ed to linux-kernel@vger.kernel.org]
>
> 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

Hamilton@sedsystems.ca
Tel: (306) 933-1453
Fax: (306) 933-1486