Re: Trying to convert old modules to newer kernels

From: linux-os (Dick Johnson)
Date: Thu Dec 20 2007 - 11:13:37 EST


On Thu, 20 Dec 2007, Lennart Sorensen wrote:

> On Wed, Dec 19, 2007 at 03:56:45PM -0500, linux-os (Dick Johnson) wrote:
>>
>> On Wed, 19 Dec 2007, Lennart Sorensen wrote:
>>
>>> On Wed, Dec 19, 2007 at 03:10:28PM -0500, linux-os (Dick Johnson) wrote:
>>>>
>>>>
>>>> Here is a so-called BUG when trying to insert the following
>>>> module into the kernel (2.6.22.1).
>>>>
>>>>
>>>> BUG: unable to handle kernel paging request at virtual address 6814ec83
>>>> printing eip:
>>>> c016d013
>>>> *pde = 00000000
>>>> Oops: 0000 [#1]
>>>> PREEMPT SMP
>>>> Modules linked in: MemDev parport_pc lp parport nfsd exportfs lockd sunrpc iptable_filter ip_tables x_tables e1000 e100 mii nls_cp437 msdos fat dm_mod usbhid ff_memless uhci_hcd ehci_hcd video container button battery ac rtc ipv6 ext3 jbd ata_piix libata aic7xxx scsi_transport_spi sd_mod scsi_mod
>>>> CPU: 0
>>>> EIP: 0060:[<c016d013>] Not tainted VLI
>>>> EFLAGS: 00010046 (2.6.22.1 #2)
>>>> EIP is at kmem_cache_alloc+0x23/0x80
>>>> eax: 00000000 ebx: 00000246 ecx: f8913300 edx: 6814ec83
>>>> esi: 00000000 edi: f8913000 ebp: ef27e000 esp: ef27ff74
>>>> ds: 007b es: 007b fs: 00d8 gs: 0033 ss: 0068
>>>> Process insmod (pid: 4593, ti=ef27e000 task=f614f550 task.ti=ef27e000)
>>>> Stack: f8913300 00000000 00000000 f8913013 f7fff880 000000d0 00000000 ef27e000
>>>> c012b907 ffffffff 00000000 c0140279 bffedc07 bffedc08 0807a018 00000000
>>>> c0102b82 0807a018 000018c9 0807a008 00000000 00000000 bffeabc8 00000080
>>>> Call Trace:
>>>> [<f8913013>] init_module+0x13/0x48 [MemDev]
>>>> [<c012b907>] blocking_notifier_call_chain+0x17/0x20
>>>> [<c0140279>] sys_init_module+0xd9/0x140
>>>> [<c0102b82>] sysenter_past_esp+0x5f/0x85
>>>> =======================
>>>> Code: 90 8d b4 26 00 00 00 00 83 ec 0c f6 c2 10 89 74 24 04 89 d6 89 7c 24 08 89 c7 89 1c 24 75 49 9c 5b fa 64 a1 04 20 47 c0 8b 14 87 <8b> 02 85 c0 74 25 c7 42 0c 01 00 00 00 48 89 02 8b 54 82 18 53
>>>> EIP: [<c016d013>] kmem_cache_alloc+0x23/0x80 SS:ESP 0068:ef27ff74
>>>>
>>>>
>>>>
>>>> Here is the code that causes the crash.
>>>>
>>>>
>>>> #include <linux/autoconf.h>
>>>> #include <linux/module.h>
>>>> #include <linux/kernel.h>
>>>> #include <linux/init.h>
>>>> #include <linux/poll.h>
>>>> #include <linux/mm.h>
>>>> static const char devname[]="Device";
>>>> #define NR_PAGES 0x10
>>>>
>>>> struct DMA {
>>>> void *ptr;
>>>> unsigned long addr;
>>>> size_t len;
>>>> };
>>>> //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>>>> //
>>>> // The top-level object that gets allocated once, when the module is
>>>> // installed.
>>>> //
>>>> struct INFO {
>>>> struct file_operations fa; // Kernel connection
>>>> struct semaphore dev_sem;
>>>> struct DMA dma[NR_PAGES]; // Can map one megabyte
>>>> uint32_t vm_start; // Where mmap() starts
>>>> uint32_t pages; // Number of pages mapped
>>>> atomic_t open; // Number of opens
>>>> };
>>>> //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>>>> static struct INFO *info;
>>>> //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>>>> //
>>>> // Initialize the module and return 0 if everything is okay.
>>>> // Return a negative error-code if not.
>>>> //
>>>> static int32_t startup()
>>>> {
>>>> if((info = kmalloc(sizeof(struct INFO), GFP_KERNEL)) == NULL) {
>>>> printk(KERN_ALERT"%s : Can't allocate memory\n", devname);
>>>
>>> Missing space after KERN_ALERT?
>>
>> I certainly hope that it's not the problem! That would
>> invalidate both the kernel and the compiler!
>
> It was the only thing that looked a bit odd. Although white space
> generally shouldn't matter in C.
>
> Well maybe the module was just compiled against a different source tree
> than the running kernel it was loaded into.
>
> I suppose comment out the printk and see if it's breaking on that line
> or somewhere else. Or just make it a printk with no variables.
>
> --
> Len Sorensen
>

It never gets to the printk(). You were right about the
compilation. Somebody changed the kernel to compile with
parameter passing in REGISTERS! This means that EVERYTHING
needs to be compiled the same way, 'C' calling conventions
were not good enough!

FYI, it has been previously shown that passing parameters
in registers on register-starved ix86 machines is always
a loss, because the registers need to be freed up, either
by saving them on the stack or as dummy memory variables.

Now, they've done it to the entire kernel!

Cheers,
Dick Johnson
Penguin : Linux version 2.6.22.1 on an i686 machine (5588.29 BogoMips).
My book : http://www.AbominableFirebug.com/
_


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