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);
return -ENOMEM;
}
return 0;
}
//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//
// Cleanup the module in preparation for removal.
//
static void quit() {
kfree(info);
printk(KERN_INFO"%s : Module removed\n", devname);
}
MODULE_LICENSE("GPL");
MODULE_ALIAS("MemDev");
module_init(startup);
module_exit(quit);
//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Anybody have a clue why this should error out? Am I using
some reserved names??? I got rid of __init and anything
else that I thought could cause the fault, plus got rid
of all the code!
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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