* pair of alloc_disk()?
@ 2009-01-07 6:00 Németh Márton
2009-01-08 5:56 ` pair of alloc_disk()? + OOPS Németh Márton
0 siblings, 1 reply; 3+ messages in thread
From: Németh Márton @ 2009-01-07 6:00 UTC (permalink / raw)
To: LKML
Hi,
I cannot find free_disk() or similar function which takes "struct gendisk"
as a parameter and can do the reverse thing what alloc_disk() do.
Could you please give me a hint what would be the correct function call
in the following example in test_exit_module() so the module do not leak?
#include <linux/module.h>
#include <linux/genhd.h>
MODULE_AUTHOR("Márton Németh <nm127@freemail.hu>");
MODULE_DESCRIPTION("Test alloc_disk");
MODULE_LICENSE("GPL");
static struct gendisk *gd_ptr;
static int test_init_module(void)
{
printk(KERN_DEBUG "starting module\n");
gd_ptr = alloc_disk(1);
if (!gd_ptr) {
return -ENOMEM;
}
printk(KERN_DEBUG "gd_ptr after alloc=%p\n", gd_ptr);
return 0;
}
static void test_exit_module(void)
{
printk(KERN_DEBUG "unloading module\n");
/* FIXME: no free_disk(gd_ptr) is available */
}
module_init(test_init_module);
module_exit(test_exit_module);
Regards,
Márton Németh
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: pair of alloc_disk()? + OOPS
2009-01-07 6:00 pair of alloc_disk()? Németh Márton
@ 2009-01-08 5:56 ` Németh Márton
2009-01-08 6:27 ` Németh Márton
0 siblings, 1 reply; 3+ messages in thread
From: Németh Márton @ 2009-01-08 5:56 UTC (permalink / raw)
To: LKML
[-- Attachment #1: Type: text/plain, Size: 4325 bytes --]
Németh Márton wrote:
> Hi,
>
> I cannot find free_disk() or similar function which takes "struct gendisk"
> as a parameter and can do the reverse thing what alloc_disk() do.
>
> Could you please give me a hint what would be the correct function call
> in the following example in test_exit_module() so the module do not leak?
>
>
> #include <linux/module.h>
> #include <linux/genhd.h>
>
> MODULE_AUTHOR("Márton Németh <nm127@freemail.hu>");
> MODULE_DESCRIPTION("Test alloc_disk");
> MODULE_LICENSE("GPL");
>
> static struct gendisk *gd_ptr;
>
> static int test_init_module(void)
> {
> printk(KERN_DEBUG "starting module\n");
>
> gd_ptr = alloc_disk(1);
> if (!gd_ptr) {
> return -ENOMEM;
> }
>
> printk(KERN_DEBUG "gd_ptr after alloc=%p\n", gd_ptr);
>
> return 0;
> }
>
>
> static void test_exit_module(void)
> {
> printk(KERN_DEBUG "unloading module\n");
>
> /* FIXME: no free_disk(gd_ptr) is available */
> }
>
> module_init(test_init_module);
> module_exit(test_exit_module);
I found a solution in "Linux Device Drivers, Third Edition", in chapter 16
"Block drivers" (page 468) where del_gendisk() is mentioned, so the
test_exit_module() should look like:
static void test_exit_module(void)
{
printk(KERN_DEBUG "unloading module\n");
del_gendisk(gd_ptr);
}
However, when I unload this module (also attached), I get the following
oops message in dmesg with kernel 2.6.28:
[ 2164.859107] starting module
[ 2164.859132] gd_ptr after alloc=f60f2a30
[ 2246.611974] unloading module
[ 2246.612648] BUG: unable to handle kernel NULL pointer dereference at 00000164
[ 2246.612666] IP: [<c0172266>] bdi_unregister+0x6/0x30
[ 2246.612684] *pde = 00000000
[ 2246.612694] Oops: 0000 [#1] PREEMPT
[ 2246.612703] last sysfs file: /sys/class/power_supply/BAT0/charge_full
[ 2246.612711] Modules linked in: test_alloc_disk(-) nls_iso8859_2 nls_cp437 vfat fat nls_base sd_mod usb_storage scsi_mod ppdev lp cpufreq_ondemand
cpufreq_conservative ipv6 xt_tcpudp iptable_filter ip_tables x_tables leds_clevo_mail led_class via via_agp drm agpgart eeprom snd_pcm_oss snd_mixer_oss
cpufreq_userspace cpufreq_powersave powernow_k8 fan snd_via82xx snd_via82xx_modem snd_mpu401_uart snd_seq_midi snd_seq_midi_event pcmcia firmware_class
snd_ac97_codec ac97_bus mousedev snd_rawmidi snd_pcm snd_seq snd_timer snd_seq_device ide_cd_mod snd i2c_viapro yenta_socket rsrc_nonstatic 8139too psmouse
serio_raw k8temp hwmon pcspkr cdrom snd_page_alloc soundcore 8250_pnp i2c_core ehci_hcd uhci_hcd pcmcia_core usbcore mii bitrev crc32 video backlight output
8250 serial_core parport_pc parport battery ac thermal button processor evdev
[ 2246.612866]
[ 2246.612874] Pid: 5121, comm: rmmod Not tainted (2.6.28 #3) K8N800
[ 2246.612881] EIP: 0060:[<c0172266>] EFLAGS: 00210206 CPU: 0
[ 2246.612889] EIP is at bdi_unregister+0x6/0x30
[ 2246.612895] EAX: 000000fc EBX: 000000fc ECX: f60f2b48 EDX: c03cb301
[ 2246.612901] ESI: f60f2a30 EDI: f60f2c78 EBP: d348df10 ESP: d348df0c
[ 2246.612908] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
[ 2246.612915] Process rmmod (pid: 5121, ti=d348c000 task=d372c860 task.ti=d348c000)
[ 2246.612920] Stack:
[ 2246.612924] f60f2a30 d348df1c c02347f6 00000000 d348df40 c01cd344 f60f2a30 00000000
[ 2246.612941] 00000000 00000003 00000000 f821d400 00000000 d348df4c f821d01c f821d088
[ 2246.612959] d348dfb0 c014f1e8 f821d40c 74736574 6c6c615f 645f636f 006b7369 ffffffff
[ 2246.612979] Call Trace:
[ 2246.612983] [<c02347f6>] ? unlink_gendisk+0x26/0x50
[ 2246.612995] [<c01cd344>] ? del_gendisk+0x84/0xd0
[ 2246.613009] [<f821d01c>] ? test_exit_module+0x1c/0x20 [test_alloc_disk]
[ 2246.613025] [<c014f1e8>] ? sys_delete_module+0x158/0x220
[ 2246.613028] [<c0103407>] ? sysenter_exit+0xf/0x16
[ 2246.613028] [<c01033d9>] ? sysenter_do_call+0x12/0x31
[ 2246.613028] Code: 00 00 c7 40 24 00 00 00 00 c7 40 28 00 00 00 00 c7 40 58 00 00 00 00 83 c0 2c e8 c6 9b 0c 00 5d c3 8d 74 26 00 55 89 e5 53 89 c3 <8b> 40 68
85 c0 74 1f 8b 43 70 e8 3b 8d 0a 00 8b 43 6c e8 33 8d
[ 2246.613028] EIP: [<c0172266>] bdi_unregister+0x6/0x30 SS:ESP 0068:d348df0c
[ 2246.613224] ---[ end trace 8f06b3a64120ba58 ]---
Do anybody know what is wrong with the attached simple example module?
Regards,
Márton Németh
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: test_alloc_disk.c --]
[-- Type: text/x-csrc; name="test_alloc_disk.c", Size: 582 bytes --]
#include <linux/module.h>
#include <linux/genhd.h>
MODULE_AUTHOR("Márton Németh <nm127@freemail.hu>");
MODULE_DESCRIPTION("Test alloc_disk");
MODULE_LICENSE("GPL");
static struct gendisk *gd_ptr;
static int test_init_module(void)
{
printk(KERN_DEBUG "starting module\n");
gd_ptr = alloc_disk(1);
if (!gd_ptr) {
return -ENOMEM;
}
printk(KERN_DEBUG "gd_ptr after alloc=%p\n", gd_ptr);
return 0;
}
static void test_exit_module(void)
{
printk(KERN_DEBUG "unloading module\n");
del_gendisk(gd_ptr);
}
module_init(test_init_module);
module_exit(test_exit_module);
[-- Attachment #3: Makefile --]
[-- Type: text/plain, Size: 184 bytes --]
ifneq ($(KERNELRELEASE),)
obj-m := test_alloc_disk.o
else
KDIR := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
default:
$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
endif
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: pair of alloc_disk()? + OOPS
2009-01-08 5:56 ` pair of alloc_disk()? + OOPS Németh Márton
@ 2009-01-08 6:27 ` Németh Márton
0 siblings, 0 replies; 3+ messages in thread
From: Németh Márton @ 2009-01-08 6:27 UTC (permalink / raw)
To: LKML
Németh Márton wrote:
> Németh Márton wrote:
>> Hi,
>>
>> I cannot find free_disk() or similar function which takes "struct gendisk"
>> as a parameter and can do the reverse thing what alloc_disk() do.
>>
>> Could you please give me a hint what would be the correct function call
>> in the following example in test_exit_module() so the module do not leak?
>>
>>
>> #include <linux/module.h>
>> #include <linux/genhd.h>
>>
>> MODULE_AUTHOR("Márton Németh <nm127@freemail.hu>");
>> MODULE_DESCRIPTION("Test alloc_disk");
>> MODULE_LICENSE("GPL");
>>
>> static struct gendisk *gd_ptr;
>>
>> static int test_init_module(void)
>> {
>> printk(KERN_DEBUG "starting module\n");
>>
>> gd_ptr = alloc_disk(1);
>> if (!gd_ptr) {
>> return -ENOMEM;
>> }
>>
>> printk(KERN_DEBUG "gd_ptr after alloc=%p\n", gd_ptr);
>>
>> return 0;
>> }
>>
>>
>> static void test_exit_module(void)
>> {
>> printk(KERN_DEBUG "unloading module\n");
>>
>> /* FIXME: no free_disk(gd_ptr) is available */
>> }
>>
>> module_init(test_init_module);
>> module_exit(test_exit_module);
>
> I found a solution in "Linux Device Drivers, Third Edition", in chapter 16
> "Block drivers" (page 468) where del_gendisk() is mentioned, so the
> test_exit_module() should look like:
>
> static void test_exit_module(void)
> {
> printk(KERN_DEBUG "unloading module\n");
>
> del_gendisk(gd_ptr);
>
> }
>
> However, when I unload this module (also attached), I get the following
> oops message in dmesg with kernel 2.6.28:
>
> [ 2164.859107] starting module
> [ 2164.859132] gd_ptr after alloc=f60f2a30
> [ 2246.611974] unloading module
> [ 2246.612648] BUG: unable to handle kernel NULL pointer dereference at 00000164
> [ 2246.612666] IP: [<c0172266>] bdi_unregister+0x6/0x30
> [ 2246.612684] *pde = 00000000
> [ 2246.612694] Oops: 0000 [#1] PREEMPT
> [ 2246.612703] last sysfs file: /sys/class/power_supply/BAT0/charge_full
> [ 2246.612711] Modules linked in: test_alloc_disk(-) nls_iso8859_2 nls_cp437 vfat fat nls_base sd_mod usb_storage scsi_mod ppdev lp cpufreq_ondemand
> cpufreq_conservative ipv6 xt_tcpudp iptable_filter ip_tables x_tables leds_clevo_mail led_class via via_agp drm agpgart eeprom snd_pcm_oss snd_mixer_oss
> cpufreq_userspace cpufreq_powersave powernow_k8 fan snd_via82xx snd_via82xx_modem snd_mpu401_uart snd_seq_midi snd_seq_midi_event pcmcia firmware_class
> snd_ac97_codec ac97_bus mousedev snd_rawmidi snd_pcm snd_seq snd_timer snd_seq_device ide_cd_mod snd i2c_viapro yenta_socket rsrc_nonstatic 8139too psmouse
> serio_raw k8temp hwmon pcspkr cdrom snd_page_alloc soundcore 8250_pnp i2c_core ehci_hcd uhci_hcd pcmcia_core usbcore mii bitrev crc32 video backlight output
> 8250 serial_core parport_pc parport battery ac thermal button processor evdev
> [ 2246.612866]
> [ 2246.612874] Pid: 5121, comm: rmmod Not tainted (2.6.28 #3) K8N800
> [ 2246.612881] EIP: 0060:[<c0172266>] EFLAGS: 00210206 CPU: 0
> [ 2246.612889] EIP is at bdi_unregister+0x6/0x30
> [ 2246.612895] EAX: 000000fc EBX: 000000fc ECX: f60f2b48 EDX: c03cb301
> [ 2246.612901] ESI: f60f2a30 EDI: f60f2c78 EBP: d348df10 ESP: d348df0c
> [ 2246.612908] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
> [ 2246.612915] Process rmmod (pid: 5121, ti=d348c000 task=d372c860 task.ti=d348c000)
> [ 2246.612920] Stack:
> [ 2246.612924] f60f2a30 d348df1c c02347f6 00000000 d348df40 c01cd344 f60f2a30 00000000
> [ 2246.612941] 00000000 00000003 00000000 f821d400 00000000 d348df4c f821d01c f821d088
> [ 2246.612959] d348dfb0 c014f1e8 f821d40c 74736574 6c6c615f 645f636f 006b7369 ffffffff
> [ 2246.612979] Call Trace:
> [ 2246.612983] [<c02347f6>] ? unlink_gendisk+0x26/0x50
> [ 2246.612995] [<c01cd344>] ? del_gendisk+0x84/0xd0
> [ 2246.613009] [<f821d01c>] ? test_exit_module+0x1c/0x20 [test_alloc_disk]
> [ 2246.613025] [<c014f1e8>] ? sys_delete_module+0x158/0x220
> [ 2246.613028] [<c0103407>] ? sysenter_exit+0xf/0x16
> [ 2246.613028] [<c01033d9>] ? sysenter_do_call+0x12/0x31
> [ 2246.613028] Code: 00 00 c7 40 24 00 00 00 00 c7 40 28 00 00 00 00 c7 40 58 00 00 00 00 83 c0 2c e8 c6 9b 0c 00 5d c3 8d 74 26 00 55 89 e5 53 89 c3 <8b> 40 68
> 85 c0 74 1f 8b 43 70 e8 3b 8d 0a 00 8b 43 6c e8 33 8d
> [ 2246.613028] EIP: [<c0172266>] bdi_unregister+0x6/0x30 SS:ESP 0068:d348df0c
> [ 2246.613224] ---[ end trace 8f06b3a64120ba58 ]---
>
> Do anybody know what is wrong with the attached simple example module?
I forget to send the links to the book:
http://lwn.net/Kernel/LDD3/
http://lwn.net/images/pdf/LDD3/ch16.pdf
Regards,
Márton Németh
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2009-01-08 6:27 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-01-07 6:00 pair of alloc_disk()? Németh Márton
2009-01-08 5:56 ` pair of alloc_disk()? + OOPS Németh Márton
2009-01-08 6:27 ` Németh Márton
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox