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Re: driver copy_to_user
by Mulyadi Santosa Dec. 24, 2010

Dec. 24, 2010

Hi...:) On Fri, Dec 24, 2010 at 13:40, Hemanth Kumar <hemwire(a)yahoo.co.in> wrote: > Hi mulyadi, > > Sorry for sending the mail directly, It's ok, but just to let you know..I am just average when dealing with kernel :) > ssize_t my_read(struct file *file,char *buf,size_t count,loff_t *pos){ > unsigned long res; > void *k = (void *)&x; > void *l = (void *)&x+1; > void *j = (void *)&x+2; > > mutex_lock(&timer); > res = copy_to_user(buf,k,sizeof(short)); hm, you say "read from user space", right? Then why "copy_to_user"? shouldn't it be "copy_from_user"? -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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copy_to_user
by Hemanth Kumar Dec. 24, 2010

Dec. 24, 2010

Hi All, I have small problem with copy_to_user in read function,below is my code,when I try to read from userspace I get segmentation fault, Can any please point me where I went wrong, #include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h> #include <linux/types.h> #include <linux/proc_fs.h> #include <linux/fs.h> #include <linux/kdev_t.h> #include <linux/jiffies.h> #include <linux/cdev.h> #include <asm/uaccess.h> #include <linux/mutex.h> struct mutex timer; static struct cdev my_cdev; dev_t devn; int maj = 300; int min = 0; int count = 1; char modname[] = "mytimer"; short x[10] = {1,2,3,4,5,6,7,8,9,10}; ssize_t my_read(struct file *file,char *buf,size_t count,loff_t *pos){ unsigned long res; void *k = (void *)&x; void *l = (void *)&x+1; void *j = (void *)&x+2; mutex_lock(&timer); res = copy_to_user(buf,k,sizeof(short)); res = copy_to_user(buf,l,sizeof(short)); res = copy_to_user(buf,j,sizeof(short)); /* res = copy_to_user(buf,&x+4,sizeof(short)); res = copy_to_user(buf,&x+5,sizeof(short)); res = copy_to_user(buf,&x+6,sizeof(short)); res = copy_to_user(buf,&x+7,sizeof(short)); res = copy_to_user(buf,&x+8,sizeof(short)); res = copy_to_user(buf,&x+9,sizeof(short)); */ mutex_unlock(&timer); return 20; } static struct file_operations my_fops = { .owner = THIS_MODULE, .read = my_read, }; static int __init my_init(void){ int ret; devn = MKDEV(maj,min); ret = register_chrdev_region(devn,count,modname); cdev_init(&my_cdev,&my_fops); cdev_add(&my_cdev,devn,count); printk("<1> Register timer maj = %d\n",maj); return 0; } static void __exit my_exit(void){ cdev_del(&my_cdev); unregister_chrdev_region(devn,count); printk("<1> Bye Bye \n"); } module_init(my_init); module_exit(my_exit); MODULE_LICENSE("Dual BSD/GPL"); my userspace App: #include <stdio.h> #include <fcntl.h> #include <stdlib.h> #include <unistd.h> int main() { int nbytes ; char n[20]; short a = *((short *)&n[0]); short b = *((short *)&n[2]); short c = *((short *)&n[4]); int fd = open( "/dev/mytimer", O_RDONLY ); if ( fd < 0 ) { perror( "/dev/mytimer" ); exit(1); } while ( 1 ) { nbytes = read( fd, n, 40 ); if ( nbytes < 0 ) break; printf( "\r a = %d \n ", a); printf("\r b = %d \n",b); printf("\r c = %d \n",c); sleep(1); fflush( stdout ); } return 0; } Best regards,

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Sound not coming after compiling new kernel 2.6.36
by Rishi Agrawal Dec. 24, 2010

Dec. 24, 2010

Hi All, I compiled the kernel 2.6.36 and now the sound is missing. I have pasted the outputs of lsmod and lspci. I have fedora 12 installed on the system. Have I done something wrong in the menuconfig stage. Sound is coming properly with the old Fedora Kernel. I tried tweaking the alsamixer but it did not work. [rishi@rishi-desktop ~]$ uname -a Linux rishi-desktop 2.6.36 #1 SMP Sat Dec 18 21:24:34 IST 2010 i686 i686 i386 GNU/Linux [rishi@rishi-desktop ~]$ lspci | grep -i audio 00:1b.0 Audio device: Intel Corporation 82801G (ICH7 Family) High Definition Audio Controller (rev 02) [rishi@rishi-desktop ~]$ lsmod | grep snd snd_hda_codec_analog 53691 1 snd_hda_intel 20031 1 snd_hda_codec 73253 2 snd_hda_codec_analog,snd_hda_intel snd_hwdep 4856 1 snd_hda_codec snd_seq 42695 0 snd_seq_device 4937 1 snd_seq snd_pcm 62570 2 snd_hda_intel,snd_hda_codec snd_timer 15387 2 snd_seq,snd_pcm snd 46823 11 snd_hda_codec_analog,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_seq,snd_seq_device,snd_pcm,snd_timer,thinkpad_acpi snd_page_alloc 6077 2 snd_hda_intel,snd_pcm soundcore 4831 1 snd -- Regards, Rishi Agrawal

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Re: Regarding Raid1
by Gaurav Mahajan Dec. 23, 2010

Dec. 23, 2010

Hi Greg... Thanks for the valuable info... I tried to understand a few more concepts..... I believe that md raid is a software raid,which makes it OS dependent whereas dmraid can be used to create a hardware raid (fakeRAID) which is OS independent... Now, what I fail to understand is that whether mdadm, which is a software tool for creating software RAID uses device mapper functionality or not. For example, lets say I create a RAID 1 array using mdadm, will the read and write operations performed on this array be passed through the device mapper or is the device mapper bypassed in this case ? The fact that the device mapper is supposed to be the lowest layer in the storage stack is what brought this question to my mind.... Basically, I'm wondering whether md and dm are at the same level or is dm at the lower level and md at a higher level.... It would be really helpful if you could elaborate on the difference between the working of md and dm.... Regards, Gaurav On Sun, Dec 19, 2010 at 10:48 AM, Mulyadi Santosa <mulyadi.santosa(a)gmail.com> wrote: > Hi Greg....... > > On Sun, Dec 19, 2010 at 07:28, Greg Freemyer <greg.freemyer(a)gmail.com> wrote: >> Both Raid 10 and Raid 1+0 effectively mean the same. >> >> The plus is basically implied unless you want Raid 0+1. I've never >> seen that call raid 01. >> >> I think the use varies on how you build the array. If you first build >> a stripeset, then mirror them as 2 separate steps, then use 1+0. >> >> If on the otherhand you make a single call to mdadm (as an example) >> and tell it do do the work in one step, then it is raid 10. The >> advantage of raid 10 over 1+0 is mdadm has several ways internally to >> build a raid 10 whereas there is basically only one way to build a >> 1+0.. > > Thanks for your kind explanation....I'll dig further about it when I > have time. I never knew 'til this you explained it to me that mdadm > might have its own way to build 1+0...I always think it always be: > build mirror, then stripe them.... > > -- > regards, > > Mulyadi Santosa > Freelance Linux trainer and consultant > > blog: the-hydra.blogspot.com > training: mulyaditraining.blogspot.com >

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Logical, Linear and Virtual Address.
by Gustavo da Silva Dec. 23, 2010

Dec. 23, 2010

Hi Everyone! Friends, could someone explain me the difference between Kernel Logical and Kernel Virtual Address? I'm reading Linux Device Drivers 3th, but I did not understand about that. I have a macro vision about Kernel Virtual Address (virtual address is used do hide the paging mechanism and physical memory, I think), and Linear is the address used in to evaluate to the physical (using page directory+page table+offset). But and the Kernel Logical Address? Why Logical Address is Virtual Address, but not all Virtual Address is a Logical Address? Regards. Atenciosamente, Gustavo da Silva

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FW: About runqueues in Linux
by Schick, Stefan Dec. 23, 2010

Dec. 23, 2010

-----Original Message----- From: Schick, Stefan Sent: Thu 12/23/2010 12:52 PM To: Sowmya Sridharan Subject: RE: About runqueues in Linux -----Original Message----- From: kernelnewbies-bounces(a)kernelnewbies.org on behalf of Sowmya Sridharan Sent: Thu 12/23/2010 11:58 AM To: kernelnewbies(a)kernelnewbies.org Subject: About runqueues in Linux Greetings List, I have certain queries regarding the maintenance of runqueues in Linux. In case of an SMP system, will a same process be added to multiple runqueues? In the sample data given below, I am seeing that the process "Appstart" is added to the runqueue on CPU1, but it is not run on that CPU. Instead it is added to CPU0's runqueue, and it is run on that CPU. I have not affined the process to any CPU, and it is not multi-threaded. CPU1 data: Cpu: 1, HRT: 1290079896.698994, Pid: 6577, Pname: Appstart added_to_runqueue, current process: irc(6103) Cpu: 1, HRT: 1290079896.706994, Pid: 6103, Pname: irc added_to_runqueue,current process: swapper(0) CPU0 data: Cpu: 0, HRT: 1290079896.702994, Pid: 6577, Pname: Appstart added_to_runqueue, Current process: eventd(5370) Cpu: 0, HRT: 1290079896.702994, Pid: 14247, Pname: Conn_agent added_to_runqueue, Current process: Appstart(6577) What is the default CPU on which a process runs, if cpu affinity is not set? Is it possible that a process added to one runqueue can be moved to another runqueue? Also I have seen swapper getting scheduled frequently even if there are runnable processes. Shouldn't swapper be run, only if there are no runnable processes? Your insights will be appreciated. Regards, Sowmya =====-----=====-----===== Notice: The information contained in this e-mail message and/or attachments to it may contain confidential or privileged information. If you are not the intended recipient, any dissemination, use, review, distribution, printing or copying of the information contained in this e-mail message and/or attachments to it are strictly prohibited. If you have received this communication in error, please notify us by reply e-mail or telephone and immediately and permanently delete the message and any attachments. Thank you Hey Sowmya, one process can only be in one runqueue at the same time. What is the default CPU on which a process runs, if cpu affinity is not set? The CPU with the shortest runqueue. Is it possible that a process added to one runqueue can be moved to another runqueue? Yes, they can be pulled over, see load_balance() in sched_fair.c Also I have seen swapper getting scheduled frequently even if there are runnable processes. Shouldn't swapper be run, only if there are no runnable processes? No, because it is possible that a Process in the expired runqueue is starving. Regards Stefan

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About runqueues in Linux
by Sowmya Sridharan Dec. 23, 2010

Dec. 23, 2010

Greetings List, I have certain queries regarding the maintenance of runqueues in Linux. In case of an SMP system, will a same process be added to multiple runqueues? In the sample data given below, I am seeing that the process "Appstart" is added to the runqueue on CPU1, but it is not run on that CPU. Instead it is added to CPU0's runqueue, and it is run on that CPU. I have not affined the process to any CPU, and it is not multi-threaded. CPU1 data: Cpu: 1, HRT: 1290079896.698994, Pid: 6577, Pname: Appstart added_to_runqueue, current process: irc(6103) Cpu: 1, HRT: 1290079896.706994, Pid: 6103, Pname: irc added_to_runqueue,current process: swapper(0) CPU0 data: Cpu: 0, HRT: 1290079896.702994, Pid: 6577, Pname: Appstart added_to_runqueue, Current process: eventd(5370) Cpu: 0, HRT: 1290079896.702994, Pid: 14247, Pname: Conn_agent added_to_runqueue, Current process: Appstart(6577) What is the default CPU on which a process runs, if cpu affinity is not set? Is it possible that a process added to one runqueue can be moved to another runqueue? Also I have seen swapper getting scheduled frequently even if there are runnable processes. Shouldn't swapper be run, only if there are no runnable processes? Your insights will be appreciated. Regards, Sowmya =====-----=====-----===== Notice: The information contained in this e-mail message and/or attachments to it may contain confidential or privileged information. If you are not the intended recipient, any dissemination, use, review, distribution, printing or copying of the information contained in this e-mail message and/or attachments to it are strictly prohibited. If you have received this communication in error, please notify us by reply e-mail or telephone and immediately and permanently delete the message and any attachments. Thank you

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QUestion on C language
by bhuvan gupta Dec. 23, 2010

Dec. 23, 2010

Respected sir, I am Bhuvan Gupta, a B.Tech student.(got your id from yours " USB LED driver - 1.1 ") ) With due respect, I humbly request you to please throw some light on to below written question. i will highly appreciate your efforts. [1] when we use C language,we use diferent library to do different thing.As also in your case you use module.h,init.h etc but how to write this library , in what language they are written in as standard ANSI C has round about 32 keywords ? what should i read and learn to the related topic . please suggest something (I do have knowledge of Assembly). please help,this question making me beacen it will be honour if you reply. thank you Bhuvan Gupta India

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struct sock change in kernel 2.6
by lijin liu Dec. 23, 2010

Dec. 23, 2010

Hello everyone! I am trying to implement a simple tcp server in the kernel. I read the ktcpvs's source code, but it works under kernel 2.4. The struct sock changed in kernel 2.6, I have two questions about the struct: 1. Is sk_wq field in 2.6 equals to sk_sleep field in 2.4? 2. How can I access the tcp accept queue in kernel 2.6? (In kernel 2.4, we could use tp_pinfo.af_tcp.accept_queue, but it was removed in 2.6) PS: Should sk_receive_queue in the struct sock be used as tp_pinfo.af_tcp.accept_queue? Thanks a lot!

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Re: Exact leak location in KMemleak Output
by Sengottuvelan S Dec. 23, 2010

Dec. 23, 2010

Sankar and All, I followed blow investigation on detecting kernel memory leak. I got different o/p which is different from yours shown. ie, 4 and 5 lines are addresses in the backtrace and not function names. http://psankar.blogspot.com/2010/11/detecting-memory-leaks-in-kernel.html comm "insmod", pid 1559, jiffies 4294961804 (age 229.610s) hex dump (first 32 bytes): fa 3e 00 00 00 00 00 00 92 5a 00 00 00 00 00 00 .>.......Z...... 0a 00 00 00 12 00 00 00 3c 38 00 00 00 00 00 00 ........<8...... backtrace: [<ffffffff8156eb1d>] kmemleak_alloc+0x2d/0x60 [<ffffffff81152469>] __vmalloc_node+0xc9/0xe0 [<ffffffff8115280c>] vmalloc+0x2c/0x30 [<ffffffffa0099047>] 0xffffffffa0099047 [<ffffffffa009906c>] 0xffffffffa009906c [<ffffffff8100204c>] do_one_initcall+0x3c/0x1a0 [<ffffffff810cea1b>] sys_init_module+0xbb/0x200 [<ffffffff81041072>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff On Wed, Oct 27, 2010 at 12:24 PM, Sankar P <sankar.curiosity(a)gmail.com>wrote: > Hi Dave, Rajat, Mulyadi and everyone, > > > Thanks for your pointers. > > Now I removed the "static __init" from the hello_init function and I > got an output of: > > unreferenced object 0xf9042000 (size 512): > comm "insmod", pid 12068, jiffies 13995923 (age 51.096s) > hex dump (first 32 bytes): > 6f 64 75 6c 65 00 00 00 00 00 00 2e 73 79 6d 74 odule.......symt > 61 62 00 2e 73 74 72 74 61 62 00 2e 73 68 73 74 ab..strtab..shst > backtrace: > [<c10b0001>] create_object+0x114/0x1db > [<c148b4d0>] kmemleak_alloc+0x21/0x3f > [<c10a43e9>] __vmalloc_node+0x83/0x90 > [<c10a44b9>] vmalloc+0x1c/0x1e > [<f9036021>] init_module+0x21/0x2f [hello_kernel] > [<c1001226>] do_one_initcall+0x71/0x113 > [<c1056c48>] sys_init_module+0x1241/0x1430 > [<c100284c>] sysenter_do_call+0x12/0x22 > [<ffffffff>] 0xffffffff > > > And, if I create a new function named myfunc and do my allocations > inside that function (instead of the init function), even though I > have a "static __init" text in the init_function I get an output: > > unreferenced object 0xf9061000 (size 512): > comm "insmod", pid 12750, jiffies 14401507 (age 110.217s) > hex dump (first 32 bytes): > 1c 0f 00 00 01 12 00 00 2a 0f 00 00 01 12 00 00 ........*....... > 38 0f 00 00 01 12 00 00 bc 0f 00 00 01 12 00 00 8............... > backtrace: > [<c10b0001>] create_object+0x114/0x1db > [<c148b4d0>] kmemleak_alloc+0x21/0x3f > [<c10a43e9>] __vmalloc_node+0x83/0x90 > [<c10a44b9>] vmalloc+0x1c/0x1e > [<f9055021>] myfunc+0x21/0x23 [hello_kernel] > [<f9058012>] 0xf9058012 > [<c1001226>] do_one_initcall+0x71/0x113 > [<c1056c48>] sys_init_module+0x1241/0x1430 > [<c100284c>] sysenter_do_call+0x12/0x22 > [<ffffffff>] 0xffffffff > > As we can see from the above output, it shows both the function name > as well as the module name where the leak is happening. Also the > address of the statement. So, my problem seems to be solved. Thank you > all for your pointers. > > Sorry for the top post and long contents. > > On Thu, Oct 28, 2010 at 12:00 AM, Rajat Sharma <fs.rajat(a)gmail.com> wrote: > > try removing static __init from function definition > > On Wed, Oct 27, 2010 at 10:40 PM, Sankar P <sankar.curiosity(a)gmail.com> > > wrote: > >> > >> Hi, > >> > >> I have an out of tree kernel module with the source: > >> > >> static __init int hello_init(void) > >> { > >> char *ptr; > >> ptr = vmalloc(512); > >> ptr = vmalloc(512); > >> ptr = vmalloc(512); > >> > >> printk(KERN_ALERT "Hello World"); > >> > >> return 0; > >> } > >> > >> Now I compile this file (hello.c) using my Makefile as follows: > >> > >> EXTRA_CFLAGS=-g > >> obj-m := hello-kernel.o > >> hello-kernel-objs := hello.o > >> > >> > >> Now if I insmod my hello-kernel.ko file and then do a `cat > >> /sys/kernel/debug/kmemleak` I get an output: > >> > >> unreferenced object 0xf8211000 (size 512): > >> comm "insmod", pid 9602, jiffies 3666022 (age 1553.469s) > >> hex dump (first 32 bytes): > >> 01 12 00 00 f2 10 00 00 01 12 00 00 fe 10 00 00 ................ > >> 01 12 00 00 0c 11 00 00 01 12 00 00 1a 11 00 00 ................ > >> backtrace: > >> [<c10b0001>] create_object+0x114/0x1db > >> [<c148b4d0>] kmemleak_alloc+0x21/0x3f > >> [<c10a43e9>] __vmalloc_node+0x83/0x90 > >> [<c10a44b9>] vmalloc+0x1c/0x1e > >> [<f8208021>] 0xf8208021 > >> [<c1001226>] do_one_initcall+0x71/0x113 > >> [<c1056c48>] sys_init_module+0x1241/0x1430 > >> [<c100284c>] sysenter_do_call+0x12/0x22 > >> [<ffffffff>] 0xffffffff > >> > >> > >> I understand that the kmemleak has correctly detected the memory leak. > >> But why is the leak showing in insmod , instead of the actual function > >> name "hello_init". Is there a way we can get the exact location inside > >> the hello.c file printed instead of the generic "insmod" location ? > >> > >> If I do a `gdb hello-kernel.ko`, the symbols are properly resolved, so > >> I am sure the .ko file has symbols. > >> > >> Any help will be appreciated. Thank you. > >> > >> -- > >> Sankar P > >> http://psankar.blogspot.com > >> > >> -- > >> To unsubscribe from this list: send an email with > >> "unsubscribe kernelnewbies" to ecartis(a)nl.linux.org > >> Please read the FAQ at http://kernelnewbies.org/FAQ > >> > > > > > > > > -- > Sankar P > http://psankar.blogspot.com > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis(a)nl.linux.org > Please read the FAQ at http://kernelnewbies.org/FAQ > > -- Regards, S. Sengottuvelan.

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