RE: capturing kernel oops
-Original Message- From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies- bou...@nl.linux.org] On Behalf Of Paavaanan Sent: Friday, December 17, 2010 11:26 AM To: Kernelnewbie Subject: capturing kernel oops Hi, kernel Panic and Crashes can be logged and traced with the help of tools like core-dump, klogd and netdump. But, is there any way to take logs or crash dumps to Kernel OOPS messages. Instead of taking a Photo with the Camera is there any handy tool to do this neatly. Attaching a serial console can be one option, if we want to see the kernel oops when it occurs. Else the logs go to 'dmesg' messages as well. I am not quite sure if we require to set certain printk level /proc/sys/kernel/printk. Thanks, Paavaanan.
RE: hi
From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies-bou...@nl.linux.org] On Behalf Of Anuz Pratap On Thu, Nov 18, 2010 at 6:46 PM, Carlo Caione carlo.cai...@gmail.com wrote: On Nov 18, 2010, at 5:23 PM, Viral Mehta wrote: Seems like kernelnewbies is becoming more popular than Google It looks like some Google Query which showed up in kernel list :D +1 :) I guess as soon as someone subscribes to mailing list, s/he should be sent with some guidelines, which can prevent this from happening. good idea would be if we can make a list of such dos and do-nots. Guess we already have the link describing the common etiquettes. http://www.tux.org/lkml/#s3 - Partially applicable to our list as well. Also as Mulyadi pointed out: http://www.catb.org/esr/faqs/smart-questions.html. -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: Kernel start code
-Original Message-
From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies-
bou...@nl.linux.org] On Behalf Of Himanshu Chauhan
Sent: Wednesday, October 06, 2010 11:50 PM
To: Sri Ram Vemulpali
Cc: Kernel-newbies
Subject: Re: Kernel start code
On Thursday 07 October 2010 04:28 AM, Sri Ram Vemulpali wrote:
Hi all,
Can anyone, please help me on pointing to kernel boot code
after
grubs loads the kernel and transfers control to it.
I want in which files this resides, location. Any explanation
on the
code or any link would be helpful to me.
I know this is kind of lousy question, but entry.S is where I
looked
at. It is overwhelming for me where to start in that file.
Thanks in advance.
Hi Sri,
Use cscope and search for kernel_entry symbol. I think its in
arch/$ARCH/boot/head.S or may in in kernel directory.
I would recommend refer Linux Kernel Primer- it explains boot process
line-by-line for X86 and PPC.
http://www.amazon.com/Linux-Kernel-Primer-Top-Down-Architectures/dp/0131181637
- Himanshu
--
Thanks,
Nilesh
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RE: memory consumed by kernel
-Original Message- From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies- bou...@nl.linux.org] On Behalf Of Arun KS Sent: Thursday, September 23, 2010 11:30 AM To: kernelnewbies@nl.linux.org Subject: memory consumed by kernel Hello There, cat /proc/meminfo will show the memory statistics of the entire system. Is there a way to see the memory consumed by the kernel alone? I do not have thorough idea. But it seems there is no ready-made tool (userspace/kernelspace) to know the complete kernel memory. To debug certain memory related issues - we can refer the /proc/kallsyms (exact place where each symbol is loaded in memory) and /proc/slabinfo - the slab allocation for different objects. But considering the total kernel memory it also includes many other allocations which we do not do explicitly - like Page tables, or some kind of metadata. Regards, Arun -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: Context of a kernel routine
-Original Message- From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies- bou...@nl.linux.org] On Behalf Of Mulyadi Santosa Sent: Sunday, September 19, 2010 8:13 AM To: Vimal Cc: Kernel Newbies Subject: Re: Context of a kernel routine Hi.. On Sun, Sep 19, 2010 at 08:50, Vimal j.vi...@gmail.com wrote: Most of the times, I just end up tracing the code path manually from the source code. I have another question, though: Is it possible in gdb to break on all function calls? Would be useful. :) None that I know :) But maybe that is doable inside system emulator such as Qemu. You need to trap the call of call, far jmp or things like that. But the problem here is it is done system widely...thus you need a way to selectively filter which function calls you want to trap and which ones are not Regarding the code trace: Another approach which I used to use. It's ugly but worked for me most of the times. :-) We can use stack_trace()/dump_stack() functions (same routines which get called when kernel panics or Oops). Pass the stack pointer as NULL and it will dump the stack, register set of current process. Question is if it gets called multiple times and flood the console? You can create a sysctl entry - enable it (non-zero) from command prompt, once you get the expected trace - make sysctl_variable = 0 (will disable the function calls) :-) Something like: if(sysctl_variable) stack_trace(NULL); -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: filesystem or database??
Hi Mohit, Probably what you want to check is http://www.linux.org/docs/ There is a list of FAQs that can help: http://www.tldp.org/FAQ/Linux-FAQ/index.html Mailing lists where you can post queries: http://www.linux.org/docs/lists.html [Hint: First link in google search Linux distributions list]. Lastly, it would be helpful for us if we use this mailing list for kernel related discussions and not for the distro and installation HOWTOs. -- Thanks, Nilesh -Original Message- From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies- bou...@nl.linux.org] On Behalf Of Srdjan Todorovic Sent: Friday, September 17, 2010 1:40 AM To: mohit verma Cc: kernelnewbies Subject: Re: filesystem or database?? On 16 September 2010 20:58, mohit verma mohit89m...@gmail.com wrote: when we install any package (like in ubuntu) ,at end the terminal shows reading database . the idea i got by my friend is that package manager uses this database (like .deb or rpm). but my question is : everything in linux is a file so it(database or files that it contains) must be placed somewhere in the filesystem.what is the difference if i say that package manager accesses nothing but the filesystem ( obviously a part of it) and database of a system( computer ) is nothing but the filesystem (part of it ) itself ? i mean: what differs between these two that imposes us to name them differently? The database will probably be in a file (ie. Sleepycat db files), or be made up of several files (IIRC this is like MySql). But I suspect this is not the best mailing list to discuss this - seems more like general Linux systems use, or applications-level development question. Regards, Srdjan -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: spin locks in uniprocessor system
-Original Message- From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies- bou...@nl.linux.org] On Behalf Of Smital Desai Sent: Wednesday, September 15, 2010 11:58 AM To: Kernel Newbies Subject: spin locks in uniprocessor system Hi everyone, It's an extract in LDD3 , regarding spink lock. I have put my query in brackets. Spinlocks are, by their nature, intended for use on multiprocessor systems, although a uniprocessor workstation running a preemptive kernel behaves like SMP, as far as concurrency is concerned. ( I need to understand , how this is true with an example preferably ) On uniprocessor system even if you have a task scheduled, the interrupt can still come and should be handled by that processor. So let's say you get a timer interrupt - the schedule() will be called on return and if there is any higher priority task waiting, your previous task can get scheduled out. This is referred to as pseudo concurrency (Please refer Robert Love). If a nonpreemptive uniprocessor system ever went into a spin on a lock, it would spin forever; no other thread would ever be able to obtain the CPU to release the lock. For this reason, spinlock operations on uniprocessor systems without pre-emption enabled are optimized to do nothing, with the exception of the ones that change the IRQ masking status. ( I don't get the meaning of last sentence with the exception of .. Please can somebody explain ) I am not sure about this statement, though. Would appreciate if someone can provide some pointers. Thanks and Regards Smital Desai -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: my driver is dropping characters
Can't it be because you are using size = 1byte in copy_from_user? Make it
'count'.
--
Thanks,
Nilesh
-
From: kernelnewbies-bou...@nl.linux.org
[mailto:kernelnewbies-bou...@nl.linux.org] On Behalf Of Bond
Sent: Wednesday, September 15, 2010 5:27 PM
To: kernelnewbies
Subject: my driver is dropping characters
I wrote my hello world type of character device driver.(First driver that I
wrote)
I created a device as follows
mknod /dev/bond c 60 0
and then tried to write something to that device as follows
echo -n abcde /dev/bond
cat /dev/bond
will show me the last
e of entered abcde
above but will drop abcd.
I can see the last character which was passed on to as argument to echo but not
the previous characters.
Any idea what improvement should I make.
Here is the code.
#include linux/init.h
#include linux/module.h
#include linux/kernel.h /* printk() */
#include linux/slab.h /* kmalloc() */
#include linux/fs.h /* everything... */
#include linux/errno.h /* error codes */
#include linux/types.h /* size_t */
#include linux/proc_fs.h
#include linux/fcntl.h /* O_ACCMODE */
#include asm/system.h /* cli(), *_flags */
#include asm/uaccess.h /* copy_from/to_user */
/* Declaration of memory.c functions */
int bond_open(struct inode *inode, struct file *filp) { return 0;};
int bond_release(struct inode *inode, struct file *filp){ return 0;};
ssize_t bond_read(struct file *filp, char *buf, size_t count, loff_t *f_pos)
{
/* Transfering data to user space */
copy_to_user(buf,bond_buffer,1);
/* Changing reading position as best suits */
if (*f_pos == 0) {
*f_pos+=1;
return 1;
} else {
return 0;
}
};
ssize_t bond_write(struct file *filp, char *buf, size_t count, loff_t *f_pos)
{
char *tmp;
tmp=buf+count-1;
copy_from_user(bond_buffer,tmp,1);
return 1;
} ;
void bond_exit(void);
int bond_init(void);
/* Structure that declares the usual file */
/* access functions */
struct file_operations bond_fops = {
read: bond_read,
write: bond_write,
open: bond_open,
release: bond_release
};
/* Global variables of the driver */
/* Major number */
int bond_major = 60;
/* Buffer to store data */
char *bond_buffer;
static int bond_init(void) {
printk(1 Hello bond new driver!\n);
int result;
/* Registering device */
result = register_chrdev(bond_major, bond, bond_fops);
if (result 0) {
printk(
1memory: cannot obtain major number %d\n, bond_major);
return result;
}
/* Allocating memory for the buffer */
bond_buffer = kmalloc(1, GFP_KERNEL);
if (!bond_buffer) {
result = -ENOMEM;
goto fail;
}
memset(bond_buffer, 0, 1);
printk(1Inserting bond module\n);
return 0;
fail:
bond_exit();
return result;
return 0;
}
static void bond_exit(void) {
printk(1 Bye, bond world\n);
/* Freeing the major number */
unregister_chrdev(bond_major, bond);
/* Freeing buffer memory */
if (bond_buffer) {
kfree(bond_buffer);
}
printk(1Removing bond module\n);
}
module_init(bond_init);
module_exit(bond_exit);
--
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RE: Struct net_device
-Original Message- From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies- bou...@nl.linux.org] On Behalf Of Tushar Dadlani Sent: Monday, September 13, 2010 8:56 PM To: kernelnewbies@nl.linux.org Subject: Struct net_device Hi , I wanted to know how do I use eth0 from kernel space. How do i get the information of running struct net_device references?? I wanted to capture the stats on eth0 from kernel space. I am really not sure what is required here. Please see if below info. helps (not an expert comment, though :)). You can get the netdev struct of the interface by name: struct net_device *netdev = dev_get_by_name(eth0); // when netdev-name is eth0. struct e1000_adapter *adapter = netdev_priv(netdev); // obtain the adapter. And you also can take a look at e1000_ethtool.c to obtain the stats for each interface using the adapter. Hope it helps. -- Tushar Dadlani Manipal Institute of Technology +919986292434 -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: knowledge sharing
From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies-bou...@nl.linux.org] On Behalf Of Bond Sent: Thursday, September 09, 2010 8:27 AM To: kernelnewbies Subject: knowledge sharing It would good if some senior members on the list share their knowledge in form of some sort of programming exercise on this list. For example decide a topic for a week and discuss about that topic in the week. Starting from some one who is absolutely new to kernel development. (Having said that I have written basic hello kernel and character device driver for myself) I really appreciate your suggestion and (hopefully) understood what you are pointing to. And nice to see you started with basics. If like this people can continue such a thing here that will be a bit helpful to those people who do not have any thing to do with IT or IT organizations but are interested But let me be clear about the notion of kernel mailing lists- It's like you do the stuffs on your own. There is a lot of material available opensource. Read, read and read. And then practice. And _certainly_ there are many things which everyone can't understand. Try to solve these issues on your own (and probably post it to the mailing list, unless it's an obvious thing!). If you are really stuck somewhere or want to contribute something and seeking opinion that's what the mailing list is for. -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: knowledge sharing
From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies-bou...@nl.linux.org] On Behalf Of Bond Sent: Thursday, September 09, 2010 12:24 PM To: kernelnewbies Subject: Re: knowledge sharing On Thu, Sep 9, 2010 at 12:01 PM, Tayade, Nilesh nilesh.tay...@netscout.com wrote: There is a lot of material available opensource. That exactly is the problem.Which one to read and which one not to read. To be able to search some thing you need to be aware of what to be searched. Agreed. But you can question yourself to know that. And then practice. practice what? Suppose I decided I want to write a driver for my monitor of my computer. Now will that be some thing good to start with. Certainly not. Atleast not for the _newbies_. :) I just want to know some thing kick off. Suggestion - google. Something to kick off- start from what operating system really is. -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: Query related to mount point identification.
-Original Message- From: Manish Katiyar [mailto:mkati...@gmail.com] Sent: Tuesday, September 07, 2010 10:51 PM To: Tayade, Nilesh Cc: kernelnewbies@nl.linux.org Subject: Re: Query related to mount point identification. On Tue, Sep 7, 2010 at 4:27 AM, Tayade, Nilesh nilesh.tay...@netscout.com wrote: Hi, I am currently working on parsing the packets for NFS protocol. I want to know, in case of a file operation, how can we identify the mount point where the file is mounted? E.g. scenario is- Client has mounted the node already. You apply the NFS parser and start reading/writing to the file. Here, parser did not know if the node is mounted or not (as we enabled the parser after mounting the node. And I want to identify that at the arrival of first packet). So is there any way to identify that based on the file name (or inode may be)? I am looking at the fstat() system call, but unable to find anything useful. Looks like given the filename you want to find the mountpoint. May be this will help. http://www.mail-archive.com/bug-coreut...@gnu.org/msg20630.html Thanks, it looks useful. The changes are recent, though. -- Thanks - Manish == [$\*.^ -- I miss being one of them == -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
Query related to mount point identification.
Hi, I am currently working on parsing the packets for NFS protocol. I want to know, in case of a file operation, how can we identify the mount point where the file is mounted? E.g. scenario is- Client has mounted the node already. You apply the NFS parser and start reading/writing to the file. Here, parser did not know if the node is mounted or not (as we enabled the parser after mounting the node. And I want to identify that at the arrival of first packet). So is there any way to identify that based on the file name (or inode may be)? I am looking at the fstat() system call, but unable to find anything useful. Any pointers will be highly appreciated. -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: A question
[Resending, I'm not sure where the previous email is lost.] From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies-bou...@nl.linux.org] On Behalf Of hiren panchasara Sent: Thursday, September 02, 2010 12:28 PM To: Prabhu nath Cc: kernelnewbies@nl.linux.org; techtrain...@tataelxsi.co.in Subject: Re: A question Thanks a lot Prabhu for great explanation, comments in-line: On Wed, Sep 1, 2010 at 10:02 PM, Prabhu nath gprabhun...@gmail.com wrote: Interrupt context is a loaded term. It is used for both top-half and bottom-half processing. I need some more reading, will do that :) [Nilesh] Also request you to keep the subject line quite specific. :) Linux defines two terms in the top-half, one is Interrupt handler (IH) and Interrupt Service Routine (ISR). Interrupt handler is a standard kernel code that is executed by the processor once the interrupt is generated. To abstract it, this generic code is executed for all the generated interrupts. This, in general saves the present processor context and paves way for the execution of ISR. ISR is a interrupt service routine written by a device driver programmer to handle the interrupt of a device. ISR is mainly responsible to verify the status register of a device to find out the cause of the interrupt and act accordingly. Both IH and ISR will not have a context of its own. Interrupts generated by a hardware device is asynchronous. i.e. it can be generated at any point in time. When such a interrupt is generated, the current execution is interrupted and the execution control is transferred to IH and ISR will be executed. Thus we can infer that both IH and ISR will be executing in an anonymous context. I am struggling to find meaning of interrupt context now. [Nilesh] Context refers to several stuffs that play role in execution . the registers, the stack etc. etc. http://book.chinaunix.net/special/ebook/Linux_Kernel_Development/0672327201/ch06lev1sec5.html For Eg. Consider there are 3 tasks T2, T3. Suppose T2 invoked a read system call to read data from the secondary media (say hard disk), driver of the hard disk will initiate the device to gather the data and put task T2 in the wait queue and invokes scheduler. Now, scheduler picks up say T3. When processor is executing task T3, there was interrupt generated by the harddisk controller indicating that data is ready. At this point IH and ISR is executed. IH and ISR of this interrupt has no relevance to task T3, but still it is executed in the context of T3. Hence we say that IH and ISR will always be executed in the anonymous context. Wow, didnt know this. So IH and ISR wont execute in interrupt context? What is interrupt context then? and if they execute in context of T3, does it have any side-effect on processing of T3? [Nilesh] May be I am not able to completely interpret what is written above. AFAIK, when the task is scheduled out in order to handle interrupt, the stack used is different for the interrupt (current pointer still points to the task_struct of the task, but that.s irrelevant for interrupt). Also the registers are stored (context switch?) when the process is scheduled out. I am not sure how it should run task T3 context. Could someone please clarify? Most of the bottom half execution happens the same way, i.e. it will be executing in the anonymous context unless the job of bottom half is relegated to respective kernel threads. In the latter case the bottom half execution will have its own context. For more details about top-half and bottom half, refer ULK 3rd edtion by Bovet, Chapter 4 Would read it. Thanks again for great insights. Regards, Prabhu Thanks, Nilesh
NFS version4 maximum on-the-wire data size.
Hi, I am unable to get the exact count for the amount of on-the-wire data size that NFSv4 supports. I could get exact figures in case of NFSv3 (http://nfs.sourceforge.net). It's 60KB when NFSv3 is used over UDP and implementation dependent in case it is used over TCP. Any idea about NFSv4 statistics? Any pointers would be appreciated. -- Thanks, Nilesh -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
RE: A question
-Original Message- From: kernelnewbies-bou...@nl.linux.org [mailto:kernelnewbies- bou...@nl.linux.org] On Behalf Of Hiren Panchasara Sent: Wednesday, September 01, 2010 9:08 PM To: kernelnewbies@nl.linux.org Subject: A question Process context is schedulable but interrupt context is not. Why and how? Interrupt line can be shared by multiple interrupts or to avoid delay in handling subsequent interrupts on single line - the handler has to be quick enough. So we avoid scheduling out or sleeping inside the interrupt handlers. Any examples I can look at? -- To unsubscribe from this list: send an email with unsubscribe kernelnewbies to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
