Re: memory management with mmap
Hi Mulyadi I am able to do mmap and access virual-memory address and pages for a single process from user-space and working fine. I am not sure how to do it for multiple processes for shared resources using mmap. I better explain in detail here what I am experimenting it. for example: Kernel allocates kmalloc or vmalloc of 100 pages and set those pages as reserved. Kernel uses these pages to send/receive data to Process A or B depends on a condition. Process A and B do mmap those region to get/set data on those virtual-addresses/pages because I want faster access from userpace to kernel. Anyone knows if this will work with mmap?. Please let me know if anyother way to do it. On Sat, Oct 27, 2012 at 10:57 PM, Mulyadi Santosa mulyadi.sant...@gmail.com wrote: Hi... On Thu, Oct 18, 2012 at 3:02 AM, Sengottuvelan S sengottuvela...@gmail.com wrote: For example, I have 2 different user space process A,B etc. I have to allocate memory in Kernel for each of those processes (for example 2 pages) . Each process is allowed to use only 1 page using mmap from user space. Is it possible to do with mmap?. Not sure, but I guess better to do it directly with page_alloc...or at least kmalloc() to better utilize slab. The thing that I think is hard to do, is to implement protection scheme to make sure say process A won't access page allocated by process B. Hopefully I understand your goal correctly. -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com -- Regards, S. Sengottuvelan. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: linux segment
2012/10/27 Jun Hu duanshui...@hotmail.com
Can you post out your codes ?
*From:* Fan Yang lljyang...@gmail.com
*Sent:* Wednesday, October 24, 2012 8:04 PM
*To:* kernelnewbies@kernelnewbies.org
*Subject:* linux segment
Hi all:
I print the cs ds and ss register in the user space, and it is same as
the __USER_CS and __USER_DS which defined in kernel as 73 and 7b. In the
kernel __KERNEL_CS and __KERNEL_DS defined as 60 and 68, but when I print
this two value in my kernel module, I get 60 and 7b. Why ? It should be 60
and 68, shouldn't it?
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Hi Jun Hu
There is my code which run at the user space:
1 #includestdio.h
2 main()
3 {
4 unsigned long cs, ds, ss, es, fs, gs;
5 asm volatile(movl %%CS,%0\n\t:=r(cs));
6 asm volatile(movl %%DS,%0\n\t:=r(ds));
7 asm volatile(movl %%SS,%0\n\t:=r(ss));
8 asm volatile(movl %%ES,%0\n\t:=r(es));
9 asm volatile(movl %%FS,%0\n\t:=r(fs));
10 asm volatile(movl %%GS,%0\n\t:=r(gs));
11 printf (**\n);
12 printf (cs %lx\t%ld\n, cs, cs);
13 printf (ds %lx\t%ld\n, ds, ds);
14 printf (ss %lx\t%ld\n, ss, ss);
15 printf (es %lx\t%ld\n, es, es);
16 printf (fs %lx\t%ld\n, fs, fs);
17 printf (gs %lx\t%ld\n, gs, gs);
18 printf (**\n);
19 }
and the result of the progress in my machine is
**
cs 73 115
ds 7b 123
ss 7b 123
es 7b 123
fs 0 0
gs 33 51
**
so, you can see the cs and ds register is 73 and 7b which are same as the
kernel defined. And the code of the kernel module is
1 #includelinux/init.h
2 #includelinux/kernel.h
3 #includelinux/module.h
4
5 static void __init print_init (void)
6 {
7 unsigned long cs, ds, ss, es, fs, gs,currenttime;
8 asm volatile(movl %%CS,%0\n\t:=r(cs));
9 asm volatile(movl %%DS,%0\n\t:=r(ds));
10 asm volatile(movl %%SS,%0\n\t:=r(ss));
11 asm volatile(movl %%ES,%0\n\t:=r(es));
12 asm volatile(movl %%FS,%0\n\t:=r(fs));
13 asm volatile(movl %%GS,%0\n\t:=r(gs));
14 printk (**\n);
15 printk (cs %lx\t%ld\n, cs, cs);
16 printk (ds %lx\t%ld\n, ds, ds);
17 printk (ss %lx\t%ld\n, ss, ss);
18 printk (es %lx\t%ld\n, es, es);
19 printk (fs %lx\t%ld\n, fs, fs);
20 printk (gs %lx\t%ld\n, gs, gs);
21 printk (**\n);
22
23 }
24
25 static void __exit print_exit (void)
26 {
27 unsigned long cs, ds, ss;
28 asm volatile(movl %%cs,%0\n\t:=r(cs));
29 asm volatile(movl %%ds,%0\n\t:=r(ds));
30 asm volatile(movl %%ss,%0\n\t:=r(ss));
31
32 printk (**\n);
33 printk (cs %lx\t%ld\n, cs, cs);
34 printk (ds %lx\t%ld\n, ds, ds);
35 printk (ss %lx\t%ld\n, ss, ss);
36 printk (**\n);
37 printk (*bye***\n);
38 }
39
40 module_init (print_init);
41 module_exit (print_exit);
42 MODULE_LICENSE (GPL);
the result of the running this module is
[root@shell--box kernel_mod]# dmesg -c
**
cs 60 96
ds 7b 123
ss 68 104
es 7b 123
fs d8 216
gs e0 224
**
The cs and ds in the kernel space is 60 and 7b. But the kernel define the
KERNEL_CS as 60 and the KERNEL_DS as 7b. Where am I wrong?
Thanks
Fan
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Re: linux segment
2012/10/28 Fan Yang lljyang...@gmail.com
2012/10/27 Jun Hu duanshui...@hotmail.com
Can you post out your codes ?
*From:* Fan Yang lljyang...@gmail.com
*Sent:* Wednesday, October 24, 2012 8:04 PM
*To:* kernelnewbies@kernelnewbies.org
*Subject:* linux segment
Hi all:
I print the cs ds and ss register in the user space, and it is same
as the __USER_CS and __USER_DS which defined in kernel as 73 and 7b. In the
kernel __KERNEL_CS and __KERNEL_DS defined as 60 and 68, but when I print
this two value in my kernel module, I get 60 and 7b. Why ? It should be 60
and 68, shouldn't it?
--
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Hi Jun Hu
There is my code which run at the user space:
1 #includestdio.h
2 main()
3 {
4 unsigned long cs, ds, ss, es, fs, gs;
5 asm volatile(movl %%CS,%0\n\t:=r(cs));
6 asm volatile(movl %%DS,%0\n\t:=r(ds));
7 asm volatile(movl %%SS,%0\n\t:=r(ss));
8 asm volatile(movl %%ES,%0\n\t:=r(es));
9 asm volatile(movl %%FS,%0\n\t:=r(fs));
10 asm volatile(movl %%GS,%0\n\t:=r(gs));
11 printf (**\n);
12 printf (cs %lx\t%ld\n, cs, cs);
13 printf (ds %lx\t%ld\n, ds, ds);
14 printf (ss %lx\t%ld\n, ss, ss);
15 printf (es %lx\t%ld\n, es, es);
16 printf (fs %lx\t%ld\n, fs, fs);
17 printf (gs %lx\t%ld\n, gs, gs);
18 printf (**\n);
19 }
and the result of the progress in my machine is
**
cs 73 115
ds 7b 123
ss 7b 123
es 7b 123
fs 0 0
gs 33 51
**
so, you can see the cs and ds register is 73 and 7b which are same as the
kernel defined. And the code of the kernel module is
1 #includelinux/init.h
2 #includelinux/kernel.h
3 #includelinux/module.h
4
5 static void __init print_init (void)
6 {
7 unsigned long cs, ds, ss, es, fs, gs,currenttime;
8 asm volatile(movl %%CS,%0\n\t:=r(cs));
9 asm volatile(movl %%DS,%0\n\t:=r(ds));
10 asm volatile(movl %%SS,%0\n\t:=r(ss));
11 asm volatile(movl %%ES,%0\n\t:=r(es));
12 asm volatile(movl %%FS,%0\n\t:=r(fs));
13 asm volatile(movl %%GS,%0\n\t:=r(gs));
14 printk (**\n);
15 printk (cs %lx\t%ld\n, cs, cs);
16 printk (ds %lx\t%ld\n, ds, ds);
17 printk (ss %lx\t%ld\n, ss, ss);
18 printk (es %lx\t%ld\n, es, es);
19 printk (fs %lx\t%ld\n, fs, fs);
20 printk (gs %lx\t%ld\n, gs, gs);
21 printk (**\n);
22
23 }
24
25 static void __exit print_exit (void)
26 {
27 unsigned long cs, ds, ss;
28 asm volatile(movl %%cs,%0\n\t:=r(cs));
29 asm volatile(movl %%ds,%0\n\t:=r(ds));
30 asm volatile(movl %%ss,%0\n\t:=r(ss));
31
32 printk (**\n);
33 printk (cs %lx\t%ld\n, cs, cs);
34 printk (ds %lx\t%ld\n, ds, ds);
35 printk (ss %lx\t%ld\n, ss, ss);
36 printk (**\n);
37 printk (*bye***\n);
38 }
39
40 module_init (print_init);
41 module_exit (print_exit);
42 MODULE_LICENSE (GPL);
the result of the running this module is
[root@shell--box kernel_mod]# dmesg -c
**
cs 60 96
ds 7b 123
ss 68 104
es 7b 123
fs d8 216
gs e0 224
**
The cs and ds in the kernel space is 60 and 7b. But the kernel define the
KERNEL_CS as 60 and the KERNEL_DS as 7b. Where am I wrong?
Thanks
Fan
sorry, the kernel define the KERNEL_DS as 68, but I get 7b in my machine.
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Re: Tools for checking incorrect usage of locking techniques in k-space
Hi, On Sun, Oct 28, 2012 at 12:36 AM, Kumar amit mehta gmate.a...@gmail.com wrote: Thank you Srivatsa. It seems that lockdep framework is enabled on my running kernel. snip amit@ubuntu:/boot$ egrep -i debug_kernel|lockdep config-3.2.0-29-generic-pae CONFIG_LOCKDEP_SUPPORT=y CONFIG_DEBUG_KERNEL=y You'll need CONFIG_LOCKDEP=y as well. An easy way to configure lock debugging checks is to run 'make menuconfig' and enable the required options under the Kernel hacking section. Regards, Srivatsa S. Bhat snip If above configuration is all that I need, then should I be seeing warning/error messages in kernel logs(/var/log/kern.log) when there is inconsistency in locking ? To test my hypothesis, I modified my simple kernel module to deliberately induce locking error (After initializing read-write semaphore, I call down_write() and do not free this semaphore lock by commenting out up_write() invocation). But still I don't see any error or warning message trace in kernel logs, I think, I'm missing something. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Etiquette of submitting patches for fixing coding style.
On Sat, Oct 27, 2012 at 10:09 AM, Robert P. J. Day rpj...@crashcourse.cawrote: On Fri, 26 Oct 2012, Greg Freemyer wrote: fyi: Robert Day just asked for help cleaning up the Doc Book stuff. Doc Book pull comments out of the .c files and creates documentation. To clean it up, patches to the source files will be required. These are more likely to be accepted. So you could to a doc book series like: 0/2 a patch series to correct the documentation for xyz subsystem 1/2 checkpatch cleanup of the 2 files with doc updates 2/2 doc updates if you want to get started making fixes and submitting patches, i suggest doc fixes as an easy way to jump in for the simple reason that just making changes to documentation shouldn't break anything. :-) there is a separate list just for kernel documentation: http://vger.kernel.org/vger-lists.html#linux-doc so you know you'll be on-topic there chatting about documentation. from the perspective of someone who has no *official* connection with the kernel but who's submitted lots of pedantic patches over the years, let me make a couple suggestions. first, a *lot* of what's under the Documentation/ directory is absurdly old and worthless, and should probably be just deleted. ignore that stuff. other stuff under there is perfectly up-to-date, and should be left alone. the middle ground is the stuff that can be updated to reflect the current kernel, so pick a single file under there that reflects something you're interested in, start going through it, make corrections, and submit the final patch to the linux-doc list. try to work with a single file or topic at a time, it's easier to get your patches accepted. post on the kernel-doc stuff coming shortly, for the interested. rday -- Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday Thanks I'll be following the documentation mailing list. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
