Re: A new way to dive into the kernel!
Yes... Just sent the solution for the 1st assignment... You not gettting? What is the issue? Thank-you, Sri On Tue, Mar 11, 2014 at 11:19 AM, Mandeep Sandhu mandeepsandhu@gmail.com wrote: Yes. Just remember to send a plain text mail. HTH, -mandeep On Tue, Mar 11, 2014 at 10:36 AM, sanjeev sharma sanjeevsharmae...@gmail.com wrote: Hello All, Have you guys getting your assignment's ? Regards Sanjeev Sharma On Wed, Mar 5, 2014 at 10:50 AM, Mallesh Koujalagi mallesh.koujalagi.sandi...@gmail.com wrote: Good info, thanks for sharing On Tue, Mar 4, 2014 at 8:38 PM, Amit Saha amitsaha...@gmail.com wrote: On Wed, Mar 5, 2014 at 2:19 PM, Mandeep Sandhu mandeepsandhu@gmail.com wrote: Came across this in Greg (KH)s G+ feed. http://eudyptula-challenge.org/ Thought I'd share it here too in case someone missed it. Looks like a fun and interesting way to start off doing stuff in the kernel! Interesting! Thanks for sharing. -- http://echorand.me ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: A new way to dive into the kernel!
It seems too many people signed up at the moment... causing the scripts to malfunction. Should be resolved in a day or two is what I was told. I have so far received four tasks. Thank you ! Aruna On Tue, Mar 11, 2014 at 2:14 AM, Srivardhan M S srivardha...@gmail.comwrote: Yes... Just sent the solution for the 1st assignment... You not gettting? What is the issue? Thank-you, Sri On Tue, Mar 11, 2014 at 11:19 AM, Mandeep Sandhu mandeepsandhu@gmail.com wrote: Yes. Just remember to send a plain text mail. HTH, -mandeep On Tue, Mar 11, 2014 at 10:36 AM, sanjeev sharma sanjeevsharmae...@gmail.com wrote: Hello All, Have you guys getting your assignment's ? Regards Sanjeev Sharma On Wed, Mar 5, 2014 at 10:50 AM, Mallesh Koujalagi mallesh.koujalagi.sandi...@gmail.com wrote: Good info, thanks for sharing On Tue, Mar 4, 2014 at 8:38 PM, Amit Saha amitsaha...@gmail.com wrote: On Wed, Mar 5, 2014 at 2:19 PM, Mandeep Sandhu mandeepsandhu@gmail.com wrote: Came across this in Greg (KH)s G+ feed. http://eudyptula-challenge.org/ Thought I'd share it here too in case someone missed it. Looks like a fun and interesting way to start off doing stuff in the kernel! Interesting! Thanks for sharing. -- http://echorand.me ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
RE: Does register_chrdev function make device file under /dev ?
Yeah, I know mknod command. I just wanted to know if the register_chrdev makes
the file or not.
To my understanding, device file is needed when a user program wants to access
the device and we don't need to generate the device file for us to use the
device in kernel. Is my understanding correct?
For example, busybox (a user program) starts shell on tty2-4 by default. (as
the assumed default inittab below)
tty2::askfirst:-/bin/sh
tty3::askfirst:-/bin/sh
tty4::askfirst:-/bin/sh
I have had some mknod commands before in /etc/init.d/rcS to make tty2~tty4
device files, but when I remove them for test, I can see busybox (almost sure
it's coming from busybox) complaining that it cannot find the tty2~tty4 device
files.
I am trying to open a shell on my LCD (is it going to be tty2 ? I don't know)
and I'm not sure if I have to make vcs1 vcs2 vcs3 files. And I don't know how
to switch to LCD shell. during the boot, the texts come out on the LCD but I
cannot see the texts (printf) from busybox. and cannot see the shell on LCD.
When I press the keyboad, it looks like it's connected to tty1(I can see using
prints on uart window). Can anybody tell me some direction?
From : Kernel bu.ker...@gmail.com
Sent : 2014-03-11 14:44:09 ( +09:00 )
To : Kim Chan c...@etri.re.kr
Cc : kernelnewbies@kernelnewbies.org kernelnewbies@kernelnewbies.org
Subject : Re: Does register_chrdev function make device file under /dev ?
On Mar 10, 2014, at 10:25 PM, 김찬 c...@etri.re.krmailto:c...@etri.re.kr
wrote:
Hi,
This should be a basic question.
Does the regisetr_chrdev function make the device file under /dev directory?
I am running linux on our embedded system and inside vcs_init, register_chrdev
is called as below.
int __init vcs_init(void)
{
unsigned int i;
if (register_chrdev(VCS_MAJOR, vcs, vcs_fops))
panic(unable to get major %d for vcs device, VCS_MAJOR);
I can see the function is returning ok but I don't see any vcs* file under /dev.
Does it only register the device on /sys or /proc directory and not under /dev?
Thanks in advance.
Chan
You have to create a device file using 'mknod'
Ex: mknod -m 666 /dev/vcs c major no minor no
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Re: Does register_chrdev function make device file under /dev ?
On Tue, Mar 11, 2014 at 1:31 PM, Kim Chan c...@etri.re.kr wrote:
Yeah, I know mknod command. I just wanted to know if the register_chrdev
makes the file or not.
It doesn't. Also note that this is the old way of registering a char
device. New code should use cdev_add() etc.
To my understanding, device file is needed when a user program wants to
access the device and we don't need to generate the device file for us to
use the device in kernel. Is my understanding correct?
Yes, device nodes are needed for userspace code to access a device
(the good ol devices are also files Unix paradigm! :)).
I'm not sure how an in-kernel access will work (maybe via directly
getting the corresponding cdec structure).
For example, busybox (a user program) starts shell on tty2-4 by default. (as
the assumed default inittab below)
tty2::askfirst:-/bin/sh
tty3::askfirst:-/bin/sh
tty4::askfirst:-/bin/sh
I have had some mknod commands before in /etc/init.d/rcS to make tty2~tty4
device files, but when I remove them for test, I can see busybox (almost
sure it's coming from busybox) complaining that it cannot find the tty2~tty4
device files.
Correct. You will have to create those nodes manually.
I am trying to open a shell on my LCD (is it going to be tty2 ? I don't
know) and I'm not sure if I have to make vcs1 vcs2 vcs3 files. And I don't
know how to switch to LCD shell. during the boot, the texts come out on the
LCD but I cannot see the texts (printf) from busybox. and cannot see the
shell on LCD. When I press the keyboad, it looks like it's connected to
tty1(I can see using prints on uart window). Can anybody tell me some
direction?
I think you need to point getty or a shell to the correct tty before
you can see o/p on the screen. Do you know which device file you're
supposed to create for the LCD? If so, just use that in your inittab.
Something like:
::askfirst:-/bin/sh
HTH,
-mandeep
From : Kernel bu.ker...@gmail.com
Sent : 2014-03-11 14:44:09 ( +09:00 )
To : Kim Chan c...@etri.re.kr
Cc : kernelnewbies@kernelnewbies.org kernelnewbies@kernelnewbies.org
Subject : Re: Does register_chrdev function make device file under /dev ?
On Mar 10, 2014, at 10:25 PM, 김찬 c...@etri.re.kr wrote:
Hi,
This should be a basic question.
Does the regisetr_chrdev function make the device file under /dev directory?
I am running linux on our embedded system and inside vcs_init,
register_chrdev is called as below.
int __init vcs_init(void)
{
unsigned int i;
if (register_chrdev(VCS_MAJOR, vcs, vcs_fops))
panic(unable to get major %d for vcs device, VCS_MAJOR);
I can see the function is returning ok but I don't see any vcs* file under
/dev.
Does it only register the device on /sys or /proc directory and not under
/dev?
Thanks in advance.
Chan
You have to create a device file using 'mknod'
Ex: mknod -m 666 /dev/vcs c major no minor no
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RE: Does register_chrdev function make device file under /dev ?
Hi, Mandeep, Thanks for clearing some things for me.
For accessing the device in kernel code, I think maybe we can use the /proc or
/sys file system.
(I remember seeing people saying something like that.. correct me if I'm wrong)
I think you need to point getty or a shell to the correct tty before you
can see o/p on the screen. Do you know which device file you're supposed
to create for the LCD? If so, just use that in your inittab.
Something like:
::askfirst:-/bin/sh
The problem is, after the final sys_execve() which executes /sbin/init of the
ramdisk, I cannot see any shell coming up so I cannot use getty command.
Using some prints on separate uart print routine, I can see from the kbd_event
function the key value is going to current vc which is using tty1. The key
value is then handed to put_queue function where the character is somehow
copied to tty buffer. Flush_to_ldisc is scheduled for it and it will probably
get passed on to the virtual console.
Added to this, there is a notifier_call_chain and the notifier block is
registered by vcs_poll_data_get function which I don't know weather is
necessary or not. So one of my questions is if vcs is necessary for my case.
(I guess not. There is no other notifier blocks registered)
I gathered without inittab (I don't use inittab which should be ok for most
cases) the assumed default inittab
tty2::askfirst:-/bin/sh
tty3::askfirst:-/bin/sh
tty4::askfirst:-/bin/sh
is being applied by the busybox so there maybe 3 shells on tty2,tty3, and tty4
running somewhere.
But even if there are shells running I don't know how to switch to those ttys.
I tried using Ctrl-Alt F2 (or F3, F4) using the USB keyboard to switch to
tty2,3,4 to see if any shell comes up on the LCD but couldn't see it.
I tried using inittab with no avail before.
I hope somebody could point me on what should be checked. Any hint will be
appreciated.
Regards,
Chan
-Original Message-
From: Mandeep Sandhu [mailto:mandeepsandhu@gmail.com]
Sent: Tuesday, March 11, 2014 6:01 PM
To: Chan Kim
Cc: Kernel; kernelnewbies@kernelnewbies.org
Subject: Re: Does register_chrdev function make device file under /dev ?
On Tue, Mar 11, 2014 at 1:31 PM, Kim Chan c...@etri.re.kr wrote:
Yeah, I know mknod command. I just wanted to know if the
register_chrdev makes the file or not.
It doesn't. Also note that this is the old way of registering a char
device. New code should use cdev_add() etc.
To my understanding, device file is needed when a user program wants
to access the device and we don't need to generate the device file for
us to use the device in kernel. Is my understanding correct?
Yes, device nodes are needed for userspace code to access a device (the
good ol devices are also files Unix paradigm! :)).
I'm not sure how an in-kernel access will work (maybe via directly getting
the corresponding cdec structure).
For example, busybox (a user program) starts shell on tty2-4 by
default. (as the assumed default inittab below)
tty2::askfirst:-/bin/sh tty3::askfirst:-/bin/sh
tty4::askfirst:-/bin/sh I have had some mknod commands before in
/etc/init.d/rcS to make tty2~tty4 device files, but when I remove them
for test, I can see busybox (almost sure it's coming from busybox)
complaining that it cannot find the tty2~tty4 device files.
Correct. You will have to create those nodes manually.
I am trying to open a shell on my LCD (is it going to be tty2 ? I
don't
know) and I'm not sure if I have to make vcs1 vcs2 vcs3 files. And I
don't know how to switch to LCD shell. during the boot, the texts come
out on the LCD but I cannot see the texts (printf) from busybox. and
cannot see the shell on LCD. When I press the keyboad, it looks like
it's connected to tty1(I can see using prints on uart window). Can
anybody tell me some direction?
I think you need to point getty or a shell to the correct tty before you
can see o/p on the screen. Do you know which device file you're supposed
to create for the LCD? If so, just use that in your inittab.
Something like:
::askfirst:-/bin/sh
HTH,
-mandeep
From : Kernel bu.ker...@gmail.com
Sent : 2014-03-11 14:44:09 ( +09:00 )
To : Kim Chan c...@etri.re.kr
Cc : kernelnewbies@kernelnewbies.org kernelnewbies@kernelnewbies.org
Subject : Re: Does register_chrdev function make device file under /dev ?
On Mar 10, 2014, at 10:25 PM, 김찬 c...@etri.re.kr wrote:
Hi,
This should be a basic question.
Does the regisetr_chrdev function make the device file under /dev
directory?
I am running linux on our embedded system and inside vcs_init,
register_chrdev is called as below.
int __init vcs_init(void)
{
unsigned int i;
if (register_chrdev(VCS_MAJOR, vcs, vcs_fops))
panic(unable to get major %d for vcs device,
VCS_MAJOR);
I can see the function is returning ok but I don't
building kernel modules for linux differnet version
Hi, I have a scenario where I need to build a driver for different kernel versions. I have kernel-headers of different version in /lib/modules/ 2.6.32- 2.6.39- and currently I am booted into 2.6.32-(which I find out by uname -r) Now in my driver makefile, I generate .ko of driver make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules but I notice that the driver .ko gets generated for 2.6.39- though I am booted into 2.6.32-. Can anyone help me figure out why this is happening? Regards, Saket Sinha ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: building kernel modules for linux differnet version
Hi, Le mardi 11 mars 2014 à 21:16 +0530, Saket Sinha a écrit : I have a scenario where I need to build a driver for different kernel versions. I have kernel-headers of different version in /lib/modules/ 2.6.32- 2.6.39- and currently I am booted into 2.6.32-(which I find out by uname -r) You don't need to boot on a specific kernel version to build external module for it. Now in my driver makefile, I generate .ko of driver make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules but I notice that the driver .ko gets generated for 2.6.39- though I am booted into 2.6.32-. Can anyone help me figure out why this is happening? Could you check that /lib/modules/2.6.32-/build is not a symbolic link to linux 2.6.39- sources ? Regards. -- Yann Droneaud OPTEYA ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: building kernel modules for linux differnet version
Le mardi 11 mars 2014 à 22:42 +0530, Saket Sinha a écrit : Please find my response inline I have a scenario where I need to build a driver for different kernel versions. I have kernel-headers of different version in /lib/modules/ 2.6.32- 2.6.39- and currently I am booted into 2.6.32-(which I find out by uname -r) You don't need to boot on a specific kernel version to build external module for it. I am aware of that. I just need the kernel header of that specific version instead. What I meant was that since I was using the expression uname -r in my makefile below- make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules so I specified that. Now in my driver makefile, I generate .ko of driver make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules but I notice that the driver .ko gets generated for 2.6.39- though I am booted into 2.6.32-. Can anyone help me figure out why this is happening? Could you check that /lib/modules/2.6.32-/build is not a symbolic link to linux 2.6.39- sources ? I am pasting the output for you to check [root@Noi1-502156 ~]# cd /lib/modules [root@Noi1-502156 modules]# ls 2.6.32-220.4.2.el6.x86_64 2.6.39-300.17.1.el6uek.x86_64 2.6.32-358.6.2.el6.x86_64 2.6.39-400.24.1.el6uek.x86_64 [root@Noi1-502156 modules]# ll total 16 drwxr-xr-x. 8 root root 4096 Feb 28 14:41 2.6.32-220.4.2.el6.x86_64 drwxr-xr-x. 7 root root 4096 Jul 15 2013 2.6.32-358.6.2.el6.x86_64 drwxr-xr-x 8 root root 4096 Aug 12 2013 2.6.39-300.17.1.el6uek.x86_64 drwxr-xr-x. 4 root root 4096 Jul 10 2013 2.6.39-400.24.1.el6uek.x86_64 [root@Noi1-502156 modules]# Now try ls -dFl /lib/modules/2.6.3*/build And grep '^\(\(VERSION\)\|\(PATCHLEVEL\)\|\(SUBLEVEL\)\|\(EXTRAVERSION\)\| \(MAKEARGS\)\)' /lib/modules/*/build/Makefile Check that matches the expected version. -- Yann Droneaud OPTEYA ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: building kernel modules for linux differnet version
On Tue, Mar 11, 2014 at 11:09 PM, Yann Droneaud ydrone...@opteya.com wrote: Le mardi 11 mars 2014 à 22:42 +0530, Saket Sinha a écrit : Please find my response inline I have a scenario where I need to build a driver for different kernel versions. I have kernel-headers of different version in /lib/modules/ 2.6.32- 2.6.39- and currently I am booted into 2.6.32-(which I find out by uname -r) You don't need to boot on a specific kernel version to build external module for it. I am aware of that. I just need the kernel header of that specific version instead. What I meant was that since I was using the expression uname -r in my makefile below- make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules so I specified that. Now in my driver makefile, I generate .ko of driver make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules but I notice that the driver .ko gets generated for 2.6.39- though I am booted into 2.6.32-. Can anyone help me figure out why this is happening? Could you check that /lib/modules/2.6.32-/build is not a symbolic link to linux 2.6.39- sources ? I am pasting the output for you to check [root@Noi1-502156 ~]# cd /lib/modules [root@Noi1-502156 modules]# ls 2.6.32-220.4.2.el6.x86_64 2.6.39-300.17.1.el6uek.x86_64 2.6.32-358.6.2.el6.x86_64 2.6.39-400.24.1.el6uek.x86_64 [root@Noi1-502156 modules]# ll total 16 drwxr-xr-x. 8 root root 4096 Feb 28 14:41 2.6.32-220.4.2.el6.x86_64 drwxr-xr-x. 7 root root 4096 Jul 15 2013 2.6.32-358.6.2.el6.x86_64 drwxr-xr-x 8 root root 4096 Aug 12 2013 2.6.39-300.17.1.el6uek.x86_64 drwxr-xr-x. 4 root root 4096 Jul 10 2013 2.6.39-400.24.1.el6uek.x86_64 [root@Noi1-502156 modules]# Now try ls -dFl /lib/modules/2.6.3*/build [root@Noi1-502156 ~]# ls -dFl /lib/modules/2.6.3*/build lrwxrwxrwx. 1 root root 50 Feb 17 2012 /lib/modules/2.6.32-220.4.2.el6.x86_64/build - ../../../usr/src/kernels/2.6.32-220.4.2.el6.x86_64/ lrwxrwxrwx. 1 root root 50 Jun 11 2013 /lib/modules/2.6.32-358.6.2.el6.x86_64/build - ../../../usr/src/kernels/2.6.32-358.6.2.el6.x86_64 lrwxrwxrwx 1 root root 54 Jul 10 2013 /lib/modules/2.6.39-300.17.1.el6uek.x86_64/build - ../../../usr/src/kernels/2.6.39-300.17.1.el6uek.x86_64/ And grep '^\(\(VERSION\)\|\(PATCHLEVEL\)\|\(SUBLEVEL\)\|\(EXTRAVERSION\)\| \(MAKEARGS\)\)' /lib/modules/*/build/Makefile [root@Noi1-502156 ~]# grep '^\(\(VERSION\)\|\(PATCHLEVEL\)\|\(SUBLEVEL\)\|\(EXTRAVERSION\)\|\(MAKEARGS\)\)' /lib/modules/*/build/Makefile /lib/modules/2.6.32-220.4.2.el6.x86_64/build/Makefile:VERSION = 2 /lib/modules/2.6.32-220.4.2.el6.x86_64/build/Makefile:PATCHLEVEL = 6 /lib/modules/2.6.32-220.4.2.el6.x86_64/build/Makefile:SUBLEVEL = 32 /lib/modules/2.6.32-220.4.2.el6.x86_64/build/Makefile:EXTRAVERSION = -220.4.2.el6.x86_64 /lib/modules/2.6.39-300.17.1.el6uek.x86_64/build/Makefile:VERSION = 3 /lib/modules/2.6.39-300.17.1.el6uek.x86_64/build/Makefile:PATCHLEVEL = 0 /lib/modules/2.6.39-300.17.1.el6uek.x86_64/build/Makefile:SUBLEVEL = 36 /lib/modules/2.6.39-300.17.1.el6uek.x86_64/build/Makefile:EXTRAVERSION = -300.17.1.el6uek.x86_64 Check that matches the expected version. As already mentioned, driver .ko gets generated for 2.6.39-. Kindly let me know what you could make out of above outputs and why exactly I am getting a 2.6.39- .ko file when I am specifying a 2.6.32- kernel header. Regards, Saket Sinha ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
How to use sparse to check my driver
I am trying to use sparse to check my driver that I developed. From http://kernelnewbies.org/Sparse, It said 'make C=2 drivers/staging/wlan-ng/', what does it check it I do 'make C=2' and how does it actually call 'spare'? Do I need to modify my Makefile to add a new target or something? Thank you. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
where is the printf source for busybox?
Hi,
I've had this question for some time past and I would like to know the answer
now..
I wanted to follow a printf in busybox but couldn't find the source of the
printf function.
Then I throught probably the printf is provided by the system library where
printf is connected to proper linux system call. (Is it printk?)
So I checkd LD_LIBRARY_PATH of my shell and found libc.so under /lib. I could
see by 'nm libc.so' that printf is in the library.
But where can I see the printf source? Is it under gcc source? in GNU sdk,
under glibc-2.16.0, I tried
# grep 'int printf(' * -r
but nothing comes up.
In linux kernel source doing the same gaves me
arch/x86/boot/boot.h:int printf(const char *fmt, ...);
arch/x86/boot/printf.c:int printf(const char *fmt, ...)
arch/um/include/shared/kern.h:extern int printf(const char *fmt, ...);
arch/um/os-Linux/user_syms.c:extern int printf(const char *, ...);
arch/powerpc/boot/stdio.h:extern int printf(const char *fmt, ...)
__attribute__((format(printf, 1, 2)));
so printf is defined only for x86 architecture?
I understand printf is for user program not kernel, so I want to see how the
printf is connected to kernel print function. (the system call, I know in
sparc, linux system call is trap 0x90, function 59 when using assembly)
Where can I find the printf (user program) source?
Thanks in advance.
Chan
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Re: where is the printf source for busybox?
On Wed, Mar 12, 2014 at 7:14 AM, Kim Chan c...@etri.re.kr wrote:
Hi,
I've had this question for some time past and I would like to know the
answer now..
I wanted to follow a printf in busybox but couldn't find the source of the
printf function.
Then I throught probably the printf is provided by the system library
where printf is connected to proper linux system call. (Is it printk?)
So I checkd LD_LIBRARY_PATH of my shell and found libc.so under /lib. I
could see by 'nm libc.so' that printf is in the library.
But where can I see the printf source? Is it under gcc source? in GNU sdk,
under glibc-2.16.0, I tried
# grep 'int printf(' * -r
but nothing comes up.
In linux kernel source doing the same gaves me
arch/x86/boot/boot.h:int printf(const char *fmt, ...);
arch/x86/boot/printf.c:int printf(const char *fmt, ...)
arch/um/include/shared/kern.h:extern int printf(const char *fmt,
...);
arch/um/os-Linux/user_syms.c:extern int printf(const char *, ...);
arch/powerpc/boot/stdio.h:extern int printf(const char *fmt, ...)
__attribute__((format(printf, 1, 2)));
so printf is defined only for x86 architecture?
I understand printf is for user program not kernel, so I want to see how
the printf is connected to kernel print function. (the system call, I know
in sparc, linux system call is trap 0x90, function 59 when using assembly)
Where can I find the printf (user program) source?
Thanks in advance.
Chan
Hi Chan,
Here is Glibc printf.c code:
int
__printf (const char *format, ...)
{
va_list arg;
int done;
va_start (arg, format);
done = vfprintf (stdout, format, arg);
va_end (arg);
return done;
}
it in turn call vfprintf. You can see Glibc vfprintf.c
(glibc-2.18/stdio-common/vfprintf.c)
Correct me If my understanding is wrong.
Thanks
Mohan L
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RE: where is the printf source for busybox?
Hi, Mohan,
Thanks! so the printf is name chagned to _printf by the compiler. I missed
that.
Chan
From : Mohan L l.mohan...@gmail.com
Sent : 2014-03-12 11:07:45 ( +09:00 )
To : Kim Chan c...@etri.re.kr
Cc : kernelnewbies@kernelnewbies.org kernelnewbies@kernelnewbies.org
Subject : Re: where is the printf source for busybox?
On Wed, Mar 12, 2014 at 7:14 AM, Kim Chan
c...@etri.re.krmailto:c...@etri.re.kr wrote:
Hi,
I've had this question for some time past and I would like to know the answer
now..
I wanted to follow a printf in busybox but couldn't find the source of the
printf function.
Then I throught probably the printf is provided by the system library where
printf is connected to proper linux system call. (Is it printk?)
So I checkd LD_LIBRARY_PATH of my shell and found libc.so under /lib. I could
see by 'nm libc.so' that printf is in the library.
But where can I see the printf source? Is it under gcc source? in GNU sdk,
under glibc-2.16.0, I tried
# grep 'int printf(' * -r
but nothing comes up.
In linux kernel source doing the same gaves me
arch/x86/boot/boot.h:int printf(const char *fmt, ...);
arch/x86/boot/printf.c:int printf(const char *fmt, ...)
arch/um/include/shared/kern.h:extern int printf(const char *fmt, ...);
arch/um/os-Linux/user_syms.c:extern int printf(const char *, ...);
arch/powerpc/boot/stdio.h:extern int printf(const char *fmt, ...)
__attribute__((format(printf, 1, 2)));
so printf is defined only for x86 architecture?
I understand printf is for user program not kernel, so I want to see how the
printf is connected to kernel print function. (the system call, I know in
sparc, linux system call is trap 0x90, function 59 when using assembly)
Where can I find the printf (user program) source?
Thanks in advance.
Chan
Hi Chan,
Here is Glibc printf.c code:
int
__printf (const char *format, ...)
{
va_list arg;
int done;
va_start (arg, format);
done = vfprintf (stdout, format, arg);
va_end (arg);
return done;
}
it in turn call vfprintf. You can see Glibc vfprintf.c
(glibc-2.18/stdio-common/vfprintf.c)
Correct me If my understanding is wrong.
Thanks
Mohan L
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Not mounting rootfs
Hi folks, I trying to boot a kernel with a rootfs generated with buildroot under qemu but with any success, the output is: [0.814014] Magic number: 6:562:333 [0.814522] tty tty54: hash matches [0.815121] rtc_cmos 00:00: setting system clock to 2014-03-11 14:19:08 UTC (1394547548) [0.820886] List of all partitions: [0.821097] No filesystem could mount root, tried: [0.821399] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) [0.821877] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.14.0-rc5-ARCH-00265-gb01d4e6 #1 [0.822184] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [0.822550] 880007107df8 814f7bc4 816e5af0 [0.822903] 880007107e70 814f4749 0010 880007107e80 [0.823216] 880007107e20 880007107e28 880007107e90 0012 [0.823421] Call Trace: That is the way I'm invoking qemu: qemu-system-x86_64 -boot c -m 128 -nographic -kernel ./path/to/bzImage -hda ./buildroot-2013.05/output/images/rootfs.ext2 -append root=/dev/ram0 console=ttyS0 init=/sbin/init Any tip is extremely welcome :) --- Flavio Ceolin ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: where is the printf source for busybox?
On Wed, Mar 12, 2014 at 10:09 AM, Dave Hylands dhyla...@gmail.com wrote: Hi, On Tue, Mar 11, 2014 at 6:44 PM, Kim Chan c...@etri.re.kr wrote: Hi, I've had this question for some time past and I would like to know the answer now.. I wanted to follow a printf in busybox but couldn't find the source of the printf function. Then I throught probably the printf is provided by the system library where printf is connected to proper linux system call. (Is it printk?) busybox is typically built using uclibc, which is here: http://www.uclibc.org/ The printf source code within uclibc is here: http://git.uclibc.org/uClibc/tree/libc/stdio/printf.c It eveentually winds up in _vfprintf here: http://git.uclibc.org/uClibc/tree/libc/stdio/_vfprintf.c Hi Dave, I missed busybox. Thanks! Mohan L ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re:Re: A new way to dive into the kernel! [Eudyptula Challenge]
Hi all, I am also thinking of taking this challenge. But I found very limited information on submission. So can you help me what we need to submit for the Assigment 1, will dmesg (or /proc/kmsg) output and module(assignement1.c and Makeflie) be enough ?? Also is there any group of forum where we can discuss assignments ? Regards Rahul ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Re: A new way to dive into the kernel! [Eudyptula Challenge]
I just completed successfully task 1 .. :) ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
RE: where is the printf source for busybox?
Hello Dave, (and Mohan)
Thanks for the nice info.
I've downloaded uClibc code and ran ctags -R and searched down printf.
It looks like the main print path is (assuming __STDIO_BUFFERS : I guess user
level buffer for stdin, stdout, stderr) and assuming STDIO_GETC/PUTC_MACRO
defined. without the macro, it seems to directly go to __fputc_unlocked..)
printf - vfprintf (very complex doing all the format conversions..) - PUTC -
putc_unlocked - __FPUTC_UNLOCKED -(after some macro conversion)
__fputc_unlocked - __stdio_WRITE (sometime write only to buffer) - __WRITE -
__gcs.write - write
in libc/stdio/_stdio.h, the __gcs.wirte is assigned to _cs_write and
in libc/stdio/_cs_funcs.c, the _cs_write function is defined as below.
ssize_t attribute_hidden _cs_write(void *cookie, const char *buf, size_t
bufsize)
{
return write(*((int *) cookie), (char *) buf, bufsize);
}
what does cs stand for here? (Hm.. seems like custom streams..in the code) and
I couldn't follow past write above. Where is the function write defined?
Any hint will be deeply appreciated and if I'm wrong with something, please
correct me.
Thanks and regards,
Chan
From : Dave Hylands dhyla...@gmail.com
Sent : 2014-03-12 13:39:11 ( +09:00 )
To : Kim Chan c...@etri.re.kr
Cc : kernelnewbies@kernelnewbies.org kernelnewbies@kernelnewbies.org
Subject : Re: where is the printf source for busybox?
Hi,
On Tue, Mar 11, 2014 at 6:44 PM, Kim Chan
c...@etri.re.krmailto:c...@etri.re.kr wrote:
Hi,
I've had this question for some time past and I would like to know the answer
now..
I wanted to follow a printf in busybox but couldn't find the source of the
printf function.
Then I throught probably the printf is provided by the system library where
printf is connected to proper linux system call. (Is it printk?)
busybox is typically built using uclibc, which is here:
http://www.uclibc.org/
The printf source code within uclibc is here:
http://git.uclibc.org/uClibc/tree/libc/stdio/printf.c
It eveentually winds up in _vfprintf here:
http://git.uclibc.org/uClibc/tree/libc/stdio/_vfprintf.c
--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.comhttp://www.davehylands.com/
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