hello everybody,<br><br>I am new to kernel programming.<br>Can anyone tell me how to start it.<br><br>kishore kumar<br><br><div class="gmail_quote">On Sun, Sep 2, 2012 at 9:30 PM, <span dir="ltr"><<a href="mailto:kernelnewbies-request@kernelnewbies.org" target="_blank">kernelnewbies-request@kernelnewbies.org</a>></span> wrote:<br>
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Today's Topics:<br>
<br>
1. Re: map bss to addr zero (Ritesh Harjani)<br>
2. Re: map bss to addr zero (Mulyadi Santosa)<br>
3. Re: Kernel booting problem. (Jim Cromie)<br>
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<br>
Message: 1<br>
Date: Sun, 2 Sep 2012 00:53:17 +0530<br>
From: Ritesh Harjani <<a href="mailto:ritesh.harjani@gmail.com">ritesh.harjani@gmail.com</a>><br>
Subject: Re: map bss to addr zero<br>
To: Srinivas Ramanan <<a href="mailto:srinivas.ramanan@gmail.com">srinivas.ramanan@gmail.com</a>>,<br>
<a href="mailto:mulyadi.santosa@gmail.com">mulyadi.santosa@gmail.com</a><br>
Cc: <a href="mailto:kernelnewbies@kernelnewbies.org">kernelnewbies@kernelnewbies.org</a><br>
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On Mon, Aug 27, 2012 at 2:01 AM, Srinivas Ramanan <<br>
<a href="mailto:srinivas.ramanan@gmail.com">srinivas.ramanan@gmail.com</a>> wrote:<br>
<br>
> Hi all,<br>
> This is an interview question.<br>
> "What is the implication of mapping BSS to the Virtual Memory Segment 0?"<br>
><br>
> I was not able to find the answer from web. So posting here.<br>
> thanks,<br>
> srinivas<br>
><br>
> _______________________________________________<br>
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> <a href="mailto:Kernelnewbies@kernelnewbies.org">Kernelnewbies@kernelnewbies.org</a><br>
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><br>
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<br>
Hi,<br>
<br>
The bss section typically includes all uninitialized variables declared<br>
with the static keyword.<br>
The zero page which is a copy-on-write page that reads as zero is used to<br>
map the BSS segment. Any process referencing the zero page sees the page<br>
filled with zeos and if it tries to writes to the page, it ends up<br>
modifying a private copy. (LDD ch15. page 429)<br>
<br>
Mulyadi,<br>
<br>
Why it will generate a page fault later when process will tries to<br>
reference it, while it already has mapped with the zero page?<br>
<br>
<br>
Sorry if i am wrong anywhere.<br>
Ritesh<br>
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Message: 2<br>
Date: Sun, 2 Sep 2012 12:46:29 +0700<br>
From: Mulyadi Santosa <<a href="mailto:mulyadi.santosa@gmail.com">mulyadi.santosa@gmail.com</a>><br>
Subject: Re: map bss to addr zero<br>
To: Ritesh Harjani <<a href="mailto:ritesh.harjani@gmail.com">ritesh.harjani@gmail.com</a>><br>
Cc: Srinivas Ramanan <<a href="mailto:srinivas.ramanan@gmail.com">srinivas.ramanan@gmail.com</a>>,<br>
<a href="mailto:kernelnewbies@kernelnewbies.org">kernelnewbies@kernelnewbies.org</a><br>
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<br>
Hi... :)<br>
<br>
On Sun, Sep 2, 2012 at 2:23 AM, Ritesh Harjani <<a href="mailto:ritesh.harjani@gmail.com">ritesh.harjani@gmail.com</a>> wrote:<br>
> Mulyadi,<br>
><br>
> Why it will generate a page fault later when process will tries to reference<br>
> it, while it already has mapped with the zero page?<br>
><br>
><br>
<br>
Hopefully I interpret it correctly that this question is for me :)<br>
<br>
Sorry, maybe I am not clear, by reference, I meant "updating " or<br>
"writing" new value.<br>
<br>
Since this zero page is mapped as read only, when writing to this zero<br>
page, page fault is triggered. Then page fault handler conclude that<br>
this is actually a write toward zero page from valid address, so it<br>
will allocate page(s).<br>
<br>
<br>
--<br>
regards,<br>
<br>
Mulyadi Santosa<br>
Freelance Linux trainer and consultant<br>
<br>
blog: <a href="http://the-hydra.blogspot.com" target="_blank">the-hydra.blogspot.com</a><br>
training: <a href="http://mulyaditraining.blogspot.com" target="_blank">mulyaditraining.blogspot.com</a><br>
<br>
<br>
<br>
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<br>
Message: 3<br>
Date: Sun, 2 Sep 2012 04:23:02 -0600<br>
From: Jim Cromie <<a href="mailto:jim.cromie@gmail.com">jim.cromie@gmail.com</a>><br>
Subject: Re: Kernel booting problem.<br>
To: Sri Ram Vemulpali <<a href="mailto:sri.ram.gmu06@gmail.com">sri.ram.gmu06@gmail.com</a>><br>
Cc: Mulyadi Santosa <<a href="mailto:mulyadi.santosa@gmail.com">mulyadi.santosa@gmail.com</a>>, Jonathan Neusch?fer<br>
<<a href="mailto:j.neuschaefer@gmx.net">j.neuschaefer@gmx.net</a>>, <a href="mailto:kernelnewbies@kernelnewbies.org">kernelnewbies@kernelnewbies.org</a><br>
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<br>
On Wed, Aug 29, 2012 at 10:06 PM, Sri Ram Vemulpali<br>
<<a href="mailto:sri.ram.gmu06@gmail.com">sri.ram.gmu06@gmail.com</a>> wrote:<br>
> Thanks for the replies again.<br>
><br>
> This time the problem is in tty specification.<br>
> Kernel supports console=tty0 (virtual terminal), where as my inittab has<br>
> entry ::sysinit:/sbin/getty -L ttyS0 vt100. I have to change the ttyS0 to tty0.<br>
><br>
> Once I changed this, I got login prompt.<br>
><br>
> But I do not understand how we tell kernel to use ttyS0 over tty0.<br>
> Because in kernel config I selected was ttyS0 but it is using tty0.<br>
<br>
try console on boot-line<br>
<br>
root@voyage:~# more /proc/cmdline<br>
root=LABEL=ROOT_FS console=ttyS0,115200n8 rootdelay=120 reboot=bios loglevel=8<br>
dynamic_debug.verbose=1<br>
<br>
> Weird?<br>
><br>
> Thanks,<br>
> Sri.<br>
><br>
<br>
<br>
<br>
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