hello everybody, I am new to kernel programming. Can anyone tell me how to start it. kishore kumar On Sun, Sep 2, 2012 at 9:30 PM, <kernelnewbies-request@kernelnewbies.org>wrote:

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Today's Topics:

1. Re: map bss to addr zero (Ritesh Harjani) 2. Re: map bss to addr zero (Mulyadi Santosa) 3. Re: Kernel booting problem. (Jim Cromie)

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Message: 1 Date: Sun, 2 Sep 2012 00:53:17 +0530 From: Ritesh Harjani <ritesh.harjani@gmail.com> Subject: Re: map bss to addr zero To: Srinivas Ramanan <srinivas.ramanan@gmail.com>, mulyadi.santosa@gmail.com Cc: kernelnewbies@kernelnewbies.org Message-ID: < CAD15agbM8jO+-KmrRByDpd0NRN3k_bcpEQi9p8W721c8_9Pefg@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1"

On Mon, Aug 27, 2012 at 2:01 AM, Srinivas Ramanan < srinivas.ramanan@gmail.com> wrote:

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Hi all, This is an interview question. "What is the implication of mapping BSS to the Virtual Memory Segment 0?"

I was not able to find the answer from web. So posting here. thanks, srinivas

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Hi,

The bss section typically includes all uninitialized variables declared with the static keyword. The zero page which is a copy-on-write page that reads as zero is used to map the BSS segment. Any process referencing the zero page sees the page filled with zeos and if it tries to writes to the page, it ends up modifying a private copy. (LDD ch15. page 429)

Mulyadi,

Why it will generate a page fault later when process will tries to reference it, while it already has mapped with the zero page?

Sorry if i am wrong anywhere. Ritesh