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Posted: **Thu Dec 25, 2008 1:42 pm**

Hi
I am referring JamesM tutorial. While setting up the heap i am getting a page fault as

Page fault! ( present read-only ) at 0xc0100000 - EIP: 0x1002e7

Its causing a page fault when i try to when it executes the following statement in initialise_paging()

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kheap = create_heap(KHEAP_START, KHEAP_START+KHEAP_INITIAL_SIZE, 0xCFFFF000, 0, 0);

Using the print command i found that the page fault actually occurs in function place_ordered_array when it tries to clear the memory in which to place heap->index.

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memset(temp.array, 0, max_size*sizeof(type_t));

I am using Bochs and gcc on Ubuntu.I have also attached my code.Any help is appreciated.

Thanks.

Posted: **Thu Dec 25, 2008 5:32 pm**

Has the memory you're trying to write to been mapped into your address space?

Posted: **Fri Dec 26, 2008 8:46 am**

Solved the problem. The pages were not loaded into the memory so had to increase the KHEAP_INITIAL_SIZE.
Also another change that was made was:

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for(i = KHEAP_START; i< KHEAP_START+KHEAP_INITIAL_SIZE; i += 0x1000)
	{
	get_page(i, 1, kernel_directory);
	}

to

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for(i = KHEAP_START; i< KHEAP_END; i += 0x1000)
	{
	get_page(i, 1, kernel_directory);
	}

so as to create entries for the entire heap in the page directory. I came across this bug on this forum itself. So if anyone using JamesM heap code do make the latter change (if not already present).

Thanks.

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page fault in setting up heap

page fault in setting up heap

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Re: page fault in setting up heap