linux-ext4 - Re: [RFC 1/1] mm: add virt to phys debug

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Date:	Thu, 1 May 2008 13:18:42 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Jiri Slaby <jirislaby@...il.com>
Subject: Re: [RFC 1/1] mm: add virt to phys debug

On Thu, 1 May 2008, Jiri Slaby wrote:

> Christoph, was you able to compile this somehow? I had to move the code
> into ioremap along 64-bit variant to allow the checking.

The 64 bit piece works fine here and I used it for debugging the vmalloc 
work. Not sure about the 32 bit piece.

> A pacth which I created is attached, I've successfully tested it by this
> module:

Great! Someone else picks this up. You can probably do a more thorough 
job than I can.

> Add some (configurable) expensive sanity checking to catch wrong address
> translations on x86.
> 
> - create linux/mmdebug.h file to be able include this file in
>   asm headers to not get unsolvable loops in header files
> - __phys_addr on x86_32 became a function in ioremap.c since
>   PAGE_OFFSET and is_vmalloc_addr is undefined if declared in
>   page_32.h (again circular dependencies)
> - add __phys_addr_const for initializing doublefault_tss.__cr3

Hmmm.. We could use include/linux/bounds.h to make 
VMALLOC_START/VMALLOC_END (or whatever you need for checking the memory 
boundaries) a cpp constant which may allow the use in page_32.h without 
circular dependencies.

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