How to safely overwrite memory in use by variables?

[CocaCola]

Hello.
I'm trying to code a Memtest-like OS, that needs to test available memory for errors.

A very crude memory test could consist of overwriting a chunk of memory with a constant value, then go back and check if the value changed anywhere.

My question is: what can I do about the kernel's variables, which appear scattered in the memory?
Are there some segment relocation tricks that could help with this?
Thanks.

[bluemoon]

1. test the region excluded by memtest
2. copy memtest to other region and jump there
3. test the region previously skipped.

This is easier to do with paging.

However, write-read test is only able to detect certain defeats, while sometime unstable ram (due to over-clock or mix of different brand of ram) may still pass the test.

[FallenAvatar]

I'm not sure how Memtest does it, but it is open source, so you can always look there: http://www.memtest.org/ That is my goto for memory testing *shrug*

- Monk