vuhlig@us.ibm.com writes:
The idea is, that the kernel can revoke pages from sigma 0, what is not implemented yet. [...]
I don't think it is a part of the Sigma0 specification that Sigma0 should be able to handle the case where the kernel revokes mappings of pages mapped into Sigma0. Instead, Sigma0 is pretty safe to assume that it magically owns---and has access to---all physically- addressable memory (maybe with the exception of the kernel-private code and data sections; the experts are still out on this one).
Michael
On 23 Feb 1999, Michael Hohmuth wrote:
vuhlig@us.ibm.com writes:
The idea is, that the kernel can revoke pages from sigma 0, what is not implemented yet. [...]
I don't think it is a part of the Sigma0 specification that Sigma0 should be able to handle the case where the kernel revokes mappings of pages mapped into Sigma0. Instead, Sigma0 is pretty safe to assume that it magically owns---and has access to---all physically- addressable memory (maybe with the exception of the kernel-private code and data sections; the experts are still out on this one).
The HotOS paper on secure web OS's outlines a sigma0 where a task requesting a page mapping donates memory back to sigma zero which is then allocated to the kernel for page table memory. It also mentions using sigma1 as a TCB pager. Unfortunately no details are really outlined for a protocol. Has anyone been working on this?
Cheers Adam
Michael
hohmuth@innocent.com, hohmuth@inf.tu-dresden.de http://home.pages.de/~hohmuth/
l4-hackers@os.inf.tu-dresden.de