Hi James, Thanks for your input !! On Wednesday 14 December 2016 04:46 PM, James Morse wrote: > Hi Pratyush, > > On 14/12/16 10:12, Pratyush Anand wrote: >> > On Wednesday 14 December 2016 03:08 PM, Pratyush Anand wrote: >>>> >>> I would go as far as to generate the page tables at 'kexec -l' time, >>>> >>> and only if >>> >> >>> >> Ok..So you mean that I create a new section which will have page table >>> >> entries mapping physicalmemory represented by remaining section, and >>> >> then purgatory can just enable mmu with page table from that section, >>> >> right? Seems doable. can do that. >> > >> > I see a problem here. If we create page table as a new segment then, how can we >> > verify in purgatory that sha for page table is correct? We need page table >> > before sha verification start,and we can not rely the page table created by >> > first kernel until it's sha is verified. So a chicken-egg problem. > There is more than one of those! What happens if your sha256 calculation code is > corrupted? You have to run it before you know. The same goes for all the > purgatory code. > OK, seems reasonable... will do it in kexec code. > This is why I think its better to do this in the kernel before we exit to > purgatory, but obviously that doesn't work for kdump. > > >> > I think, creating page table will just take fraction of second and should be >> > good even in purgatory, What do you say? > If it's for kdump its best-effort. I think its easier/simpler to generate and > debug them at 'kexec -l' time, but if you're worried about the increased area > that could be corrupted then do it in purgatory. > ~Pratyush
