On Thu, Mar 28, 2019 at 11:15:53AM -0700, H. Peter Anvin wrote: > So, per our conversation today, lets create a new, readonly, data structure > pointed to by a single field in setup_header, in order to preserve what little > space we have left in that structure (a whopping 24 bytes...) > > The new data structure will have a header consisting of a magic number and a > length field; if we want to be really paranoid we could add a checksum/crc. > > The existence of this new readonly structure will be announced by bumping the > boot protocol to 2.15. > > The presence of your new boot launch capability (trenchboot) will be indicated > by a new bit in xloadflags. > > I thought hard about this, and I have come to the conclusion that the new > structure is better off in the .rodata section of the compressed kernel rather > than in the setup area, for the following reasons, some of which are > theoretical and unlikely to apply anywhere in the near future, but don't > actually hurt to address right off the bat: > > a. The future size of the structure would not be artificially constrained by > the 32K hard limit on the setup area; > b. It is one less level of indirection in the build tools; > c. It adds a possibly unnecessary dependency on the setup area, which could > possibly be awkward for some boot loaders (unlikely, but...); > d. It would allow this new structure to also carry information that might be > useful to the decompressor for whatever reason. Thank you for your help. I will try to post the patches next week. Daniel
