On Fri, Oct 26, 2018 at 7:22 PM, Joel Fernandes <j...@joelfernandes.org> wrote: > On Fri, Oct 26, 2018 at 07:16:28PM +0100, Kees Cook wrote: >> On Fri, Oct 26, 2018 at 7:00 PM, Joel Fernandes (Google) >> <j...@joelfernandes.org> wrote: >> > This reverts commit 25b63da64708212985c06c7f8b089d356efdd9cf. >> > >> > Due to the commit which is being reverted here, it is not possible to >> > know if pstore's messages were from a previous boot, or from very old >> > boots. This creates an awkard situation where its unclear if crash or >> > other logs are from the previous boot or from very old boots. Also >> > typically we dump the pstore buffers after one reboot and are interested >> > in only the previous boot's crash so let us reset the buffer after we >> > save them. >> > >> > Lastly, if we don't zap them, then I think it is possible that part of >> > the buffer will be from this boot and the other parts will be from >> > previous boots. So this revert fixes all of this by calling >> > persistent_ram_zap always. >> >> I like the other patches (comments coming), but not this one: it's >> very intentional to keep all crashes around until they're explicitly >> unlinked from the pstore filesystem from userspace. Especially true >> for catching chains of kernel crashes, or a failed log collection, >> etc. Surviving multiple reboots is the expected behavior on Chrome OS >> too. > > Oh, ok. Hence the RFC tag ;-) We can drop this one then. I forgot that > unlinking was another way to clear the logs.
In another thread I discovered that the "single prz" ones actually _are_ zapped at boot. I didn't realize, but it explains why pmsg would vanish on me sometimes. ;) I always thought I was just doing something wrong with it. (And I wonder if it's actually a bug that pmsg is zapped -- console doesn't matter: it's overwritten every boot by design.) -- Kees Cook
