Hi Petr, On Fri, 16 Oct 2020 17:24:19 +0200 Petr Tesarik <ptesarik@xxxxxxx> wrote: > Hi Philipp, > > On Fri, 16 Oct 2020 16:11:25 +0200 > Philipp Rudo <prudo@xxxxxxxxxxxxx> wrote: > > > Hi Petr, > > > > sorry for the late reply. > > No problem. ;-) > > > It's an interface for non-Linux systems for the stand-alone kdump. > > > > But that's all I'm sure of. I'm afraid only Michael knows the full history > > behind the implementation. Unfortunately he left IBM ~2 years ago so this piece > > of knowledge is lost... > > > > My theory is that originally it was planned to use this mechanism for the > > "normal" kdump as well. But for kdump common code "corrupts" the vmcoreinfo by > > adding the CRASHTIME shortly before kexec'ing the crash kernel. So the crash > > kernel would refuse to load the os_info anyway and thus it is never set. > > Sure, the checksum would have to be recalculated after setting CRASHTIME. But that's perfectly possible. True. But it's not working out of the box and there's a working workaround. So let's live with the workaround and implement the proper solution at a later date. You know, the usual stuff... > > Hope this helps you at least a little > > Yes, to some extent. The reason I asked was that I also implemented parsing of OS_INFO_VMCOREINFO in libkdumpfile a few years ago, but it has no test coverage. So, I looked around a bit and to my surprise all dump files contained a NULL pointer there, which looked somewhat suspicious. > > Anyway, if nobody knows for certain, then my plan is to add the necessary code to the Linux kernel. Patch coming soon on the mailing list. ;-) Not to discourage you, but my long term goal was to remove the mechanism. Anyhow I'm willing to revisit this plan. You definitely got me curious :) Thanks Philipp > Thanks, > Petr T > > > Philipp > > > > > > On Tue, 13 Oct 2020 14:53:03 +0200 > > Petr Tesarik <ptesarik@xxxxxxx> wrote: > > > > > Hi all, > > > > > > I've been looking into kernel crash dump analysis for some time now, > > > and I've noticed that none of my sample dumps for z/Architecture sets > > > OS_INFO_VMCOREINFO. > > > > > > Commit 4857d4bbe9821c8d732cb84455e18e12b3d79add suggests that the > > > "os_info" structure should contain vmcoreinfo, but it seems that the > > > corresponding fields are always zero, and a quick grep for > > > OS_INFO_VMCOREINFO finds only code that tries to read this entry in the > > > panic kernel, but no code that would initialize it in the old (crashed) > > > kernel. > > > > > > In short, the panic kernel always prints an informational message that > > > entry 0 is not available and falls back to get_vmcoreinfo_old(). > > > > > > Is this a bug, or is this interface used by a non-Linux operating > > > system that I'm not aware of? > > > > > > TIA, > > > Petr Tesarik > > > SUSE HW Enablement >
