On 11/03/2017 15:31, Dave Anderson wrote: > ----- Original Message ----- >> Hi, >> >> Latest linux kernel enabled kaslr to randomize phys/virt memory >> addresses. There has been some effort to support kexec/kdump so that >> crash utility can still works in case crashed kernel has kaslr >> enabled. >> >> This series aims to provide enough information in qemu dumps so that >> crash utility can work with kaslr kernel too, with x86_64 guests (it >> hasn't been tested on other archs, help welcome). >> >> Two pieces of informations are necessary: the phys_base (the physical >> address where the kernel is loaded) and the kaslr offset. Other useful >> informations for debugging are provided in Linux vmcoreinfo too. >> >> There has been discussions to provide those details in early boot, >> with ACPI, fw_cfg, virtio-pstore etc, but none has reached a consensus >> yet. A possiblity for now is to provide the information when qemu-ga >> starts. This has the advantage of working with older guests and may >> not be incompatible with future methods (in this case it could ignore >> qga info for example). The drawback is that qemu will have to parse >> the json stream. For now it stops processing it whem VMDUMP_INFO is >> received. It would be wise to introduce a QMP welcome message, so that >> qemu would stop immediately processing the stream if the agent doesn't >> have the event. Another option is to create a seperate channel... >> I welcome other ideas and discussion. >> >> crash upstream doesn't yet parse NUMBER(phys_base). You may pass it to >> crash with --machdep phys_base=0x.. provided you snooped on qga. > > FYI: a patch to utilize NUMBER(phys_base) has been checked in upstream: > > > https://github.com/crash-utility/crash/commit/ed60e97e319a1cfc9e2779aa1baac305677393d8 > > Linux 4.10 commit 401721ecd1dcb0a428aa5d6832ee05ffbdbffbbe finally > exports the x86_64 "phys_base" value in the VMCOREINFO note, so > utilize it whenever it exists. > (ander...@redhat.com)
Marc-André, what is the plan here? Do we still need it (maybe for Windows)? Paolo
