[Crash-utility] [PATCH v2] ppc64: do page traversal if vmemmap_list not populated

[Aditya Gupta]

On Wed, Sep 27, 2023 at 07:25:16AM +0000, HAGIO KAZUHITO(萩尾 一仁) wrote:
> On 2023/09/26 15:12, lijiang wrote:
> > Hi, Aditya
> > Thank you for the update.
> > On Mon, Sep 25, 2023 at 5:28 PM Aditya Gupta <adityag at linux.ibm.com> wrote:
> > 
> >> Currently 'crash-tool' fails on vmcore collected on upstream kernel on
> >> PowerPC64 with the error:
> >>
> >>      crash: invalid kernel virtual address: 0  type: "first list entry
> >>
> >> Presently the address translation for vmemmap addresses is done using
> >> the vmemmap_list. But with the below commit in Linux, vmemmap_list can
> >> be empty, in case of Radix MMU on PowerPC64
> >>
> >>      368a0590d954: (powerpc/book3s64/vmemmap: switch radix to use a
> >>      different vmemmap handling function)
> >>
> >> In case vmemmap_list is empty, then it's head is NULL, which crash tries
> >> to access and fails due to accessing NULL.
> >>
> >> Instead of depending on 'vmemmap_list' for address translation for
> >> vmemmap addresses, do a kernel pagetable walk to get the physical
> >> address associated with given virtual address
> >>
> >> Tested-by: Sachin Sant <sachinp at linux.ibm.com>
> >> Reviewed-by: Hari Bathini <hbathini at linux.ibm.com>
> >> Signed-off-by: Aditya Gupta <adityag at linux.ibm.com>
> >>
> >> ---
> >>
> >> Testing
> >> =======
> >>
> >> Git tree with patch applied:
> >> https://github.com/adi-g15-ibm/crash/tree/bugzilla-203296-list-v2
> >>
> >> This can be tested with '/proc/vmcore' as the vmcore, since makedumpfile
> >> also fails in absence of 'vmemmap_list' in upstream linux
> >>
> >> The fix for makedumpfile will also been sent to upstream
> >>
> >> Changelog
> >> =========
> >>
> >> V2
> >> + handle the case of 'vmemmap_list' symbol missing according to reviews
> >>
> >>
> > The v2 looks good to me, so: Ack.
> 
> Looks good, and applied.
> https://github.com/crash-utility/crash/commit/a9291fc1bf61309c74078f757f58c47ff887da10

Thanks.
- Aditya Gupta

> 
> Thanks,
> Kazu