[Bug 1869465] Re: Kdump-Tools: Makedumpfile Failed, Falling Back To 'Cp'

[Mauricio Faria de Oliveira]

Hi Jo, Eric,

Eric, thanks for uploading to Groovy!
(Sorry, I had made similar changes to groovy v2 debdiff -- no worries, but just wanted to let you know I checked those for groovy too, to not give you more trouble in helping here! :-)

The changes have landed in Groovy, so I just uploaded to
Focal/Eoan/Bionic/Xenial.

cheers,
Mauricio


** Changed in: makedumpfile (Ubuntu Focal)
       Status: New => In Progress

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Title:
  Kdump-Tools: Makedumpfile Failed, Falling Back To 'Cp'

Status in makedumpfile package in Ubuntu:
  Fix Released
Status in makedumpfile source package in Xenial:
  New
Status in makedumpfile source package in Bionic:
  New
Status in makedumpfile source package in Eoan:
  New
Status in makedumpfile source package in Focal:
  In Progress
Status in makedumpfile source package in Groovy:
  Fix Released
Status in makedumpfile package in Debian:
  New

Bug description:
  [Impact]

  On some arm systems makedumpfile fails to translate virtual to physical addresses properly.
  This may result in makedumpfile looping forever exhausting
  all memory, or  translating a virtual address to an invalid physical address 
  and then failing and falling back to cp.
  The reason it cannot resolve some addresses is because the PMD mask is wrong. 
  When physical address mask allows up to 48bits pmd mask should allow the
  same, currently pmd mask is set to 40bits (see commit [1]).

  Commit [1] fixes this bug.

  [Test Case]

  To hit this bug you need a system that needs physical addresses over 1TB.
  This may be either because you have a lot
  of memory or because the firmware mapped some memory above 1TB for some
  reason [1].

  A user hit this bug because firmware mapped memory above 1TB and provided a 
  dump so I could reproduce the bug when running makedumpfile on the dump.

  [Regression Potential]

  This commit changes the PMD_SECTION_MASK for arm64. So any regression potential
  would only affect arm64 systems. In addition PMD_SECTION_MASK is used in translation
  from virtual to physical addresses and therefore any regression would happen during
  this process.

  [Other]

  [1]
  https://github.com/makedumpfile/makedumpfile/commit/7242ae4cb5288df626f464ced0a8b60fd669100b

  
  When testing kdump on Ubuntu 18.04.4 (arm64) GA kernel, makedumpfile fails. The test steps are as follows:
  # echo 1> / proc / sys / kernel / sysrq
  # echo c> / proc / sysrq-trigger
  The logs are as follows:

  kdump-tools[646]: starting kdump-tools: * running makedumpfile -c -d 31 /proc/vmcore /var/crash/202003251128/dump-incomplete
  kdump-tools[646]: readpage_elf: Attempt to read non-existent page at 0x0
  kdump-tools[646]: readmem: type_addr: 1, addr:ff0, size:8
  kdump-tools[646]: vaddr_to_paddr_arm64: Can't read pud
  kdump-tools[646]: readmem: Can't convert a virtual address(ffff9e653690) to physical address.
  kdump-tools[646]: readmem: type_addr: 0, addr:ffff9e653690, size:1032
  kdump-tools[646]: validate_mem_section: Can't read mem_section array.
  kdump-tools[646]: get_mem_section: Could not validate mem_section.
  kdump-tools[646]: get_mm_sparsemem: Can't get the address of mem_section.
  kdump-tools[646]: makedumpfile Failed.
  kdump-tools[646]: * kdump-tools: makedumpfile failed, falling back to 'cp'

  But when I use the HWE kernel, I find that there is no such problem.
  The HEW kernel version: 5.3.0-42-generic

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