[Bug 1472650] Re: [arm64] gccgo runtime crashes with CONFIG_ARM64_PGTABLE_LEVELS=4

[Launchpad Bug Tracker]

This bug was fixed in the package gccgo-5 - 5.1~rc1-0ubuntu1.1

---------------
gccgo-5 (5.1~rc1-0ubuntu1.1) vivid; urgency=medium

  * libgo: Fix PR go/67508, rewrite lfstack packing/unpacking to look more
    like that in Go (Michael Hudson). LP: #1472650.

 -- dann frazier <dannf at ubuntu.com>  Wed, 16 Sep 2015 13:56:48 +0000

** Changed in: gccgo-5 (Ubuntu Vivid)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1472650

Title:
  [arm64] gccgo runtime crashes with CONFIG_ARM64_PGTABLE_LEVELS=4

Status in gcc:
  Unknown
Status in gcc-5 package in Ubuntu:
  Fix Released
Status in gccgo-4.9 package in Ubuntu:
  Invalid
Status in gccgo-5 package in Ubuntu:
  Invalid
Status in gccgo-4.9 source package in Trusty:
  In Progress
Status in gccgo-4.9 source package in Vivid:
  Invalid
Status in gccgo-5 source package in Vivid:
  Fix Released
Status in gccgo-4.9 source package in Wily:
  Invalid

Bug description:
  [Impact]
  Various go-based packages crash on startup on arm64 when booted with a kernel where CONFIG_ARM64_PGTABLE_LEVELS=4. LXD, docker and juju are examples.

  Ubuntu does not ship with this config, so it is currently not
  impacted. However, we would like to enable this config to add new
  hardware support in 15.10. The 15.10 kernel will eventually be
  provided in trusty as an lts backport, at which point this will begin
  to break users.

  [Test Case]
  Boot an arm64 system with CONFIG_ARM64_PGTABLE_LEVELS=4 enabled in the kernel. Install docker.io and run "docker help". If it fails, you'll see "fatal error: runtime_lfstackpush" followed by a stack trace. If it succeeds, you'll get normal help output.

  [Regression Risk]
  The risk of regression is lessened by testing this release on existing Ubuntu kernels w/ 3 level page tables.

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