[Bug 2004039] [NEW] libunwind 1.6.2-0 assumes 4k page sizes and crashes on systems with bigger page sizes

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You have been subscribed to a public bug by Tobias Heider (tobhe):

[ Impact ]

 * On kernels with page size > 4K Xorg (and presumably other applications
   relying on libunwind) crashes on startup. This affects anyone
   running the official arm64 generic-64k kernel or custom non 4k kernels
   (as used by e.g. apple silicon).

   The exact error I am seeing in the logs is:

Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE) 0: /usr/lib/xorg/Xorg (OsLookupColor+0x188) [0xaaab456ca998]
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE) unw_get_proc_info failed: no unwind info found [-10]
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE)
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE) Segmentation fault at address 0x0
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE)
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: Fatal server error:
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE) Caught signal 11 (Segmentation fault). Server aborting
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE)
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE)
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: Please consult the The X.Org Foundation support
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]:          at http://wiki.x.org
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]:  for help.
Jan 30 11:16:20 ubuntu /usr/libexec/gdm-x-session[3199]: (EE)

  I have not found a workaround other than using wayland (which has other
  limitations). To reproduce use a kernel configured with a page size of
  16K (CONFIG_ARM64_16K_PAGES=y or CONFIG_ARM64_64K_PAGES=y or) and try
  to start "Ubuntu on Xorg" in gdm.

[ Test Plan ]

 * Make sure Xorg doesn't crash on 4K, 16K and 64K kernels.

[ Where problems could occur ]

 * We will have to make sure the fixed version still works with 4k
   kernels. The patch is already widely in use so the risk seems low if
   we test properly.

[ Other Info ]

 * The lunar version ships the bug fix synced from debian

 * Debian bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1026217

 * Upstream fix:
https://github.com/libunwind/libunwind/commit/e85b65cec757ef589f28957d0c6c21c498a03bdf

** Affects: libunwind (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: libunwind (Ubuntu Kinetic)
     Importance: Undecided
         Status: New

-- 
libunwind 1.6.2-0 assumes 4k page sizes and crashes on systems with bigger page sizes
https://bugs.launchpad.net/bugs/2004039
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