[Bug 1926355] Re: Snap applications segfault with new core20 (rev: 1015+)

[Ian Johnson]

With the test snap that uses core20 as it's base, test-snapd-rsync-
core20 (installable on the edge channel), I see it segfaulting when
running the snap on both a UC20 system with the core20 snap as a base
snap, as well as on my groovy desktop:

https://pastebin.ubuntu.com/p/qbq86DYw5Q/

You can reproduce this with:
```
snap install core20 --beta || snap refresh core20 --beta
snap install test-snapd-rsync-core20 --edge
snap run --experimental-gdbserver test-snapd-rsync-core20.rsync 

... you will see the gdb command to use to connect to the gdbserver running inside the snap's mount namespace
gdb -ex="target remote :33021" -ex=continue -ex="signal SIGCONT" # in another window
```

My gdb output seems to imply the segfault is coming from
0x000056287d57a2d4 in time at plt ? I haven't been able to load debug
symbols for this gdb version into the snap mount namespace yet so I
don't have more info, but presumably you could copy debug symbols into
the snap's dir somewhere like $HOME/snap/test-snapd-rsync-
core20/current/debug.sym and then load it from the gdb shell.

For reference, I've also attached the output of strace too in case
that's more useful: https://pastebin.ubuntu.com/p/rpqKrnBHrg/

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https://bugs.launchpad.net/bugs/1926355

Title:
  Snap applications segfault with new core20 (rev: 1015+)

Status in snap-core20:
  New
Status in glibc package in Ubuntu:
  Incomplete

Bug description:
  It seems that with our new core20 in the beta channel all snaps seem
  to be segfaulting. We recently had a new glibc landed in focal-updates
  - might be related.

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