This comes from the BPF changes done on 4.15.0-147.

i386 uses the interpreter, while other arches have JIT. The JIT cannot
be disabled on the arches that support it and have
CONFIG_BPF_JIT_ALWAYS_ON, which is our default.

The interpreter change that causes this has been identified. It doesn't
check that the source register is zero anymore, relying on either eBPF
fixup_bpf_calls or classic BPF bpf_convert_filter doing the job of
testing for it.

The test_bpf module, though, does not go through any of these
conversions, which leads to the test failure. Partial revert of the
interpreter changes would fix it up.

We have yet to determine if any other legitimate path for either eBPF or
cBPF will skip any of these conversions. If none do, we may leave this
for a later cycle.

Cascardo.

** Also affects: linux (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu)
       Status: New => Invalid

** Changed in: linux (Ubuntu Bionic)
       Status: New => In Progress

** Changed in: linux (Ubuntu Bionic)
     Assignee: (unassigned) => Thadeu Lima de Souza Cascardo (cascardo)

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https://bugs.launchpad.net/bugs/1934414

Title:
  test_bpf.sh from ubuntu_kernel_selftests.net from linux ADT test
  failure with linux/4.15.0-149.153

Status in linux package in Ubuntu:
  Invalid
Status in linux source package in Bionic:
  In Progress

Bug description:
  This is a scripted bug report about ADT failures while running linux
  tests for linux/4.15.0-149.153 on bionic. Whether this is caused by
  the dep8 tests of the tested source or the kernel has yet to be
  determined.

  Testing failed on:
      i386: 
https://autopkgtest.ubuntu.com/results/autopkgtest-bionic/bionic/i386/l/linux/20210702_010055_445cd@/log.gz

  
  03:37:02 DEBUG| [stdout] selftests: test_bpf.sh
  03:37:02 DEBUG| [stdout] ========================================
  03:37:03 ERROR| [stderr] Segmentation fault
  03:37:03 DEBUG| [stdout] test_bpf: [FAIL]
  03:37:03 DEBUG| [stdout] not ok 1..8 selftests:  test_bpf.sh [FAIL]
  03:37:03 DEBUG| [stdout] selftests: netdevice.sh
  03:37:03 DEBUG| [stdout] ========================================

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