[PATCH v3 0/2] gitlab-ci.yml: Add jobs to test CFI

[Daniele Buono]

For a few months now QEMU has had options to enable compiler-based
control-flow integrity if built with clang.

While this feature has a low maintenance, It's probably still better to
add tests to the CI environment to check that an update doesn't break it.

The patchset allow gitlab testing of:
* --enable-cfi: forward-edge cfi (function pointers)
* --enable-safe-stack: backward-edge cfi (return pointers)
As an added benefit, this also inherently tests LTO. 

The first patch allows a custom selection for linker parallelism.
Currently, make parallelism at build time is based on the number
of cpus available.
This doesn't work well with LTO at linking, because the linker has to
load in memory all the intermediate object files for optimization.
If the gitlab runner happens to run two linking processes at the same
time, the job will fail with an out-of-memory error,
The patch leverages the ability to maintain high parallelism at
compile time, but limit the number of linkers executed in parallel.

The second patch introduces the ci/cd jobs in the gitlab pipeline.
To maintain a limited number of short jobs, Daniel suggested to only
test targets where KVM is available. This restricted the jobs to
x86_64, ppc64, aarch64 and s390x. To keep the jobs under 1 hour, I
created three chains of build -> check -> acceptance jobs, divided by
architecture vendor (Intel, ARM, IBM).

For build, we have to select --enable-slirp=git, because CFI needs a
statically linked version of slirp, with CFI information. More info on
this can be found in a comment in .gitlab-ci.yml, or on a patch for
mason currently in ML:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg787636.html

Test runs of the full pipeline are here (cfi-ci-v3 branch):
https://gitlab.com/dbuono/qemu/-/pipelines/264484574

v3:
- Restricted the targets to x86_64, ppc64, aarch64 and s390x, under
  suggestion from Daniel.

v2:
- More details in the code about the issue of using system-wide slirp
- Use meson to only limit linker parallelism instead of forcing no
  parallelism on the whole compilation process.

Daniele Buono (2):
  gitlab-ci.yml: Allow custom # of parallel linkers
  gitlab-ci.yml: Add jobs to test CFI flags

 .gitlab-ci.yml | 123 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)

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2.30.0