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

Message ID 20210304030948.9367-1-dbuono@linux.vnet.ibm.com
Headers show
Series gitlab-ci.yml: Add jobs to test CFI | expand

Message

Daniele Buono March 4, 2021, 3:09 a.m. UTC 
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(+)

Comments

Alex Bennée March 4, 2021, 7:56 p.m. UTC | #1 
Daniele Buono <dbuono@linux.vnet.ibm.com> writes:

> 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

Queued to testing/next, thanks.