fix(driver/bpf): fixed old bpf probe with clang-18.

[FedeDP]

What type of PR is this?

/kind bug

Any specific area of the project related to this PR?

/area driver-bpf

Does this PR require a change in the driver versions?

What this PR does / why we need it:

Fixes old probe bpf verifier when built with clang-18.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

fix(driver/bpf): fixed old bpf probe with clang-18.

[FedeDP]

/milestone 7.2.0+driver

[github-actions]

Please double check driver/SCHEMA_VERSION file. See versioning.

/hold

[FedeDP]

Verifier log on master (part of):

8,umax=0xfffffffffffffff8,smax32=0x7ffffff8,umax32=0xfffffff8,var_off=(0x0; 0xfffffffffffffff8)) R9=scalar(id=16,smax=0x7ffffffffffffff8,umax=0xfffffffffffffff8,smax32=0x7ffffff8,umax32=0xfffffff8,var_off=(0x0; 0xfffffffffffffff8))
369: (85) call bpf_probe_read_user#112
R2 min value is negative, either use unsigned or 'var &= const'
processed 316 insns (limit 1000000) max_states_per_insn 0 total_states 16 peak_states 16 mark_read 13

-- END PROG LOAD LOG --
libscap: bpf_load_program() event=raw_tracepoint/filler/sys_poll_e: Operation not permitted (1)

[FedeDP]

I will run kernel-testing framework against this branch (even if the fix looks correct under any circumstance): https://github.com/falcosecurity/libs/actions/runs/9159697747

[FedeDP]

as expected, no new failures:
amd64:

KERNEL	CMAKE-CONFIGURE	KMOD BUILD	KMOD SCAP-OPEN	BPF-PROBE BUILD	BPF-PROBE SCAP-OPEN	MODERN-BPF SCAP-OPEN
amazonlinux2-4.19	🟢	🟢	🟢	🟢	❌	🟡
amazonlinux2-5.10	🟢	🟢	🟢	🟢	🟢	🟢
amazonlinux2-5.15	🟢	🟢	🟢	🟢	🟢	🟢
amazonlinux2-5.4	🟢	🟢	🟢	🟢	🟢	🟡
amazonlinux2022-5.15	🟢	🟢	🟢	🟢	🟢	🟢
amazonlinux2023-6.1	🟢	🟢	🟢	🟢	🟢	🟢
archlinux-6.0	🟢	🟢	🟢	🟢	🟢	🟢
archlinux-6.7	🟢	🟢	🟢	🟢	🟢	🟢
centos-3.10	🟢	🟢	🟢	🟡	🟡	🟡
centos-4.18	🟢	🟢	🟢	🟢	🟢	🟢
centos-5.14	🟢	🟢	🟢	🟢	🟢	🟢
fedora-5.17	🟢	🟢	🟢	🟢	🟢	🟢
fedora-5.8	🟢	🟢	🟢	🟢	🟢	🟢
fedora-6.2	🟢	🟢	🟢	🟢	🟢	🟢
oraclelinux-3.10	🟢	🟢	🟢	🟡	🟡	🟡
oraclelinux-4.14	🟢	🟢	🟢	🟢	🟢	🟡
oraclelinux-5.15	🟢	🟢	🟢	🟢	🟢	🟢
oraclelinux-5.4	🟢	🟢	🟢	🟢	🟢	🟡
ubuntu-4.15	🟢	🟢	🟢	🟢	🟢	🟡
ubuntu-5.8	🟢	🟢	🟢	🟢	🟢	🟡
ubuntu-6.5	🟢	🟢	🟢	🟢	🟢	🟢

arm64:

KERNEL	CMAKE-CONFIGURE	KMOD BUILD	KMOD SCAP-OPEN	BPF-PROBE BUILD	BPF-PROBE SCAP-OPEN	MODERN-BPF SCAP-OPEN
amazonlinux2-5.4	🟢	🟢	🟢	🟢	🟢	🟡
amazonlinux2022-5.15	🟢	🟢	🟢	🟢	🟢	🟢
fedora-6.2	🟢	🟢	🟢	🟢	🟢	🟢
oraclelinux-4.14	🟢	🟢	🟢	🟡	🟡	🟡
oraclelinux-5.15	🟢	🟢	🟢	🟢	🟢	🟢
ubuntu-6.5	🟢	🟢	🟢	🟢	🟢	🟢

[Andreagit97]

Great catch! thank you!

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Andreagit97, FedeDP, LucaGuerra

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• driver/OWNERS [Andreagit97,FedeDP,LucaGuerra]

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[FedeDP]

/unhold