Keep the license passed in bpf_attr

[gnosek]

This reverts half of commit 8918b95.
It makes eBPF work at all again, at least on Ubuntu 16.04 and 20.04

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area build

/area driver-kmod

/area driver-ebpf

/area libscap

/area libsinsp

/area tests

What this PR does / why we need it:

Without an explicit license in the bpf_attr struct, the bpf() syscall returns -EFAULT when loading any eBPF program:

bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_RAW_TRACEPOINT, insn_cnt=83, insns=0x7f76ed3b0040, license=NULL, log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = -1 EFAULT (Bad address)
bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_RAW_TRACEPOINT, insn_cnt=83, insns=0x7f76ed3b0040, license=NULL, log_level=1, log_size=262144, log_buf="", kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = -1 EFAULT (Bad address)

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Based on my reading of https://man7.org/linux/man-pages/man7/bpf-helpers.7.html#LICENSE, fetching the license from a dedicated section is a userspace feature (libbpf, maybe?)

cc @fntlnz

Does this PR introduce a user-facing change?:

eBPF works again

[poiana]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[leogr]

I'm approving this with the main purpose of unblocking falcosecurity/falco#1552

See the comment above.

[leogr]

I see this as a workaround. The root issue should be in our loader (that is not parsing 'license' section).

Could we add a comment so we won't forget to fix the loader in the future?

[poiana]

LGTM label has been added.

Git tree hash: 3d2145b9f25a640c37f1a489213c789a1561f694

[leogr]

Since #42 fixed the root issue, IMO we don't need this workaround anymore.

Thanks anyway!

[leodido]

Thanks for bringing this up Grzeg.

#42 is in. I believe we can close this

/close

[poiana]

@leodido: Closed this PR.

In response to this:

Thanks for bringing this up Grzeg.

#42 is in. I believe we can close this

/close

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