Merge branch 'bpf-register-bounds-logic-and-testing-improvements'

Andrii Nakryiko says:

====================
BPF register bounds logic and testing improvements

This patch set adds a big set of manual and auto-generated test cases
validating BPF verifier's register bounds tracking and deduction logic. See
details in the last patch.

We start with building a tester that validates existing <range> vs <scalar>
verifier logic for range bounds. To make all this work, BPF verifier's logic
needed a bunch of improvements to handle some cases that previously were not
covered. This had no implications as to correctness of verifier logic, but it
was incomplete enough to cause significant disagreements with alternative
implementation of register bounds logic that tests in this patch set
implement. So we need BPF verifier logic improvements to make all the tests
pass. This is what we do in patches #3 through #9.

The end goal of this work, though, is to extend BPF verifier range state
tracking such as to allow to derive new range bounds when comparing non-const
registers. There is some more investigative work required to investigate and
fix existing potential issues with range tracking as part of ALU/ALU64
operations, so <range> x <range> part of v5 patch set ([0]) is dropped until
these issues are sorted out.

For now, we include preparatory refactorings and clean ups, that set up BPF
verifier code base to extend the logic to <range> vs <range> logic in
subsequent patch set. Patches #10-#16 perform preliminary refactorings without
functionally changing anything. But they do clean up check_cond_jmp_op() logic
and generalize a bunch of other pieces in is_branch_taken() logic.

[0] https://patchwork.kernel.org/project/netdevbpf/list/?series=797178&state=*

v5->v6:
- dropped <range> vs <range> patches (original patches #18 through #23) to
add more register range sanity checks and fix preexisting issues;
- comments improvements, addressing other feedback on first 17 patches
(Eduard, Alexei);
v4->v5:
- added entirety of verifier reg bounds tracking changes, now handling
<range> vs <range> cases (Alexei);
- added way more comments trying to explain why deductions added are
correct, hopefully they are useful and clarify things a bit (Daniel,
Shung-Hsi);
- added two preliminary selftests fixes necessary for RELEASE=1 build to
work again, it keeps breaking.
v3->v4:
- improvements to reg_bounds tester (progress report, split 32-bit and
64-bit ranges, fix various verbosity output issues, etc);
v2->v3:
- fix a subtle little-endianness assumption inside parge_reg_state() (CI);
v1->v2:
- fix compilation when building selftests with llvm-16 toolchain (CI).
====================

Link: https://lore.kernel.org/r/20231102033759.2541186-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>