[PATCH bpf-next 0/2] bpf: unify state pruning handling of invalid/misc stack slots

[Eduard Zingerman <eddyz87@gmail.com>]

This change unifies states pruning handling of NOT_INIT registers,
STACK_INVALID/STACK_MISC stack slots for regular and iterator/callback
based loop cases.

The change results in a modest verifier performance improvement:

========= selftests: master vs loop-stack-misc-pruning =========

File                             Program               Insns (A)  Insns (B)  Insns     (DIFF)
-------------------------------  --------------------  ---------  ---------  ----------------
test_tcp_custom_syncookie.bpf.o  tcp_custom_syncookie      38307      18430  -19877 (-51.89%)
xdp_synproxy_kern.bpf.o          syncookie_tc              23035      19067   -3968 (-17.23%)
xdp_synproxy_kern.bpf.o          syncookie_xdp             21022      18516   -2506 (-11.92%)

Total progs: 4173
Old success: 2520
New success: 2521
total_insns diff min:  -99.99%
total_insns diff max:    0.00%
0 -> value: 0
value -> 0: 0
total_insns abs max old: 837,487
total_insns abs max new: 837,487
-100 .. -90  %: 1
 -60 .. -50  %: 3
 -50 .. -40  %: 2
 -40 .. -30  %: 2
 -30 .. -20  %: 8
 -20 .. -10  %: 4
 -10 .. 0    %: 5
   0 .. 5    %: 4148

========= scx: master vs loop-stack-misc-pruning =========

File                       Program           Insns (A)  Insns (B)  Insns     (DIFF)
-------------------------  ----------------  ---------  ---------  ----------------
scx_arena_selftests.bpf.o  arena_selftest       257545     243678   -13867 (-5.38%)
scx_chaos.bpf.o            chaos_dispatch        13989      12804    -1185 (-8.47%)
scx_layered.bpf.o          layered_dispatch      27600      13925  -13675 (-49.55%)

Total progs: 305
Old success: 292
New success: 292
total_insns diff min:  -49.55%
total_insns diff max:    0.00%
0 -> value: 0
value -> 0: 0
total_insns abs max old: 257,545
total_insns abs max new: 243,678
 -50 .. -45  %: 7
 -30 .. -20  %: 5
 -20 .. -10  %: 14
 -10 .. 0    %: 18
   0 .. 5    %: 261

There is also a significant verifier performance improvement for some
bpf_loop() heavy Meta internal programs (~ -40% processed instructions).

---
Eduard Zingerman (2):
      bpf: allow states pruning for misc/invalid slots in iterator loops
      selftests/bpf: iterator based loop and STACK_MISC states pruning

 kernel/bpf/verifier.c                     | 10 ++---
 tools/testing/selftests/bpf/progs/iters.c | 65 +++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 6 deletions(-)
---
base-commit: ccaa6d2c9635a8db06a494d67ef123b56b967a78
change-id: 20251230-loop-stack-misc-pruning-18b1ac62ae1a