Daniel Xu d2102f2f5d bpf: verifier: Support eliding map lookup nullness ... This commit allows progs to elide a null check on statically known map lookup keys. In other words, if the verifier can statically prove that the lookup will be in-bounds, allow the prog to drop the null check. This is useful for two reasons: 1. Large numbers of nullness checks (especially when they cannot fail) unnecessarily pushes prog towards BPF_COMPLEXITY_LIMIT_JMP_SEQ. 2. It forms a tighter contract between programmer and verifier. For (1), bpftrace is starting to make heavier use of percpu scratch maps. As a result, for user scripts with large number of unrolled loops, we are starting to hit jump complexity verification errors. These percpu lookups cannot fail anyways, as we only use static key values. Eliding nullness probably results in less work for verifier as well. For (2), percpu scratch maps are often used as a larger stack, as the currrent stack is limited to 512 bytes. In these situations, it is desirable for the programmer to express: "this lookup should never fail, and if it does, it means I messed up the code". By omitting the null check, the programmer can "ask" the verifier to double check the logic. Tests also have to be updated in sync with these changes, as the verifier is more efficient with this change. Notable, iters.c tests had to be changed to use a map type that still requires null checks, as it's exercising verifier tracking logic w.r.t iterators. Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Link: https://lore.kernel.org/r/68f3ea96ff3809a87e502a11a4bd30177fc5823e.1736886479.git.dxu@dxuuu.xyz Signed-off-by: Alexei Starovoitov <ast@kernel.org>		2025-01-16 17:51:10 -08:00
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.gitignore
atomic_and.c	bpf, x86: Fix BPF_FETCH atomic and/or/xor with r0 as src	2021-02-22 18:03:11 +01:00
atomic_bounds.c	bpf: Propagate stack bounds to registers in atomics w/ BPF_FETCH	2021-02-02 18:23:29 -08:00
atomic_cmpxchg.c	bpf: Fix accesses to uninit stack slots	2023-12-08 14:19:00 -08:00
atomic_fetch_add.c	bpf: Add tests for new BPF atomic operations	2021-01-14 18:34:29 -08:00
atomic_fetch.c	bpf, selftests: Add test case for atomic fetch on spilled pointer	2021-12-14 19:33:06 -08:00
atomic_invalid.c	bpf: Small BPF verifier log improvements	2022-03-03 16:54:10 +01:00
atomic_or.c	bpf: Explicitly zero-extend R0 after 32-bit cmpxchg	2021-03-04 19:06:03 -08:00
atomic_xchg.c	bpf: Add tests for new BPF atomic operations	2021-01-14 18:34:29 -08:00
atomic_xor.c	selftests/bpf: Fix endianness issues in atomic tests	2021-02-10 11:55:22 -08:00
basic_call.c
basic_instr.c	selftests/bpf: Fix a test_verifier failure	2023-07-27 18:54:16 -07:00
basic_stx_ldx.c
basic.c	selftests/bpf: Fix test_verifier after introducing resolve_pseudo_ldimm64	2020-10-06 20:16:57 -07:00
bpf_loop_inline.c	selftests/bpf: Skip callback tests if jit is disabled in test_verifier	2024-01-23 20:27:41 -08:00
bpf_st_mem.c	selftests/bpf: Add test for immediate spilled to stack	2023-11-01 22:30:27 -07:00
calls.c	bpf: verifier: Refactor helper access type tracking	2025-01-16 17:51:10 -08:00
ctx_sk_lookup.c	selftests/bpf: Add tests for accessing ingress_ifindex in bpf_sk_lookup	2021-11-10 16:29:59 -08:00
ctx_skb.c	selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests	2023-07-05 14:34:23 +02:00
dead_code.c	selftests, bpf: Test that dead ldx_w insns are accepted	2021-08-13 17:46:26 +02:00
direct_value_access.c	selftests/bpf: Mark tests that require unaligned memory access	2020-11-18 17:45:35 -08:00
event_output.c	selftests/bpf: Fix cgroup sockopt verifier test	2020-07-11 01:32:15 +02:00
jit.c	bpf: add selftests for lsh, rsh, arsh with reg operand	2022-10-19 16:53:51 -07:00
jmp32.c	selftests/bpf: Add F_NEEDS_EFFICIENT_UNALIGNED_ACCESS to some tests	2023-07-05 14:34:23 +02:00
jset.c	bpf, selftests: Adjust few selftest outcomes wrt unreachable code	2021-06-14 23:06:38 +02:00
jump.c	bpf, selftests: Add verifier test case for imm=0,umin=0,umax=1 scalar	2022-07-01 12:56:27 -07:00
junk_insn.c
ld_abs.c
ld_dw.c
ld_imm64.c	bpf: handle ldimm64 properly in check_cfg()	2023-11-09 20:11:20 -08:00
map_kptr.c	bpf: verifier: Support eliding map lookup nullness	2025-01-16 17:51:10 -08:00
perf_event_sample_period.c	selftests/bpf: Use __BYTE_ORDER__	2021-10-25 20:39:42 -07:00
precise.c	bpf: Remove mark_precise_scalar_ids()	2024-07-29 12:53:14 -07:00
scale.c
sleepable.c	bpf: Allow BPF_PROG_TYPE_STRUCT_OPS programs to be sleepable	2023-01-25 10:25:57 -08:00
wide_access.c	selftests/bpf: Mark tests that require unaligned memory access	2020-11-18 17:45:35 -08:00