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bpf: Avoid retpoline for bpf_for_each_map_elem

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Similarly to 09772d92cd ("bpf: avoid retpoline for
lookup/update/delete calls on maps") and 84430d4232 ("bpf, verifier:
avoid retpoline for map push/pop/peek operation") avoid indirect call
while calling bpf_for_each_map_elem.

Before (a program fragment):

  ; if (rules_map) {
   142: (15) if r4 == 0x0 goto pc+8
   143: (bf) r3 = r10
  ; bpf_for_each_map_elem(rules_map, process_each_rule, &ctx, 0);
   144: (07) r3 += -24
   145: (bf) r1 = r4
   146: (18) r2 = subprog[+5]
   148: (b7) r4 = 0
   149: (85) call bpf_for_each_map_elem#143680  <-- indirect call via
                                                    helper

After (same program fragment):

   ; if (rules_map) {
    142: (15) if r4 == 0x0 goto pc+8
    143: (bf) r3 = r10
   ; bpf_for_each_map_elem(rules_map, process_each_rule, &ctx, 0);
    144: (07) r3 += -24
    145: (bf) r1 = r4
    146: (18) r2 = subprog[+5]
    148: (b7) r4 = 0
    149: (85) call bpf_for_each_array_elem#170336  <-- direct call

On a benchmark that calls bpf_for_each_map_elem() once and does many
other things (mostly checking fields in skb) with CONFIG_RETPOLINE=y it
makes program faster.

Before:

  ============================================================================
  Benchmark.cpp                                              time/iter iters/s
  ============================================================================
  IngressMatchByRemoteEndpoint                                80.78ns 12.38M
  IngressMatchByRemoteIP                                      80.66ns 12.40M
  IngressMatchByRemotePort                                    80.87ns 12.37M

After:

  ============================================================================
  Benchmark.cpp                                              time/iter iters/s
  ============================================================================
  IngressMatchByRemoteEndpoint                                73.49ns 13.61M
  IngressMatchByRemoteIP                                      71.48ns 13.99M
  IngressMatchByRemotePort                                    70.39ns 14.21M

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211006001838.75607-1-rdna@fb.com
This commit is contained in:
Andrey Ignatov 2021-10-05 17:18:38 -07:00 committed by Alexei Starovoitov
parent 32a16f6bfe
commit 0640c77c46
1 changed files with 10 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
kernel/bpf/verifier.c
View File

@ -13112,7 +13112,8 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
insn->imm == BPF_FUNC_map_push_elem ||
insn->imm == BPF_FUNC_map_pop_elem ||
insn->imm == BPF_FUNC_map_peek_elem ||
insn->imm == BPF_FUNC_redirect_map)) {
insn->imm == BPF_FUNC_redirect_map ||
insn->imm == BPF_FUNC_for_each_map_elem)) {
aux = &env->insn_aux_data[i + delta];
if (bpf_map_ptr_poisoned(aux))
goto patch_call_imm;
@ -13156,6 +13157,11 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
(int (*)(struct bpf_map *map, void *value))NULL));
BUILD_BUG_ON(!__same_type(ops->map_redirect,
(int (*)(struct bpf_map *map, u32 ifindex, u64 flags))NULL));
BUILD_BUG_ON(!__same_type(ops->map_for_each_callback,
(int (*)(struct bpf_map *map,
bpf_callback_t callback_fn,
void *callback_ctx,
u64 flags))NULL));
patch_map_ops_generic:
switch (insn->imm) {
@ -13180,6 +13186,9 @@ patch_map_ops_generic:
case BPF_FUNC_redirect_map:
insn->imm = BPF_CALL_IMM(ops->map_redirect);
continue;
case BPF_FUNC_for_each_map_elem:
insn->imm = BPF_CALL_IMM(ops->map_for_each_callback);
continue;
}
goto patch_call_imm;