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nfp: bpf: support optimizing dead branches 

Verifier will now optimize out branches to dead code, implement
the replace_insn callback to take advantage of that optimization.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Jakub Kicinski 2019-01-22 22:45:28 -08:00 committed by Alexei Starovoitov
parent e2fc61146a
commit a32014b351
3 changed files with 49 additions and 0 deletions
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14
drivers/net/ethernet/netronome/nfp/bpf/main.h
View File

@ -412,6 +412,17 @@ static inline bool is_mbpf_div(const struct nfp_insn_meta *meta)
return is_mbpf_alu(meta) && mbpf_op(meta) == BPF_DIV;
}
static inline bool is_mbpf_cond_jump(const struct nfp_insn_meta *meta)
{
u8 op;
if (BPF_CLASS(meta->insn.code) != BPF_JMP)
return false;
op = BPF_OP(meta->insn.code);
return op != BPF_JA && op != BPF_EXIT && op != BPF_CALL;
}
static inline bool is_mbpf_helper_call(const struct nfp_insn_meta *meta)
{
struct bpf_insn insn = meta->insn;
@ -520,6 +531,9 @@ int nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx,
int prev_insn_idx);
int nfp_bpf_finalize(struct bpf_verifier_env *env);
int nfp_bpf_opt_replace_insn(struct bpf_verifier_env *env, u32 off,
struct bpf_insn *insn);
extern const struct bpf_prog_offload_ops nfp_bpf_dev_ops;
struct netdev_bpf;

1
drivers/net/ethernet/netronome/nfp/bpf/offload.c
View File

@ -592,6 +592,7 @@ int nfp_net_bpf_offload(struct nfp_net *nn, struct bpf_prog *prog,
const struct bpf_prog_offload_ops nfp_bpf_dev_ops = {
.insn_hook = nfp_verify_insn,
.finalize = nfp_bpf_finalize,
.replace_insn = nfp_bpf_opt_replace_insn,
.prepare = nfp_bpf_verifier_prep,
.translate = nfp_bpf_translate,
.destroy = nfp_bpf_destroy,

34
drivers/net/ethernet/netronome/nfp/bpf/verifier.c
View File

@ -786,3 +786,37 @@ int nfp_bpf_finalize(struct bpf_verifier_env *env)
return 0;
}
int nfp_bpf_opt_replace_insn(struct bpf_verifier_env *env, u32 off,
struct bpf_insn *insn)
{
struct nfp_prog *nfp_prog = env->prog->aux->offload->dev_priv;
struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
struct nfp_insn_meta *meta = nfp_prog->verifier_meta;
meta = nfp_bpf_goto_meta(nfp_prog, meta, aux_data[off].orig_idx);
nfp_prog->verifier_meta = meta;
/* conditional jump to jump conversion */
if (is_mbpf_cond_jump(meta) &&
insn->code == (BPF_JMP | BPF_JA | BPF_K)) {
unsigned int tgt_off;
tgt_off = off + insn->off + 1;
if (!insn->off) {
meta->jmp_dst = list_next_entry(meta, l);
meta->jump_neg_op = false;
} else if (meta->jmp_dst->n != aux_data[tgt_off].orig_idx) {
pr_vlog(env, "branch hard wire at %d changes target %d -> %d\n",
off, meta->jmp_dst->n,
aux_data[tgt_off].orig_idx);
return -EINVAL;
}
return 0;
}
pr_vlog(env, "unsupported instruction replacement %hhx -> %hhx\n",
meta->insn.code, insn->code);
return -EINVAL;
}