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nfp: bpf: support removing dead code 

Add a verifier callback to the nfp JIT to remove the instructions
the verifier deemed to be dead.

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 22:45:29 -08:00 committed by Alexei Starovoitov
parent a32014b351
commit 9a06927e77
3 changed files with 34 additions and 1 deletions
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6
drivers/net/ethernet/netronome/nfp/bpf/main.h
View File

@ -247,9 +247,12 @@ struct nfp_bpf_reg_state {
#define FLAG_INSN_SKIP_NOOP BIT(3)
/* Instruction is optimized out based on preceding instructions */
#define FLAG_INSN_SKIP_PREC_DEPENDENT BIT(4)
/* Instruction is optimized by the verifier */
#define FLAG_INSN_SKIP_VERIFIER_OPT BIT(5)
#define FLAG_INSN_SKIP_MASK (FLAG_INSN_SKIP_NOOP | \
FLAG_INSN_SKIP_PREC_DEPENDENT)
FLAG_INSN_SKIP_PREC_DEPENDENT | \
FLAG_INSN_SKIP_VERIFIER_OPT)
/**
* struct nfp_insn_meta - BPF instruction wrapper
@ -533,6 +536,7 @@ 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);
int nfp_bpf_opt_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
extern const struct bpf_prog_offload_ops nfp_bpf_dev_ops;

5
drivers/net/ethernet/netronome/nfp/bpf/offload.c
View File

@ -220,6 +220,10 @@ static int nfp_bpf_translate(struct bpf_prog *prog)
unsigned int max_instr;
int err;
/* We depend on dead code elimination succeeding */
if (prog->aux->offload->opt_failed)
return -EINVAL;
max_instr = nn_readw(nn, NFP_NET_CFG_BPF_MAX_LEN);
nfp_prog->__prog_alloc_len = max_instr * sizeof(u64);
@ -593,6 +597,7 @@ 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,
.remove_insns = nfp_bpf_opt_remove_insns,
.prepare = nfp_bpf_verifier_prep,
.translate = nfp_bpf_translate,
.destroy = nfp_bpf_destroy,

24
drivers/net/ethernet/netronome/nfp/bpf/verifier.c
View File

@ -820,3 +820,27 @@ int nfp_bpf_opt_replace_insn(struct bpf_verifier_env *env, u32 off,
meta->insn.code, insn->code);
return -EINVAL;
}
int nfp_bpf_opt_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt)
{
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;
unsigned int i;
meta = nfp_bpf_goto_meta(nfp_prog, meta, aux_data[off].orig_idx);
for (i = 0; i < cnt; i++) {
if (WARN_ON_ONCE(&meta->l == &nfp_prog->insns))
return -EINVAL;
/* doesn't count if it already has the flag */
if (meta->flags & FLAG_INSN_SKIP_VERIFIER_OPT)
i--;
meta->flags |= FLAG_INSN_SKIP_VERIFIER_OPT;
meta = list_next_entry(meta, l);
}
return 0;
}