nfp: bpf: add basic support for atomic adds

Implement atomic add operation for 32 and 64 bit values.  Depend
on the verifier to ensure alignment.  Values have to be kept in
big endian and swapped upon read/write.  For now only support
atomic add of a constant.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 105 insertions, 0 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
index 7d67ffc897dd..40619efea77d 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
@@ -285,6 +285,72 @@ nfp_bpf_check_stack_access(struct nfp_prog *nfp_prog,
 	return -EINVAL;
 }
 
+static const char *nfp_bpf_map_use_name(enum nfp_bpf_map_use use)
+{
+	static const char * const names[] = {
+		[NFP_MAP_UNUSED]	= "unused",
+		[NFP_MAP_USE_READ]	= "read",
+		[NFP_MAP_USE_WRITE]	= "write",
+		[NFP_MAP_USE_ATOMIC_CNT] = "atomic",
+	};
+
+	if (use >= ARRAY_SIZE(names) || !names[use])
+		return "unknown";
+	return names[use];
+}
+
+static int
+nfp_bpf_map_mark_used_one(struct bpf_verifier_env *env,
+			  struct nfp_bpf_map *nfp_map,
+			  unsigned int off, enum nfp_bpf_map_use use)
+{
+	if (nfp_map->use_map[off / 4] != NFP_MAP_UNUSED &&
+	    nfp_map->use_map[off / 4] != use) {
+		pr_vlog(env, "map value use type conflict %s vs %s off: %u\n",
+			nfp_bpf_map_use_name(nfp_map->use_map[off / 4]),
+			nfp_bpf_map_use_name(use), off);
+		return -EOPNOTSUPP;
+	}
+
+	nfp_map->use_map[off / 4] = use;
+
+	return 0;
+}
+
+static int
+nfp_bpf_map_mark_used(struct bpf_verifier_env *env, struct nfp_insn_meta *meta,
+		      const struct bpf_reg_state *reg,
+		      enum nfp_bpf_map_use use)
+{
+	struct bpf_offloaded_map *offmap;
+	struct nfp_bpf_map *nfp_map;
+	unsigned int size, off;
+	int i, err;
+
+	if (!tnum_is_const(reg->var_off)) {
+		pr_vlog(env, "map value offset is variable\n");
+		return -EOPNOTSUPP;
+	}
+
+	off = reg->var_off.value + meta->insn.off + reg->off;
+	size = BPF_LDST_BYTES(&meta->insn);
+	offmap = map_to_offmap(reg->map_ptr);
+	nfp_map = offmap->dev_priv;
+
+	if (off + size > offmap->map.value_size) {
+		pr_vlog(env, "map value access out-of-bounds\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < size; i += 4 - (off + i) % 4) {
+		err = nfp_bpf_map_mark_used_one(env, nfp_map, off + i, use);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 static int
 nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 		  struct bpf_verifier_env *env, u8 reg_no)
@@ -307,10 +373,22 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	}
 
 	if (reg->type == PTR_TO_MAP_VALUE) {
+		if (is_mbpf_load(meta)) {
+			err = nfp_bpf_map_mark_used(env, meta, reg,
+						    NFP_MAP_USE_READ);
+			if (err)
+				return err;
+		}
 		if (is_mbpf_store(meta)) {
 			pr_vlog(env, "map writes not supported\n");
 			return -EOPNOTSUPP;
 		}
+		if (is_mbpf_xadd(meta)) {
+			err = nfp_bpf_map_mark_used(env, meta, reg,
+						    NFP_MAP_USE_ATOMIC_CNT);
+			if (err)
+				return err;
+		}
 	}
 
 	if (meta->ptr.type != NOT_INIT && meta->ptr.type != reg->type) {
@@ -325,6 +403,31 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 }
 
 static int
+nfp_bpf_check_xadd(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
+		   struct bpf_verifier_env *env)
+{
+	const struct bpf_reg_state *sreg = cur_regs(env) + meta->insn.src_reg;
+	const struct bpf_reg_state *dreg = cur_regs(env) + meta->insn.dst_reg;
+
+	if (dreg->type != PTR_TO_MAP_VALUE) {
+		pr_vlog(env, "atomic add not to a map value pointer: %d\n",
+			dreg->type);
+		return -EOPNOTSUPP;
+	}
+	if (sreg->type != SCALAR_VALUE ||
+	    sreg->var_off.value > 0xffff || sreg->var_off.mask > 0xffff) {
+		char tn_buf[48];
+
+		tnum_strn(tn_buf, sizeof(tn_buf), sreg->var_off);
+		pr_vlog(env, "atomic add not of a small constant scalar: %s\n",
+			tn_buf);
+		return -EOPNOTSUPP;
+	}
+
+	return nfp_bpf_check_ptr(nfp_prog, meta, env, meta->insn.dst_reg);
+}
+
+static int
 nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 {
 	struct nfp_prog *nfp_prog = env->prog->aux->offload->dev_priv;
@@ -356,6 +459,8 @@ nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx, int prev_insn_idx)
 	if (is_mbpf_store(meta))
 		return nfp_bpf_check_ptr(nfp_prog, meta, env,
 					 meta->insn.dst_reg);
+	if (is_mbpf_xadd(meta))
+		return nfp_bpf_check_xadd(nfp_prog, meta, env);
 
 	return 0;
 }