netdev - [PATCH bpf-next 2/5] bpf: allow for tailcalls in BPF subprograms

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Message-Id: <20200715233634.3868-3-maciej.fijalkowski@intel.com>
Date:   Thu, 16 Jul 2020 01:36:31 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     ast@...nel.org, daniel@...earbox.net
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, bjorn.topel@...el.com,
        magnus.karlsson@...el.com,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Subject: [PATCH bpf-next 2/5] bpf: allow for tailcalls in BPF subprograms

Relax verifier's restriction that was meant to forbid tailcall usage
when subprog count was higher than 1.

Also, do not max out the stack depth of program that utilizes tailcalls.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 kernel/bpf/verifier.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3c1efc9d08fd..6481342b31ba 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4172,10 +4172,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
 	case BPF_FUNC_tail_call:
 		if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
 			goto error;
-		if (env->subprog_cnt > 1) {
-			verbose(env, "tail_calls are not allowed in programs with bpf-to-bpf calls\n");
-			return -EINVAL;
-		}
 		break;
 	case BPF_FUNC_perf_event_read:
 	case BPF_FUNC_perf_event_output:
@@ -10252,7 +10248,6 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
 			 * the program array.
 			 */
 			prog->cb_access = 1;
-			env->prog->aux->stack_depth = MAX_BPF_STACK;
 			env->prog->aux->max_pkt_offset = MAX_PACKET_OFF;
 
 			/* mark bpf_tail_call as different opcode to avoid
-- 
2.20.1