bpf: disable and remove registers chain based liveness

Remove register chain based liveness tracking:
- struct bpf_reg_state->{parent,live} fields are no longer needed;
- REG_LIVE_WRITTEN marks are superseded by bpf_mark_stack_write()
  calls;
- mark_reg_read() calls are superseded by bpf_mark_stack_read();
- log.c:print_liveness() is superseded by logging in liveness.c;
- propagate_liveness() is superseded by bpf_update_live_stack();
- no need to establish register chains in is_state_visited() anymore;
- fix a bunch of tests expecting "_w" suffixes in verifier log
  messages.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250918-callchain-sensitive-liveness-v3-9-c3cd27bacc60@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 4 insertions, 22 deletions

diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 0d6d7bfb2fd0..f50533169cc3 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -542,17 +542,6 @@ static char slot_type_char[] = {
 	[STACK_IRQ_FLAG] = 'f'
 };
 
-static void print_liveness(struct bpf_verifier_env *env,
-			   enum bpf_reg_liveness live)
-{
-	if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN))
-		verbose(env, "_");
-	if (live & REG_LIVE_READ)
-		verbose(env, "r");
-	if (live & REG_LIVE_WRITTEN)
-		verbose(env, "w");
-}
-
 #define UNUM_MAX_DECIMAL U16_MAX
 #define SNUM_MAX_DECIMAL S16_MAX
 #define SNUM_MIN_DECIMAL S16_MIN
@@ -770,7 +759,6 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_verifie
 		if (!print_all && !reg_scratched(env, i))
 			continue;
 		verbose(env, " R%d", i);
-		print_liveness(env, reg->live);
 		verbose(env, "=");
 		print_reg_state(env, state, reg);
 	}
@@ -803,9 +791,7 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_verifie
 					break;
 			types_buf[j] = '\0';
 
-			verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
-			print_liveness(env, reg->live);
-			verbose(env, "=%s", types_buf);
+			verbose(env, " fp%d=%s", (-i - 1) * BPF_REG_SIZE, types_buf);
 			print_reg_state(env, state, reg);
 			break;
 		case STACK_DYNPTR:
@@ -814,7 +800,6 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_verifie
 			reg = &state->stack[i].spilled_ptr;
 
 			verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
-			print_liveness(env, reg->live);
 			verbose(env, "=dynptr_%s(", dynptr_type_str(reg->dynptr.type));
 			if (reg->id)
 				verbose_a("id=%d", reg->id);
@@ -829,9 +814,8 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_verifie
 			if (!reg->ref_obj_id)
 				continue;
 
-			verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
-			print_liveness(env, reg->live);
-			verbose(env, "=iter_%s(ref_id=%d,state=%s,depth=%u)",
+			verbose(env, " fp%d=iter_%s(ref_id=%d,state=%s,depth=%u)",
+				(-i - 1) * BPF_REG_SIZE,
 				iter_type_str(reg->iter.btf, reg->iter.btf_id),
 				reg->ref_obj_id, iter_state_str(reg->iter.state),
 				reg->iter.depth);
@@ -839,9 +823,7 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_verifie
 		case STACK_MISC:
 		case STACK_ZERO:
 		default:
-			verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
-			print_liveness(env, reg->live);
-			verbose(env, "=%s", types_buf);
+			verbose(env, " fp%d=%s", (-i - 1) * BPF_REG_SIZE, types_buf);
 			break;
 		}
 	}