diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index edb19ada0405..40ac67a04ab7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1359,7 +1359,7 @@ static void __mark_reg_unknown(const struct bpf_verifier_env *env,
 	reg->type = SCALAR_VALUE;
 	reg->var_off = tnum_unknown;
 	reg->frameno = 0;
-	reg->precise = env->subprog_cnt > 1 || !env->bpf_capable;
+	reg->precise = !env->bpf_capable;
 	__mark_reg_unbounded(reg);
 }
 
@@ -2097,12 +2097,42 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int frame, int r
 		return 0;
 	if (!reg_mask && !stack_mask)
 		return 0;
+
 	for (;;) {
 		DECLARE_BITMAP(mask, 64);
 		u32 history = st->jmp_history_cnt;
 
 		if (env->log.level & BPF_LOG_LEVEL)
 			verbose(env, "last_idx %d first_idx %d\n", last_idx, first_idx);
+
+		if (last_idx < 0) {
+			/* we are at the entry into subprog, which
+			 * is expected for global funcs, but only if
+			 * requested precise registers are R1-R5
+			 * (which are global func's input arguments)
+			 */
+			if (st->curframe == 0 &&
+			    st->frame[0]->subprogno > 0 &&
+			    st->frame[0]->callsite == BPF_MAIN_FUNC &&
+			    stack_mask == 0 && (reg_mask & ~0x3e) == 0) {
+				bitmap_from_u64(mask, reg_mask);
+				for_each_set_bit(i, mask, 32) {
+					reg = &st->frame[0]->regs[i];
+					if (reg->type != SCALAR_VALUE) {
+						reg_mask &= ~(1u << i);
+						continue;
+					}
+					reg->precise = true;
+				}
+				return 0;
+			}
+
+			verbose(env, "BUG backtracing func entry subprog %d reg_mask %x stack_mask %llx\n",
+				st->frame[0]->subprogno, reg_mask, stack_mask);
+			WARN_ONCE(1, "verifier backtracking bug");
+			return -EFAULT;
+		}
+
 		for (i = last_idx;;) {
 			if (skip_first) {
 				err = 0;
@@ -11846,6 +11876,9 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
 			0 /* frameno */,
 			subprog);
 
+	state->first_insn_idx = env->subprog_info[subprog].start;
+	state->last_insn_idx = -1;
+
 	regs = state->frame[state->curframe]->regs;
 	if (subprog || env->prog->type == BPF_PROG_TYPE_EXT) {
 		ret = btf_prepare_func_args(env, subprog, regs);