[PATCH/RFC v2 bpf-next 02/19] bpf: refactor propagate_liveness to eliminate code redundance

[Jiong Wang <jiong.wang@xxxxxxxxxxxxx>]

Access to reg states were not factored out, the consequence is long code
for dereferencing them which made the indentation not good for reading.

This patch factor out these code so the core code in the loop could be
easier to follow.

Signed-off-by: Jiong Wang <jiong.wang@xxxxxxxxxxxxx>
---
 kernel/bpf/verifier.c | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f6ebe80..d57082a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6201,8 +6201,9 @@ static int propagate_liveness(struct bpf_verifier_env *env,
 			      const struct bpf_verifier_state *vstate,
 			      struct bpf_verifier_state *vparent)
 {
-	int i, frame, err = 0;
+	struct bpf_reg_state *state_reg, *parent_reg;
 	struct bpf_func_state *state, *parent;
+	int i, frame, err = 0;
 
 	if (vparent->curframe != vstate->curframe) {
 		WARN(1, "propagate_live: parent frame %d current frame %d\n",
@@ -6212,28 +6213,33 @@ static int propagate_liveness(struct bpf_verifier_env *env,
 	/* Propagate read liveness of registers... */
 	BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);
 	for (frame = 0; frame <= vstate->curframe; frame++) {
+		parent = vparent->frame[frame];
+		state = vstate->frame[frame];
+		parent_reg = parent->regs;
+		state_reg = state->regs;
 		/* We don't need to worry about FP liveness, it's read-only */
 		for (i = frame < vstate->curframe ? BPF_REG_6 : 0; i < BPF_REG_FP; i++) {
-			if (vparent->frame[frame]->regs[i].live & REG_LIVE_READ)
+			if (parent_reg[i].live & REG_LIVE_READ)
 				continue;
-			if (vstate->frame[frame]->regs[i].live & REG_LIVE_READ) {
-				err = mark_reg_read(env, &vstate->frame[frame]->regs[i],
-						    &vparent->frame[frame]->regs[i]);
-				if (err)
-					return err;
-			}
+			if (!(state_reg[i].live & REG_LIVE_READ))
+				continue;
+			err = mark_reg_read(env, &state_reg[i], &parent_reg[i]);
+			if (err)
+				return err;
 		}
 
 		/* Propagate stack slots. */
-		state = vstate->frame[frame];
-		parent = vparent->frame[frame];
 		for (i = 0; i < state->allocated_stack / BPF_REG_SIZE &&
 			    i < parent->allocated_stack / BPF_REG_SIZE; i++) {
-			if (parent->stack[i].spilled_ptr.live & REG_LIVE_READ)
+			parent_reg = &parent->stack[i].spilled_ptr;
+			state_reg = &state->stack[i].spilled_ptr;
+			if (parent_reg->live & REG_LIVE_READ)
 				continue;
-			if (state->stack[i].spilled_ptr.live & REG_LIVE_READ)
-				mark_reg_read(env, &state->stack[i].spilled_ptr,
-					      &parent->stack[i].spilled_ptr);
+			if (!(state_reg->live & REG_LIVE_READ))
+				continue;
+			err = mark_reg_read(env, state_reg, parent_reg);
+			if (err)
+				return err;
 		}
 	}
 	return err;
-- 
2.7.4