bpf: rename bpf_reg_state->off to bpf_reg_state->delta

This field is now used only for linked scalar registers tracking.
Rename it to 'delta' to better describe it's purpose:
constant delta between "linked" scalars with the same ID.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260212-ptrs-off-migration-v2-4-00820e4d3438@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 16 insertions, 16 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index a97bdbf3a07b..c1e30096ea7b 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -40,7 +40,7 @@ struct bpf_reg_state {
 	/*
 	 * Constant delta between "linked" scalars with the same ID.
 	 */
-	s32 off;
+	s32 delta;
 	union {
 		/* valid when type == PTR_TO_PACKET */
 		int range;
@@ -145,9 +145,9 @@ struct bpf_reg_state {
 	 * Upper bit of ID is used to remember relationship between "linked"
 	 * registers. Example:
 	 * r1 = r2;    both will have r1->id == r2->id == N
-	 * r1 += 10;   r1->id == N | BPF_ADD_CONST and r1->off == 10
+	 * r1 += 10;   r1->id == N | BPF_ADD_CONST and r1->delta == 10
 	 * r3 = r2;    both will have r3->id == r2->id == N
-	 * w3 += 10;   r3->id == N | BPF_ADD_CONST32 and r3->off == 10
+	 * w3 += 10;   r3->id == N | BPF_ADD_CONST32 and r3->delta == 10
 	 */
 #define BPF_ADD_CONST64 (1U << 31)
 #define BPF_ADD_CONST32 (1U << 30)
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 39a731392d65..37d72b052192 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -694,7 +694,7 @@ static void print_reg_state(struct bpf_verifier_env *env,
 		if (state->frameno != reg->frameno)
 			verbose(env, "[%d]", reg->frameno);
 		if (tnum_is_const(reg->var_off)) {
-			verbose_snum(env, reg->var_off.value + reg->off);
+			verbose_snum(env, reg->var_off.value + reg->delta);
 			return;
 		}
 	}
@@ -704,7 +704,7 @@ static void print_reg_state(struct bpf_verifier_env *env,
 	if (reg->id)
 		verbose_a("id=%d", reg->id & ~BPF_ADD_CONST);
 	if (reg->id & BPF_ADD_CONST)
-		verbose(env, "%+d", reg->off);
+		verbose(env, "%+d", reg->delta);
 	if (reg->ref_obj_id)
 		verbose_a("ref_obj_id=%d", reg->ref_obj_id);
 	if (type_is_non_owning_ref(reg->type))
@@ -716,9 +716,9 @@ static void print_reg_state(struct bpf_verifier_env *env,
 			  reg->map_ptr->key_size,
 			  reg->map_ptr->value_size);
 	}
-	if (t != SCALAR_VALUE && reg->off) {
+	if (t != SCALAR_VALUE && reg->delta) {
 		verbose_a("off=");
-		verbose_snum(env, reg->off);
+		verbose_snum(env, reg->delta);
 	}
 	if (type_is_pkt_pointer(t)) {
 		verbose_a("r=");
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2c5794dad668..0162f946032f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5095,7 +5095,7 @@ static void assign_scalar_id_before_mov(struct bpf_verifier_env *env,
 		 * Cleared it, since multiple rX += const are not supported.
 		 */
 		src_reg->id = 0;
-		src_reg->off = 0;
+		src_reg->delta = 0;
 	}
 
 	if (!src_reg->id && !tnum_is_const(src_reg->var_off))
@@ -16219,14 +16219,14 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 			 * we cannot accumulate another val into rx->off.
 			 */
 clear_id:
-			dst_reg->off = 0;
+			dst_reg->delta = 0;
 			dst_reg->id = 0;
 		} else {
 			if (alu32)
 				dst_reg->id |= BPF_ADD_CONST32;
 			else
 				dst_reg->id |= BPF_ADD_CONST64;
-			dst_reg->off = off;
+			dst_reg->delta = off;
 		}
 	} else {
 		/*
@@ -17305,18 +17305,18 @@ static void sync_linked_regs(struct bpf_verifier_env *env, struct bpf_verifier_s
 		if ((reg->id & ~BPF_ADD_CONST) != (known_reg->id & ~BPF_ADD_CONST))
 			continue;
 		if ((!(reg->id & BPF_ADD_CONST) && !(known_reg->id & BPF_ADD_CONST)) ||
-		    reg->off == known_reg->off) {
+		    reg->delta == known_reg->delta) {
 			s32 saved_subreg_def = reg->subreg_def;
 
 			copy_register_state(reg, known_reg);
 			reg->subreg_def = saved_subreg_def;
 		} else {
 			s32 saved_subreg_def = reg->subreg_def;
-			s32 saved_off = reg->off;
+			s32 saved_off = reg->delta;
 			u32 saved_id = reg->id;
 
 			fake_reg.type = SCALAR_VALUE;
-			__mark_reg_known(&fake_reg, (s64)reg->off - (s64)known_reg->off);
+			__mark_reg_known(&fake_reg, (s64)reg->delta - (s64)known_reg->delta);
 
 			/* reg = known_reg; reg += delta */
 			copy_register_state(reg, known_reg);
@@ -17324,7 +17324,7 @@ static void sync_linked_regs(struct bpf_verifier_env *env, struct bpf_verifier_s
 			 * Must preserve off, id and subreg_def flag,
 			 * otherwise another sync_linked_regs() will be incorrect.
 			 */
-			reg->off = saved_off;
+			reg->delta = saved_off;
 			reg->id = saved_id;
 			reg->subreg_def = saved_subreg_def;
 
@@ -19629,7 +19629,7 @@ static void clear_singular_ids(struct bpf_verifier_env *env,
 			continue;
 		if (idset_cnt_get(idset, reg->id & ~BPF_ADD_CONST) == 1) {
 			reg->id = 0;
-			reg->off = 0;
+			reg->delta = 0;
 		}
 	}));
 }
@@ -19766,7 +19766,7 @@ static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold,
 			return false;
 
 		/* Both have offset linkage: offsets must match */
-		if ((rold->id & BPF_ADD_CONST) && rold->off != rcur->off)
+		if ((rold->id & BPF_ADD_CONST) && rold->delta != rcur->delta)
 			return false;
 
 		if (!check_scalar_ids(rold->id, rcur->id, idmap))