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

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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>
This commit is contained in:
Eduard Zingerman
2026-02-12 13:34:24 -08:00
committed by Alexei Starovoitov
parent 6363fc17c9
commit 3d91c618ac
3 changed files with 16 additions and 16 deletions
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6
include/linux/bpf_verifier.h
View File

@@ -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)

8
kernel/bpf/log.c
View File

@@ -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=");

18
kernel/bpf/verifier.c
View File

@@ -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))