From: Amery Hung <ameryhung@gmail.com>
To: bpf@vger.kernel.org
Cc: alexei.starovoitov@gmail.com, andrii@kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, memxor@gmail.com,
ameryhung@gmail.com, kernel-team@meta.com
Subject: [PATCH bpf-next v2 7/7] bpf: Unify helper and kfunc call argument meta
Date: Tue, 14 Jul 2026 23:40:47 -0700 [thread overview]
Message-ID: <20260715064047.1793790-8-ameryhung@gmail.com> (raw)
In-Reply-To: <20260715064047.1793790-1-ameryhung@gmail.com>
Helper and kfunc argument checking carried two separate meta structs: the
verifier-local struct bpf_call_arg_meta and bpf_kfunc_call_arg_meta.
Merge them into a single struct bpf_call_arg_meta. This is groundwork for
sharing argument checking between helpers and kfuncs.
While merging, drop the btf_id field from the helper meta since it is
never used.
No functional change.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
include/linux/bpf_verifier.h | 38 +++++++++------
kernel/bpf/cfg.c | 2 +-
kernel/bpf/verifier.c | 94 +++++++++++++++---------------------
3 files changed, 62 insertions(+), 72 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index e3eda72cbf67..682c2cd3b844 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -1479,18 +1479,23 @@ struct ret_mem_desc {
bool found;
};
-struct bpf_kfunc_call_arg_meta {
- /* In parameters */
+struct bpf_call_arg_meta {
+ /* Common */
struct btf *btf;
u32 func_id;
- u32 kfunc_flags;
- const struct btf_type *func_proto;
- const char *func_name;
- /* Out parameters */
u8 release_regno;
- bool r0_rdonly;
u32 ret_btf_id;
u32 subprogno;
+ struct bpf_map_desc map;
+ struct bpf_dynptr_desc dynptr;
+ struct ref_obj_desc ref_obj;
+ struct ret_mem_desc ret_mem;
+
+ /* Only set by kfunc */
+ bool r0_rdonly;
+ u32 kfunc_flags;
+ const struct btf_type *func_proto;
+ const char *func_name;
struct {
u64 value;
bool found;
@@ -1521,28 +1526,31 @@ struct bpf_kfunc_call_arg_meta {
u8 spi;
u8 frameno;
} iter;
- struct bpf_map_desc map;
- struct bpf_dynptr_desc dynptr;
- struct ref_obj_desc ref_obj;
- struct ret_mem_desc ret_mem;
+
+ /* Only set by helper */
+ u64 msize_max_value;
+ s64 const_map_key;
+ struct btf *ret_btf;
+ struct btf_field *kptr_field;
+ struct arg_raw_mem_desc arg_raw_mem;
};
int bpf_get_helper_proto(struct bpf_verifier_env *env, int func_id,
const struct bpf_func_proto **ptr);
int bpf_fetch_kfunc_arg_meta(struct bpf_verifier_env *env, s32 func_id,
- s16 offset, struct bpf_kfunc_call_arg_meta *meta);
+ s16 offset, struct bpf_call_arg_meta *meta);
bool bpf_is_async_callback_calling_insn(struct bpf_insn *insn);
bool bpf_is_sync_callback_calling_insn(struct bpf_insn *insn);
-static inline bool bpf_is_iter_next_kfunc(struct bpf_kfunc_call_arg_meta *meta)
+static inline bool bpf_is_iter_next_kfunc(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_ITER_NEXT;
}
-static inline bool bpf_is_kfunc_sleepable(struct bpf_kfunc_call_arg_meta *meta)
+static inline bool bpf_is_kfunc_sleepable(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_SLEEPABLE;
}
-bool bpf_is_kfunc_pkt_changing(struct bpf_kfunc_call_arg_meta *meta);
+bool bpf_is_kfunc_pkt_changing(struct bpf_call_arg_meta *meta);
struct bpf_iarray *bpf_iarray_realloc(struct bpf_iarray *old, size_t n_elem);
int bpf_copy_insn_array_uniq(struct bpf_map *map, u32 start, u32 end, u32 *off);
bool bpf_insn_is_cond_jump(u8 code);
diff --git a/kernel/bpf/cfg.c b/kernel/bpf/cfg.c
index 26d37066465f..db3416a7c904 100644
--- a/kernel/bpf/cfg.c
+++ b/kernel/bpf/cfg.c
@@ -491,7 +491,7 @@ static int visit_insn(int t, struct bpf_verifier_env *env)
return ret;
}
} else if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
- struct bpf_kfunc_call_arg_meta meta;
+ struct bpf_call_arg_meta meta;
ret = bpf_fetch_kfunc_arg_meta(env, insn->imm, insn->off, &meta);
if (ret == 0 && bpf_is_iter_next_kfunc(&meta)) {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 37127ae1ff28..de816063ae63 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -252,24 +252,6 @@ static int validate_ref_obj(struct bpf_verifier_env *env, struct ref_obj_desc *r
return 0;
}
-struct bpf_call_arg_meta {
- struct bpf_map_desc map;
- struct bpf_dynptr_desc dynptr;
- struct ref_obj_desc ref_obj;
- struct arg_raw_mem_desc arg_raw_mem;
- struct ret_mem_desc ret_mem;
- u8 release_regno;
- u64 msize_max_value;
- int func_id;
- struct btf *btf;
- u32 btf_id;
- struct btf *ret_btf;
- u32 ret_btf_id;
- u32 subprogno;
- struct btf_field *kptr_field;
- s64 const_map_key;
-};
-
struct bpf_kfunc_meta {
struct btf *btf;
const struct btf_type *proto;
@@ -927,10 +909,10 @@ static void __mark_reg_known_zero(struct bpf_reg_state *reg);
static bool in_rcu_cs(struct bpf_verifier_env *env);
-static bool is_kfunc_rcu_protected(struct bpf_kfunc_call_arg_meta *meta);
+static bool is_kfunc_rcu_protected(struct bpf_call_arg_meta *meta);
static int mark_stack_slots_iter(struct bpf_verifier_env *env,
- struct bpf_kfunc_call_arg_meta *meta,
+ struct bpf_call_arg_meta *meta,
struct bpf_reg_state *reg, int insn_idx,
struct btf *btf, u32 btf_id, int nr_slots)
{
@@ -1063,7 +1045,7 @@ static int acquire_irq_state(struct bpf_verifier_env *env, int insn_idx);
static int release_irq_state(struct bpf_verifier_state *state, int id);
static int mark_stack_slot_irq_flag(struct bpf_verifier_env *env,
- struct bpf_kfunc_call_arg_meta *meta,
+ struct bpf_call_arg_meta *meta,
struct bpf_reg_state *reg, int insn_idx,
int kfunc_class)
{
@@ -7245,7 +7227,7 @@ static int process_timer_helper(struct bpf_verifier_env *env, struct bpf_reg_sta
}
static int process_timer_kfunc(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
return process_timer_func(env, reg, argno, &meta->map);
}
@@ -7412,23 +7394,23 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat
return err;
}
-static bool is_iter_kfunc(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_iter_kfunc(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & (KF_ITER_NEW | KF_ITER_NEXT | KF_ITER_DESTROY);
}
-static bool is_iter_new_kfunc(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_iter_new_kfunc(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_ITER_NEW;
}
-static bool is_iter_destroy_kfunc(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_iter_destroy_kfunc(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_ITER_DESTROY;
}
-static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg_idx,
+static bool is_kfunc_arg_iter(struct bpf_call_arg_meta *meta, int arg_idx,
const struct btf_param *arg)
{
/* btf_check_iter_kfuncs() guarantees that first argument of any iter
@@ -7442,7 +7424,7 @@ static bool is_kfunc_arg_iter(struct bpf_kfunc_call_arg_meta *meta, int arg_idx,
}
static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno, int insn_idx,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
struct bpf_func_state *state = bpf_func(env, reg);
const struct btf_type *t;
@@ -7609,7 +7591,7 @@ static int widen_imprecise_scalars(struct bpf_verifier_env *env,
}
static struct bpf_reg_state *get_iter_from_state(struct bpf_verifier_state *cur_st,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
int iter_frameno = meta->iter.frameno;
int iter_spi = meta->iter.spi;
@@ -7696,7 +7678,7 @@ static struct bpf_reg_state *get_iter_from_state(struct bpf_verifier_state *cur_
* bpf_iter_num_destroy(&it);
*/
static int process_iter_next_call(struct bpf_verifier_env *env, int insn_idx,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
struct bpf_verifier_state *cur_st = env->cur_state, *queued_st, *prev_st;
struct bpf_func_state *cur_fr = cur_st->frame[cur_st->curframe], *queued_fr;
@@ -10750,27 +10732,27 @@ static void mark_btf_func_reg_size(struct bpf_verifier_env *env, u32 regno,
return __mark_btf_func_reg_size(env, cur_regs(env), regno, reg_size);
}
-static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_acquire(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_ACQUIRE;
}
-static bool is_kfunc_release(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_release(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_RELEASE;
}
-static bool is_kfunc_destructive(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_destructive(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_DESTRUCTIVE;
}
-static bool is_kfunc_rcu(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_rcu(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_RCU;
}
-static bool is_kfunc_rcu_protected(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_rcu_protected(struct bpf_call_arg_meta *meta)
{
return meta->kfunc_flags & KF_RCU_PROTECTED;
}
@@ -10991,7 +10973,7 @@ static bool is_kfunc_arg_prog_aux(const struct btf *btf, const struct btf_param
* To determine whether an argument is implicit, we compare its position
* against the number of arguments in the prototype w/o implicit args.
*/
-static bool is_kfunc_arg_implicit(const struct bpf_kfunc_call_arg_meta *meta, u32 arg_idx)
+static bool is_kfunc_arg_implicit(const struct bpf_call_arg_meta *meta, u32 arg_idx)
{
const struct btf_type *func, *func_proto;
u32 argn;
@@ -11290,7 +11272,7 @@ static bool is_task_work_add_kfunc(u32 func_id)
func_id == special_kfunc_list[KF_bpf_task_work_schedule_resume];
}
-static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_ret_null(struct bpf_call_arg_meta *meta)
{
if (is_bpf_refcount_acquire_kfunc(meta->func_id) && meta->arg_owning_ref)
return false;
@@ -11298,34 +11280,34 @@ static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
return meta->kfunc_flags & KF_RET_NULL;
}
-static bool is_kfunc_bpf_rcu_read_lock(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_bpf_rcu_read_lock(struct bpf_call_arg_meta *meta)
{
return meta->func_id == special_kfunc_list[KF_bpf_rcu_read_lock];
}
-static bool is_kfunc_bpf_rcu_read_unlock(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_bpf_rcu_read_unlock(struct bpf_call_arg_meta *meta)
{
return meta->func_id == special_kfunc_list[KF_bpf_rcu_read_unlock];
}
-static bool is_kfunc_bpf_preempt_disable(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_bpf_preempt_disable(struct bpf_call_arg_meta *meta)
{
return meta->func_id == special_kfunc_list[KF_bpf_preempt_disable];
}
-static bool is_kfunc_bpf_preempt_enable(struct bpf_kfunc_call_arg_meta *meta)
+static bool is_kfunc_bpf_preempt_enable(struct bpf_call_arg_meta *meta)
{
return meta->func_id == special_kfunc_list[KF_bpf_preempt_enable];
}
-bool bpf_is_kfunc_pkt_changing(struct bpf_kfunc_call_arg_meta *meta)
+bool bpf_is_kfunc_pkt_changing(struct bpf_call_arg_meta *meta)
{
return meta->func_id == special_kfunc_list[KF_bpf_xdp_pull_data];
}
static enum kfunc_ptr_arg_type
get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, struct bpf_func_state *caller,
- struct bpf_reg_state *regs, struct bpf_kfunc_call_arg_meta *meta,
+ struct bpf_reg_state *regs, struct bpf_call_arg_meta *meta,
const struct btf_type *t, const struct btf_type *ref_t,
const char *ref_tname, const struct btf_param *args,
int arg, int nargs, argno_t argno, struct bpf_reg_state *reg)
@@ -11431,7 +11413,7 @@ static int process_kf_arg_ptr_to_btf_id(struct bpf_verifier_env *env,
struct bpf_reg_state *reg,
const struct btf_type *ref_t,
const char *ref_tname, u32 ref_id,
- struct bpf_kfunc_call_arg_meta *meta,
+ struct bpf_call_arg_meta *meta,
int arg, argno_t argno)
{
const struct btf_type *reg_ref_t;
@@ -11501,7 +11483,7 @@ static int process_kf_arg_ptr_to_btf_id(struct bpf_verifier_env *env,
}
static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
int err, spi, kfunc_class = IRQ_NATIVE_KFUNC;
bool irq_save;
@@ -11826,7 +11808,7 @@ static bool check_kfunc_is_graph_node_api(struct bpf_verifier_env *env,
static int
__process_kf_arg_ptr_to_graph_root(struct bpf_verifier_env *env,
struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta,
+ struct bpf_call_arg_meta *meta,
enum btf_field_type head_field_type,
struct btf_field **head_field)
{
@@ -11876,7 +11858,7 @@ __process_kf_arg_ptr_to_graph_root(struct bpf_verifier_env *env,
static int process_kf_arg_ptr_to_list_head(struct bpf_verifier_env *env,
struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
return __process_kf_arg_ptr_to_graph_root(env, reg, argno, meta, BPF_LIST_HEAD,
&meta->arg_list_head.field);
@@ -11884,7 +11866,7 @@ static int process_kf_arg_ptr_to_list_head(struct bpf_verifier_env *env,
static int process_kf_arg_ptr_to_rbtree_root(struct bpf_verifier_env *env,
struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
return __process_kf_arg_ptr_to_graph_root(env, reg, argno, meta, BPF_RB_ROOT,
&meta->arg_rbtree_root.field);
@@ -11893,7 +11875,7 @@ static int process_kf_arg_ptr_to_rbtree_root(struct bpf_verifier_env *env,
static int
__process_kf_arg_ptr_to_graph_node(struct bpf_verifier_env *env,
struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta,
+ struct bpf_call_arg_meta *meta,
enum btf_field_type head_field_type,
enum btf_field_type node_field_type,
struct btf_field **node_field)
@@ -11958,7 +11940,7 @@ __process_kf_arg_ptr_to_graph_node(struct bpf_verifier_env *env,
static int process_kf_arg_ptr_to_list_node(struct bpf_verifier_env *env,
struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
return __process_kf_arg_ptr_to_graph_node(env, reg, argno, meta,
BPF_LIST_HEAD, BPF_LIST_NODE,
@@ -11967,7 +11949,7 @@ static int process_kf_arg_ptr_to_list_node(struct bpf_verifier_env *env,
static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env,
struct bpf_reg_state *reg, argno_t argno,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
return __process_kf_arg_ptr_to_graph_node(env, reg, argno, meta,
BPF_RB_ROOT, BPF_RB_NODE,
@@ -11996,7 +11978,7 @@ static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env)
}
}
-static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta,
+static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
int insn_idx)
{
const char *func_name = meta->func_name, *ref_tname;
@@ -12575,7 +12557,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
int bpf_fetch_kfunc_arg_meta(struct bpf_verifier_env *env,
s32 func_id,
s16 offset,
- struct bpf_kfunc_call_arg_meta *meta)
+ struct bpf_call_arg_meta *meta)
{
struct bpf_kfunc_meta kfunc;
int err;
@@ -12734,7 +12716,7 @@ s64 bpf_kfunc_stack_access_bytes(struct bpf_verifier_env *env, struct bpf_insn *
int arg, int insn_idx)
{
struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx];
- struct bpf_kfunc_call_arg_meta meta;
+ struct bpf_call_arg_meta meta;
const struct btf_param *args;
const struct btf_type *t, *ref_t;
const struct btf *btf;
@@ -12795,7 +12777,7 @@ s64 bpf_kfunc_stack_access_bytes(struct bpf_verifier_env *env, struct bpf_insn *
* 0 - fall-through to 'else' branch
* < 0 - not fall-through to 'else' branch, return error
*/
-static int check_special_kfunc(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta,
+static int check_special_kfunc(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
struct bpf_reg_state *regs, struct bpf_insn_aux_data *insn_aux,
const struct btf_type *ptr_type, struct btf *desc_btf)
{
@@ -12974,7 +12956,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
struct bpf_reg_state *regs = cur_regs(env);
const char *func_name, *ptr_type_name;
const struct btf_type *t, *ptr_type;
- struct bpf_kfunc_call_arg_meta meta;
+ struct bpf_call_arg_meta meta;
struct bpf_insn_aux_data *insn_aux;
int err, insn_idx = *insn_idx_p;
const struct btf_param *args;
@@ -16728,7 +16710,7 @@ bool bpf_verifier_inlines_helper_call(struct bpf_verifier_env *env, s32 imm)
bool bpf_get_call_summary(struct bpf_verifier_env *env, struct bpf_insn *call,
struct bpf_call_summary *cs)
{
- struct bpf_kfunc_call_arg_meta meta;
+ struct bpf_call_arg_meta meta;
const struct bpf_func_proto *fn;
int i;
--
2.52.0
next prev parent reply other threads:[~2026-07-15 6:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-15 6:40 [PATCH bpf-next v2 0/7] Unify helper and kfunc call_arg_meta Amery Hung
2026-07-15 6:40 ` [PATCH bpf-next v2 1/7] bpf: Remove dynptr check in check_stack_range_initialized() Amery Hung
2026-07-15 6:40 ` [PATCH bpf-next v2 2/7] bpf: Factor out raw_mode-related fields in bpf_call_arg_meta Amery Hung
2026-07-15 7:09 ` sashiko-bot
2026-07-15 7:48 ` bot+bpf-ci
2026-07-15 6:40 ` [PATCH bpf-next v2 3/7] bpf: Pass argno to callees in check_func_arg() instead of argno_from_reg(regno) Amery Hung
2026-07-15 6:40 ` [PATCH bpf-next v2 4/7] bpf: Unify helper and kfunc allocation-size argument handling Amery Hung
2026-07-15 6:40 ` [PATCH bpf-next v2 5/7] selftests/bpf: Test kfunc returning zero-sized allocation buffer Amery Hung
2026-07-15 6:40 ` [PATCH bpf-next v2 6/7] bpf: Drop redundant pkt_access from bpf_call_arg_meta Amery Hung
2026-07-15 6:40 ` Amery Hung [this message]
2026-07-15 7:00 ` [PATCH bpf-next v2 7/7] bpf: Unify helper and kfunc call argument meta sashiko-bot
2026-07-15 9:10 ` [PATCH bpf-next v2 0/7] Unify helper and kfunc call_arg_meta patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260715064047.1793790-8-ameryhung@gmail.com \
--to=ameryhung@gmail.com \
--cc=alexei.starovoitov@gmail.com \
--cc=andrii@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=eddyz87@gmail.com \
--cc=kernel-team@meta.com \
--cc=memxor@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.