[PATCHv5 bpf-next 7/9] bpf: Add trampoline ip hash table

Jiri Olsa
2025-12-15T21:15:29Z

Following changes need to lookup trampoline based on its ip address,
adding hash table for that.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/linux/bpf.h | 7 +++++--
kernel/bpf/trampoline.c | 30 +++++++++++++++++++-----------
2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 28d8d6b7bb1e..7bcb33e2ec9f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1307,14 +1307,17 @@ struct bpf_tramp_image {
};

struct bpf_trampoline {
- /* hlist for trampoline_table */
- struct hlist_node hlist;
+ /* hlist for trampoline_key_table */
+ struct hlist_node hlist_key;
+ /* hlist for trampoline_ip_table */
+ struct hlist_node hlist_ip;
struct ftrace_ops *fops;
/* serializes access to fields of this trampoline */
struct mutex mutex;
refcount_t refcnt;
u32 flags;
u64 key;
+ unsigned long ip;
struct {
struct btf_func_model model;
void *addr;
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index b9a358d7a78f..f298bafab76e 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -24,9 +24,10 @@ const struct bpf_prog_ops bpf_extension_prog_ops = {
#define TRAMPOLINE_HASH_BITS 10
#define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)

-static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
+static struct hlist_head trampoline_key_table[TRAMPOLINE_TABLE_SIZE];
+static struct hlist_head trampoline_ip_table[TRAMPOLINE_TABLE_SIZE];

-/* serializes access to trampoline_table */
+/* serializes access to trampoline tables */
static DEFINE_MUTEX(trampoline_mutex);

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
@@ -135,15 +136,15 @@ void bpf_image_ksym_del(struct bpf_ksym *ksym)
PAGE_SIZE, true, ksym->name);
}

-static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
+static struct bpf_trampoline *bpf_trampoline_lookup(u64 key, unsigned long ip)
{
struct bpf_trampoline *tr;
struct hlist_head *head;
int i;

mutex_lock(&trampoline_mutex);
- head = &trampoline_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
- hlist_for_each_entry(tr, head, hlist) {
+ head = &trampoline_key_table[hash_64(key, TRAMPOLINE_HASH_BITS)];
+ hlist_for_each_entry(tr, head, hlist_key) {
if (tr->key == key) {
refcount_inc(&tr->refcnt);
goto out;
@@ -164,8 +165,12 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
#endif

tr->key = key;
- INIT_HLIST_NODE(&tr->hlist);
- hlist_add_head(&tr->hlist, head);
+ tr->ip = ftrace_location(ip);
+ INIT_HLIST_NODE(&tr->hlist_key);
+ INIT_HLIST_NODE(&tr->hlist_ip);
+ hlist_add_head(&tr->hlist_key, head);
+ head = &trampoline_ip_table[hash_64(tr->ip, TRAMPOLINE_HASH_BITS)];
+ hlist_add_head(&tr->hlist_ip, head);
refcount_set(&tr->refcnt, 1);
mutex_init(&tr->mutex);
for (i = 0; i < BPF_TRAMP_MAX; i++)
@@ -846,7 +851,7 @@ void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog)
prog->aux->attach_btf_id);

bpf_lsm_find_cgroup_shim(prog, &bpf_func);
- tr = bpf_trampoline_lookup(key);
+ tr = bpf_trampoline_lookup(key, 0);
if (WARN_ON_ONCE(!tr))
return;

@@ -866,7 +871,7 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key,
{
struct bpf_trampoline *tr;

- tr = bpf_trampoline_lookup(key);
+ tr = bpf_trampoline_lookup(key, tgt_info->tgt_addr);
if (!tr)
return NULL;

@@ -902,7 +907,8 @@ void bpf_trampoline_put(struct bpf_trampoline *tr)
* fexit progs. The fentry-only trampoline will be freed via
* multiple rcu callbacks.
*/
- hlist_del(&tr->hlist);
+ hlist_del(&tr->hlist_key);
+ hlist_del(&tr->hlist_ip);
if (tr->fops) {
ftrace_free_filter(tr->fops);
kfree(tr->fops);
@@ -1175,7 +1181,9 @@ static int __init init_trampolines(void)
int i;

for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
- INIT_HLIST_HEAD(&trampoline_table[i]);
+ INIT_HLIST_HEAD(&trampoline_key_table[i]);
+ for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++)
+ INIT_HLIST_HEAD(&trampoline_ip_table[i]);
return 0;
}
late_initcall(init_trampolines);
--
2.52.0