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Message-ID: <20251113123750.2507435-9-jolsa@kernel.org>
Date: Thu, 13 Nov 2025 13:37:50 +0100
From: Jiri Olsa <jolsa@...nel.org>
To: Steven Rostedt <rostedt@...nel.org>,
Florent Revest <revest@...gle.com>,
Mark Rutland <mark.rutland@....com>
Cc: bpf@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Menglong Dong <menglong8.dong@...il.com>,
Song Liu <song@...nel.org>
Subject: [PATCHv2 bpf-next 8/8] bpf, x86: Use single ftrace_ops for direct calls
Using single ftrace_ops for direct calls update instead of allocating
ftrace_ops object for each trampoline.
With single ftrace_ops object we can use update_ftrace_direct_* api
that allows multiple ip sites updates on single ftrace_ops object.
Adding HAVE_SINGLE_FTRACE_DIRECT_OPS config option to be enabled on
each arch that supports this.
At the moment we can enable this only on x86 arch, because arm relies
on ftrace_ops object representing just single trampoline image (stored
in ftrace_ops::direct_call). Ach that do not support this will continue
to use *_ftrace_direct api.
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
arch/x86/Kconfig | 1 +
kernel/bpf/trampoline.c | 166 ++++++++++++++++++++++++++++++++++++----
kernel/trace/Kconfig | 3 +
kernel/trace/ftrace.c | 7 +-
4 files changed, 160 insertions(+), 17 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fa3b616af03a..65a2fc279b46 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -332,6 +332,7 @@ config X86
select SCHED_SMT if SMP
select ARCH_SUPPORTS_SCHED_CLUSTER if SMP
select ARCH_SUPPORTS_SCHED_MC if SMP
+ select HAVE_SINGLE_FTRACE_DIRECT_OPS if X86_64 && DYNAMIC_FTRACE_WITH_DIRECT_CALLS
config INSTRUCTION_DECODER
def_bool y
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 26887a0db955..436d393591a5 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -33,12 +33,40 @@ static DEFINE_MUTEX(trampoline_mutex);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex);
+#ifdef CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
+static struct bpf_trampoline *direct_ops_ip_lookup(struct ftrace_ops *ops, unsigned long ip)
+{
+ struct hlist_head *head_ip;
+ struct bpf_trampoline *tr;
+
+ mutex_lock(&trampoline_mutex);
+ head_ip = &trampoline_ip_table[hash_64(ip, TRAMPOLINE_HASH_BITS)];
+ hlist_for_each_entry(tr, head_ip, hlist_ip) {
+ if (tr->ip == ip)
+ goto out;
+ }
+ tr = NULL;
+out:
+ mutex_unlock(&trampoline_mutex);
+ return tr;
+}
+#else
+static struct bpf_trampoline *direct_ops_ip_lookup(struct ftrace_ops *ops, unsigned long ip)
+{
+ return ops->private;
+}
+#endif /* CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS */
+
static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip,
enum ftrace_ops_cmd cmd)
{
- struct bpf_trampoline *tr = ops->private;
+ struct bpf_trampoline *tr;
int ret = 0;
+ tr = direct_ops_ip_lookup(ops, ip);
+ if (!tr)
+ return -EINVAL;
+
if (cmd == FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF) {
/* This is called inside register_ftrace_direct_multi(), so
* tr->mutex is already locked.
@@ -137,6 +165,122 @@ void bpf_image_ksym_del(struct bpf_ksym *ksym)
PAGE_SIZE, true, ksym->name);
}
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+#ifdef CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
+/*
+ * We have only single direct_ops which contains all the direct call
+ * sites and is the only global ftrace_ops for all trampolines.
+ *
+ * We use 'update_ftrace_direct_*' api for attachment.
+ */
+struct ftrace_ops direct_ops = {
+ .ops_func = bpf_tramp_ftrace_ops_func,
+};
+
+static int direct_ops_alloc(struct bpf_trampoline *tr)
+{
+ tr->fops = &direct_ops;
+ return 0;
+}
+
+static void direct_ops_free(struct bpf_trampoline *tr) { }
+
+static struct ftrace_hash *hash_from(unsigned long ip, void *addr)
+{
+ struct ftrace_hash *hash;
+
+ ip = ftrace_location(ip);
+ if (!ip)
+ return NULL;
+ hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
+ if (!hash)
+ return NULL;
+ if (!add_hash_entry_direct(hash, ip, (unsigned long) addr)) {
+ free_ftrace_hash(hash);
+ return NULL;
+ }
+ return hash;
+}
+
+static int direct_ops_add(struct ftrace_ops *ops, unsigned long ip, void *addr)
+{
+ struct ftrace_hash *hash = hash_from(ip, addr);
+ int err = -ENOMEM;
+
+ if (hash)
+ err = update_ftrace_direct_add(ops, hash);
+ free_ftrace_hash(hash);
+ return err;
+}
+
+static int direct_ops_del(struct ftrace_ops *ops, unsigned long ip, void *addr)
+{
+ struct ftrace_hash *hash = hash_from(ip, addr);
+ int err = -ENOMEM;
+
+ if (hash)
+ err = update_ftrace_direct_del(ops, hash);
+ free_ftrace_hash(hash);
+ return err;
+}
+
+static int direct_ops_mod(struct ftrace_ops *ops, unsigned long ip, void *addr, bool lock_direct_mutex)
+{
+ struct ftrace_hash *hash = hash_from(ip, addr);
+ int err = -ENOMEM;
+
+ if (hash)
+ err = update_ftrace_direct_mod(ops, hash, lock_direct_mutex);
+ free_ftrace_hash(hash);
+ return err;
+}
+#else
+/*
+ * We allocate ftrace_ops object for each trampoline and it contains
+ * call site specific for that trampoline.
+ *
+ * We use *_ftrace_direct api for attachment.
+ */
+static int direct_ops_alloc(struct bpf_trampoline *tr)
+{
+ tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
+ if (!tr->fops)
+ return -ENOMEM;
+ tr->fops->private = tr;
+ tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
+ return 0;
+}
+
+static void direct_ops_free(struct bpf_trampoline *tr)
+{
+ if (tr->fops) {
+ ftrace_free_filter(tr->fops);
+ kfree(tr->fops);
+ }
+}
+
+static int direct_ops_add(struct ftrace_ops *ops, unsigned long ip, void *addr)
+{
+ ftrace_set_filter_ip(ops, (unsigned long)ip, 0, 1);
+ return register_ftrace_direct(ops, (long)addr);
+}
+
+static int direct_ops_del(struct ftrace_ops *ops, unsigned long ip, void *addr)
+{
+ return unregister_ftrace_direct(ops, (long)addr, false);
+}
+
+static int direct_ops_mod(struct ftrace_ops *ops, unsigned long ip, void *addr, bool lock_direct_mutex)
+{
+ if (lock_direct_mutex)
+ return modify_ftrace_direct(ops, (long)addr);
+ return modify_ftrace_direct_nolock(ops, (long)addr);
+}
+#endif /* CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS */
+#else
+static void direct_ops_free(struct bpf_trampoline *tr) { }
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+
static struct bpf_trampoline *bpf_trampoline_lookup(u64 key, unsigned long ip)
{
struct bpf_trampoline *tr;
@@ -155,14 +299,11 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key, unsigned long ip)
if (!tr)
goto out;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
- tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
- if (!tr->fops) {
+ if (direct_ops_alloc(tr)) {
kfree(tr);
tr = NULL;
goto out;
}
- tr->fops->private = tr;
- tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
#endif
tr->key = key;
@@ -187,7 +328,7 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
int ret;
if (tr->func.ftrace_managed)
- ret = unregister_ftrace_direct(tr->fops, (long)old_addr, false);
+ ret = direct_ops_del(tr->fops, tr->ip, old_addr);
else
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
@@ -201,10 +342,7 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
int ret;
if (tr->func.ftrace_managed) {
- if (lock_direct_mutex)
- ret = modify_ftrace_direct(tr->fops, (long)new_addr);
- else
- ret = modify_ftrace_direct_nolock(tr->fops, (long)new_addr);
+ ret = direct_ops_mod(tr->fops, tr->ip, new_addr, lock_direct_mutex);
} else {
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
}
@@ -226,8 +364,7 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
}
if (tr->func.ftrace_managed) {
- ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
- ret = register_ftrace_direct(tr->fops, (long)new_addr);
+ ret = direct_ops_add(tr->fops, tr->ip, new_addr);
} else {
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
}
@@ -863,10 +1000,7 @@ void bpf_trampoline_put(struct bpf_trampoline *tr)
*/
hlist_del(&tr->hlist_key);
hlist_del(&tr->hlist_ip);
- if (tr->fops) {
- ftrace_free_filter(tr->fops);
- kfree(tr->fops);
- }
+ direct_ops_free(tr);
kfree(tr);
out:
mutex_unlock(&trampoline_mutex);
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index d2c79da81e4f..4bf5beb04a5b 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -50,6 +50,9 @@ config HAVE_DYNAMIC_FTRACE_WITH_REGS
config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
bool
+config HAVE_SINGLE_FTRACE_DIRECT_OPS
+ bool
+
config HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
bool
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 03948ec81434..e223fc196567 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2605,8 +2605,13 @@ unsigned long ftrace_find_rec_direct(unsigned long ip)
static void call_direct_funcs(unsigned long ip, unsigned long pip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
- unsigned long addr = READ_ONCE(ops->direct_call);
+ unsigned long addr;
+#ifdef CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
+ addr = ftrace_find_rec_direct(ip);
+#else
+ addr = READ_ONCE(ops->direct_call);
+#endif
if (!addr)
return;
--
2.51.1
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