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Message-ID: <20250923215147.1571952-10-jolsa@kernel.org>
Date: Tue, 23 Sep 2025 23:51:47 +0200
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>
Subject: [PATCH 9/9] bpf, x86: Use single ftrace_ops for direct calls
Using single ftrace_ops for direct calls update instead of allocating
ftrace_ops obejct for each trampoline.
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).
Adding HAVE_SINGLE_FTRACE_DIRECT_OPS config option to be enabled on
each arch that supports this.
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
arch/x86/Kconfig | 1 +
kernel/bpf/trampoline.c | 85 +++++++++++++++++++++++++++++++++++------
kernel/trace/Kconfig | 3 ++
kernel/trace/ftrace.c | 15 +++++++-
4 files changed, 92 insertions(+), 12 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 52c8910ba2ef..bfc9115baa6f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -330,6 +330,7 @@ config X86
imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
select HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
select ARCH_SUPPORTS_PT_RECLAIM if X86_64
+ 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 3464859189a2..e3b721773dfb 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->func.addr == (void *) 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 +165,48 @@ 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
+struct ftrace_ops direct_ops = {
+ .ops_func = bpf_tramp_ftrace_ops_func,
+};
+
+static int direct_ops_get(struct bpf_trampoline *tr)
+{
+ tr->fops = &direct_ops;
+ return 0;
+}
+static void direct_ops_clear(struct bpf_trampoline *tr) { }
+static void direct_ops_free(struct bpf_trampoline *tr) { }
+#else
+static int direct_ops_get(struct bpf_trampoline *tr)
+{
+ tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
+ if (!tr->fops)
+ return -1;
+ tr->fops->private = tr;
+ tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
+ return 0;
+}
+
+static void direct_ops_clear(struct bpf_trampoline *tr)
+{
+ tr->fops->func = NULL;
+ tr->fops->trampoline = 0;
+}
+
+static void direct_ops_free(struct bpf_trampoline *tr)
+{
+ if (tr->fops) {
+ ftrace_free_filter(tr->fops);
+ kfree(tr->fops);
+ }
+}
+#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 +225,11 @@ 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_get(tr)) {
kfree(tr);
tr = NULL;
goto out;
}
- tr->fops->private = tr;
- tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
#endif
tr->key = key;
@@ -482,8 +549,7 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
* trampoline again, and retry register.
*/
/* reset fops->func and fops->trampoline for re-register */
- tr->fops->func = NULL;
- tr->fops->trampoline = 0;
+ direct_ops_clear(tr);
/* free im memory and reallocate later */
bpf_tramp_image_free(im);
@@ -864,10 +930,7 @@ 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 2af1304d1a83..c4b969fb1010 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2592,8 +2592,13 @@ 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;
@@ -5986,6 +5991,10 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long ip, unsigned lo
if (!hash)
return -ENOMEM;
+#ifndef CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
+ ops->direct_call = addr;
+#endif
+
err = register_ftrace_direct_hash(ops, hash);
free_ftrace_hash(hash);
return err;
@@ -6050,6 +6059,10 @@ int modify_ftrace_direct(struct ftrace_ops *ops, unsigned long ip, unsigned long
return -ENOMEM;
err = modify_ftrace_direct_hash(ops, hash, lock_direct_mutex);
+#ifndef CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS
+ if (!err)
+ ops->direct_call = addr;
+#endif
free_ftrace_hash(hash);
return err;
}
--
2.51.0
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