* [PATCH v5 bpf-next 1/4] ftrace: Add modify_ftrace_direct_multi_nolock
2022-07-20 0:21 [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
@ 2022-07-20 0:21 ` Song Liu
2022-07-20 0:21 ` [PATCH v5 bpf-next 2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function Song Liu
` (4 subsequent siblings)
5 siblings, 0 replies; 14+ messages in thread
From: Song Liu @ 2022-07-20 0:21 UTC (permalink / raw)
To: bpf, linux-kernel, live-patching
Cc: daniel, kernel-team, jolsa, rostedt, Song Liu
This is similar to modify_ftrace_direct_multi, but does not acquire
direct_mutex. This is useful when direct_mutex is already locked by the
user.
Signed-off-by: Song Liu <song@kernel.org>
---
include/linux/ftrace.h | 5 +++
kernel/trace/ftrace.c | 86 ++++++++++++++++++++++++++++++------------
2 files changed, 67 insertions(+), 24 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 979f6bfa2c25..acb35243ce5d 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -340,6 +340,7 @@ unsigned long ftrace_find_rec_direct(unsigned long ip);
int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
+int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr);
#else
struct ftrace_ops;
@@ -384,6 +385,10 @@ static inline int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned lo
{
return -ENODEV;
}
+static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr)
+{
+ return -ENODEV;
+}
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 601ccf1b2f09..5d67dc12231d 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5691,22 +5691,8 @@ int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
}
EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);
-/**
- * modify_ftrace_direct_multi - Modify an existing direct 'multi' call
- * to call something else
- * @ops: The address of the struct ftrace_ops object
- * @addr: The address of the new trampoline to call at @ops functions
- *
- * This is used to unregister currently registered direct caller and
- * register new one @addr on functions registered in @ops object.
- *
- * Note there's window between ftrace_shutdown and ftrace_startup calls
- * where there will be no callbacks called.
- *
- * Returns: zero on success. Non zero on error, which includes:
- * -EINVAL - The @ops object was not properly registered.
- */
-int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
+static int
+__modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
{
struct ftrace_hash *hash;
struct ftrace_func_entry *entry, *iter;
@@ -5717,12 +5703,7 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
int i, size;
int err;
- if (check_direct_multi(ops))
- return -EINVAL;
- if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
- return -EINVAL;
-
- mutex_lock(&direct_mutex);
+ lockdep_assert_held_once(&direct_mutex);
/* Enable the tmp_ops to have the same functions as the direct ops */
ftrace_ops_init(&tmp_ops);
@@ -5730,7 +5711,7 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
err = register_ftrace_function(&tmp_ops);
if (err)
- goto out_direct;
+ return err;
/*
* Now the ftrace_ops_list_func() is called to do the direct callers.
@@ -5754,7 +5735,64 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
/* Removing the tmp_ops will add the updated direct callers to the functions */
unregister_ftrace_function(&tmp_ops);
- out_direct:
+ return err;
+}
+
+/**
+ * modify_ftrace_direct_multi_nolock - Modify an existing direct 'multi' call
+ * to call something else
+ * @ops: The address of the struct ftrace_ops object
+ * @addr: The address of the new trampoline to call at @ops functions
+ *
+ * This is used to unregister currently registered direct caller and
+ * register new one @addr on functions registered in @ops object.
+ *
+ * Note there's window between ftrace_shutdown and ftrace_startup calls
+ * where there will be no callbacks called.
+ *
+ * Caller should already have direct_mutex locked, so we don't lock
+ * direct_mutex here.
+ *
+ * Returns: zero on success. Non zero on error, which includes:
+ * -EINVAL - The @ops object was not properly registered.
+ */
+int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr)
+{
+ if (check_direct_multi(ops))
+ return -EINVAL;
+ if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
+ return -EINVAL;
+
+ return __modify_ftrace_direct_multi(ops, addr);
+}
+EXPORT_SYMBOL_GPL(modify_ftrace_direct_multi_nolock);
+
+/**
+ * modify_ftrace_direct_multi - Modify an existing direct 'multi' call
+ * to call something else
+ * @ops: The address of the struct ftrace_ops object
+ * @addr: The address of the new trampoline to call at @ops functions
+ *
+ * This is used to unregister currently registered direct caller and
+ * register new one @addr on functions registered in @ops object.
+ *
+ * Note there's window between ftrace_shutdown and ftrace_startup calls
+ * where there will be no callbacks called.
+ *
+ * Returns: zero on success. Non zero on error, which includes:
+ * -EINVAL - The @ops object was not properly registered.
+ */
+int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
+{
+ int err;
+
+ if (check_direct_multi(ops))
+ return -EINVAL;
+ if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
+ return -EINVAL;
+
+ mutex_lock(&direct_mutex);
+ err = __modify_ftrace_direct_multi(ops, addr);
mutex_unlock(&direct_mutex);
return err;
}
--
2.30.2
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 bpf-next 2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function
2022-07-20 0:21 [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
2022-07-20 0:21 ` [PATCH v5 bpf-next 1/4] ftrace: Add modify_ftrace_direct_multi_nolock Song Liu
@ 2022-07-20 0:21 ` Song Liu
2022-09-09 11:58 ` Naveen N. Rao
2022-07-20 0:21 ` [PATCH v5 bpf-next 3/4] bpf, x64: Allow to use caller address from stack Song Liu
` (3 subsequent siblings)
5 siblings, 1 reply; 14+ messages in thread
From: Song Liu @ 2022-07-20 0:21 UTC (permalink / raw)
To: bpf, linux-kernel, live-patching
Cc: daniel, kernel-team, jolsa, rostedt, Song Liu
IPMODIFY (livepatch) and DIRECT (bpf trampoline) ops are both important
users of ftrace. It is necessary to allow them work on the same function
at the same time.
First, DIRECT ops no longer specify IPMODIFY flag. Instead, DIRECT flag is
handled together with IPMODIFY flag in __ftrace_hash_update_ipmodify().
Then, a callback function, ops_func, is added to ftrace_ops. This is used
by ftrace core code to understand whether the DIRECT ops can share with an
IPMODIFY ops. To share with IPMODIFY ops, the DIRECT ops need to implement
the callback function and adjust the direct trampoline accordingly.
If DIRECT ops is attached before the IPMODIFY ops, ftrace core code calls
ENABLE_SHARE_IPMODIFY_PEER on the DIRECT ops before registering the
IPMODIFY ops.
If IPMODIFY ops is attached before the DIRECT ops, ftrace core code calls
ENABLE_SHARE_IPMODIFY_SELF in __ftrace_hash_update_ipmodify. Owner of the
DIRECT ops may return 0 if the DIRECT trampoline can share with IPMODIFY,
so error code otherwise. The error code is propagated to
register_ftrace_direct_multi so that onwer of the DIRECT trampoline can
handle it properly.
For more details, please refer to comment before enum ftrace_ops_cmd.
Link: https://lore.kernel.org/all/20220602193706.2607681-2-song@kernel.org/
Link: https://lore.kernel.org/all/20220718055449.3960512-1-song@kernel.org/
Signed-off-by: Song Liu <song@kernel.org>
---
include/linux/ftrace.h | 38 +++++++
kernel/trace/ftrace.c | 242 ++++++++++++++++++++++++++++++++++++-----
2 files changed, 254 insertions(+), 26 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index acb35243ce5d..0b61371e287b 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -208,6 +208,43 @@ enum {
FTRACE_OPS_FL_DIRECT = BIT(17),
};
+/*
+ * FTRACE_OPS_CMD_* commands allow the ftrace core logic to request changes
+ * to a ftrace_ops. Note, the requests may fail.
+ *
+ * ENABLE_SHARE_IPMODIFY_SELF - enable a DIRECT ops to work on the same
+ * function as an ops with IPMODIFY. Called
+ * when the DIRECT ops is being registered.
+ * This is called with both direct_mutex and
+ * ftrace_lock are locked.
+ *
+ * ENABLE_SHARE_IPMODIFY_PEER - enable a DIRECT ops to work on the same
+ * function as an ops with IPMODIFY. Called
+ * when the other ops (the one with IPMODIFY)
+ * is being registered.
+ * This is called with direct_mutex locked.
+ *
+ * DISABLE_SHARE_IPMODIFY_PEER - disable a DIRECT ops to work on the same
+ * function as an ops with IPMODIFY. Called
+ * when the other ops (the one with IPMODIFY)
+ * is being unregistered.
+ * This is called with direct_mutex locked.
+ */
+enum ftrace_ops_cmd {
+ FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF,
+ FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER,
+ FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER,
+};
+
+/*
+ * For most ftrace_ops_cmd,
+ * Returns:
+ * 0 - Success.
+ * Negative on failure. The return value is dependent on the
+ * callback.
+ */
+typedef int (*ftrace_ops_func_t)(struct ftrace_ops *op, enum ftrace_ops_cmd cmd);
+
#ifdef CONFIG_DYNAMIC_FTRACE
/* The hash used to know what functions callbacks trace */
struct ftrace_ops_hash {
@@ -250,6 +287,7 @@ struct ftrace_ops {
unsigned long trampoline;
unsigned long trampoline_size;
struct list_head list;
+ ftrace_ops_func_t ops_func;
#endif
};
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5d67dc12231d..bc921a3f7ea8 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1861,6 +1861,8 @@ static void ftrace_hash_rec_enable_modify(struct ftrace_ops *ops,
ftrace_hash_rec_update_modify(ops, filter_hash, 1);
}
+static bool ops_references_ip(struct ftrace_ops *ops, unsigned long ip);
+
/*
* Try to update IPMODIFY flag on each ftrace_rec. Return 0 if it is OK
* or no-needed to update, -EBUSY if it detects a conflict of the flag
@@ -1869,6 +1871,13 @@ static void ftrace_hash_rec_enable_modify(struct ftrace_ops *ops,
* - If the hash is NULL, it hits all recs (if IPMODIFY is set, this is rejected)
* - If the hash is EMPTY_HASH, it hits nothing
* - Anything else hits the recs which match the hash entries.
+ *
+ * DIRECT ops does not have IPMODIFY flag, but we still need to check it
+ * against functions with FTRACE_FL_IPMODIFY. If there is any overlap, call
+ * ops_func(SHARE_IPMODIFY_SELF) to make sure current ops can share with
+ * IPMODIFY. If ops_func(SHARE_IPMODIFY_SELF) returns non-zero, propagate
+ * the return value to the caller and eventually to the owner of the DIRECT
+ * ops.
*/
static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
struct ftrace_hash *old_hash,
@@ -1877,17 +1886,26 @@ static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
struct ftrace_page *pg;
struct dyn_ftrace *rec, *end = NULL;
int in_old, in_new;
+ bool is_ipmodify, is_direct;
/* Only update if the ops has been registered */
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return 0;
- if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
+ is_ipmodify = ops->flags & FTRACE_OPS_FL_IPMODIFY;
+ is_direct = ops->flags & FTRACE_OPS_FL_DIRECT;
+
+ /* neither IPMODIFY nor DIRECT, skip */
+ if (!is_ipmodify && !is_direct)
+ return 0;
+
+ if (WARN_ON_ONCE(is_ipmodify && is_direct))
return 0;
/*
- * Since the IPMODIFY is a very address sensitive action, we do not
- * allow ftrace_ops to set all functions to new hash.
+ * Since the IPMODIFY and DIRECT are very address sensitive
+ * actions, we do not allow ftrace_ops to set all functions to new
+ * hash.
*/
if (!new_hash || !old_hash)
return -EINVAL;
@@ -1905,12 +1923,32 @@ static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
continue;
if (in_new) {
- /* New entries must ensure no others are using it */
- if (rec->flags & FTRACE_FL_IPMODIFY)
- goto rollback;
- rec->flags |= FTRACE_FL_IPMODIFY;
- } else /* Removed entry */
+ if (rec->flags & FTRACE_FL_IPMODIFY) {
+ int ret;
+
+ /* Cannot have two ipmodify on same rec */
+ if (is_ipmodify)
+ goto rollback;
+
+ FTRACE_WARN_ON(rec->flags & FTRACE_FL_DIRECT);
+
+ /*
+ * Another ops with IPMODIFY is already
+ * attached. We are now attaching a direct
+ * ops. Run SHARE_IPMODIFY_SELF, to check
+ * whether sharing is supported.
+ */
+ if (!ops->ops_func)
+ return -EBUSY;
+ ret = ops->ops_func(ops, FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF);
+ if (ret)
+ return ret;
+ } else if (is_ipmodify) {
+ rec->flags |= FTRACE_FL_IPMODIFY;
+ }
+ } else if (is_ipmodify) {
rec->flags &= ~FTRACE_FL_IPMODIFY;
+ }
} while_for_each_ftrace_rec();
return 0;
@@ -2454,8 +2492,7 @@ static void call_direct_funcs(unsigned long ip, unsigned long pip,
struct ftrace_ops direct_ops = {
.func = call_direct_funcs,
- .flags = FTRACE_OPS_FL_IPMODIFY
- | FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS
+ .flags = FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS
| FTRACE_OPS_FL_PERMANENT,
/*
* By declaring the main trampoline as this trampoline
@@ -3072,14 +3109,14 @@ static inline int ops_traces_mod(struct ftrace_ops *ops)
}
/*
- * Check if the current ops references the record.
+ * Check if the current ops references the given ip.
*
* If the ops traces all functions, then it was already accounted for.
* If the ops does not trace the current record function, skip it.
* If the ops ignores the function via notrace filter, skip it.
*/
-static inline bool
-ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
+static bool
+ops_references_ip(struct ftrace_ops *ops, unsigned long ip)
{
/* If ops isn't enabled, ignore it */
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
@@ -3091,16 +3128,29 @@ ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
/* The function must be in the filter */
if (!ftrace_hash_empty(ops->func_hash->filter_hash) &&
- !__ftrace_lookup_ip(ops->func_hash->filter_hash, rec->ip))
+ !__ftrace_lookup_ip(ops->func_hash->filter_hash, ip))
return false;
/* If in notrace hash, we ignore it too */
- if (ftrace_lookup_ip(ops->func_hash->notrace_hash, rec->ip))
+ if (ftrace_lookup_ip(ops->func_hash->notrace_hash, ip))
return false;
return true;
}
+/*
+ * Check if the current ops references the record.
+ *
+ * If the ops traces all functions, then it was already accounted for.
+ * If the ops does not trace the current record function, skip it.
+ * If the ops ignores the function via notrace filter, skip it.
+ */
+static bool
+ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
+{
+ return ops_references_ip(ops, rec->ip);
+}
+
static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
{
bool init_nop = ftrace_need_init_nop();
@@ -5215,6 +5265,8 @@ static struct ftrace_direct_func *ftrace_alloc_direct_func(unsigned long addr)
return direct;
}
+static int register_ftrace_function_nolock(struct ftrace_ops *ops);
+
/**
* register_ftrace_direct - Call a custom trampoline directly
* @ip: The address of the nop at the beginning of a function
@@ -5286,7 +5338,7 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
ret = ftrace_set_filter_ip(&direct_ops, ip, 0, 0);
if (!ret && !(direct_ops.flags & FTRACE_OPS_FL_ENABLED)) {
- ret = register_ftrace_function(&direct_ops);
+ ret = register_ftrace_function_nolock(&direct_ops);
if (ret)
ftrace_set_filter_ip(&direct_ops, ip, 1, 0);
}
@@ -5545,8 +5597,7 @@ int modify_ftrace_direct(unsigned long ip,
}
EXPORT_SYMBOL_GPL(modify_ftrace_direct);
-#define MULTI_FLAGS (FTRACE_OPS_FL_IPMODIFY | FTRACE_OPS_FL_DIRECT | \
- FTRACE_OPS_FL_SAVE_REGS)
+#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS)
static int check_direct_multi(struct ftrace_ops *ops)
{
@@ -5639,7 +5690,7 @@ int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
ops->flags = MULTI_FLAGS;
ops->trampoline = FTRACE_REGS_ADDR;
- err = register_ftrace_function(ops);
+ err = register_ftrace_function_nolock(ops);
out_remove:
if (err)
@@ -5709,7 +5760,7 @@ __modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
ftrace_ops_init(&tmp_ops);
tmp_ops.func_hash = ops->func_hash;
- err = register_ftrace_function(&tmp_ops);
+ err = register_ftrace_function_nolock(&tmp_ops);
if (err)
return err;
@@ -8003,6 +8054,143 @@ int ftrace_is_dead(void)
return ftrace_disabled;
}
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+/*
+ * When registering ftrace_ops with IPMODIFY, it is necessary to make sure
+ * it doesn't conflict with any direct ftrace_ops. If there is existing
+ * direct ftrace_ops on a kernel function being patched, call
+ * FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER on it to enable sharing.
+ *
+ * @ops: ftrace_ops being registered.
+ *
+ * Returns:
+ * 0 on success;
+ * Negative on failure.
+ */
+static int prepare_direct_functions_for_ipmodify(struct ftrace_ops *ops)
+{
+ struct ftrace_func_entry *entry;
+ struct ftrace_hash *hash;
+ struct ftrace_ops *op;
+ int size, i, ret;
+
+ lockdep_assert_held_once(&direct_mutex);
+
+ if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
+ return 0;
+
+ hash = ops->func_hash->filter_hash;
+ size = 1 << hash->size_bits;
+ for (i = 0; i < size; i++) {
+ hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
+ unsigned long ip = entry->ip;
+ bool found_op = false;
+
+ mutex_lock(&ftrace_lock);
+ do_for_each_ftrace_op(op, ftrace_ops_list) {
+ if (!(op->flags & FTRACE_OPS_FL_DIRECT))
+ continue;
+ if (ops_references_ip(op, ip)) {
+ found_op = true;
+ break;
+ }
+ } while_for_each_ftrace_op(op);
+ mutex_unlock(&ftrace_lock);
+
+ if (found_op) {
+ if (!op->ops_func)
+ return -EBUSY;
+
+ ret = op->ops_func(op, FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER);
+ if (ret)
+ return ret;
+ }
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Similar to prepare_direct_functions_for_ipmodify, clean up after ops
+ * with IPMODIFY is unregistered. The cleanup is optional for most DIRECT
+ * ops.
+ */
+static void cleanup_direct_functions_after_ipmodify(struct ftrace_ops *ops)
+{
+ struct ftrace_func_entry *entry;
+ struct ftrace_hash *hash;
+ struct ftrace_ops *op;
+ int size, i;
+
+ if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
+ return;
+
+ mutex_lock(&direct_mutex);
+
+ hash = ops->func_hash->filter_hash;
+ size = 1 << hash->size_bits;
+ for (i = 0; i < size; i++) {
+ hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
+ unsigned long ip = entry->ip;
+ bool found_op = false;
+
+ mutex_lock(&ftrace_lock);
+ do_for_each_ftrace_op(op, ftrace_ops_list) {
+ if (!(op->flags & FTRACE_OPS_FL_DIRECT))
+ continue;
+ if (ops_references_ip(op, ip)) {
+ found_op = true;
+ break;
+ }
+ } while_for_each_ftrace_op(op);
+ mutex_unlock(&ftrace_lock);
+
+ /* The cleanup is optional, ignore any errors */
+ if (found_op && op->ops_func)
+ op->ops_func(op, FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER);
+ }
+ }
+ mutex_unlock(&direct_mutex);
+}
+
+#define lock_direct_mutex() mutex_lock(&direct_mutex)
+#define unlock_direct_mutex() mutex_unlock(&direct_mutex)
+
+#else /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+
+static int prepare_direct_functions_for_ipmodify(struct ftrace_ops *ops)
+{
+ return 0;
+}
+
+static void cleanup_direct_functions_after_ipmodify(struct ftrace_ops *ops)
+{
+}
+
+#define lock_direct_mutex() do { } while (0)
+#define unlock_direct_mutex() do { } while (0)
+
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+
+/*
+ * Similar to register_ftrace_function, except we don't lock direct_mutex.
+ */
+static int register_ftrace_function_nolock(struct ftrace_ops *ops)
+{
+ int ret;
+
+ ftrace_ops_init(ops);
+
+ mutex_lock(&ftrace_lock);
+
+ ret = ftrace_startup(ops, 0);
+
+ mutex_unlock(&ftrace_lock);
+
+ return ret;
+}
+
/**
* register_ftrace_function - register a function for profiling
* @ops: ops structure that holds the function for profiling.
@@ -8018,14 +8206,15 @@ int register_ftrace_function(struct ftrace_ops *ops)
{
int ret;
- ftrace_ops_init(ops);
-
- mutex_lock(&ftrace_lock);
-
- ret = ftrace_startup(ops, 0);
+ lock_direct_mutex();
+ ret = prepare_direct_functions_for_ipmodify(ops);
+ if (ret < 0)
+ goto out_unlock;
- mutex_unlock(&ftrace_lock);
+ ret = register_ftrace_function_nolock(ops);
+out_unlock:
+ unlock_direct_mutex();
return ret;
}
EXPORT_SYMBOL_GPL(register_ftrace_function);
@@ -8044,6 +8233,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
ret = ftrace_shutdown(ops, 0);
mutex_unlock(&ftrace_lock);
+ cleanup_direct_functions_after_ipmodify(ops);
return ret;
}
EXPORT_SYMBOL_GPL(unregister_ftrace_function);
--
2.30.2
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH v5 bpf-next 2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function
2022-07-20 0:21 ` [PATCH v5 bpf-next 2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function Song Liu
@ 2022-09-09 11:58 ` Naveen N. Rao
2022-09-09 14:05 ` Song Liu
0 siblings, 1 reply; 14+ messages in thread
From: Naveen N. Rao @ 2022-09-09 11:58 UTC (permalink / raw)
To: bpf, linux-kernel, live-patching, Song Liu, rostedt
Cc: daniel, jolsa, kernel-team
Song Liu wrote:
> IPMODIFY (livepatch) and DIRECT (bpf trampoline) ops are both important
> users of ftrace. It is necessary to allow them work on the same function
> at the same time.
>
> First, DIRECT ops no longer specify IPMODIFY flag. Instead, DIRECT flag is
> handled together with IPMODIFY flag in __ftrace_hash_update_ipmodify().
>
> Then, a callback function, ops_func, is added to ftrace_ops. This is used
> by ftrace core code to understand whether the DIRECT ops can share with an
> IPMODIFY ops. To share with IPMODIFY ops, the DIRECT ops need to implement
> the callback function and adjust the direct trampoline accordingly.
>
> If DIRECT ops is attached before the IPMODIFY ops, ftrace core code calls
> ENABLE_SHARE_IPMODIFY_PEER on the DIRECT ops before registering the
> IPMODIFY ops.
>
> If IPMODIFY ops is attached before the DIRECT ops, ftrace core code calls
> ENABLE_SHARE_IPMODIFY_SELF in __ftrace_hash_update_ipmodify. Owner of the
> DIRECT ops may return 0 if the DIRECT trampoline can share with IPMODIFY,
> so error code otherwise. The error code is propagated to
> register_ftrace_direct_multi so that onwer of the DIRECT trampoline can
> handle it properly.
>
> For more details, please refer to comment before enum ftrace_ops_cmd.
>
> Link: https://lore.kernel.org/all/20220602193706.2607681-2-song@kernel.org/
> Link: https://lore.kernel.org/all/20220718055449.3960512-1-song@kernel.org/
> Signed-off-by: Song Liu <song@kernel.org>
> ---
> include/linux/ftrace.h | 38 +++++++
> kernel/trace/ftrace.c | 242 ++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 254 insertions(+), 26 deletions(-)
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index acb35243ce5d..0b61371e287b 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -208,6 +208,43 @@ enum {
> FTRACE_OPS_FL_DIRECT = BIT(17),
> };
>
> +/*
> + * FTRACE_OPS_CMD_* commands allow the ftrace core logic to request changes
> + * to a ftrace_ops. Note, the requests may fail.
> + *
> + * ENABLE_SHARE_IPMODIFY_SELF - enable a DIRECT ops to work on the same
> + * function as an ops with IPMODIFY. Called
> + * when the DIRECT ops is being registered.
> + * This is called with both direct_mutex and
> + * ftrace_lock are locked.
> + *
> + * ENABLE_SHARE_IPMODIFY_PEER - enable a DIRECT ops to work on the same
> + * function as an ops with IPMODIFY. Called
> + * when the other ops (the one with IPMODIFY)
> + * is being registered.
> + * This is called with direct_mutex locked.
> + *
> + * DISABLE_SHARE_IPMODIFY_PEER - disable a DIRECT ops to work on the same
> + * function as an ops with IPMODIFY. Called
> + * when the other ops (the one with IPMODIFY)
> + * is being unregistered.
> + * This is called with direct_mutex locked.
> + */
> +enum ftrace_ops_cmd {
> + FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF,
> + FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER,
> + FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER,
> +};
> +
> +/*
> + * For most ftrace_ops_cmd,
> + * Returns:
> + * 0 - Success.
> + * Negative on failure. The return value is dependent on the
> + * callback.
> + */
> +typedef int (*ftrace_ops_func_t)(struct ftrace_ops *op, enum ftrace_ops_cmd cmd);
> +
> #ifdef CONFIG_DYNAMIC_FTRACE
> /* The hash used to know what functions callbacks trace */
> struct ftrace_ops_hash {
> @@ -250,6 +287,7 @@ struct ftrace_ops {
> unsigned long trampoline;
> unsigned long trampoline_size;
> struct list_head list;
> + ftrace_ops_func_t ops_func;
> #endif
> };
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 5d67dc12231d..bc921a3f7ea8 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1861,6 +1861,8 @@ static void ftrace_hash_rec_enable_modify(struct ftrace_ops *ops,
> ftrace_hash_rec_update_modify(ops, filter_hash, 1);
> }
>
> +static bool ops_references_ip(struct ftrace_ops *ops, unsigned long ip);
> +
> /*
> * Try to update IPMODIFY flag on each ftrace_rec. Return 0 if it is OK
> * or no-needed to update, -EBUSY if it detects a conflict of the flag
> @@ -1869,6 +1871,13 @@ static void ftrace_hash_rec_enable_modify(struct ftrace_ops *ops,
> * - If the hash is NULL, it hits all recs (if IPMODIFY is set, this is rejected)
> * - If the hash is EMPTY_HASH, it hits nothing
> * - Anything else hits the recs which match the hash entries.
> + *
> + * DIRECT ops does not have IPMODIFY flag, but we still need to check it
> + * against functions with FTRACE_FL_IPMODIFY. If there is any overlap, call
> + * ops_func(SHARE_IPMODIFY_SELF) to make sure current ops can share with
> + * IPMODIFY. If ops_func(SHARE_IPMODIFY_SELF) returns non-zero, propagate
> + * the return value to the caller and eventually to the owner of the DIRECT
> + * ops.
> */
> static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
> struct ftrace_hash *old_hash,
> @@ -1877,17 +1886,26 @@ static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
> struct ftrace_page *pg;
> struct dyn_ftrace *rec, *end = NULL;
> int in_old, in_new;
> + bool is_ipmodify, is_direct;
>
> /* Only update if the ops has been registered */
> if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
> return 0;
>
> - if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
> + is_ipmodify = ops->flags & FTRACE_OPS_FL_IPMODIFY;
> + is_direct = ops->flags & FTRACE_OPS_FL_DIRECT;
> +
> + /* neither IPMODIFY nor DIRECT, skip */
> + if (!is_ipmodify && !is_direct)
> + return 0;
> +
> + if (WARN_ON_ONCE(is_ipmodify && is_direct))
> return 0;
>
> /*
> - * Since the IPMODIFY is a very address sensitive action, we do not
> - * allow ftrace_ops to set all functions to new hash.
> + * Since the IPMODIFY and DIRECT are very address sensitive
> + * actions, we do not allow ftrace_ops to set all functions to new
> + * hash.
> */
> if (!new_hash || !old_hash)
> return -EINVAL;
> @@ -1905,12 +1923,32 @@ static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
> continue;
>
> if (in_new) {
> - /* New entries must ensure no others are using it */
> - if (rec->flags & FTRACE_FL_IPMODIFY)
> - goto rollback;
> - rec->flags |= FTRACE_FL_IPMODIFY;
> - } else /* Removed entry */
> + if (rec->flags & FTRACE_FL_IPMODIFY) {
> + int ret;
> +
> + /* Cannot have two ipmodify on same rec */
> + if (is_ipmodify)
> + goto rollback;
> +
> + FTRACE_WARN_ON(rec->flags & FTRACE_FL_DIRECT);
> +
> + /*
> + * Another ops with IPMODIFY is already
> + * attached. We are now attaching a direct
> + * ops. Run SHARE_IPMODIFY_SELF, to check
> + * whether sharing is supported.
> + */
> + if (!ops->ops_func)
> + return -EBUSY;
> + ret = ops->ops_func(ops, FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF);
> + if (ret)
> + return ret;
> + } else if (is_ipmodify) {
> + rec->flags |= FTRACE_FL_IPMODIFY;
> + }
> + } else if (is_ipmodify) {
> rec->flags &= ~FTRACE_FL_IPMODIFY;
> + }
> } while_for_each_ftrace_rec();
>
> return 0;
> @@ -2454,8 +2492,7 @@ static void call_direct_funcs(unsigned long ip, unsigned long pip,
>
> struct ftrace_ops direct_ops = {
> .func = call_direct_funcs,
> - .flags = FTRACE_OPS_FL_IPMODIFY
> - | FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS
> + .flags = FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS
> | FTRACE_OPS_FL_PERMANENT,
> /*
> * By declaring the main trampoline as this trampoline
> @@ -3072,14 +3109,14 @@ static inline int ops_traces_mod(struct ftrace_ops *ops)
> }
>
> /*
> - * Check if the current ops references the record.
> + * Check if the current ops references the given ip.
> *
> * If the ops traces all functions, then it was already accounted for.
> * If the ops does not trace the current record function, skip it.
> * If the ops ignores the function via notrace filter, skip it.
> */
> -static inline bool
> -ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
> +static bool
> +ops_references_ip(struct ftrace_ops *ops, unsigned long ip)
> {
> /* If ops isn't enabled, ignore it */
> if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
> @@ -3091,16 +3128,29 @@ ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
>
> /* The function must be in the filter */
> if (!ftrace_hash_empty(ops->func_hash->filter_hash) &&
> - !__ftrace_lookup_ip(ops->func_hash->filter_hash, rec->ip))
> + !__ftrace_lookup_ip(ops->func_hash->filter_hash, ip))
> return false;
>
> /* If in notrace hash, we ignore it too */
> - if (ftrace_lookup_ip(ops->func_hash->notrace_hash, rec->ip))
> + if (ftrace_lookup_ip(ops->func_hash->notrace_hash, ip))
> return false;
>
> return true;
> }
>
> +/*
> + * Check if the current ops references the record.
> + *
> + * If the ops traces all functions, then it was already accounted for.
> + * If the ops does not trace the current record function, skip it.
> + * If the ops ignores the function via notrace filter, skip it.
> + */
> +static bool
> +ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
> +{
> + return ops_references_ip(ops, rec->ip);
> +}
> +
> static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs)
> {
> bool init_nop = ftrace_need_init_nop();
> @@ -5215,6 +5265,8 @@ static struct ftrace_direct_func *ftrace_alloc_direct_func(unsigned long addr)
> return direct;
> }
>
> +static int register_ftrace_function_nolock(struct ftrace_ops *ops);
> +
> /**
> * register_ftrace_direct - Call a custom trampoline directly
> * @ip: The address of the nop at the beginning of a function
> @@ -5286,7 +5338,7 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
> ret = ftrace_set_filter_ip(&direct_ops, ip, 0, 0);
>
> if (!ret && !(direct_ops.flags & FTRACE_OPS_FL_ENABLED)) {
> - ret = register_ftrace_function(&direct_ops);
> + ret = register_ftrace_function_nolock(&direct_ops);
> if (ret)
> ftrace_set_filter_ip(&direct_ops, ip, 1, 0);
> }
> @@ -5545,8 +5597,7 @@ int modify_ftrace_direct(unsigned long ip,
> }
> EXPORT_SYMBOL_GPL(modify_ftrace_direct);
>
> -#define MULTI_FLAGS (FTRACE_OPS_FL_IPMODIFY | FTRACE_OPS_FL_DIRECT | \
> - FTRACE_OPS_FL_SAVE_REGS)
> +#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS)
>
> static int check_direct_multi(struct ftrace_ops *ops)
> {
> @@ -5639,7 +5690,7 @@ int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
> ops->flags = MULTI_FLAGS;
> ops->trampoline = FTRACE_REGS_ADDR;
>
> - err = register_ftrace_function(ops);
> + err = register_ftrace_function_nolock(ops);
>
> out_remove:
> if (err)
> @@ -5709,7 +5760,7 @@ __modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
> ftrace_ops_init(&tmp_ops);
> tmp_ops.func_hash = ops->func_hash;
>
> - err = register_ftrace_function(&tmp_ops);
> + err = register_ftrace_function_nolock(&tmp_ops);
> if (err)
> return err;
>
> @@ -8003,6 +8054,143 @@ int ftrace_is_dead(void)
> return ftrace_disabled;
> }
>
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> +/*
> + * When registering ftrace_ops with IPMODIFY, it is necessary to make sure
> + * it doesn't conflict with any direct ftrace_ops. If there is existing
> + * direct ftrace_ops on a kernel function being patched, call
> + * FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER on it to enable sharing.
> + *
> + * @ops: ftrace_ops being registered.
> + *
> + * Returns:
> + * 0 on success;
> + * Negative on failure.
> + */
> +static int prepare_direct_functions_for_ipmodify(struct ftrace_ops *ops)
> +{
> + struct ftrace_func_entry *entry;
> + struct ftrace_hash *hash;
> + struct ftrace_ops *op;
> + int size, i, ret;
> +
> + lockdep_assert_held_once(&direct_mutex);
> +
> + if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
> + return 0;
> +
> + hash = ops->func_hash->filter_hash;
> + size = 1 << hash->size_bits;
> + for (i = 0; i < size; i++) {
> + hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> + unsigned long ip = entry->ip;
> + bool found_op = false;
> +
> + mutex_lock(&ftrace_lock);
> + do_for_each_ftrace_op(op, ftrace_ops_list) {
> + if (!(op->flags & FTRACE_OPS_FL_DIRECT))
> + continue;
> + if (ops_references_ip(op, ip)) {
> + found_op = true;
> + break;
> + }
> + } while_for_each_ftrace_op(op);
> + mutex_unlock(&ftrace_lock);
> +
> + if (found_op) {
> + if (!op->ops_func)
> + return -EBUSY;
> +
> + ret = op->ops_func(op, FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER);
> + if (ret)
> + return ret;
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * Similar to prepare_direct_functions_for_ipmodify, clean up after ops
> + * with IPMODIFY is unregistered. The cleanup is optional for most DIRECT
> + * ops.
> + */
> +static void cleanup_direct_functions_after_ipmodify(struct ftrace_ops *ops)
> +{
> + struct ftrace_func_entry *entry;
> + struct ftrace_hash *hash;
> + struct ftrace_ops *op;
> + int size, i;
> +
> + if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
> + return;
> +
> + mutex_lock(&direct_mutex);
> +
> + hash = ops->func_hash->filter_hash;
> + size = 1 << hash->size_bits;
> + for (i = 0; i < size; i++) {
> + hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> + unsigned long ip = entry->ip;
> + bool found_op = false;
> +
> + mutex_lock(&ftrace_lock);
> + do_for_each_ftrace_op(op, ftrace_ops_list) {
> + if (!(op->flags & FTRACE_OPS_FL_DIRECT))
> + continue;
> + if (ops_references_ip(op, ip)) {
> + found_op = true;
> + break;
> + }
> + } while_for_each_ftrace_op(op);
> + mutex_unlock(&ftrace_lock);
> +
> + /* The cleanup is optional, ignore any errors */
> + if (found_op && op->ops_func)
> + op->ops_func(op, FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER);
> + }
> + }
> + mutex_unlock(&direct_mutex);
> +}
> +
> +#define lock_direct_mutex() mutex_lock(&direct_mutex)
> +#define unlock_direct_mutex() mutex_unlock(&direct_mutex)
> +
> +#else /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
> +
> +static int prepare_direct_functions_for_ipmodify(struct ftrace_ops *ops)
> +{
> + return 0;
> +}
> +
> +static void cleanup_direct_functions_after_ipmodify(struct ftrace_ops *ops)
> +{
> +}
> +
> +#define lock_direct_mutex() do { } while (0)
> +#define unlock_direct_mutex() do { } while (0)
> +
> +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
> +
> +/*
> + * Similar to register_ftrace_function, except we don't lock direct_mutex.
> + */
> +static int register_ftrace_function_nolock(struct ftrace_ops *ops)
> +{
> + int ret;
> +
> + ftrace_ops_init(ops);
> +
> + mutex_lock(&ftrace_lock);
> +
> + ret = ftrace_startup(ops, 0);
> +
> + mutex_unlock(&ftrace_lock);
> +
> + return ret;
> +}
> +
> /**
> * register_ftrace_function - register a function for profiling
> * @ops: ops structure that holds the function for profiling.
> @@ -8018,14 +8206,15 @@ int register_ftrace_function(struct ftrace_ops *ops)
> {
> int ret;
>
> - ftrace_ops_init(ops);
> -
> - mutex_lock(&ftrace_lock);
> -
> - ret = ftrace_startup(ops, 0);
> + lock_direct_mutex();
Trying to enable ftrace direct on powerpc, this is resulting in a hung
task when testing samples/ftrace/ftrace-direct-modify.c
Essentially, the sample calls modify_ftrace_direct(), which grabs
direct_mutex before calling
ftrace_modify_direct_caller()->register_ftrace_function().
- Naveen
> + ret = prepare_direct_functions_for_ipmodify(ops);
> + if (ret < 0)
> + goto out_unlock;
>
> - mutex_unlock(&ftrace_lock);
> + ret = register_ftrace_function_nolock(ops);
>
> +out_unlock:
> + unlock_direct_mutex();
> return ret;
> }
> EXPORT_SYMBOL_GPL(register_ftrace_function);
> @@ -8044,6 +8233,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
> ret = ftrace_shutdown(ops, 0);
> mutex_unlock(&ftrace_lock);
>
> + cleanup_direct_functions_after_ipmodify(ops);
> return ret;
> }
> EXPORT_SYMBOL_GPL(unregister_ftrace_function);
> --
> 2.30.2
>
>
>
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH v5 bpf-next 2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function
2022-09-09 11:58 ` Naveen N. Rao
@ 2022-09-09 14:05 ` Song Liu
2022-09-09 18:13 ` Naveen N. Rao
0 siblings, 1 reply; 14+ messages in thread
From: Song Liu @ 2022-09-09 14:05 UTC (permalink / raw)
To: Naveen N. Rao
Cc: bpf, linux-kernel, live-patching, Song Liu, rostedt, daniel,
jolsa, Kernel Team
> On Sep 9, 2022, at 4:58 AM, Naveen N. Rao <naveen.n.rao@linux.ibm.com> wrote:
>
> Song Liu wrote:
[...]
>> +
>> /**
>> * register_ftrace_function - register a function for profiling
>> * @ops: ops structure that holds the function for profiling.
>> @@ -8018,14 +8206,15 @@ int register_ftrace_function(struct ftrace_ops *ops)
>> {
>> int ret;
>> - ftrace_ops_init(ops);
>> -
>> - mutex_lock(&ftrace_lock);
>> -
>> - ret = ftrace_startup(ops, 0);
>> + lock_direct_mutex();
>
> Trying to enable ftrace direct on powerpc, this is resulting in a hung task when testing samples/ftrace/ftrace-direct-modify.c
>
> Essentially, the sample calls modify_ftrace_direct(), which grabs direct_mutex before calling ftrace_modify_direct_caller()->register_ftrace_function().
>
Thanks for the report. Would the following change fix the issue?
Song
diff --git i/kernel/trace/ftrace.c w/kernel/trace/ftrace.c
index bc921a3f7ea8..2f1e6cfa834e 100644
--- i/kernel/trace/ftrace.c
+++ w/kernel/trace/ftrace.c
@@ -5496,7 +5496,7 @@ int __weak ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
if (ret)
goto out_lock;
- ret = register_ftrace_function(&stub_ops);
+ ret = register_ftrace_function_nolock(&stub_ops);
if (ret) {
ftrace_set_filter_ip(&stub_ops, ip, 1, 0);
goto out_lock;
>
> - Naveen
>
>
>> + ret = prepare_direct_functions_for_ipmodify(ops);
>> + if (ret < 0)
>> + goto out_unlock;
>> - mutex_unlock(&ftrace_lock);
>> + ret = register_ftrace_function_nolock(ops);
>> +out_unlock:
>> + unlock_direct_mutex();
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(register_ftrace_function);
>> @@ -8044,6 +8233,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
>> ret = ftrace_shutdown(ops, 0);
>> mutex_unlock(&ftrace_lock);
>> + cleanup_direct_functions_after_ipmodify(ops);
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(unregister_ftrace_function);
>> --
>> 2.30.2
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH v5 bpf-next 2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function
2022-09-09 14:05 ` Song Liu
@ 2022-09-09 18:13 ` Naveen N. Rao
0 siblings, 0 replies; 14+ messages in thread
From: Naveen N. Rao @ 2022-09-09 18:13 UTC (permalink / raw)
To: Song Liu
Cc: Kernel Team, bpf, daniel, jolsa, linux-kernel, live-patching,
rostedt, Song Liu
Hi Song,
Song Liu wrote:
>
>
>> On Sep 9, 2022, at 4:58 AM, Naveen N. Rao <naveen.n.rao@linux.ibm.com> wrote:
>>
>> Song Liu wrote:
>
> [...]
>
>>> +
>>> /**
>>> * register_ftrace_function - register a function for profiling
>>> * @ops: ops structure that holds the function for profiling.
>>> @@ -8018,14 +8206,15 @@ int register_ftrace_function(struct ftrace_ops *ops)
>>> {
>>> int ret;
>>> - ftrace_ops_init(ops);
>>> -
>>> - mutex_lock(&ftrace_lock);
>>> -
>>> - ret = ftrace_startup(ops, 0);
>>> + lock_direct_mutex();
>>
>> Trying to enable ftrace direct on powerpc, this is resulting in a hung task when testing samples/ftrace/ftrace-direct-modify.c
>>
>> Essentially, the sample calls modify_ftrace_direct(), which grabs direct_mutex before calling ftrace_modify_direct_caller()->register_ftrace_function().
>>
>
> Thanks for the report. Would the following change fix the issue?
>
> Song
>
> diff --git i/kernel/trace/ftrace.c w/kernel/trace/ftrace.c
> index bc921a3f7ea8..2f1e6cfa834e 100644
> --- i/kernel/trace/ftrace.c
> +++ w/kernel/trace/ftrace.c
> @@ -5496,7 +5496,7 @@ int __weak ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
> if (ret)
> goto out_lock;
>
> - ret = register_ftrace_function(&stub_ops);
> + ret = register_ftrace_function_nolock(&stub_ops);
> if (ret) {
> ftrace_set_filter_ip(&stub_ops, ip, 1, 0);
> goto out_lock;
>
That fixes it for me.
Reported-and-Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Thanks!
- Naveen
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v5 bpf-next 3/4] bpf, x64: Allow to use caller address from stack
2022-07-20 0:21 [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
2022-07-20 0:21 ` [PATCH v5 bpf-next 1/4] ftrace: Add modify_ftrace_direct_multi_nolock Song Liu
2022-07-20 0:21 ` [PATCH v5 bpf-next 2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function Song Liu
@ 2022-07-20 0:21 ` Song Liu
2022-07-20 0:21 ` [PATCH v5 bpf-next 4/4] bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch) Song Liu
` (2 subsequent siblings)
5 siblings, 0 replies; 14+ messages in thread
From: Song Liu @ 2022-07-20 0:21 UTC (permalink / raw)
To: bpf, linux-kernel, live-patching
Cc: daniel, kernel-team, jolsa, rostedt, Song Liu
From: Jiri Olsa <jolsa@kernel.org>
Currently we call the original function by using the absolute address
given at the JIT generation. That's not usable when having trampoline
attached to multiple functions, or the target address changes dynamically
(in case of live patch). In such cases we need to take the return address
from the stack.
Adding support to retrieve the original function address from the stack
by adding new BPF_TRAMP_F_ORIG_STACK flag for arch_prepare_bpf_trampoline
function.
Basically we take the return address of the 'fentry' call:
function + 0: call fentry # stores 'function + 5' address on stack
function + 5: ...
The 'function + 5' address will be used as the address for the
original function to call.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
---
arch/x86/net/bpf_jit_comp.c | 13 +++++++++----
include/linux/bpf.h | 5 +++++
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 54c7f46c453f..e1b0c5ed0b7c 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2119,10 +2119,15 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
if (flags & BPF_TRAMP_F_CALL_ORIG) {
restore_regs(m, &prog, nr_args, regs_off);
- /* call original function */
- if (emit_call(&prog, orig_call, prog)) {
- ret = -EINVAL;
- goto cleanup;
+ if (flags & BPF_TRAMP_F_ORIG_STACK) {
+ emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
+ EMIT2(0xff, 0xd0); /* call *rax */
+ } else {
+ /* call original function */
+ if (emit_call(&prog, orig_call, prog)) {
+ ret = -EINVAL;
+ goto cleanup;
+ }
}
/* remember return value in a stack for bpf prog to access */
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a5bf00649995..7496842a4671 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -751,6 +751,11 @@ struct btf_func_model {
/* Return the return value of fentry prog. Only used by bpf_struct_ops. */
#define BPF_TRAMP_F_RET_FENTRY_RET BIT(4)
+/* Get original function from stack instead of from provided direct address.
+ * Makes sense for trampolines with fexit or fmod_ret programs.
+ */
+#define BPF_TRAMP_F_ORIG_STACK BIT(5)
+
/* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50
* bytes on x86.
*/
--
2.30.2
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH v5 bpf-next 4/4] bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)
2022-07-20 0:21 [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
` (2 preceding siblings ...)
2022-07-20 0:21 ` [PATCH v5 bpf-next 3/4] bpf, x64: Allow to use caller address from stack Song Liu
@ 2022-07-20 0:21 ` Song Liu
2022-07-22 7:31 ` Jiri Olsa
2022-07-21 22:59 ` [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
2022-07-22 20:10 ` patchwork-bot+netdevbpf
5 siblings, 1 reply; 14+ messages in thread
From: Song Liu @ 2022-07-20 0:21 UTC (permalink / raw)
To: bpf, linux-kernel, live-patching
Cc: daniel, kernel-team, jolsa, rostedt, Song Liu
When tracing a function with IPMODIFY ftrace_ops (livepatch), the bpf
trampoline must follow the instruction pointer saved on stack. This needs
extra handling for bpf trampolines with BPF_TRAMP_F_CALL_ORIG flag.
Implement bpf_tramp_ftrace_ops_func and use it for the ftrace_ops used
by BPF trampoline. This enables tracing functions with livepatch.
This also requires moving bpf trampoline to *_ftrace_direct_mult APIs.
Link: https://lore.kernel.org/all/20220602193706.2607681-2-song@kernel.org/
Signed-off-by: Song Liu <song@kernel.org>
---
include/linux/bpf.h | 8 ++
kernel/bpf/trampoline.c | 158 +++++++++++++++++++++++++++++++++++-----
2 files changed, 149 insertions(+), 17 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7496842a4671..f35c59e0b742 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -47,6 +47,7 @@ struct kobject;
struct mem_cgroup;
struct module;
struct bpf_func_state;
+struct ftrace_ops;
extern struct idr btf_idr;
extern spinlock_t btf_idr_lock;
@@ -756,6 +757,11 @@ struct btf_func_model {
*/
#define BPF_TRAMP_F_ORIG_STACK BIT(5)
+/* This trampoline is on a function with another ftrace_ops with IPMODIFY,
+ * e.g., a live patch. This flag is set and cleared by ftrace call backs,
+ */
+#define BPF_TRAMP_F_SHARE_IPMODIFY BIT(6)
+
/* Each call __bpf_prog_enter + call bpf_func + call __bpf_prog_exit is ~50
* bytes on x86.
*/
@@ -838,9 +844,11 @@ struct bpf_tramp_image {
struct bpf_trampoline {
/* hlist for trampoline_table */
struct hlist_node hlist;
+ struct ftrace_ops *fops;
/* serializes access to fields of this trampoline */
struct mutex mutex;
refcount_t refcnt;
+ u32 flags;
u64 key;
struct {
struct btf_func_model model;
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 6691dbf9e467..42e387a12694 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -13,6 +13,7 @@
#include <linux/static_call.h>
#include <linux/bpf_verifier.h>
#include <linux/bpf_lsm.h>
+#include <linux/delay.h>
/* dummy _ops. The verifier will operate on target program's ops. */
const struct bpf_verifier_ops bpf_extension_verifier_ops = {
@@ -29,6 +30,81 @@ static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
/* serializes access to trampoline_table */
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);
+
+static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, enum ftrace_ops_cmd cmd)
+{
+ struct bpf_trampoline *tr = ops->private;
+ int ret = 0;
+
+ if (cmd == FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF) {
+ /* This is called inside register_ftrace_direct_multi(), so
+ * tr->mutex is already locked.
+ */
+ lockdep_assert_held_once(&tr->mutex);
+
+ /* Instead of updating the trampoline here, we propagate
+ * -EAGAIN to register_ftrace_direct_multi(). Then we can
+ * retry register_ftrace_direct_multi() after updating the
+ * trampoline.
+ */
+ if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
+ !(tr->flags & BPF_TRAMP_F_ORIG_STACK)) {
+ if (WARN_ON_ONCE(tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY))
+ return -EBUSY;
+
+ tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
+ return -EAGAIN;
+ }
+
+ return 0;
+ }
+
+ /* The normal locking order is
+ * tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c)
+ *
+ * The following two commands are called from
+ *
+ * prepare_direct_functions_for_ipmodify
+ * cleanup_direct_functions_after_ipmodify
+ *
+ * In both cases, direct_mutex is already locked. Use
+ * mutex_trylock(&tr->mutex) to avoid deadlock in race condition
+ * (something else is making changes to this same trampoline).
+ */
+ if (!mutex_trylock(&tr->mutex)) {
+ /* sleep 1 ms to make sure whatever holding tr->mutex makes
+ * some progress.
+ */
+ msleep(1);
+ return -EAGAIN;
+ }
+
+ switch (cmd) {
+ case FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_PEER:
+ tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
+
+ if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
+ !(tr->flags & BPF_TRAMP_F_ORIG_STACK))
+ ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
+ break;
+ case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
+ tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
+
+ if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
+ ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ };
+
+ mutex_unlock(&tr->mutex);
+ return ret;
+}
+#endif
+
bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
{
enum bpf_attach_type eatype = prog->expected_attach_type;
@@ -89,6 +165,16 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
tr = kzalloc(sizeof(*tr), GFP_KERNEL);
if (!tr)
goto out;
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
+ if (!tr->fops) {
+ kfree(tr);
+ tr = NULL;
+ goto out;
+ }
+ tr->fops->private = tr;
+ tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
+#endif
tr->key = key;
INIT_HLIST_NODE(&tr->hlist);
@@ -128,7 +214,7 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
int ret;
if (tr->func.ftrace_managed)
- ret = unregister_ftrace_direct((long)ip, (long)old_addr);
+ ret = unregister_ftrace_direct_multi(tr->fops, (long)old_addr);
else
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
@@ -137,15 +223,20 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
return ret;
}
-static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr)
+static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr,
+ bool lock_direct_mutex)
{
void *ip = tr->func.addr;
int ret;
- if (tr->func.ftrace_managed)
- ret = modify_ftrace_direct((long)ip, (long)old_addr, (long)new_addr);
- else
+ if (tr->func.ftrace_managed) {
+ if (lock_direct_mutex)
+ ret = modify_ftrace_direct_multi(tr->fops, (long)new_addr);
+ else
+ ret = modify_ftrace_direct_multi_nolock(tr->fops, (long)new_addr);
+ } else {
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
+ }
return ret;
}
@@ -163,10 +254,12 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
if (bpf_trampoline_module_get(tr))
return -ENOENT;
- if (tr->func.ftrace_managed)
- ret = register_ftrace_direct((long)ip, (long)new_addr);
- else
+ if (tr->func.ftrace_managed) {
+ ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 0);
+ ret = register_ftrace_direct_multi(tr->fops, (long)new_addr);
+ } else {
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
+ }
if (ret)
bpf_trampoline_module_put(tr);
@@ -332,11 +425,11 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
return ERR_PTR(err);
}
-static int bpf_trampoline_update(struct bpf_trampoline *tr)
+static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex)
{
struct bpf_tramp_image *im;
struct bpf_tramp_links *tlinks;
- u32 flags = BPF_TRAMP_F_RESTORE_REGS;
+ u32 orig_flags = tr->flags;
bool ip_arg = false;
int err, total;
@@ -358,18 +451,31 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
goto out;
}
+ /* clear all bits except SHARE_IPMODIFY */
+ tr->flags &= BPF_TRAMP_F_SHARE_IPMODIFY;
+
if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
- tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links)
+ tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) {
/* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
* should not be set together.
*/
- flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
+ tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
+ } else {
+ tr->flags |= BPF_TRAMP_F_RESTORE_REGS;
+ }
if (ip_arg)
- flags |= BPF_TRAMP_F_IP_ARG;
+ tr->flags |= BPF_TRAMP_F_IP_ARG;
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+again:
+ if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) &&
+ (tr->flags & BPF_TRAMP_F_CALL_ORIG))
+ tr->flags |= BPF_TRAMP_F_ORIG_STACK;
+#endif
err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
- &tr->func.model, flags, tlinks,
+ &tr->func.model, tr->flags, tlinks,
tr->func.addr);
if (err < 0)
goto out;
@@ -378,17 +484,34 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
WARN_ON(!tr->cur_image && tr->selector);
if (tr->cur_image)
/* progs already running at this address */
- err = modify_fentry(tr, tr->cur_image->image, im->image);
+ err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
else
/* first time registering */
err = register_fentry(tr, im->image);
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ if (err == -EAGAIN) {
+ /* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
+ * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
+ * trampoline again, and retry register.
+ */
+ /* reset fops->func and fops->trampoline for re-register */
+ tr->fops->func = NULL;
+ tr->fops->trampoline = 0;
+ goto again;
+ }
+#endif
if (err)
goto out;
+
if (tr->cur_image)
bpf_tramp_image_put(tr->cur_image);
tr->cur_image = im;
tr->selector++;
out:
+ /* If any error happens, restore previous flags */
+ if (err)
+ tr->flags = orig_flags;
kfree(tlinks);
return err;
}
@@ -454,7 +577,7 @@ static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_tr
hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
tr->progs_cnt[kind]++;
- err = bpf_trampoline_update(tr);
+ err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
if (err) {
hlist_del_init(&link->tramp_hlist);
tr->progs_cnt[kind]--;
@@ -487,7 +610,7 @@ static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_
}
hlist_del_init(&link->tramp_hlist);
tr->progs_cnt[kind]--;
- return bpf_trampoline_update(tr);
+ return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
}
/* bpf_trampoline_unlink_prog() should never fail. */
@@ -715,6 +838,7 @@ void bpf_trampoline_put(struct bpf_trampoline *tr)
* multiple rcu callbacks.
*/
hlist_del(&tr->hlist);
+ kfree(tr->fops);
kfree(tr);
out:
mutex_unlock(&trampoline_mutex);
--
2.30.2
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH v5 bpf-next 4/4] bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)
2022-07-20 0:21 ` [PATCH v5 bpf-next 4/4] bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch) Song Liu
@ 2022-07-22 7:31 ` Jiri Olsa
2022-07-22 15:58 ` Song Liu
0 siblings, 1 reply; 14+ messages in thread
From: Jiri Olsa @ 2022-07-22 7:31 UTC (permalink / raw)
To: Song Liu; +Cc: bpf, linux-kernel, live-patching, daniel, kernel-team, rostedt
On Tue, Jul 19, 2022 at 05:21:26PM -0700, Song Liu wrote:
SNIP
> + tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
> +
> + if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
> + !(tr->flags & BPF_TRAMP_F_ORIG_STACK))
> + ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
> + break;
> + case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
> + tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
> +
> + if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
> + ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
> + break;
> + default:
> + ret = -EINVAL;
> + break;
> + };
> +
> + mutex_unlock(&tr->mutex);
> + return ret;
> +}
> +#endif
> +
> bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
> {
> enum bpf_attach_type eatype = prog->expected_attach_type;
> @@ -89,6 +165,16 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
> tr = kzalloc(sizeof(*tr), GFP_KERNEL);
> if (!tr)
> goto out;
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> + tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
> + if (!tr->fops) {
> + kfree(tr);
> + tr = NULL;
> + goto out;
> + }
would it be easier to put ftrace_ops directly to bpf_trampoline,
not just pointer.. it's allocated and freed at the same point
I recall there were some include issues when I tried that long
time ago [1], but could make the change bit simpler
[1] https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?h=bpf/batch&id=52a1d4acdf55df41e99ca2cea51865e6821036ce
jirka
> + tr->fops->private = tr;
> + tr->fops->ops_func = bpf_tramp_ftrace_ops_func;
> +#endif
>
> tr->key = key;
> INIT_HLIST_NODE(&tr->hlist);
> @@ -128,7 +214,7 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
> int ret;
>
> if (tr->func.ftrace_managed)
> - ret = unregister_ftrace_direct((long)ip, (long)old_addr);
> + ret = unregister_ftrace_direct_multi(tr->fops, (long)old_addr);
> else
> ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, NULL);
>
> @@ -137,15 +223,20 @@ static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
> return ret;
> }
>
> -static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr)
> +static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_addr,
> + bool lock_direct_mutex)
> {
> void *ip = tr->func.addr;
> int ret;
>
> - if (tr->func.ftrace_managed)
> - ret = modify_ftrace_direct((long)ip, (long)old_addr, (long)new_addr);
> - else
> + if (tr->func.ftrace_managed) {
> + if (lock_direct_mutex)
> + ret = modify_ftrace_direct_multi(tr->fops, (long)new_addr);
> + else
> + ret = modify_ftrace_direct_multi_nolock(tr->fops, (long)new_addr);
> + } else {
> ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, old_addr, new_addr);
> + }
> return ret;
> }
>
> @@ -163,10 +254,12 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
> if (bpf_trampoline_module_get(tr))
> return -ENOENT;
>
> - if (tr->func.ftrace_managed)
> - ret = register_ftrace_direct((long)ip, (long)new_addr);
> - else
> + if (tr->func.ftrace_managed) {
> + ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 0);
> + ret = register_ftrace_direct_multi(tr->fops, (long)new_addr);
> + } else {
> ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
> + }
>
> if (ret)
> bpf_trampoline_module_put(tr);
> @@ -332,11 +425,11 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
> return ERR_PTR(err);
> }
>
> -static int bpf_trampoline_update(struct bpf_trampoline *tr)
> +static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex)
> {
> struct bpf_tramp_image *im;
> struct bpf_tramp_links *tlinks;
> - u32 flags = BPF_TRAMP_F_RESTORE_REGS;
> + u32 orig_flags = tr->flags;
> bool ip_arg = false;
> int err, total;
>
> @@ -358,18 +451,31 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
> goto out;
> }
>
> + /* clear all bits except SHARE_IPMODIFY */
> + tr->flags &= BPF_TRAMP_F_SHARE_IPMODIFY;
> +
> if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
> - tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links)
> + tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links) {
> /* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
> * should not be set together.
> */
> - flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
> + tr->flags |= BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
> + } else {
> + tr->flags |= BPF_TRAMP_F_RESTORE_REGS;
> + }
>
> if (ip_arg)
> - flags |= BPF_TRAMP_F_IP_ARG;
> + tr->flags |= BPF_TRAMP_F_IP_ARG;
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> +again:
> + if ((tr->flags & BPF_TRAMP_F_SHARE_IPMODIFY) &&
> + (tr->flags & BPF_TRAMP_F_CALL_ORIG))
> + tr->flags |= BPF_TRAMP_F_ORIG_STACK;
> +#endif
>
> err = arch_prepare_bpf_trampoline(im, im->image, im->image + PAGE_SIZE,
> - &tr->func.model, flags, tlinks,
> + &tr->func.model, tr->flags, tlinks,
> tr->func.addr);
> if (err < 0)
> goto out;
> @@ -378,17 +484,34 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
> WARN_ON(!tr->cur_image && tr->selector);
> if (tr->cur_image)
> /* progs already running at this address */
> - err = modify_fentry(tr, tr->cur_image->image, im->image);
> + err = modify_fentry(tr, tr->cur_image->image, im->image, lock_direct_mutex);
> else
> /* first time registering */
> err = register_fentry(tr, im->image);
> +
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> + if (err == -EAGAIN) {
> + /* -EAGAIN from bpf_tramp_ftrace_ops_func. Now
> + * BPF_TRAMP_F_SHARE_IPMODIFY is set, we can generate the
> + * trampoline again, and retry register.
> + */
> + /* reset fops->func and fops->trampoline for re-register */
> + tr->fops->func = NULL;
> + tr->fops->trampoline = 0;
> + goto again;
> + }
> +#endif
> if (err)
> goto out;
> +
> if (tr->cur_image)
> bpf_tramp_image_put(tr->cur_image);
> tr->cur_image = im;
> tr->selector++;
> out:
> + /* If any error happens, restore previous flags */
> + if (err)
> + tr->flags = orig_flags;
> kfree(tlinks);
> return err;
> }
> @@ -454,7 +577,7 @@ static int __bpf_trampoline_link_prog(struct bpf_tramp_link *link, struct bpf_tr
>
> hlist_add_head(&link->tramp_hlist, &tr->progs_hlist[kind]);
> tr->progs_cnt[kind]++;
> - err = bpf_trampoline_update(tr);
> + err = bpf_trampoline_update(tr, true /* lock_direct_mutex */);
> if (err) {
> hlist_del_init(&link->tramp_hlist);
> tr->progs_cnt[kind]--;
> @@ -487,7 +610,7 @@ static int __bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_
> }
> hlist_del_init(&link->tramp_hlist);
> tr->progs_cnt[kind]--;
> - return bpf_trampoline_update(tr);
> + return bpf_trampoline_update(tr, true /* lock_direct_mutex */);
> }
>
> /* bpf_trampoline_unlink_prog() should never fail. */
> @@ -715,6 +838,7 @@ void bpf_trampoline_put(struct bpf_trampoline *tr)
> * multiple rcu callbacks.
> */
> hlist_del(&tr->hlist);
> + kfree(tr->fops);
> kfree(tr);
> out:
> mutex_unlock(&trampoline_mutex);
> --
> 2.30.2
>
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH v5 bpf-next 4/4] bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)
2022-07-22 7:31 ` Jiri Olsa
@ 2022-07-22 15:58 ` Song Liu
0 siblings, 0 replies; 14+ messages in thread
From: Song Liu @ 2022-07-22 15:58 UTC (permalink / raw)
To: Jiri Olsa
Cc: Song Liu, bpf, lkml, live-patching, Daniel Borkmann, Kernel Team,
rostedt
> On Jul 22, 2022, at 12:31 AM, Jiri Olsa <olsajiri@gmail.com> wrote:
>
> On Tue, Jul 19, 2022 at 05:21:26PM -0700, Song Liu wrote:
>
> SNIP
>
>> + tr->flags |= BPF_TRAMP_F_SHARE_IPMODIFY;
>> +
>> + if ((tr->flags & BPF_TRAMP_F_CALL_ORIG) &&
>> + !(tr->flags & BPF_TRAMP_F_ORIG_STACK))
>> + ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
>> + break;
>> + case FTRACE_OPS_CMD_DISABLE_SHARE_IPMODIFY_PEER:
>> + tr->flags &= ~BPF_TRAMP_F_SHARE_IPMODIFY;
>> +
>> + if (tr->flags & BPF_TRAMP_F_ORIG_STACK)
>> + ret = bpf_trampoline_update(tr, false /* lock_direct_mutex */);
>> + break;
>> + default:
>> + ret = -EINVAL;
>> + break;
>> + };
>> +
>> + mutex_unlock(&tr->mutex);
>> + return ret;
>> +}
>> +#endif
>> +
>> bool bpf_prog_has_trampoline(const struct bpf_prog *prog)
>> {
>> enum bpf_attach_type eatype = prog->expected_attach_type;
>> @@ -89,6 +165,16 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
>> tr = kzalloc(sizeof(*tr), GFP_KERNEL);
>> if (!tr)
>> goto out;
>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
>> + tr->fops = kzalloc(sizeof(struct ftrace_ops), GFP_KERNEL);
>> + if (!tr->fops) {
>> + kfree(tr);
>> + tr = NULL;
>> + goto out;
>> + }
>
> would it be easier to put ftrace_ops directly to bpf_trampoline,
> not just pointer.. it's allocated and freed at the same point
>
> I recall there were some include issues when I tried that long
> time ago [1], but could make the change bit simpler
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git/commit/?h=bpf/batch&id=52a1d4acdf55df41e99ca2cea51865e6821036ce
I was not aware the CC_USING_FENTRY issue. However, I think we
would like to avoid including ftrace.h in bpf.h, which will
slow down the build.
Thanks,
Song
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together
2022-07-20 0:21 [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
` (3 preceding siblings ...)
2022-07-20 0:21 ` [PATCH v5 bpf-next 4/4] bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch) Song Liu
@ 2022-07-21 22:59 ` Song Liu
2022-07-22 16:56 ` Steven Rostedt
2022-07-22 20:10 ` patchwork-bot+netdevbpf
5 siblings, 1 reply; 14+ messages in thread
From: Song Liu @ 2022-07-21 22:59 UTC (permalink / raw)
To: Steven Rostedt
Cc: bpf, lkml, live-patching, Daniel Borkmann, Kernel Team,
Jiri Olsa, Song Liu
Hi Steven,
> On Jul 19, 2022, at 5:21 PM, Song Liu <song@kernel.org> wrote:
>
> Changes v4 => v5:
> 1. Cleanup direct_mutex handling in register_ftrace_function.
> (Steven Rostedt, Petr Mladek).
> 2. Various smallish fixes. (Steven Rostedt, Petr Mladek).
>
> Changes v3 => v4:
> 1. Fix build errors for different config. (kernel test robot)
>
> Changes v2 => v3:
> 1. Major rewrite after discussions with Steven Rostedt. [1]
> 2. Remove SHARE_IPMODIFY flag from ftrace code. Instead use the callback
> function to communicate this information. (Steven)
> 3. Add cleanup_direct_functions_after_ipmodify() to clear SHARE_IPMODIFY
> on the DIRECT ops when the IPMODIFY ops is removed.
>
> Changes v1 => v2:
> 1. Fix build errors for different config. (kernel test robot)
>
> Kernel Live Patch (livepatch, or klp) and bpf trampoline are important
> features for modern systems. This set allows the two to work on the same
> kernel function as the same time.
>
> live patch uses ftrace with IPMODIFY, while bpf trampoline use direct
> ftrace. Existing policy does not allow the two to attach to the same kernel
> function. This is changed by fine tuning ftrace IPMODIFY policy, and allows
> one IPMODIFY ftrace_ops and one DIRECT ftrace_ops on the same kernel
> function at the same time. Please see patch 2 and 4 for more details.
>
> Note that, one of the constraint here is to let bpf trampoline use direct
> call when it is not working on the same function as live patch. This is
> achieved by allowing ftrace code to ask bpf trampoline to make changes.
>
> [1] https://lore.kernel.org/all/20220602193706.2607681-2-song@kernel.org/
How does this version look to you?
Thanks,
Song
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together
2022-07-21 22:59 ` [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
@ 2022-07-22 16:56 ` Steven Rostedt
2022-07-22 18:02 ` Song Liu
0 siblings, 1 reply; 14+ messages in thread
From: Steven Rostedt @ 2022-07-22 16:56 UTC (permalink / raw)
To: Song Liu
Cc: bpf, lkml, live-patching, Daniel Borkmann, Kernel Team,
Jiri Olsa, Song Liu
On Thu, 21 Jul 2022 22:59:30 +0000
Song Liu <songliubraving@fb.com> wrote:
> How does this version look to you?
Looks good. Thanks Song!
For the first two patches:
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
-- Steve
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together
2022-07-22 16:56 ` Steven Rostedt
@ 2022-07-22 18:02 ` Song Liu
0 siblings, 0 replies; 14+ messages in thread
From: Song Liu @ 2022-07-22 18:02 UTC (permalink / raw)
To: Steven Rostedt
Cc: bpf, lkml, live-patching, Daniel Borkmann, Kernel Team,
Jiri Olsa, Song Liu
> On Jul 22, 2022, at 9:56 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Thu, 21 Jul 2022 22:59:30 +0000
> Song Liu <songliubraving@fb.com> wrote:
>
>> How does this version look to you?
>
> Looks good. Thanks Song!
>
> For the first two patches:
>
> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Thanks!
Song
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together
2022-07-20 0:21 [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
` (4 preceding siblings ...)
2022-07-21 22:59 ` [PATCH v5 bpf-next 0/4] ftrace: host klp and bpf trampoline together Song Liu
@ 2022-07-22 20:10 ` patchwork-bot+netdevbpf
5 siblings, 0 replies; 14+ messages in thread
From: patchwork-bot+netdevbpf @ 2022-07-22 20:10 UTC (permalink / raw)
To: Song Liu
Cc: bpf, linux-kernel, live-patching, daniel, kernel-team, jolsa, rostedt
Hello:
This series was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:
On Tue, 19 Jul 2022 17:21:22 -0700 you wrote:
> Changes v4 => v5:
> 1. Cleanup direct_mutex handling in register_ftrace_function.
> (Steven Rostedt, Petr Mladek).
> 2. Various smallish fixes. (Steven Rostedt, Petr Mladek).
>
> Changes v3 => v4:
> 1. Fix build errors for different config. (kernel test robot)
>
> [...]
Here is the summary with links:
- [v5,bpf-next,1/4] ftrace: Add modify_ftrace_direct_multi_nolock
https://git.kernel.org/bpf/bpf-next/c/f96f644ab97a
- [v5,bpf-next,2/4] ftrace: Allow IPMODIFY and DIRECT ops on the same function
https://git.kernel.org/bpf/bpf-next/c/53cd885bc5c3
- [v5,bpf-next,3/4] bpf, x64: Allow to use caller address from stack
https://git.kernel.org/bpf/bpf-next/c/316cba62dfb7
- [v5,bpf-next,4/4] bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)
https://git.kernel.org/bpf/bpf-next/c/00963a2e75a8
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 14+ messages in thread