From f96f644ab97abeed3f7007c953836a574ce928cc Mon Sep 17 00:00:00 2001 From: Song Liu Date: Tue, 19 Jul 2022 17:21:23 -0700 Subject: [PATCH] ftrace: Add modify_ftrace_direct_multi_nolock 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 Signed-off-by: Daniel Borkmann Reviewed-by: Steven Rostedt (Google) Link: https://lore.kernel.org/bpf/20220720002126.803253-2-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; } -- 2.34.1