This is a revert of commit 013bf0da047481 ("ftrace: Add ftrace_find_direct_func()")
ftrace_find_direct_func() was meant for use in the function graph tracer by architecture specific code. However, commit ff205766dbbee0 ("ftrace: Fix function_graph tracer interaction with BPF trampoline") disabled function graph tracer for direct calls leaving this without any users. In addition, modify_ftrace_direct() allowed redirecting the direct call to a different trampoline that was never registered through register_ftrace_direct(). This meant that ftrace_direct_funcs didn't capture all trampolines. Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com> --- include/linux/ftrace.h | 5 --- kernel/trace/ftrace.c | 84 ++---------------------------------------- 2 files changed, 4 insertions(+), 85 deletions(-) diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 1bd3a0356ae478..46b4b7ee28c41f 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -285,7 +285,6 @@ extern int ftrace_direct_func_count; int register_ftrace_direct(unsigned long ip, unsigned long addr); int unregister_ftrace_direct(unsigned long ip, unsigned long addr); int modify_ftrace_direct(unsigned long ip, unsigned long old_addr, unsigned long new_addr); -struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr); int ftrace_modify_direct_caller(struct ftrace_func_entry *entry, struct dyn_ftrace *rec, unsigned long old_addr, @@ -306,10 +305,6 @@ static inline int modify_ftrace_direct(unsigned long ip, { return -ENOTSUPP; } -static inline struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr) -{ - return NULL; -} static inline int ftrace_modify_direct_caller(struct ftrace_func_entry *entry, struct dyn_ftrace *rec, unsigned long old_addr, diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 3844a4a1346a9c..7476f2458b6d95 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5005,46 +5005,6 @@ ftrace_set_addr(struct ftrace_ops *ops, unsigned long ip, int remove, } #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS - -struct ftrace_direct_func { - struct list_head next; - unsigned long addr; - int count; -}; - -static LIST_HEAD(ftrace_direct_funcs); - -/** - * ftrace_find_direct_func - test an address if it is a registered direct caller - * @addr: The address of a registered direct caller - * - * This searches to see if a ftrace direct caller has been registered - * at a specific address, and if so, it returns a descriptor for it. - * - * This can be used by architecture code to see if an address is - * a direct caller (trampoline) attached to a fentry/mcount location. - * This is useful for the function_graph tracer, as it may need to - * do adjustments if it traced a location that also has a direct - * trampoline attached to it. - */ -struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr) -{ - struct ftrace_direct_func *entry; - bool found = false; - - /* May be called by fgraph trampoline (protected by rcu tasks) */ - list_for_each_entry_rcu(entry, &ftrace_direct_funcs, next) { - if (entry->addr == addr) { - found = true; - break; - } - } - if (found) - return entry; - - return NULL; -} - /** * register_ftrace_direct - Call a custom trampoline directly * @ip: The address of the nop at the beginning of a function @@ -5064,7 +5024,6 @@ struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr) */ int register_ftrace_direct(unsigned long ip, unsigned long addr) { - struct ftrace_direct_func *direct; struct ftrace_func_entry *entry; struct ftrace_hash *free_hash = NULL; struct dyn_ftrace *rec; @@ -5118,19 +5077,7 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr) if (!entry) goto out_unlock; - direct = ftrace_find_direct_func(addr); - if (!direct) { - direct = kmalloc(sizeof(*direct), GFP_KERNEL); - if (!direct) { - kfree(entry); - goto out_unlock; - } - direct->addr = addr; - direct->count = 0; - list_add_rcu(&direct->next, &ftrace_direct_funcs); - ftrace_direct_func_count++; - } - + ftrace_direct_func_count++; entry->ip = ip; entry->direct = addr; __add_hash_entry(direct_functions, entry); @@ -5145,18 +5092,8 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr) if (ret) { remove_hash_entry(direct_functions, entry); + ftrace_direct_func_count--; kfree(entry); - if (!direct->count) { - list_del_rcu(&direct->next); - synchronize_rcu_tasks(); - kfree(direct); - if (free_hash) - free_ftrace_hash(free_hash); - free_hash = NULL; - ftrace_direct_func_count--; - } - } else { - direct->count++; } out_unlock: mutex_unlock(&direct_mutex); @@ -5199,7 +5136,6 @@ static struct ftrace_func_entry *find_direct_entry(unsigned long *ip, int unregister_ftrace_direct(unsigned long ip, unsigned long addr) { - struct ftrace_direct_func *direct; struct ftrace_func_entry *entry; int ret = -ENODEV; @@ -5217,20 +5153,8 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr) WARN_ON(ret); remove_hash_entry(direct_functions, entry); - - direct = ftrace_find_direct_func(addr); - if (!WARN_ON(!direct)) { - /* This is the good path (see the ! before WARN) */ - direct->count--; - WARN_ON(direct->count < 0); - if (!direct->count) { - list_del_rcu(&direct->next); - synchronize_rcu_tasks(); - kfree(direct); - kfree(entry); - ftrace_direct_func_count--; - } - } + ftrace_direct_func_count--; + kfree(entry); out_unlock: mutex_unlock(&direct_mutex); -- 2.25.4