ftrace: Add modify_ftrace_direct() (0567d680) · Commits · 戴 / test

include/linux/ftrace.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -250,6 +250,7 @@ static inline void ftrace_free_mem(struct module mod, void start, void *end) {
		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);
		#else
		# define ftrace_direct_func_count 0
		@@ -261,6 +262,11 @@ static inline int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
		{
		return -ENODEV;
		}
		static inline int modify_ftrace_direct(unsigned long ip,
		unsigned long old_addr, unsigned long new_addr)
		{
		return -ENODEV;
		}
		static inline struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr)
		{
		return NULL;

kernel/trace/ftrace.c

+78 −0

Original line number	Diff line number	Diff line
		@@ -5160,6 +5160,84 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
		return ret;
		}
		EXPORT_SYMBOL_GPL(unregister_ftrace_direct);

		static struct ftrace_ops stub_ops = {
		.func = ftrace_stub,
		};

		/**
		* modify_ftrace_direct - Modify an existing direct call to call something else
		* @ip: The instruction pointer to modify
		* @old_addr: The address that the current @ip calls directly
		* @new_addr: The address that the @ip should call
		*
		* This modifies a ftrace direct caller at an instruction pointer without
		* having to disable it first. The direct call will switch over to the
		* @new_addr without missing anything.
		*
		* Returns: zero on success. Non zero on error, which includes:
		* -ENODEV : the @ip given has no direct caller attached
		* -EINVAL : the @old_addr does not match the current direct caller
		*/
		int modify_ftrace_direct(unsigned long ip,
		unsigned long old_addr, unsigned long new_addr)
		{
		struct ftrace_func_entry *entry;
		struct dyn_ftrace *rec;
		int ret = -ENODEV;

		mutex_lock(&direct_mutex);
		entry = __ftrace_lookup_ip(direct_functions, ip);
		if (!entry) {
		/* OK if it is off by a little */
		rec = lookup_rec(ip, ip);
		if (!rec \|\| rec->ip == ip)
		goto out_unlock;

		entry = __ftrace_lookup_ip(direct_functions, rec->ip);
		if (!entry)
		goto out_unlock;

		ip = rec->ip;
		WARN_ON(!(rec->flags & FTRACE_FL_DIRECT));
		}

		ret = -EINVAL;
		if (entry->direct != old_addr)
		goto out_unlock;

		/*
		* By setting a stub function at the same address, we force
		* the code to call the iterator and the direct_ops helper.
		* This means that @ip does not call the direct call, and
		* we can simply modify it.
		*/
		ret = ftrace_set_filter_ip(&stub_ops, ip, 0, 0);
		if (ret)
		goto out_unlock;

		ret = register_ftrace_function(&stub_ops);
		if (ret) {
		ftrace_set_filter_ip(&stub_ops, ip, 1, 0);
		goto out_unlock;
		}

		entry->direct = new_addr;

		/*
		* By removing the stub, we put back the direct call, calling
		* the @new_addr.
		*/
		unregister_ftrace_function(&stub_ops);
		ftrace_set_filter_ip(&stub_ops, ip, 1, 0);

		ret = 0;

		out_unlock:
		mutex_unlock(&direct_mutex);
		return ret;
		}
		EXPORT_SYMBOL_GPL(modify_ftrace_direct);
		#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */

		/**

Admin message