Re: [PATCH 6/8] ftrace: Add multi direct register/unregister interface

[Jiri Olsa <jolsa@redhat.com>]

On Tue, Sep 14, 2021 at 05:35:55PM -0400, Steven Rostedt wrote:
> On Tue, 31 Aug 2021 11:50:15 +0200
> Jiri Olsa <jolsa@redhat.com> wrote:
> 
> > Adding interface to register multiple direct functions
> > within single call. Adding following functions:
> > 
> >   register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
> >   unregister_ftrace_direct_multi(struct ftrace_ops *ops)
> > 
> > The register_ftrace_direct_multi registers direct function (addr)
> > with all functions in ops filter. The ops filter can be updated
> > before with ftrace_set_filter_ip calls.
> > 
> > All requested functions must not have direct function currently
> > registered, otherwise register_ftrace_direct_multi will fail.
> > 
> > The unregister_ftrace_direct_multi unregisters ops related direct
> > functions.
> > 
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  include/linux/ftrace.h |  11 ++++
> >  kernel/trace/ftrace.c  | 111 +++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 122 insertions(+)
> > 
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index d399621a67ee..e40b5201c16e 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -316,7 +316,10 @@ int ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
> >  				unsigned long old_addr,
> >  				unsigned long new_addr);
> >  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);
> >  #else
> > +struct ftrace_ops;
> >  # define ftrace_direct_func_count 0
> >  static inline int register_ftrace_direct(unsigned long ip, unsigned long addr)
> >  {
> > @@ -346,6 +349,14 @@ static inline unsigned long ftrace_find_rec_direct(unsigned long ip)
> >  {
> >  	return 0;
> >  }
> > +static inline int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
> > +{
> > +	return -ENODEV;
> > +}
> > +static inline int unregister_ftrace_direct_multi(struct ftrace_ops *ops)
> > +{
> > +	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 c60217d81040..7243769493c9 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -5407,6 +5407,117 @@ int modify_ftrace_direct(unsigned long ip,
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL_GPL(modify_ftrace_direct);
> > +
> > +#define MULTI_FLAGS (FTRACE_OPS_FL_IPMODIFY | FTRACE_OPS_FL_DIRECT | \
> > +		     FTRACE_OPS_FL_SAVE_REGS)
> > +
> > +static int check_direct_multi(struct ftrace_ops *ops)
> > +{
> > +	if (!(ops->flags & FTRACE_OPS_FL_INITIALIZED))
> > +		return -EINVAL;
> > +	if ((ops->flags & MULTI_FLAGS) != MULTI_FLAGS)
> > +		return -EINVAL;
> > +	return 0;
> > +}
> > +
> 
> Needs kernel doc comments as this is an interface outside this file.

right, will add

> 
> > +int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
> > +{
> > +	struct ftrace_hash *hash, *free_hash = NULL;
> > +	struct ftrace_func_entry *entry, *new;
> > +	int err = -EBUSY, size, i;
> > +
> > +	if (ops->func || ops->trampoline)
> > +		return -EINVAL;
> > +	if (!(ops->flags & FTRACE_OPS_FL_INITIALIZED))
> > +		return -EINVAL;
> > +	if (ops->flags & FTRACE_OPS_FL_ENABLED)
> > +		return -EINVAL;
> > +
> > +	hash = ops->func_hash->filter_hash;
> > +	if (ftrace_hash_empty(hash))
> > +		return -EINVAL;
> > +
> > +	mutex_lock(&direct_mutex);
> > +
> > +	/* Make sure requested entries are not already registered.. */
> > +	size = 1 << hash->size_bits;
> > +	for (i = 0; i < size; i++) {
> > +		hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> > +			if (ftrace_find_rec_direct(entry->ip))
> > +				goto out_unlock;
> > +		}
> > +	}
> > +
> > +	/* ... and insert them to direct_functions hash. */
> > +	err = -ENOMEM;
> > +	for (i = 0; i < size; i++) {
> > +		hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> > +			new = ftrace_add_rec_direct(entry->ip, addr, &free_hash);
> > +			if (!new)
> > +				goto out_remove;
> > +			entry->direct = addr;
> > +		}
> > +	}
> > +
> > +	ops->func = call_direct_funcs;
> > +	ops->flags = MULTI_FLAGS;
> > +	ops->trampoline = FTRACE_REGS_ADDR;
> > +
> > +	err = register_ftrace_function(ops);
> > +
> > + out_remove:
> > +	if (err) {
> 
> The below code:
> 
> > +		for (i = 0; i < size; i++) {
> > +			hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> > +				new = __ftrace_lookup_ip(direct_functions, entry->ip);
> > +				if (new) {
> > +					remove_hash_entry(direct_functions, new);
> > +					kfree(new);
> > +				}
> > +			}
> > +		}
> 
> is identical to code below.
> 
> > +	}
> > +
> > + out_unlock:
> > +	mutex_unlock(&direct_mutex);
> > +
> > +	if (free_hash) {
> > +		synchronize_rcu_tasks();
> > +		free_ftrace_hash(free_hash);
> > +	}
> > +	return err;
> > +}
> > +EXPORT_SYMBOL_GPL(register_ftrace_direct_multi);
> > +
> 
> Should have kernel doc as well.

ok

> 
> > +int unregister_ftrace_direct_multi(struct ftrace_ops *ops)
> > +{
> > +	struct ftrace_hash *hash = ops->func_hash->filter_hash;
> > +	struct ftrace_func_entry *entry, *new;
> > +	int err, size, i;
> > +
> > +	if (check_direct_multi(ops))
> > +		return -EINVAL;
> > +	if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
> > +		return -EINVAL;
> > +
> > +	mutex_lock(&direct_mutex);
> > +	err = unregister_ftrace_function(ops);
> > +
> > +	size = 1 << hash->size_bits;
> 
> 
> > +	for (i = 0; i < size; i++) {
> > +		hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> > +			new = __ftrace_lookup_ip(direct_functions, entry->ip);
> > +			if (new) {
> > +				remove_hash_entry(direct_functions, new);
> > +				kfree(new);
> > +			}
> > +		}
> > +	}
> 
> Would probably make sense to turn this into a static inline helper.

ok

thanks,
jirka

> 
> -- Steve
> 
> 
> > +
> > +	mutex_unlock(&direct_mutex);
> > +	return err;
> > +}
> > +EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);
> >  #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
> >  
> >  /**
>