Subject: Re: [PATCH v5 1/9] ftrace: Add ftrace_set_filter_ips function

From: Jiri Olsa <[email-masked]>
Date: Tue, 25 Jan 2022 17:46:07 +0100

On Tue, Jan 25, 2022 at 11:06:59AM -0500, Steven Rostedt wrote:

SNIP

> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index be5f6b32a012..39350aa38649 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -4958,7 +4958,7 @@ ftrace_notrace_write(struct file *file, const char __user *ubuf,
> >  }
> >  
> >  static int
> > -ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
> > +__ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
> >  {
> >  	struct ftrace_func_entry *entry;
> >  
> > @@ -4976,9 +4976,25 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
> >  	return add_hash_entry(hash, ip);
> >  }
> >  
> > +static int
> > +ftrace_match_addr(struct ftrace_hash *hash, unsigned long *ips,
> > +		  unsigned int cnt, int remove)
> > +{
> > +	unsigned int i;
> > +	int err;
> > +
> > +	for (i = 0; i < cnt; i++) {
> > +		err = __ftrace_match_addr(hash, ips[i], remove);
> > +		if (err)
> > +			return err;
> 
> On error should we revert what was done?
> 
> 			goto err;
> > +	}
> > +	return 0;
> 
> err:
> 	for (i--; i >= 0; i--)
> 		__ftrace_match_addr(hash, ips[i], !remove);
> 	return err;
> 
> Although it may not matter as it looks like it is only used on a temporary
> hash. But either it should be commented that is the case, or we do the above
> just to be more robust.

yes, that's the case.. it populates just the hash at this point
and if __ftrace_match_addr fails, the thehash is relased after
jumping to out_regex_unlock

> 
> > +}
> > +
> >  static int
> >  ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
> > -		unsigned long ip, int remove, int reset, int enable)
> > +		unsigned long *ips, unsigned int cnt,
> > +		int remove, int reset, int enable)
> >  {
> >  	struct ftrace_hash **orig_hash;
> >  	struct ftrace_hash *hash;
> > @@ -5008,8 +5024,8 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
> >  		ret = -EINVAL;
> >  		goto out_regex_unlock;
> >  	}
> > -	if (ip) {
> > -		ret = ftrace_match_addr(hash, ip, remove);
> > +	if (ips) {
> > +		ret = ftrace_match_addr(hash, ips, cnt, remove);
> >  		if (ret < 0)
> >  			goto out_regex_unlock;
> >  	}
> > @@ -5026,10 +5042,10 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
> >  }
> >  
> >  static int
> > -ftrace_set_addr(struct ftrace_ops *ops, unsigned long ip, int remove,
> > -		int reset, int enable)
> > +ftrace_set_addr(struct ftrace_ops *ops, unsigned long *ips, unsigned int cnt,
> > +		int remove, int reset, int enable)
> >  {
> > -	return ftrace_set_hash(ops, NULL, 0, ip, remove, reset, enable);
> > +	return ftrace_set_hash(ops, NULL, 0, ips, cnt, remove, reset, enable);
> >  }
> >  
> >  #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> > @@ -5634,10 +5650,29 @@ int ftrace_set_filter_ip(struct ftrace_ops *ops, unsigned long ip,
> >  			 int remove, int reset)
> >  {
> >  	ftrace_ops_init(ops);
> > -	return ftrace_set_addr(ops, ip, remove, reset, 1);
> > +	return ftrace_set_addr(ops, &ip, 1, remove, reset, 1);
> >  }
> >  EXPORT_SYMBOL_GPL(ftrace_set_filter_ip);
> >  
> > +/**
> > + * ftrace_set_filter_ips - set a functions to filter on in ftrace by addresses
> 
> 		- set functions to filter on ...

will fix,

thanks,
jirka