netdev - Re: [PATCH v5 1/9] ftrace: Add ftrace_set_filter

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Date:   Fri, 28 Jan 2022 11:05:23 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH v5 1/9] ftrace: Add ftrace_set_filter_ips function

Hi Jiri,

On Tue, 25 Jan 2022 17:46:07 +0100
Jiri Olsa <jolsa@...hat.com> wrote:

> 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,

So, I wrote a below change for the next version. Is that OK for you?

Thank you,

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f305e18f699f..a28b1bdb234a 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4985,8 +4985,13 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long *ips,
 
 	for (i = 0; i < cnt; i++) {
 		err = __ftrace_match_addr(hash, ips[i], remove);
-		if (err)
+		if (err) {
+			/*
+			 * This expects the @hash is a temporary hash and if this
+			 * fails the caller must free the @hash.
+			 */
 			return err;
+		}
 	}
 	return 0;
 }
@@ -5649,7 +5654,7 @@ int ftrace_set_filter_ip(struct ftrace_ops *ops, unsigned long ip,
 EXPORT_SYMBOL_GPL(ftrace_set_filter_ip);
 
 /**
- * ftrace_set_filter_ips - set a functions to filter on in ftrace by addresses
+ * ftrace_set_filter_ips - set functions to filter on in ftrace by addresses
  * @ops - the ops to set the filter with
  * @ips - the array of addresses to add to or remove from the filter.
  * @cnt - the number of addresses in @ips








> 
> thanks,
> jirka
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>