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

Masami Hiramatsu
2022-01-28T02:05:34Z

Hi Jiri,

On Tue, 25 Jan 2022 17:46:07 +0100
Jiri Olsa <jolsa@redhat.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@kernel.org>