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SubjectRe: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location
On Thu, 24 Feb 2022 10:58:47 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 25 Feb 2022 00:55:20 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > > unsigned long ftrace_location(unsigned long ip)
> > > {
> > > - return ftrace_location_range(ip, ip);
> > > + struct dyn_ftrace *rec;
> > > + unsigned long offset;
> > > + unsigned long size;
> > > +
> > > + rec = lookup_rec(ip, ip);
> > > + if (!rec) {
> > > + if (!kallsyms_lookup_size_offset(ip, &size, &offset))
> > > + goto out;
> > > +
> > > + if (!offset)
> >
> > Isn't this 'if (offset)' ?
>
> No, the point to only look for the fentry location if the ip passed in
> points to the start of the function. IOW, +0 offset.
>

I do agree with Masami that it is confusing. Please add a comment:

/* Search the entire function if ip is the start of the function */
if (!offset)
[..]

-- Steve

>
>
> >
> > > + rec = lookup_rec(ip - offset, (ip - offset) + size);
> > > + }
> > > +
> > > + if (rec)
> > > + return rec->ip;
> > > +
> > > +out:
> > > + return 0;

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