linux-kernel - Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry_

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Message-Id: <1646159447.ngbqgzj71t.naveen@linux.ibm.com>
Date:   Wed, 02 Mar 2022 00:27:51 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     alexei.starovoitov@...il.com, alyssa.milburn@...el.com,
        andrew.cooper3@...rix.com, hjl.tools@...il.com,
        joao@...rdrivepizza.com, jpoimboe@...hat.com,
        keescook@...omium.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, mbenes@...e.cz, ndesaulniers@...gle.com,
        Peter Zijlstra <peterz@...radead.org>, samitolvanen@...gle.com,
        x86@...nel.org
Subject: Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location

Steven Rostedt wrote:
> On Fri, 25 Feb 2022 19:20:08 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
>> > No. It only acts like ftrace_location_range(sym, sym_end) if the passed
>> > in argument is the ip of the function (kallsyms returns offset = 0)  
>> 
>> Got it. So now ftrace_location() will return the ftrace address
>> when the ip == func or ip == mcount-call.

Won't this cause issues with ftrace_set_filter_ip() and others? If the 
passed-in ip points to func+0 when the actual ftrace location is at some 
offset, the ftrace location check in ftrace_match_addr() will now pass, 
resulting in adding func+0 to the hash. Should we also update 
ftrace_match_addr() to use the ip returned by ftrace_location()?


- Naveen