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

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Message-ID: <20220301142016.22e787fb@gandalf.local.home>
Date:   Tue, 1 Mar 2022 14:20:16 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        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

On Wed, 02 Mar 2022 00:27:51 +0530
"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:

> 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()?
> 

Yes, ftrace_match_addr() would need to be updated, or at least
ftrace_set_filter_ip() which is the only user ftrace_match_addr(), and is
currently only used by kprobes, live kernel patching and the direct
trampoline example code.

-- Steve