linux-kernel - Re: [PATCH v4 00/45] x86: Kernel IBT

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Message-ID: <20220310093731.78a6a8d5@gandalf.local.home>
Date:   Thu, 10 Mar 2022 09:37:31 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>, x86@...nel.org,
        joao@...rdrivepizza.com, hjl.tools@...il.com, jpoimboe@...hat.com,
        andrew.cooper3@...rix.com, linux-kernel@...r.kernel.org,
        ndesaulniers@...gle.com, keescook@...omium.org,
        samitolvanen@...gle.com, mark.rutland@....com,
        alyssa.milburn@...el.com, mbenes@...e.cz, mhiramat@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v4 00/45] x86: Kernel IBT

On Thu, 10 Mar 2022 14:47:18 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index acb50fb7ed2d..2d86d3c09d64 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -5354,6 +5381,11 @@ int modify_ftrace_direct(unsigned long ip,
>  	mutex_lock(&direct_mutex);
>  
>  	mutex_lock(&ftrace_lock);
> +
> +	ip = ftrace_location(ip);
> +	if (!ip)
> +		goto out_unlock;
> +

Perhaps this should go into find_direct_entry() instead, as I think you are
adding it before all the find_direct_entry() callers.

And find_direct_entry will update the ip.

-- Steve

>  	entry = find_direct_entry(&ip, &rec);
>  	if (!entry)
>  		goto out_unlock;