linux-kernel - Re: [PATCH] x86: Disable CET instrumentation in the kernel

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Date:   Fri, 29 Jan 2021 08:23:23 +0200
From:   Nikolay Borisov <nborisov@...e.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org
Cc:     Masami Hiramatsu <masami.hiramatsu@...il.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>, bpf@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] x86: Disable CET instrumentation in the kernel



On 28.01.21 г. 23:52 ч., Josh Poimboeuf wrote:
> 
> With retpolines disabled, some configurations of GCC will add Intel CET
> instrumentation to the kernel by default.  That breaks certain tracing
> scenarios by adding a superfluous ENDBR64 instruction before the fentry
> call, for functions which can be called indirectly.
> 
> CET instrumentation isn't currently necessary in the kernel, as CET is
> only supported in user space.  Disable it unconditionally.
> 
> Reported-by: Nikolay Borisov <nborisov@...e.com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>

Tested-by: Nikolay Borisov <nborisov@...e.com>
Reviewed-by: Nikolay Borisov <nborisov@...e.com>