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Date:   Wed, 28 Apr 2021 13:39:26 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
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Subject: Re: [PATCH v26 9/9] x86/vdso: Add ENDBR to __vdso_sgx_enter_enclave
Message-ID: <202104281339.E21514F9D@keescook>
References: <20210427204720.25007-1-yu-cheng.yu@intel.com>
 <20210427204720.25007-10-yu-cheng.yu@intel.com>
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On Tue, Apr 27, 2021 at 01:47:20PM -0700, Yu-cheng Yu wrote:
> ENDBR is a special new instruction for the Indirect Branch Tracking (IBT)
> component of CET.  IBT prevents attacks by ensuring that (most) indirect
> branches and function calls may only land at ENDBR instructions.  Branches
> that don't follow the rules will result in control flow (#CF) exceptions.
> 
> ENDBR is a noop when IBT is unsupported or disabled.  Most ENDBR
> instructions are inserted automatically by the compiler, but branch
> targets written in assembly must have ENDBR added manually.
> 
> Add ENDBR to __vdso_sgx_enter_enclave() branch targets.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook