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Subject: Re: [PATCH v23 6/9] x86/entry: Introduce ENDBR macro
To:     Borislav Petkov <bp@alien8.de>
Cc:     Dave Hansen <dave.hansen@intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
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        Jonathan Corbet <corbet@lwn.net>,
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References: <20210316151320.6123-1-yu-cheng.yu@intel.com>
 <20210316151320.6123-7-yu-cheng.yu@intel.com>
 <f98c600a-80e4-62f0-9c97-eeed708d998d@intel.com>
 <15966857-9be7-3029-7e93-e40596b4649a@intel.com>
 <20210316173032.GE18003@zn.tnic>
From:   "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Message-ID: <b0de1933-29ca-6c18-5a11-e293e9415f19@intel.com>
Date:   Tue, 16 Mar 2021 10:42:13 -0700
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On 3/16/2021 10:30 AM, Borislav Petkov wrote:
> On Tue, Mar 16, 2021 at 10:12:39AM -0700, Yu, Yu-cheng wrote:
>> Alternatively, there is another compiler-defined macro _CET_ENDBR that can
>> be used.  We can put the following in calling.h:
> 
> Not calling.h - this is apparently needed in vdso code only so I guess
> some header there, arch/x86/include/asm/vdso.h maybe? In the
> 
> #else /* __ASSEMBLER__ */
> 
> branch maybe...
> 
>> #ifdef __CET__
>> #include <cet.h>
>> #else
>> #define _CET_ENDBR
>> #endif
>>
>> and then use _CET_ENDBR in other files.  How is that?
> 
> What does that macro do? Issue an ENDBR only?
> 

Yes, issue endbr32, endbr64, or nothing when cet is not enabled.