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Subject: Re: [PATCH v26 6/9] x86/vdso: Insert endbr32/endbr64 to vDSO
To:     Kees Cook <keescook@chromium.org>
Cc:     x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
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        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
        Dave Martin <Dave.Martin@arm.com>,
        Weijiang Yang <weijiang.yang@intel.com>,
        Pengfei Xu <pengfei.xu@intel.com>,
        Haitao Huang <haitao.huang@intel.com>
References: <20210427204720.25007-1-yu-cheng.yu@intel.com>
 <20210427204720.25007-7-yu-cheng.yu@intel.com>
 <202104281332.94A153C@keescook>
From:   "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Message-ID: <88dc2e45-5fd4-9a1a-c493-3ff868a627f4@intel.com>
Date:   Wed, 28 Apr 2021 13:49:08 -0700
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On 4/28/2021 1:33 PM, Kees Cook wrote:
> On Tue, Apr 27, 2021 at 01:47:17PM -0700, Yu-cheng Yu wrote:
>> From: "H.J. Lu" <hjl.tools@gmail.com>
>>
>> When Indirect Branch Tracking (IBT) is enabled, vDSO functions may be
>> called indirectly, and must have ENDBR32 or ENDBR64 as the first
>> instruction.  The compiler must support -fcf-protection=branch so that it
>> can be used to compile vDSO.
> 
> If you respin this, you can maybe rephrase this since CONFIG_X86_IBT
> has already tested for the compiler support.
> 

Yes, I will fix this.  Thanks for reviewing!

Yu-cheng

>>
>> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
>> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
>> Cc: Andy Lutomirski <luto@kernel.org>
>> Cc: Kees Cook <keescook@chromium.org>
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 
> -Kees
> 
>> ---
>> v24:
>> - Replace CONFIG_X86_CET with CONFIG_X86_IBT to reflect splitting of shadow
>>    stack and ibt.
>>
>>   arch/x86/entry/vdso/Makefile | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
>> index 05c4abc2fdfd..a773a5f03b63 100644
>> --- a/arch/x86/entry/vdso/Makefile
>> +++ b/arch/x86/entry/vdso/Makefile
>> @@ -93,6 +93,10 @@ endif
>>   
>>   $(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
>>   
>> +ifdef CONFIG_X86_IBT
>> +$(vobjs) $(vobjs32): KBUILD_CFLAGS += -fcf-protection=branch
>> +endif
>> +
>>   #
>>   # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
>>   #
>> -- 
>> 2.21.0
>>
>