lkml.org 
[lkml]   [2021]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v24 9/9] x86/vdso: Add ENDBR to __vdso_sgx_enter_enclave
From
Date
On 5/24/2021 11:51 AM, Sean Christopherson wrote:
> On Thu, Apr 01, 2021, 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.
> ^
> |- indirect
>
> After reading the changelog, I was expecting ENDBR on every label.
>

Sorry about the confusion.

>> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
>> Cc: Andy Lutomirski <luto@kernel.org>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: Dave Hansen <dave.hansen@linux.intel.com>
>> Cc: Jarkko Sakkinen <jarkko@kernel.org>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> ---
>> arch/x86/entry/vdso/vsgx.S | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/entry/vdso/vsgx.S b/arch/x86/entry/vdso/vsgx.S
>> index 86a0e94f68df..c63eafa54abd 100644
>> --- a/arch/x86/entry/vdso/vsgx.S
>> +++ b/arch/x86/entry/vdso/vsgx.S
>> @@ -4,6 +4,7 @@
>> #include <asm/export.h>
>> #include <asm/errno.h>
>> #include <asm/enclu.h>
>> +#include <asm/vdso.h>
>>
>> #include "extable.h"
>>
>> @@ -27,6 +28,7 @@
>> SYM_FUNC_START(__vdso_sgx_enter_enclave)
>> /* Prolog */
>> .cfi_startproc
>> + ENDBR
>> push %rbp
>> .cfi_adjust_cfa_offset 8
>> .cfi_rel_offset %rbp, 0
>> @@ -62,6 +64,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
>> .Lasync_exit_pointer:
>> .Lenclu_eenter_eresume:
>> enclu
>> + ENDBR
>
> It would be better to move this below the comment about EEXIT. As is, it looks
> like a misplaced annotation on the AEP. The AEP doesn't need ENDBR, it's the
> EEXIT target that needs ENDBR because EEXIT is treated as an indirect branch.
>
> Might also be helpful for future readers to explicitly state in the changelog
> that EEXIT is considered an indirect branch.
>
> I.e.
>
>> /* EEXIT jumps here unless the enclave is doing something fancy. */
> ENDBR
>> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx
>> @@ -91,6 +94,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
>> jmp .Lout
>>
>> .Lhandle_exception:
>> + ENDBR
>> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx
>>
>> /* Set the exception info. */

Thanks, I will fix that.

Yu-cheng

\
 
 \ /
  Last update: 2021-05-24 21:02    [W:0.088 / U:0.424 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site