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Message-ID: <YFEFhoi/SB12HUrg@kernel.org>
Date: Tue, 16 Mar 2021 21:22:46 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc: x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-mm@...ck.org,
linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>,
Andy Lutomirski <luto@...nel.org>,
Balbir Singh <bsingharora@...il.com>,
Borislav Petkov <bp@...en8.de>,
Cyrill Gorcunov <gorcunov@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Eugene Syromiatnikov <esyr@...hat.com>,
Florian Weimer <fweimer@...hat.com>,
"H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Nadav Amit <nadav.amit@...il.com>,
Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
Peter Zijlstra <peterz@...radead.org>,
Randy Dunlap <rdunlap@...radead.org>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
Dave Martin <Dave.Martin@....com>,
Weijiang Yang <weijiang.yang@...el.com>,
Pengfei Xu <pengfei.xu@...el.com>,
Haitao Huang <haitao.huang@...el.com>
Subject: Re: [PATCH v23 9/9] x86/vdso: Add ENDBR to __vdso_sgx_enter_enclave
On Tue, Mar 16, 2021 at 08:13:19AM -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@...el.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Jarkko Sakkinen <jarkko@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.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..1baa9b49053e 100644
> --- a/arch/x86/entry/vdso/vsgx.S
> +++ b/arch/x86/entry/vdso/vsgx.S
> @@ -6,6 +6,7 @@
> #include <asm/enclu.h>
>
> #include "extable.h"
> +#include "../calling.h"
>
> /* Relative to %rbp. */
> #define SGX_ENCLAVE_OFFSET_OF_RUN 16
> @@ -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
>
> /* EEXIT jumps here unless the enclave is doing something fancy. */
> 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. */
> --
> 2.21.0
>
>
Looks good to me.
Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
/Jarkko
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