UefiCpuPkg/SmmCpuFeaturesLib: [CVE-2017-5715] Stuff RSB before RSM

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1093

Return Stack Buffer (RSB) is used to predict the target of RET
instructions. When the RSB underflows, some processors may fall back to
using branch predictors. This might impact software using the retpoline
mitigation strategy on those processors.

This commit will add RSB stuffing logic before returning from SMM (the RSM
instruction) to avoid interfering with non-SMM usage of the retpoline
technique.

After the stuffing, RSB entries will contain a trap like:

@SpecTrap:
    pause
    lfence
    jmp     @SpecTrap

A more detailed explanation of the purpose of commit is under the
'Branch target injection mitigation' section of the below link:
https://software.intel.com/security-software-guidance/insights/host-firmware-speculative-execution-side-channel-mitigation

Please note that this commit requires further actions (BZ 1091) to remove
the duplicated 'StuffRsb.inc' files and merge them into one under a
UefiCpuPkg package-level directory (such as UefiCpuPkg/Include/).

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1091

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>

UefiCpuPkg/Library/SmmCpuFeaturesLib/Ia32/SmiEntry.nasm

@@ -18,6 +18,8 @@
 ;
 ;-------------------------------------------------------------------------------
 
+%include "StuffRsb.inc"
+
 %define MSR_IA32_MISC_ENABLE 0x1A0
 %define MSR_EFER      0xc0000080
 %define MSR_EFER_XD   0x800
@@ -206,6 +208,7 @@ CommonHandler:
     wrmsr
 
 .7:
+    StuffRsb32
     rsm
 
 

UefiCpuPkg/Library/SmmCpuFeaturesLib/Ia32/SmiException.nasm

@@ -1,5 +1,5 @@
 ;------------------------------------------------------------------------------ ;
-; Copyright (c) 2009 - 2017, Intel Corporation. All rights reserved.<BR>
+; Copyright (c) 2009 - 2018, Intel Corporation. All rights reserved.<BR>
 ; This program and the accompanying materials
 ; are licensed and made available under the terms and conditions of the BSD License
 ; which accompanies this distribution.  The full text of the license may be found at
@@ -18,6 +18,8 @@
 ;
 ;-------------------------------------------------------------------------------
 
+%include "StuffRsb.inc"
+
 global  ASM_PFX(gcStmPsd)
 
 extern  ASM_PFX(SmmStmExceptionHandler)
@@ -130,6 +132,7 @@ ASM_PFX(OnStmSetup):
     wrmsr
 
 .71:
+    StuffRsb32
     rsm
 
 global  ASM_PFX(OnStmTeardown)
@@ -172,4 +175,5 @@ ASM_PFX(OnStmTeardown):
     wrmsr
 
 .72:
+    StuffRsb32
     rsm

UefiCpuPkg/Library/SmmCpuFeaturesLib/Ia32/StuffRsb.inc

@@ -0,0 +1,55 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2018, Intel Corporation. All rights reserved.<BR>
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution.  The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+; Abstract:
+;
+;   This file provides macro definitions for stuffing the Return Stack Buffer (RSB).
+;
+;------------------------------------------------------------------------------
+
+%define RSB_STUFF_ENTRIES 0x20
+
+;
+; parameters:
+; @param 1: register to use as counter (e.g. IA32:eax, X64:rax)
+; @param 2: stack pointer to restore   (IA32:esp, X64:rsp)
+; @param 3: the size of a stack frame  (IA32:4, X64:8)
+;
+%macro StuffRsb 3
+      mov     %1, RSB_STUFF_ENTRIES / 2
+  %%Unroll1:
+      call    %%Unroll2
+  %%SpecTrap1:
+      pause
+      lfence
+      jmp     %%SpecTrap1
+  %%Unroll2:
+      call    %%StuffLoop
+  %%SpecTrap2:
+      pause
+      lfence
+      jmp     %%SpecTrap2
+  %%StuffLoop:
+      dec     %1
+      jnz     %%Unroll1
+      add     %2, RSB_STUFF_ENTRIES * %3 ; Restore the stack pointer
+%endmacro
+
+;
+; RSB stuffing macros for IA32 and X64
+;
+%macro StuffRsb32 0
+      StuffRsb     eax, esp, 4
+%endmacro
+
+%macro StuffRsb64 0
+      StuffRsb     rax, rsp, 8
+%endmacro

UefiCpuPkg/Library/SmmCpuFeaturesLib/X64/SmiEntry.nasm

@@ -18,6 +18,8 @@
 ;
 ;-------------------------------------------------------------------------------
 
+%include "StuffRsb.inc"
+
 ;
 ; Variables referrenced by C code
 ;
@@ -221,6 +223,7 @@ CommonHandler:
     wrmsr
 
 .1:
+    StuffRsb64
     rsm
 
 _StmSmiHandler:

UefiCpuPkg/Library/SmmCpuFeaturesLib/X64/SmiException.nasm

@@ -18,6 +18,8 @@
 ;
 ;-------------------------------------------------------------------------------
 
+%include "StuffRsb.inc"
+
 global  ASM_PFX(gcStmPsd)
 
 extern  ASM_PFX(SmmStmExceptionHandler)
@@ -131,6 +133,7 @@ ASM_PFX(OnStmSetup):
     wrmsr
 
 .11:
+    StuffRsb64
     rsm
 
 global ASM_PFX(OnStmTeardown)
@@ -175,4 +178,5 @@ ASM_PFX(OnStmTeardown):
     wrmsr
 
 .12:
+    StuffRsb64
     rsm

UefiCpuPkg/Library/SmmCpuFeaturesLib/X64/StuffRsb.inc

@@ -0,0 +1,55 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2018, Intel Corporation. All rights reserved.<BR>
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution.  The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+; Abstract:
+;
+;   This file provides macro definitions for stuffing the Return Stack Buffer (RSB).
+;
+;------------------------------------------------------------------------------
+
+%define RSB_STUFF_ENTRIES 0x20
+
+;
+; parameters:
+; @param 1: register to use as counter (e.g. IA32:eax, X64:rax)
+; @param 2: stack pointer to restore   (IA32:esp, X64:rsp)
+; @param 3: the size of a stack frame  (IA32:4, X64:8)
+;
+%macro StuffRsb 3
+      mov     %1, RSB_STUFF_ENTRIES / 2
+  %%Unroll1:
+      call    %%Unroll2
+  %%SpecTrap1:
+      pause
+      lfence
+      jmp     %%SpecTrap1
+  %%Unroll2:
+      call    %%StuffLoop
+  %%SpecTrap2:
+      pause
+      lfence
+      jmp     %%SpecTrap2
+  %%StuffLoop:
+      dec     %1
+      jnz     %%Unroll1
+      add     %2, RSB_STUFF_ENTRIES * %3 ; Restore the stack pointer
+%endmacro
+
+;
+; RSB stuffing macros for IA32 and X64
+;
+%macro StuffRsb32 0
+      StuffRsb     eax, esp, 4
+%endmacro
+
+%macro StuffRsb64 0
+      StuffRsb     rax, rsp, 8
+%endmacro