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
This commit introduces a .INC file that contains the RSB logic and it can
be included by .ASM files. This file is placed at directory
'UefiCpuPkg/Include/'.
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Laszlo Ersek <ler...@redhat.com>
Cc: Michael D Kinney <michael.d.kin...@intel.com>
Cc: Eric Dong <eric.d...@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a...@intel.com>
---
UefiCpuPkg/Include/StuffRsbAsm.inc | 60 ++++++++++++++++++++
UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.asm | 5 +-
UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.asm | 5 +-
UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.asm | 5 +-
UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.asm | 5 +-
5 files changed, 76 insertions(+), 4 deletions(-)
diff --git a/UefiCpuPkg/Include/StuffRsbAsm.inc
b/UefiCpuPkg/Include/StuffRsbAsm.inc
new file mode 100644
index 0000000000..daaaaf36ad
--- /dev/null
+++ b/UefiCpuPkg/Include/StuffRsbAsm.inc
@@ -0,0 +1,60 @@
+;------------------------------------------------------------------------------
;
+; 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.
+;
+; Module Name:
+;
+; StuffRsbAsm.inc
+;
+; Abstract:
+;
+; This file provides macro definitions for stuffing the Return Stack Buffer
(RSB)
+; for .ASM files.
+;
+;-------------------------------------------------------------------------------
+
+RSB_STUFF_ENTRIES Equ 20h
+
+;
+; 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)
+;
+StuffRsb MACRO Reg, StackPointer, Size
+ local Unroll1, Unroll2, SpecTrap1, SpecTrap2, StuffLoop
+ mov Reg, RSB_STUFF_ENTRIES / 2
+Unroll1:
+ call Unroll2
+SpecTrap1:
+ pause
+ lfence
+ jmp SpecTrap1
+Unroll2:
+ call StuffLoop
+SpecTrap2:
+ pause
+ lfence
+ jmp SpecTrap2
+StuffLoop:
+ dec Reg
+ jnz Unroll1
+ add StackPointer, RSB_STUFF_ENTRIES * Size ; Restore the
stack pointer
+ ENDM
+
+;
+; RSB stuffing macros for IA32 and X64
+;
+StuffRsb32 MACRO
+ StuffRsb eax, esp, 4
+ ENDM
+
+StuffRsb64 MACRO
+ StuffRsb rax, rsp, 8
+ ENDM
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.asm
b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.asm
index ac1a9b48dd..ea906d6434 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.asm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.asm
@@ -1,5 +1,5 @@
;------------------------------------------------------------------------------
;
-; Copyright (c) 2009 - 2015, 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
@@ -22,6 +22,8 @@
.model flat,C
.xmm
+INCLUDE StuffRsbAsm.inc
+
DSC_OFFSET EQU 0fb00h
DSC_GDTPTR EQU 30h
DSC_GDTSIZ EQU 38h
@@ -169,6 +171,7 @@ _SmiHandler PROC
call eax
pop ecx
+ StuffRsb32
rsm
_SmiHandler ENDP
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.asm
b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.asm
index 9ba2aebe69..a606bde749 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.asm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.asm
@@ -1,5 +1,5 @@
;------------------------------------------------------------------------------
;
-; Copyright (c) 2009 - 2015, 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
@@ -22,6 +22,8 @@
.xmm
.model flat,C
+INCLUDE StuffRsbAsm.inc
+
SmmInitHandler PROTO C
EXTERNDEF C gSmmCr0:DWORD
@@ -70,6 +72,7 @@ gSmmJmpAddr LABEL QWORD
DB 0bch ; mov esp, imm32
gSmmInitStack DD ?
call SmmInitHandler
+ StuffRsb32
rsm
SmmStartup ENDP
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.asm
b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.asm
index 094cf2c3da..a4063cb0dc 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.asm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.asm
@@ -1,5 +1,5 @@
;------------------------------------------------------------------------------
;
-; Copyright (c) 2009 - 2015, 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 StuffRsbAsm.inc
+
;
; Variables referenced by C code
;
@@ -189,6 +191,7 @@ _SmiHandler:
DB 48h ; FXRSTOR64
fxrstor [rsp]
+ StuffRsb64
rsm
gcSmiHandlerSize DW $ - _SmiEntryPoint
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.asm
b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.asm
index 9182f0293a..2301a208d6 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.asm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmInit.asm
@@ -1,5 +1,5 @@
;------------------------------------------------------------------------------
;
-; Copyright (c) 2009 - 2015, 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 StuffRsbAsm.inc
+
EXTERNDEF SmmInitHandler:PROC
EXTERNDEF gSmmCr0:DWORD
EXTERNDEF gSmmCr3:DWORD
@@ -88,6 +90,7 @@ gSmmInitStack DQ ?
movdqa xmm4, [rsp + 40h]
movdqa xmm5, [rsp + 50h]
+ StuffRsb64
rsm
SmmStartup ENDP
--
2.12.0.windows.1
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