34a5f0e3e3
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>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
(cherry picked from commit 02f7fd158e)
95 lines
2.6 KiB
NASM
95 lines
2.6 KiB
NASM
;------------------------------------------------------------------------------ ;
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; Copyright (c) 2016 - 2018, Intel Corporation. All rights reserved.<BR>
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; This program and the accompanying materials
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; are licensed and made available under the terms and conditions of the BSD License
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; which accompanies this distribution. The full text of the license may be found at
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; http://opensource.org/licenses/bsd-license.php.
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;
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; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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;
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; Module Name:
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;
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; SmmInit.nasm
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;
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; Abstract:
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;
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; Functions for relocating SMBASE's for all processors
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;
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;-------------------------------------------------------------------------------
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%include "StuffRsb.inc"
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extern ASM_PFX(SmmInitHandler)
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extern ASM_PFX(mRebasedFlag)
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extern ASM_PFX(mSmmRelocationOriginalAddress)
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global ASM_PFX(gSmmCr3)
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global ASM_PFX(gSmmCr4)
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global ASM_PFX(gSmmCr0)
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global ASM_PFX(gSmmJmpAddr)
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global ASM_PFX(gSmmInitStack)
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global ASM_PFX(gcSmiInitGdtr)
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global ASM_PFX(gcSmmInitSize)
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global ASM_PFX(gcSmmInitTemplate)
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%define PROTECT_MODE_CS 0x8
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%define PROTECT_MODE_DS 0x20
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SECTION .text
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ASM_PFX(gcSmiInitGdtr):
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DW 0
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DQ 0
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global ASM_PFX(SmmStartup)
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ASM_PFX(SmmStartup):
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DB 0x66, 0xb8
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ASM_PFX(gSmmCr3): DD 0
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mov cr3, eax
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DB 0x67, 0x66
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lgdt [cs:ebp + (ASM_PFX(gcSmiInitGdtr) - ASM_PFX(SmmStartup))]
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DB 0x66, 0xb8
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ASM_PFX(gSmmCr4): DD 0
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mov cr4, eax
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DB 0x66, 0xb8
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ASM_PFX(gSmmCr0): DD 0
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DB 0xbf, PROTECT_MODE_DS, 0 ; mov di, PROTECT_MODE_DS
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mov cr0, eax
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DB 0x66, 0xea ; jmp far [ptr48]
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ASM_PFX(gSmmJmpAddr):
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DD @32bit
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DW PROTECT_MODE_CS
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@32bit:
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mov ds, edi
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mov es, edi
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mov fs, edi
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mov gs, edi
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mov ss, edi
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DB 0xbc ; mov esp, imm32
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ASM_PFX(gSmmInitStack): DD 0
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call ASM_PFX(SmmInitHandler)
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StuffRsb32
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rsm
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BITS 16
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ASM_PFX(gcSmmInitTemplate):
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mov ebp, ASM_PFX(SmmStartup)
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sub ebp, 0x30000
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jmp ebp
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ASM_PFX(gcSmmInitSize): DW $ - ASM_PFX(gcSmmInitTemplate)
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BITS 32
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global ASM_PFX(SmmRelocationSemaphoreComplete)
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ASM_PFX(SmmRelocationSemaphoreComplete):
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push eax
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mov eax, [ASM_PFX(mRebasedFlag)]
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mov byte [eax], 1
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pop eax
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jmp [ASM_PFX(mSmmRelocationOriginalAddress)]
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global ASM_PFX(PiSmmCpuSmmInitFixupAddress)
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ASM_PFX(PiSmmCpuSmmInitFixupAddress):
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ret
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