OS may enable CET-IBT feature by set MSR IA32_U_CET.bit2.
If IA32_U_CET.bit2 is set, CPU is in WAIT_FOR_ENDBRANCH state and
the next assemble code is not ENDBR, it will trigger #CP exception
when set CR4.CET bit.
SMI handler needs to backup MSR IA32_U_CET and clear MSR IA32_U_CET
before set CR4.CET bit,
And SMI handler needs to restore MSR IA32_U_CET when exit SMI handler.
Signed-off-by: Sheng Wei <w.sh...@intel.com>
Cc: Eric Dong <eric.d...@intel.com>
Cc: Ray Ni <ray...@intel.com>
Cc: Laszlo Ersek <ler...@redhat.com>
Cc: Wu Jiaxin <jiaxin...@intel.com>
Cc: Tan Dun <dun....@intel.com>
---
UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm | 15 +++++++++++++++
UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm | 15 +++++++++++++++
2 files changed, 30 insertions(+)
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm
b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm
index 1da9afab97..9e1155dee6 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm
@@ -202,11 +202,21 @@ ASM_PFX(mPatchCetSupported):
push edx
push eax
+ mov ecx, MSR_IA32_U_CET
+ rdmsr
+ push edx
+ push eax
+
mov ecx, MSR_IA32_PL0_SSP
rdmsr
push edx
push eax
+ mov ecx, MSR_IA32_U_CET
+ xor eax, eax
+ xor edx, edx
+ wrmsr
+
mov ecx, MSR_IA32_S_CET
mov eax, MSR_IA32_CET_SH_STK_EN
xor edx, edx
@@ -276,6 +286,11 @@ CetDone:
pop edx
wrmsr
+ mov ecx, MSR_IA32_U_CET
+ pop eax
+ pop edx
+ wrmsr
+
mov ecx, MSR_IA32_S_CET
pop eax
pop edx
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
index abf9f1a90a..881d3177f7 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
@@ -217,6 +217,11 @@ ASM_PFX(mPatchCetSupported):
push rdx
push rax
+ mov ecx, MSR_IA32_U_CET
+ rdmsr
+ push rdx
+ push rax
+
mov ecx, MSR_IA32_PL0_SSP
rdmsr
push rdx
@@ -227,6 +232,11 @@ ASM_PFX(mPatchCetSupported):
push rdx
push rax
+ mov ecx, MSR_IA32_U_CET
+ xor eax, eax
+ xor edx, edx
+ wrmsr
+
mov ecx, MSR_IA32_S_CET
mov eax, MSR_IA32_CET_SH_STK_EN
xor edx, edx
@@ -325,6 +335,11 @@ mCetSupportedAbsAddr:
pop rdx
wrmsr
+ mov ecx, MSR_IA32_U_CET
+ pop rax
+ pop rdx
+ wrmsr
+
mov ecx, MSR_IA32_S_CET
pop rax
pop rdx
--
2.26.2.windows.1
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