CET - Control-flow Enforcement Technology, it's used to
protect against return/jump oriented programming (ROP)
attacks. It provides the following capabilities to defend
against ROP/JOP style control-flow subversion attacks:
- Shadow Stack (SHSTK):
A second stack for the program that is
used exclusively for control transfer
operations.
- Indirect Branch Tracking (IBT):
Free branch protection to defend against
Jump/Call Oriented Programming.
On processors that support CET, VMX saves/restores
the states of IA32_S_CET, SSP and IA32_INTR_SSP_TABL_ADDR MSR
to the VMCS area for Guest/Host unconditionally.
If VM_EXIT_LOAD_HOST_CET_STATE = 1, the host CET MSRs are
restored from VMCS host-state area at VM exit as follows:
- HOST_S_CET: Host supervisor mode IA32_S_CET MSR is loaded
from this field.
- HOST_SSP : Host SSP is loaded from this field.
- HOST_INTR_SSP_TABLE : Host IA32_INTR_SSP_TABL_ADDR
MSR is loaded from this field.
If VM_ENTRY_LOAD_GUEST_CET_STATE = 1, the guest CET MSRs are loaded
from VMCS guest-state area at VM entry as follows:
- GUEST_S_CET : Guest supervisor mode IA32_S_CET MSR is loaded
from this field.
- GUEST_SSP : Guest SSP is loaded from this field.
- GUEST_INTR_SSP_TABLE : Guest IA32_INTR_SSP_TABL_ADDR
MSR is loaded from this field.
Additionally, to context switch guest and host CET states, the VMM
uses xsaves/xrstors instructions to save/restore the guest CET states
at VM exit/entry. The CET xsave area is within thread_struct.fpu area.
If OS execution flow changes during task switch/interrupt/exception etc.,
the OS also relies on xsaves/xrstors to switch CET states accordingly.
Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
arch/x86/include/asm/vmx.h | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index ade0f153947d..fd70c4577c5a 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -98,6 +98,7 @@
#define VM_EXIT_LOAD_IA32_EFER 0x00200000
#define VM_EXIT_SAVE_VMX_PREEMPTION_TIMER 0x00400000
#define VM_EXIT_CLEAR_BNDCFGS 0x00800000
+#define VM_EXIT_LOAD_HOST_CET_STATE 0x10000000
#define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR 0x00036dff
@@ -109,6 +110,7 @@
#define VM_ENTRY_LOAD_IA32_PAT 0x00004000
#define VM_ENTRY_LOAD_IA32_EFER 0x00008000
#define VM_ENTRY_LOAD_BNDCFGS 0x00010000
+#define VM_ENTRY_LOAD_GUEST_CET_STATE 0x00100000
#define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR 0x000011ff
@@ -325,6 +327,9 @@ enum vmcs_field {
GUEST_PENDING_DBG_EXCEPTIONS = 0x00006822,
GUEST_SYSENTER_ESP = 0x00006824,
GUEST_SYSENTER_EIP = 0x00006826,
+ GUEST_S_CET = 0x00006828,
+ GUEST_SSP = 0x0000682a,
+ GUEST_INTR_SSP_TABLE = 0x0000682c,
HOST_CR0 = 0x00006c00,
HOST_CR3 = 0x00006c02,
HOST_CR4 = 0x00006c04,
@@ -337,6 +342,9 @@ enum vmcs_field {
HOST_IA32_SYSENTER_EIP = 0x00006c12,
HOST_RSP = 0x00006c14,
HOST_RIP = 0x00006c16,
+ HOST_S_CET = 0x00006c18,
+ HOST_SSP = 0x00006c1a,
+ HOST_INTR_SSP_TABLE = 0x00006c1c
};
/*
--
2.17.1
