On Tue, Feb 26, 2019 at 11:31:11AM -0800, Jim Mattson wrote: > On Mon, Feb 25, 2019 at 10:32 PM Yang Weijiang <weijiang.yang@xxxxxxxxx> wrote: > > > > 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_IA32_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_TABL_ADDR : 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_IA32_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_TABL_ADDR : 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..395c1f7e5938 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_IA32_S_CET = 0x00006828, > > + GUEST_SSP = 0x0000682a, > > + GUEST_INTR_SSP_TABL_ADDR = 0x0000682c, > > Nit: TABL is an unusual abbreviation. Perhaps TBL here and below? I don't see any reason to abbreviate TABLE, we don't need the two characters for anything. > And why did you drop the 'IA32' here, but not in GUEST_IA32_S_CET above? > (It is true that there seems to be no rhyme or reason to the mnemonics > chosen here. For example, EFER keeps its IA32, but SYSENTER_EIP > doesn't. Sigh.) My vote is to always drop IA32, IMO it's redundant.