[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v1 4/6] x86/hvm: Add SMAP support to HVM guest
> -----Original Message----- > From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx] > Sent: Tuesday, April 15, 2014 6:37 PM > To: Wu, Feng > Cc: JBeulich@xxxxxxxx; Ian.Campbell@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; > Dong, Eddie; Nakajima, Jun > Subject: Re: [Xen-devel] [PATCH v1 4/6] x86/hvm: Add SMAP support to HVM > guest > > On 15/04/14 14:02, Feng Wu wrote: > > Intel new CPU supports SMAP (Supervisor Mode Access Prevention). > > SMAP prevents supervisor-mode accesses to any linear address with > > a valid translation for which the U/S flag (bit 2) is 1 in every > > paging-structure entry controlling the translation for the linear > > address. > > > > This patch enable SMAP for HVM geust. > > > > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx> > > --- > > xen/arch/x86/hvm/hvm.c | 3 +++ > > xen/arch/x86/mm/guest_walk.c | 27 +++++++++++++++++++++++---- > > xen/include/asm-x86/hvm/hvm.h | 13 +++++++++++++ > > 3 files changed, 39 insertions(+), 4 deletions(-) > > > > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c > > index b0da8e7..b52476d 100644 > > --- a/xen/arch/x86/hvm/hvm.c > > +++ b/xen/arch/x86/hvm/hvm.c > > @@ -3036,6 +3036,9 @@ void hvm_cpuid(unsigned int input, unsigned int > *eax, unsigned int *ebx, > > if ( (count == 0) && !cpu_has_smep ) > > *ebx &= ~cpufeat_mask(X86_FEATURE_SMEP); > > > > + if ( (count == 0) && !cpu_has_smap ) > > + *ebx &= ~cpufeat_mask(X86_FEATURE_SMAP); > > + > > /* Don't expose MPX to hvm when VMX support is not available > */ > > if ( (count == 0) && > > (!(vmx_vmexit_control & VM_EXIT_CLEAR_BNDCFGS) || > > diff --git a/xen/arch/x86/mm/guest_walk.c b/xen/arch/x86/mm/guest_walk.c > > index 70460b6..1d5f1fc 100644 > > --- a/xen/arch/x86/mm/guest_walk.c > > +++ b/xen/arch/x86/mm/guest_walk.c > > @@ -29,6 +29,7 @@ > > #include <xen/sched.h> > > #include <asm/page.h> > > #include <asm/guest_pt.h> > > +#include <asm/hvm/vmx/vmx.h> > > > > > > /* Flags that are needed in a pagetable entry, with the sense of NX > > inverted > */ > > @@ -144,14 +145,18 @@ guest_walk_tables(struct vcpu *v, struct > p2m_domain *p2m, > > guest_l4e_t *l4p; > > #endif > > uint32_t gflags, mflags, iflags, rc = 0; > > - int smep; > > + int smep, smap; > > bool_t pse1G = 0, pse2M = 0; > > + unsigned long sel = 0; > > + uint64_t eflags = guest_cpu_user_regs()->eflags; > > p2m_query_t qt = P2M_ALLOC | P2M_UNSHARE; > > > > perfc_incr(guest_walk); > > memset(gw, 0, sizeof(*gw)); > > gw->va = va; > > > > + __vmread(GUEST_CS_SELECTOR, &sel); > > + > > /* Mandatory bits that must be set in every entry. We invert NX and > > * the invalid bits, to calculate as if there were an "X" bit that > > * allowed access. We will accumulate, in rc, the set of flags that > > @@ -165,7 +170,21 @@ guest_walk_tables(struct vcpu *v, struct > p2m_domain *p2m, > > * whole walk as if it were a user-mode one and then invert the > answer. */ > > smep = (is_hvm_vcpu(v) && hvm_smep_enabled(v) > > && (pfec & PFEC_insn_fetch) && !(pfec & > PFEC_user_mode) ); > > - if ( smep ) > > + > > + /* > > + * SMAP: kernel-mode data accesses from user-mode mappings should > fault > > + * A fault is considered as a SMAP violation if the following > > + * conditions come ture: > > + * - X86_CR4_SMAP is set in CR4 > > + * - An user page is accessed > > + * - CPL = 3 or X86_EFLAGS_AC clear set) > > "X86_EFLAGS_AC clear set" ? What do you mean by this? > > ~Andrew It should be "CPL = 3 or X86_EFLAGS_AC is clear", sorry for this typo. > > > + * - Page fault in kernel mode > > + */ > > + smap = ( is_hvm_vcpu(v) && hvm_smap_enabled(v) > > + && !(!((sel & 3) == 3) && (eflags & X86_EFLAGS_AC)) > > + && !(pfec & PFEC_user_mode) ); > > + > > + if ( smep || smap ) > > mflags |= _PAGE_USER; > > > > #if GUEST_PAGING_LEVELS >= 3 /* PAE or 64... */ > > @@ -338,8 +357,8 @@ guest_walk_tables(struct vcpu *v, struct > p2m_domain *p2m, > > #if GUEST_PAGING_LEVELS >= 4 /* 64-bit only... */ > > set_ad: > > #endif > > - /* Now re-invert the user-mode requirement for SMEP. */ > > - if ( smep ) > > + /* Now re-invert the user-mode requirement for SMEP and SMAP */ > > + if ( smep || smap ) > > rc ^= _PAGE_USER; > > > > /* Go back and set accessed and dirty bits only if the walk was a > > diff --git a/xen/include/asm-x86/hvm/hvm.h > b/xen/include/asm-x86/hvm/hvm.h > > index dcc3483..b703b93 100644 > > --- a/xen/include/asm-x86/hvm/hvm.h > > +++ b/xen/include/asm-x86/hvm/hvm.h > > @@ -257,6 +257,8 @@ int hvm_girq_dest_2_vcpu_id(struct domain *d, > uint8_t dest, uint8_t dest_mode); > > (hvm_paging_enabled(v) && ((v)->arch.hvm_vcpu.guest_cr[4] & > X86_CR4_PAE)) > > #define hvm_smep_enabled(v) \ > > (hvm_paging_enabled(v) && ((v)->arch.hvm_vcpu.guest_cr[4] & > X86_CR4_SMEP)) > > +#define hvm_smap_enabled(v) \ > > + (hvm_paging_enabled(v) && ((v)->arch.hvm_vcpu.guest_cr[4] & > X86_CR4_SMAP)) > > #define hvm_nx_enabled(v) \ > > (!!((v)->arch.hvm_vcpu.guest_efer & EFER_NX)) > > > > @@ -363,6 +365,16 @@ static inline int hvm_event_pending(struct vcpu *v) > > #define HVM_CR4_HOST_MASK (mmu_cr4_features & \ > > (X86_CR4_VMXE | X86_CR4_PAE | X86_CR4_MCE)) > > > > +static inline bool_t hvm_cpuid_has_smap(void) > > +{ > > + unsigned int eax = 0, ebx = 0, ecx = 0, edx = 0; > > + unsigned int leaf = 0x7; > > + > > + hvm_cpuid(leaf, &eax, &ebx, &ecx, &edx); > > + > > + return !!(ebx & cpufeat_mask(X86_FEATURE_SMAP)); > > +} > > + > > /* These bits in CR4 cannot be set by the guest. */ > > #define HVM_CR4_GUEST_RESERVED_BITS(_v) \ > > (~((unsigned long) \ > > @@ -371,6 +383,7 @@ static inline int hvm_event_pending(struct vcpu *v) > > X86_CR4_MCE | X86_CR4_PGE | X86_CR4_PCE | \ > > X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT | \ > > (cpu_has_smep ? X86_CR4_SMEP : 0) | \ > > + (hvm_cpuid_has_smap() ? X86_CR4_SMAP : 0) | \ > > (cpu_has_fsgsbase ? X86_CR4_FSGSBASE : 0) | \ > > ((nestedhvm_enabled((_v)->domain) && cpu_has_vmx)\ > > ? X86_CR4_VMXE : 0) | \ Thanks, Feng _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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