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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH V8 2/5] x86/hvm: pkeys, add pkeys support for guest_walk_tables
Protection keys define a new 4-bit protection key field(PKEY) in bits 62:59 of
leaf entries of the page tables.
PKRU register defines 32 bits, there are 16 domains and 2 attribute bits per
domain in pkru, for each i (0 â i â 15), PKRU[2i] is the access-disable bit for
protection key i (ADi); PKRU[2i+1] is the write-disable bit for protection key
i (WDi). PKEY is index to a defined domain.
A fault is considered as a PKU violation if all of the following conditions are
true:
1.CR4_PKE=1.
2.EFER_LMA=1.
3.Page is present with no reserved bit violations.
4.The access is not an instruction fetch.
5.The access is to a user page.
6.PKRU.AD=1
or The access is a data write and PKRU.WD=1
and either CR0.WP=1 or it is a user access.
Signed-off-by: Huaitong Han <huaitong.han@xxxxxxxxx>
---
Changes in v8:
*Abstract out _write_cr4.
Changes in v7:
*Add static for pkey_fault.
*Add a comment for page present check and adjust indentation.
*Init pkru_ad and pkru_wd.
*Delete l3e_get_pkey the outer parentheses.
*The first parameter of read_pkru_* use uint32_t type.
xen/arch/x86/mm/guest_walk.c | 54 +++++++++++++++++++++++++++++++++++++++
xen/arch/x86/mm/hap/guest_walk.c | 3 +++
xen/include/asm-x86/guest_pt.h | 12 +++++++++
xen/include/asm-x86/hvm/hvm.h | 2 ++
xen/include/asm-x86/page.h | 5 ++++
xen/include/asm-x86/processor.h | 47 +++++++++++++++++++++++++++++++++-
xen/include/asm-x86/x86_64/page.h | 12 +++++++++
7 files changed, 134 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/mm/guest_walk.c b/xen/arch/x86/mm/guest_walk.c
index 18d1acf..5e1111b 100644
--- a/xen/arch/x86/mm/guest_walk.c
+++ b/xen/arch/x86/mm/guest_walk.c
@@ -90,6 +90,54 @@ static uint32_t set_ad_bits(void *guest_p, void *walk_p, int
set_dirty)
return 0;
}
+#if GUEST_PAGING_LEVELS >= 4
+static bool_t pkey_fault(struct vcpu *vcpu, uint32_t pfec,
+ uint32_t pte_flags, uint32_t pte_pkey)
+{
+ uint32_t pkru = 0;
+ bool_t pkru_ad = 0, pkru_wd = 0;
+
+ /* When page isn't present, PKEY isn't checked. */
+ if ( !(pfec & PFEC_page_present) || is_pv_vcpu(vcpu) )
+ return 0;
+
+ /*
+ * PKU: additional mechanism by which the paging controls
+ * access to user-mode addresses based on the value in the
+ * PKRU register. A fault is considered as a PKU violation if all
+ * of the following conditions are true:
+ * 1.CR4_PKE=1.
+ * 2.EFER_LMA=1.
+ * 3.Page is present with no reserved bit violations.
+ * 4.The access is not an instruction fetch.
+ * 5.The access is to a user page.
+ * 6.PKRU.AD=1 or
+ * the access is a data write and PKRU.WD=1 and
+ * either CR0.WP=1 or it is a user access.
+ */
+ if ( !hvm_pku_enabled(vcpu) ||
+ !hvm_long_mode_enabled(vcpu) ||
+ /* The persent bit is guaranteed by the caller. */
+ (pfec & PFEC_reserved_bit) ||
+ (pfec & PFEC_insn_fetch) ||
+ !(pte_flags & _PAGE_USER) )
+ return 0;
+
+ pkru = read_pkru();
+ if ( unlikely(pkru) )
+ {
+ pkru_ad = read_pkru_ad(pkru, pte_pkey);
+ pkru_wd = read_pkru_wd(pkru, pte_pkey);
+ /* Condition 6 */
+ if ( pkru_ad || (pkru_wd && (pfec & PFEC_write_access) &&
+ (hvm_wp_enabled(vcpu) || (pfec & PFEC_user_mode))))
+ return 1;
+ }
+
+ return 0;
+}
+#endif
+
/* Walk the guest pagetables, after the manner of a hardware walker. */
/* Because the walk is essentially random, it can cause a deadlock
* warning in the p2m locking code. Highly unlikely this is an actual
@@ -107,6 +155,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m,
guest_l3e_t *l3p = NULL;
guest_l4e_t *l4p;
#endif
+ unsigned int pkey;
uint32_t gflags, mflags, iflags, rc = 0;
bool_t smep = 0, smap = 0;
bool_t pse1G = 0, pse2M = 0;
@@ -190,6 +239,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m,
goto out;
/* Get the l3e and check its flags*/
gw->l3e = l3p[guest_l3_table_offset(va)];
+ pkey = guest_l3e_get_pkey(gw->l3e);
gflags = guest_l3e_get_flags(gw->l3e) ^ iflags;
if ( !(gflags & _PAGE_PRESENT) ) {
rc |= _PAGE_PRESENT;
@@ -261,6 +311,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m,
#endif /* All levels... */
+ pkey = guest_l2e_get_pkey(gw->l2e);
gflags = guest_l2e_get_flags(gw->l2e) ^ iflags;
if ( !(gflags & _PAGE_PRESENT) ) {
rc |= _PAGE_PRESENT;
@@ -324,6 +375,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m,
if(l1p == NULL)
goto out;
gw->l1e = l1p[guest_l1_table_offset(va)];
+ pkey = guest_l1e_get_pkey(gw->l1e);
gflags = guest_l1e_get_flags(gw->l1e) ^ iflags;
if ( !(gflags & _PAGE_PRESENT) ) {
rc |= _PAGE_PRESENT;
@@ -334,6 +386,8 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m,
#if GUEST_PAGING_LEVELS >= 4 /* 64-bit only... */
set_ad:
+ if ( pkey_fault(v, pfec, gflags, pkey) )
+ rc |= _PAGE_PKEY_BITS;
#endif
/* Now re-invert the user-mode requirement for SMEP and SMAP */
if ( smep || smap )
diff --git a/xen/arch/x86/mm/hap/guest_walk.c b/xen/arch/x86/mm/hap/guest_walk.c
index 11c1b35..49d0328 100644
--- a/xen/arch/x86/mm/hap/guest_walk.c
+++ b/xen/arch/x86/mm/hap/guest_walk.c
@@ -130,6 +130,9 @@ unsigned long hap_p2m_ga_to_gfn(GUEST_PAGING_LEVELS)(
if ( missing & _PAGE_INVALID_BITS )
pfec[0] |= PFEC_reserved_bit;
+ if ( missing & _PAGE_PKEY_BITS )
+ pfec[0] |= PFEC_prot_key;
+
if ( missing & _PAGE_PAGED )
pfec[0] = PFEC_page_paged;
diff --git a/xen/include/asm-x86/guest_pt.h b/xen/include/asm-x86/guest_pt.h
index 3447973..eb29e62 100644
--- a/xen/include/asm-x86/guest_pt.h
+++ b/xen/include/asm-x86/guest_pt.h
@@ -81,6 +81,11 @@ static inline u32 guest_l1e_get_flags(guest_l1e_t gl1e)
static inline u32 guest_l2e_get_flags(guest_l2e_t gl2e)
{ return gl2e.l2 & 0xfff; }
+static inline u32 guest_l1e_get_pkey(guest_l1e_t gl1e)
+{ return 0; }
+static inline u32 guest_l2e_get_pkey(guest_l2e_t gl2e)
+{ return 0; }
+
static inline guest_l1e_t guest_l1e_from_gfn(gfn_t gfn, u32 flags)
{ return (guest_l1e_t) { (gfn_x(gfn) << PAGE_SHIFT) | flags }; }
static inline guest_l2e_t guest_l2e_from_gfn(gfn_t gfn, u32 flags)
@@ -154,6 +159,13 @@ static inline u32 guest_l4e_get_flags(guest_l4e_t gl4e)
{ return l4e_get_flags(gl4e); }
#endif
+static inline u32 guest_l1e_get_pkey(guest_l1e_t gl1e)
+{ return l1e_get_pkey(gl1e); }
+static inline u32 guest_l2e_get_pkey(guest_l2e_t gl2e)
+{ return l2e_get_pkey(gl2e); }
+static inline u32 guest_l3e_get_pkey(guest_l3e_t gl3e)
+{ return l3e_get_pkey(gl3e); }
+
static inline guest_l1e_t guest_l1e_from_gfn(gfn_t gfn, u32 flags)
{ return l1e_from_pfn(gfn_x(gfn), flags); }
static inline guest_l2e_t guest_l2e_from_gfn(gfn_t gfn, u32 flags)
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index a87224b..731dd44 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -277,6 +277,8 @@ 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_SMAP))
#define hvm_nx_enabled(v) \
(!!((v)->arch.hvm_vcpu.guest_efer & EFER_NX))
+#define hvm_pku_enabled(v) \
+ (hvm_paging_enabled(v) && ((v)->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PKE))
/* Can we use superpages in the HAP p2m table? */
#define hap_has_1gb (!!(hvm_funcs.hap_capabilities & HVM_HAP_SUPERPAGE_1GB))
diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
index a095a93..9202f3d 100644
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -93,6 +93,11 @@
#define l3e_get_flags(x) (get_pte_flags((x).l3))
#define l4e_get_flags(x) (get_pte_flags((x).l4))
+/* Get pte pkeys (unsigned int). */
+#define l1e_get_pkey(x) get_pte_pkey((x).l1)
+#define l2e_get_pkey(x) get_pte_pkey((x).l2)
+#define l3e_get_pkey(x) get_pte_pkey((x).l3)
+
/* Construct an empty pte. */
#define l1e_empty() ((l1_pgentry_t) { 0 })
#define l2e_empty() ((l2_pgentry_t) { 0 })
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 26ba141..da5d0e8 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -332,6 +332,11 @@ static inline unsigned long read_cr2(void)
DECLARE_PER_CPU(unsigned long, cr4);
+static inline void _write_cr4(unsigned long val)
+{
+ asm volatile ( "mov %0,%%cr4" : : "r" (val) );
+}
+
static inline unsigned long read_cr4(void)
{
return this_cpu(cr4);
@@ -340,7 +345,7 @@ static inline unsigned long read_cr4(void)
static inline void write_cr4(unsigned long val)
{
this_cpu(cr4) = val;
- asm volatile ( "mov %0,%%cr4" : : "r" (val) );
+ _write_cr4(val);
}
/* Clear and set 'TS' bit respectively */
@@ -374,6 +379,46 @@ static always_inline void clear_in_cr4 (unsigned long mask)
write_cr4(read_cr4() & ~mask);
}
+static inline unsigned int read_pkru(void)
+{
+ unsigned int pkru;
+ unsigned long cr4 = read_cr4();
+
+ /*
+ * _PAGE_PKEY_BITS have a conflict with _PAGE_GNTTAB used by PV guests,
+ * so that X86_CR4_PKE is disabled on hypervisor. To use RDPKRU, CR4.PKE
+ * gets temporarily enabled.
+ */
+ _write_cr4(cr4 | X86_CR4_PKE);
+ asm volatile (".byte 0x0f,0x01,0xee"
+ : "=a" (pkru) : "c" (0) : "dx");
+ _write_cr4(cr4);
+
+ return pkru;
+}
+
+/* Macros for PKRU domain */
+#define PKRU_READ (0)
+#define PKRU_WRITE (1)
+#define PKRU_ATTRS (2)
+
+/*
+ * PKRU defines 32 bits, there are 16 domains and 2 attribute bits per
+ * domain in pkru, pkeys is index to a defined domain, so the value of
+ * pte_pkeys * PKRU_ATTRS + R/W is offset of a defined domain attribute.
+ */
+static inline bool_t read_pkru_ad(uint32_t pkru, unsigned int pkey)
+{
+ ASSERT(pkey < 16);
+ return (pkru >> (pkey * PKRU_ATTRS + PKRU_READ)) & 1;
+}
+
+static inline bool_t read_pkru_wd(uint32_t pkru, unsigned int pkey)
+{
+ ASSERT(pkey < 16);
+ return (pkru >> (pkey * PKRU_ATTRS + PKRU_WRITE)) & 1;
+}
+
/*
* NSC/Cyrix CPU configuration register indexes
*/
diff --git a/xen/include/asm-x86/x86_64/page.h
b/xen/include/asm-x86/x86_64/page.h
index 19ab4d0..86abb94 100644
--- a/xen/include/asm-x86/x86_64/page.h
+++ b/xen/include/asm-x86/x86_64/page.h
@@ -134,6 +134,18 @@ typedef l4_pgentry_t root_pgentry_t;
#define get_pte_flags(x) (((int)((x) >> 40) & ~0xFFF) | ((int)(x) & 0xFFF))
#define put_pte_flags(x) (((intpte_t)((x) & ~0xFFF) << 40) | ((x) & 0xFFF))
+/*
+ * Protection keys define a new 4-bit protection key field
+ * (PKEY) in bits 62:59 of leaf entries of the page tables.
+ * This corresponds to bit 22:19 of a 24-bit flags.
+ *
+ * Notice: Bit 22 is used by _PAGE_GNTTAB which is visible to PV guests,
+ * so Protection keys must be disabled on PV guests.
+ */
+#define _PAGE_PKEY_BITS (0x780000) /* Protection Keys, 22:19 */
+
+#define get_pte_pkey(x) (MASK_EXTR(get_pte_flags(x), _PAGE_PKEY_BITS))
+
/* Bit 23 of a 24-bit flag mask. This corresponds to bit 63 of a pte.*/
#define _PAGE_NX_BIT (1U<<23)
--
2.4.3
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