diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index f735c30163252f5566e17c63deb50ef0ab63cc16..af38d93c4fbbb361fc5578cc6b0847259772f245 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -909,7 +909,11 @@ static inline int pgd_none(pgd_t pgd)
* pgd_offset() returns a (pgd_t *)
* pgd_index() is used get the offset into the pgd page's array of pgd_t's;
*/
-#define pgd_offset(mm, address) ((mm)->pgd + pgd_index((address)))
+#define pgd_offset_pgd(pgd, address) (pgd + pgd_index((address)))
+/*
+ * a shortcut to get a pgd_t in a given mm
+ */
+#define pgd_offset(mm, address) pgd_offset_pgd((mm)->pgd, (address))
/*
* a shortcut which implies the use of the kernel's pgd, instead
* of a process's
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index e9f05331e732a057b341e78977d666b8cfe35289..81462e9a34f6af49645a08f55c7d67e0144dbb77 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -131,9 +131,97 @@ static inline pud_t native_pudp_get_and_clear(pud_t *xp)
#endif
}
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+/*
+ * All top-level PAGE_TABLE_ISOLATION page tables are order-1 pages
+ * (8k-aligned and 8k in size). The kernel one is at the beginning 4k and
+ * the user one is in the last 4k. To switch between them, you
+ * just need to flip the 12th bit in their addresses.
+ */
+#define PTI_PGTABLE_SWITCH_BIT PAGE_SHIFT
+
+/*
+ * This generates better code than the inline assembly in
+ * __set_bit().
+ */
+static inline void *ptr_set_bit(void *ptr, int bit)
+{
+ unsigned long __ptr = (unsigned long)ptr;
+
+ __ptr |= BIT(bit);
+ return (void *)__ptr;
+}
+static inline void *ptr_clear_bit(void *ptr, int bit)
+{
+ unsigned long __ptr = (unsigned long)ptr;
+
+ __ptr &= ~BIT(bit);
+ return (void *)__ptr;
+}
+
+static inline pgd_t *kernel_to_user_pgdp(pgd_t *pgdp)
+{
+ return ptr_set_bit(pgdp, PTI_PGTABLE_SWITCH_BIT);
+}
+
+static inline pgd_t *user_to_kernel_pgdp(pgd_t *pgdp)
+{
+ return ptr_clear_bit(pgdp, PTI_PGTABLE_SWITCH_BIT);
+}
+
+static inline p4d_t *kernel_to_user_p4dp(p4d_t *p4dp)
+{
+ return ptr_set_bit(p4dp, PTI_PGTABLE_SWITCH_BIT);
+}
+
+static inline p4d_t *user_to_kernel_p4dp(p4d_t *p4dp)
+{
+ return ptr_clear_bit(p4dp, PTI_PGTABLE_SWITCH_BIT);
+}
+#endif /* CONFIG_PAGE_TABLE_ISOLATION */
+
+/*
+ * Page table pages are page-aligned. The lower half of the top
+ * level is used for userspace and the top half for the kernel.
+ *
+ * Returns true for parts of the PGD that map userspace and
+ * false for the parts that map the kernel.
+ */
+static inline bool pgdp_maps_userspace(void *__ptr)
+{
+ unsigned long ptr = (unsigned long)__ptr;
+
+ return (ptr & ~PAGE_MASK) < (PAGE_SIZE / 2);
+}
+
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd);
+
+/*
+ * Take a PGD location (pgdp) and a pgd value that needs to be set there.
+ * Populates the user and returns the resulting PGD that must be set in
+ * the kernel copy of the page tables.
+ */
+static inline pgd_t pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
+{
+ if (!static_cpu_has(X86_FEATURE_PTI))
+ return pgd;
+ return __pti_set_user_pgd(pgdp, pgd);
+}
+#else
+static inline pgd_t pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
+{
+ return pgd;
+}
+#endif
+
static inline void native_set_p4d(p4d_t *p4dp, p4d_t p4d)
{
+#if defined(CONFIG_PAGE_TABLE_ISOLATION) && !defined(CONFIG_X86_5LEVEL)
+ p4dp->pgd = pti_set_user_pgd(&p4dp->pgd, p4d.pgd);
+#else
*p4dp = p4d;
+#endif
}
static inline void native_p4d_clear(p4d_t *p4d)
@@ -147,7 +235,11 @@ static inline void native_p4d_clear(p4d_t *p4d)
static inline void native_set_pgd(pgd_t *pgdp, pgd_t pgd)
{
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+ *pgdp = pti_set_user_pgd(pgdp, pgd);
+#else
*pgdp = pgd;
+#endif
}
static inline void native_pgd_clear(pgd_t *pgd)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index a13f6b1098651a2777de81e403ae8e61350df66a..69a983365392961358ddbb719a9ab7fe5f4e2965 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -96,6 +96,47 @@ void __init pti_check_boottime_disable(void)
setup_force_cpu_cap(X86_FEATURE_PTI);
}
+pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
+{
+ /*
+ * Changes to the high (kernel) portion of the kernelmode page
+ * tables are not automatically propagated to the usermode tables.
+ *
+ * Users should keep in mind that, unlike the kernelmode tables,
+ * there is no vmalloc_fault equivalent for the usermode tables.
+ * Top-level entries added to init_mm's usermode pgd after boot
+ * will not be automatically propagated to other mms.
+ */
+ if (!pgdp_maps_userspace(pgdp))
+ return pgd;
+
+ /*
+ * The user page tables get the full PGD, accessible from
+ * userspace:
+ */
+ kernel_to_user_pgdp(pgdp)->pgd = pgd.pgd;
+
+ /*
+ * If this is normal user memory, make it NX in the kernel
+ * pagetables so that, if we somehow screw up and return to
+ * usermode with the kernel CR3 loaded, we'll get a page fault
+ * instead of allowing user code to execute with the wrong CR3.
+ *
+ * As exceptions, we don't set NX if:
+ * - _PAGE_USER is not set. This could be an executable
+ * EFI runtime mapping or something similar, and the kernel
+ * may execute from it
+ * - we don't have NX support
+ * - we're clearing the PGD (i.e. the new pgd is not present).
+ */
+ if ((pgd.pgd & (_PAGE_USER|_PAGE_PRESENT)) == (_PAGE_USER|_PAGE_PRESENT) &&
+ (__supported_pte_mask & _PAGE_NX))
+ pgd.pgd |= _PAGE_NX;
+
+ /* return the copy of the PGD we want the kernel to use: */
+ return pgd;
+}
+
/*
* Initialize kernel page table isolation
*/