arm64: add encodings of PIRx_ELx registers

The encodings used in the permission indirection registers means that the
values that Linux puts in the PTEs do not need to be changed.

The E0 values are replicated in E1, with the execute permissions removed.
This is needed as the futex operations access user mappings with privileged
loads/stores.

Signed-off-by: Joey Gouly <[email protected]>
Cc: Will Deacon <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

Author: jgouly

arch/arm64/include/asm/pgtable-hwdef.h

@@ -170,6 +170,14 @@
 #define PTE_ATTRINDX(t)		(_AT(pteval_t, (t)) << 2)
 #define PTE_ATTRINDX_MASK	(_AT(pteval_t, 7) << 2)
 
+/*
+ * PIIndex[3:0] encoding (Permission Indirection Extension)
+ */
+#define PTE_PI_IDX_0	6	/* AP[1], USER */
+#define PTE_PI_IDX_1	51	/* DBM */
+#define PTE_PI_IDX_2	53	/* PXN */
+#define PTE_PI_IDX_3	54	/* UXN */
+
 /*
  * Memory Attribute override for Stage-2 (MemAttr[3:0])
  */

arch/arm64/include/asm/pgtable-prot.h

@@ -107,4 +107,54 @@ extern bool arm64_use_ng_mappings;
 
 #endif /* __ASSEMBLY__ */
 
+#define pte_pi_index(pte) ( \
+	((pte & BIT(PTE_PI_IDX_3)) >> (PTE_PI_IDX_3 - 3)) | \
+	((pte & BIT(PTE_PI_IDX_2)) >> (PTE_PI_IDX_2 - 2)) | \
+	((pte & BIT(PTE_PI_IDX_1)) >> (PTE_PI_IDX_1 - 1)) | \
+	((pte & BIT(PTE_PI_IDX_0)) >> (PTE_PI_IDX_0 - 0)))
+
+/*
+ * Page types used via Permission Indirection Extension (PIE). PIE uses
+ * the USER, DBM, PXN and UXN bits to to generate an index which is used
+ * to look up the actual permission in PIR_ELx and PIRE0_EL1. We define
+ * combinations we use on non-PIE systems with the same encoding, for
+ * convenience these are listed here as comments as are the unallocated
+ * encodings.
+ */
+
+/* 0: PAGE_DEFAULT                                                  */
+/* 1:                                                      PTE_USER */
+/* 2:                                          PTE_WRITE            */
+/* 3:                                          PTE_WRITE | PTE_USER */
+/* 4: PAGE_EXECONLY                  PTE_PXN                        */
+/* 5: PAGE_READONLY_EXEC             PTE_PXN |             PTE_USER */
+/* 6:                                PTE_PXN | PTE_WRITE            */
+/* 7: PAGE_SHARED_EXEC               PTE_PXN | PTE_WRITE | PTE_USER */
+/* 8: PAGE_KERNEL_ROX      PTE_UXN                                  */
+/* 9:                      PTE_UXN |                       PTE_USER */
+/* a: PAGE_KERNEL_EXEC     PTE_UXN |           PTE_WRITE            */
+/* b:                      PTE_UXN |           PTE_WRITE | PTE_USER */
+/* c: PAGE_KERNEL_RO       PTE_UXN | PTE_PXN                        */
+/* d: PAGE_READONLY        PTE_UXN | PTE_PXN |             PTE_USER */
+/* e: PAGE_KERNEL          PTE_UXN | PTE_PXN | PTE_WRITE            */
+/* f: PAGE_SHARED          PTE_UXN | PTE_PXN | PTE_WRITE | PTE_USER */
+
+#define PIE_E0	( \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_EXECONLY),      PIE_X_O) | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY_EXEC), PIE_RX)  | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED_EXEC),   PIE_RWX) | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY),      PIE_R)   | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED),        PIE_RW))
+
+#define PIE_E1	( \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_EXECONLY),      PIE_NONE_O) | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY_EXEC), PIE_R)      | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED_EXEC),   PIE_RW)     | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY),      PIE_R)      | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED),        PIE_RW)     | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL_ROX),    PIE_RX)     | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL_EXEC),   PIE_RWX)    | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL_RO),     PIE_R)      | \
+	PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL),        PIE_RW))
+
 #endif /* __ASM_PGTABLE_PROT_H */