+
+#ifdef CONFIG_ARM64_SW_TTBR0_PAN
+ /*
+ * Set the TTBR0 PAN bit in SPSR. When the exception is taken from
+ * EL0, there is no need to check the state of TTBR0_EL1 since
+ * accesses are always enabled.
+ * Note that the meaning of this bit differs from the ARMv8.1 PAN
+ * feature as all TTBR0_EL1 accesses are disabled, not just those to
+ * user mappings.
+ */
+alternative_if ARM64_HAS_PAN
+ b 1f // skip TTBR0 PAN
+alternative_else_nop_endif
+
+ .if \el != 0
+ mrs x21, ttbr0_el1
+ tst x21, #0xffff << 48 // Check for the reserved ASID
+ orr x23, x23, #PSR_PAN_BIT // Set the emulated PAN in the saved SPSR
+ b.eq 1f // TTBR0 access already disabled
+ and x23, x23, #~PSR_PAN_BIT // Clear the emulated PAN in the saved SPSR
+ .endif
+
+ __uaccess_ttbr0_disable x21
+1:
+#endif
+