morello: Ensure that trapframe_set_elr sets SPRS when using the bench…

…mark ABI.

In a benchmark ABI kernel, the elr argument will not have the LSB set.
Assume that all kernel addresses ever passed to trapframe_set_elr
use the C64 encoding and artificially set it.
In practice, this is only used by the pcb_onfault and generic_bs_fault.

sys/arm64/include/cheric.h

@@ -28,6 +28,8 @@
 #ifndef _MACHINE_CHERIC_H_
 #define	_MACHINE_CHERIC_H_
 
+#include <machine/vmparam.h>
+
 #if __has_feature(capabilities) && defined(_KERNEL)
 /*
  * ERET in Morello does not use the LSB of the saved elr to set
@@ -44,6 +46,13 @@ trapframe_set_elr(struct trapframe *tf, uintcap_t elr)
 	if (cheri_getsealed(elr))
 		elr = cheri_unseal(elr, sentry_unsealcap);
 
+#ifdef __ARM_MORELLO_PURECAP_BENCHMARK_ABI
+	/* Assume that kernel ELR addresses are C64 */
+	if (elr > VM_MAXUSER_ADDRESS) {
+		elr |= 1;
+	}
+#endif
+
 	if (elr & 0x1) {
 		tf->tf_spsr |= PSR_C64;
 		--elr;