Index: head/sys/riscv/riscv/genassym.c
===================================================================
--- head/sys/riscv/riscv/genassym.c
+++ head/sys/riscv/riscv/genassym.c
@@ -55,6 +55,7 @@
 #include <machine/cpufunc.h>
 #include <machine/pte.h>
 #include <machine/intr.h>
+#include <machine/machdep.h>
 
 ASSYM(KERNBASE, KERNBASE);
 ASSYM(VM_MAXUSER_ADDRESS, VM_MAXUSER_ADDRESS);
@@ -98,3 +99,5 @@
 ASSYM(TF_STVAL, offsetof(struct trapframe, tf_stval));
 ASSYM(TF_SCAUSE, offsetof(struct trapframe, tf_scause));
 ASSYM(TF_SSTATUS, offsetof(struct trapframe, tf_sstatus));
+
+ASSYM(RISCV_BOOTPARAMS_SIZE, sizeof(struct riscv_bootparams));
Index: head/sys/riscv/riscv/locore.S
===================================================================
--- head/sys/riscv/riscv/locore.S
+++ head/sys/riscv/riscv/locore.S
@@ -188,7 +188,7 @@
 	mv	sp, s3
 
 	/* Allocate space for thread0 PCB and riscv_bootparams */
-	addi	sp, sp, -(PCB_SIZE + 40) & ~STACKALIGNBYTES
+	addi	sp, sp, -(PCB_SIZE + RISCV_BOOTPARAMS_SIZE) & ~STACKALIGNBYTES
 
 	/* Clear BSS */
 	la	s0, _C_LABEL(__bss_start)