diff --git a/lib/Makefile b/lib/Makefile
index 2eac42a8b96a..ad9a768817ed 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -112,7 +112,7 @@ SUBDIR=	${SUBDIR_BOOTSTRAP} \
 	ncurses \
 	nss_tacplus
 
-.if ${MACHINE_ABI:Mpurecap} && ${MACHINE_CPUARCH} == "aarch64"
+.if ${MACHINE_ABI:Mpurecap} && (${MACHINE_CPUARCH} == "aarch64" || ${MACHINE_CPUARCH} == "riscv")
 .if !defined(COMPAT_LIBCOMPAT) || ${COMPAT_LIBCOMPAT} == "64CB"
 SUBDIR+=	c18n
 .endif
diff --git a/lib/libc/riscv/gen/_setjmp.S b/lib/libc/riscv/gen/_setjmp.S
index 050113cb0e26..0d22ae268167 100644
--- a/lib/libc/riscv/gen/_setjmp.S
+++ b/lib/libc/riscv/gen/_setjmp.S
@@ -80,8 +80,19 @@ ENTRY(_setjmp)
 #endif
 
 	/* Return value */
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	cmove	ca1, ca0
+#endif
 	li	a0, 0
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	/*
+	 * Tail-call to save trusted stack state
+	 */
+	clgc	ct0, _C_LABEL(c18n_get_trusted_stk)
+	cjr	ct0
+#else
 	cret
+#endif
 #else
 	/* Store the magic value and stack pointer */
 	ld	t0, .Lmagic
@@ -140,7 +151,11 @@ ENTRY(_longjmp)
 	bne	t0, t1, botch
 
 	/* Restore the stack pointer */
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	clc	ca3, 16(ca0)
+#else
 	clc	csp, 16(ca0)
+#endif
 	cincoffset ca0, ca0, (2 * 16)
 
 	/* Restore the general purpose registers and ra */
@@ -179,8 +194,20 @@ ENTRY(_longjmp)
 #endif
 
 	/* Load the return value */
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	clc	ca2, 0(ca0)
+#endif
 	mv	a0, a1
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	cmove	ca1, ca3
+	/*
+	 * Tail-call to restore trusted stack state
+	 */
+	clgc	ct0, _C_LABEL(c18n_unwind_trusted_stk)
+	cjr	ct0
+#else
 	cret
+#endif
 #else
 	/* Check the magic value */
 	ld	t0, 0(a0)
diff --git a/lib/libc/riscv/gen/setjmp.S b/lib/libc/riscv/gen/setjmp.S
index 672f7f50482b..7421f2cf99ea 100644
--- a/lib/libc/riscv/gen/setjmp.S
+++ b/lib/libc/riscv/gen/setjmp.S
@@ -35,6 +35,11 @@
 #include <machine/asm.h>
 #include <machine/setjmp.h>
 
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+.weak _rtld_setjmp
+.weak _rtld_longjmp
+#endif
+
 ENTRY(setjmp)
 #ifdef __CHERI_PURE_CAPABILITY__
 	cincoffset csp, csp, -(2 * 16)
@@ -95,8 +100,19 @@ ENTRY(setjmp)
 #endif
 
 	/* Return value */
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	cmove	ca1, ca0
+#endif
 	li	a0, 0
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	/*
+	 * Tail-call to save trusted stack state
+	 */
+	clgc	ct0, _C_LABEL(c18n_get_trusted_stk)
+	cjr	ct0
+#else
 	cret
+#endif
 #else
 	addi	sp, sp, -(2 * 8)
 	sd	a0, 0(sp)
@@ -186,7 +202,11 @@ ENTRY(longjmp)
 	cincoffset csp, csp, (3 * 16)
 
 	/* Restore the stack pointer */
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	clc	ca3, 16(ca0)
+#else
 	clc	csp, 16(ca0)
+#endif
 	cincoffset ca0, ca0, (2 * 16)
 
 	/* Restore the general purpose registers and ra */
@@ -225,8 +245,20 @@ ENTRY(longjmp)
 #endif
 
 	/* Load the return value */
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	clc	ca2, 0(ca0)
+#endif
 	mv	a0, a1
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(CHERI_LIB_C18N)
+	cmove	ca1, ca3
+	/*
+	 * Tail-call to restore trusted stack state
+	 */
+	clgc	ct0, _C_LABEL(c18n_unwind_trusted_stk)
+	cjr	ct0
+#else
 	cret
+#endif
 
 botch:
 	clgc	ct0, _C_LABEL(longjmperror)
diff --git a/lib/libsys/riscv/Makefile.sys b/lib/libsys/riscv/Makefile.sys
index 2ff84735f484..5cfd48643944 100644
--- a/lib/libsys/riscv/Makefile.sys
+++ b/lib/libsys/riscv/Makefile.sys
@@ -1,5 +1,8 @@
 SRCS+=	__vdso_gettc.c \
 	sched_getcpu_gen.c
 
-MDASM=	cerror.S \
-	vfork.S
+MDASM=	cerror.S
+
+.ifndef CHERI_LIB_C18N
+MDASM+=	vfork.S
+.endif