diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h
index 6da8885251d65d9499fbf5b3cc4491f9ee1170cd..670f14a228e55bb42c4cc516b660f91431a4cb0a 100644
--- a/arch/s390/include/asm/timex.h
+++ b/arch/s390/include/asm/timex.h
@@ -194,9 +194,9 @@ static inline unsigned long long get_tod_clock_monotonic(void)
 {
 	unsigned long long tod;
 
-	preempt_disable();
+	preempt_disable_notrace();
 	tod = get_tod_clock() - *(unsigned long long *) &tod_clock_base[1];
-	preempt_enable();
+	preempt_enable_notrace();
 	return tod;
 }
 
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index 9e1660a6b9db6e49be93e4b145bb639dee52d773..c3597d2e2ae0e2ff57f2d1d3b80f89152968da17 100644
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -35,6 +35,7 @@ EXPORT_SYMBOL(_mcount)
 ENTRY(ftrace_caller)
 	.globl	ftrace_regs_caller
 	.set	ftrace_regs_caller,ftrace_caller
+	stg	%r14,(__SF_GPRS+8*8)(%r15)	# save traced function caller
 	lgr	%r1,%r15
 #if !(defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT))
 	aghi	%r0,MCOUNT_RETURN_FIXUP
diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c
index da2d4d4c5b0e0252186df8d985cf3dafa7fb6994..707fd99f6734d86ca1f037887f6be085b7366a3c 100644
--- a/arch/s390/kernel/unwind_bc.c
+++ b/arch/s390/kernel/unwind_bc.c
@@ -36,10 +36,17 @@ static bool update_stack_info(struct unwind_state *state, unsigned long sp)
 	return true;
 }
 
-static inline bool is_task_pt_regs(struct unwind_state *state,
-				   struct pt_regs *regs)
+static inline bool is_final_pt_regs(struct unwind_state *state,
+				    struct pt_regs *regs)
 {
-	return task_pt_regs(state->task) == regs;
+	/* user mode or kernel thread pt_regs at the bottom of task stack */
+	if (task_pt_regs(state->task) == regs)
+		return true;
+
+	/* user mode pt_regs at the bottom of irq stack */
+	return state->stack_info.type == STACK_TYPE_IRQ &&
+	       state->stack_info.end - sizeof(struct pt_regs) == (unsigned long)regs &&
+	       READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE;
 }
 
 bool unwind_next_frame(struct unwind_state *state)
@@ -80,7 +87,7 @@ bool unwind_next_frame(struct unwind_state *state)
 			if (!on_stack(info, sp, sizeof(struct pt_regs)))
 				goto out_err;
 			regs = (struct pt_regs *) sp;
-			if (is_task_pt_regs(state, regs))
+			if (is_final_pt_regs(state, regs))
 				goto out_stop;
 			ip = READ_ONCE_NOCHECK(regs->psw.addr);
 			sp = READ_ONCE_NOCHECK(regs->gprs[15]);
diff --git a/arch/s390/purgatory/.gitignore b/arch/s390/purgatory/.gitignore
index 04a03433c72013b0bbf5a93bb72b477d0cd2d709..c82157f46b18693cf6ed6272934ed6cb5a205490 100644
--- a/arch/s390/purgatory/.gitignore
+++ b/arch/s390/purgatory/.gitignore
@@ -1,3 +1,4 @@
 purgatory
+purgatory.chk
 purgatory.lds
 purgatory.ro
diff --git a/arch/s390/purgatory/Makefile b/arch/s390/purgatory/Makefile
index bc0d7a0d039453d28464432c2d74994b827b4c1d..c57f8c40e992685812170f3db796256b7e620934 100644
--- a/arch/s390/purgatory/Makefile
+++ b/arch/s390/purgatory/Makefile
@@ -4,7 +4,7 @@ OBJECT_FILES_NON_STANDARD := y
 
 purgatory-y := head.o purgatory.o string.o sha256.o mem.o
 
-targets += $(purgatory-y) purgatory.lds purgatory purgatory.ro
+targets += $(purgatory-y) purgatory.lds purgatory purgatory.chk purgatory.ro
 PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
 
 $(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE
@@ -15,8 +15,10 @@ CFLAGS_sha256.o := -D__DISABLE_EXPORTS
 $(obj)/mem.o: $(srctree)/arch/s390/lib/mem.S FORCE
 	$(call if_changed_rule,as_o_S)
 
-$(obj)/string.o: $(srctree)/arch/s390/lib/string.c FORCE
-	$(call if_changed_rule,cc_o_c)
+KCOV_INSTRUMENT := n
+GCOV_PROFILE := n
+UBSAN_SANITIZE := n
+KASAN_SANITIZE := n
 
 KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes
 KBUILD_CFLAGS += -Wno-pointer-sign -Wno-sign-compare
@@ -26,15 +28,22 @@ KBUILD_CFLAGS += $(CLANG_FLAGS)
 KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
 KBUILD_AFLAGS := $(filter-out -DCC_USING_EXPOLINE,$(KBUILD_AFLAGS))
 
-LDFLAGS_purgatory := -r --no-undefined -nostdlib -z nodefaultlib -T
+# Since we link purgatory with -r unresolved symbols are not checked, so we
+# also link a purgatory.chk binary without -r to check for unresolved symbols.
+PURGATORY_LDFLAGS := -nostdlib -z nodefaultlib
+LDFLAGS_purgatory := -r $(PURGATORY_LDFLAGS) -T
+LDFLAGS_purgatory.chk := -e purgatory_start $(PURGATORY_LDFLAGS)
 $(obj)/purgatory: $(obj)/purgatory.lds $(PURGATORY_OBJS) FORCE
 		$(call if_changed,ld)
 
+$(obj)/purgatory.chk: $(obj)/purgatory FORCE
+		$(call if_changed,ld)
+
 OBJCOPYFLAGS_purgatory.ro := -O elf64-s390
 OBJCOPYFLAGS_purgatory.ro += --remove-section='*debug*'
 OBJCOPYFLAGS_purgatory.ro += --remove-section='.comment'
 OBJCOPYFLAGS_purgatory.ro += --remove-section='.note.*'
-$(obj)/purgatory.ro: $(obj)/purgatory FORCE
+$(obj)/purgatory.ro: $(obj)/purgatory $(obj)/purgatory.chk FORCE
 		$(call if_changed,objcopy)
 
 $(obj)/kexec-purgatory.o: $(obj)/kexec-purgatory.S $(obj)/purgatory.ro FORCE
diff --git a/arch/s390/purgatory/string.c b/arch/s390/purgatory/string.c
new file mode 100644
index 0000000000000000000000000000000000000000..c98c22a72db717834085c4ef00f66475144c780e
--- /dev/null
+++ b/arch/s390/purgatory/string.c
@@ -0,0 +1,3 @@
+// SPDX-License-Identifier: GPL-2.0
+#define __HAVE_ARCH_MEMCMP	/* arch function */
+#include "../lib/string.c"