From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 16 Apr 2018 12:22:24 +0200
Subject: s390/uprobes: implement arch_uretprobe_is_alive()
Patch-mainline: v4.17-rc3
Git-commit: 783c3b53b9506db3e05daacfe34e0287eebb09d8
References: bnc#1093148, LTC#167307

Implement s390 specific arch_uretprobe_is_alive() to avoid SIGSEGVs
observed with uretprobes in combination with setjmp/longjmp.

See commit 2dea1d9c38e4 ("powerpc/uprobes: Implement
arch_uretprobe_is_alive()") for more details.

With this implemented all test cases referenced in the above commit
pass.

Reported-by: Ziqian SUN <zsun@redhat.com>
Cc: <stable@vger.kernel.org> # v4.3+
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 arch/s390/kernel/uprobes.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/arch/s390/kernel/uprobes.c
+++ b/arch/s390/kernel/uprobes.c
@@ -149,6 +149,15 @@ unsigned long arch_uretprobe_hijack_retu
 	return orig;
 }
 
+bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
+			     struct pt_regs *regs)
+{
+	if (ctx == RP_CHECK_CHAIN_CALL)
+		return user_stack_pointer(regs) <= ret->stack;
+	else
+		return user_stack_pointer(regs) < ret->stack;
+}
+
 /* Instruction Emulation */
 
 static void adjust_psw_addr(psw_t *psw, unsigned long len)