[SRU][Bionic][PATCH 1/1] s390/uprobes: implement arch_uretprobe_is_alive()

[Joseph Salisbury]

From: Heiko Carstens <heiko.carstens at de.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1777840

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 at redhat.com>
Cc: <stable at vger.kernel.org> # v4.3+
Signed-off-by: Heiko Carstens <heiko.carstens at de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky at de.ibm.com>
(cherry picked from commit 783c3b53b9506db3e05daacfe34e0287eebb09d8)
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 arch/s390/kernel/uprobes.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/s390/kernel/uprobes.c b/arch/s390/kernel/uprobes.c
index d9d1f51..5007fac 100644
--- a/arch/s390/kernel/uprobes.c
+++ b/arch/s390/kernel/uprobes.c
@@ -150,6 +150,15 @@ unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline,
 	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)
-- 
2.7.4