From 2317b07d05d2b136eb4dc9609807c9111bda3b2a Mon Sep 17 00:00:00 2001
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Fri, 20 Apr 2018 10:21:21 +0200
Subject: [PATCH] s390: update sampling tag after task pid change

In a multi-threaded program any thread can call execve(). If this
is not done by the thread group leader, the de_thread() function
replaces the pid of the task that calls execve() with the pid of
thread group leader. If the task reaches user space again without
going over __switch_to() the sampling tag is still set to the old
pid.

Define the arch_setup_new_exec function to verify the task pid
and udpate the tag with LPP if it has changed.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 arch/s390/include/asm/thread_info.h |  3 +++
 arch/s390/kernel/process.c          | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index 83ba575..3c883c3 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -45,6 +45,9 @@ struct thread_info {
 void arch_release_task_struct(struct task_struct *tsk);
 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 
+void arch_setup_new_exec(void);
+#define arch_setup_new_exec arch_setup_new_exec
+
 #endif
 
 /*
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 70576a2..6e758bb 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -29,6 +29,7 @@
 #include <linux/random.h>
 #include <linux/export.h>
 #include <linux/init_task.h>
+#include <asm/cpu_mf.h>
 #include <asm/io.h>
 #include <asm/processor.h>
 #include <asm/vtimer.h>
@@ -48,6 +49,15 @@ void flush_thread(void)
 {
 }
 
+void arch_setup_new_exec(void)
+{
+	if (S390_lowcore.current_pid != current->pid) {
+		S390_lowcore.current_pid = current->pid;
+		if (test_facility(40))
+			lpp(&S390_lowcore.lpp);
+	}
+}
+
 void arch_release_task_struct(struct task_struct *tsk)
 {
 	runtime_instr_release(tsk);
-- 
2.7.4