Subject: [PATCH 2/5] selftests/powerpc: Add fork() test to check for spr being preserved

From: Cyril Bur <[email-masked]>
Date: Wed, 23 Mar 2016 16:47:02 +1100

Signed-off-by: Cyril Bur <[email-masked]>
---
 tools/testing/selftests/powerpc/syscalls/Makefile  |  3 +-
 .../testing/selftests/powerpc/syscalls/spr_fork.c  | 78 ++++++++++++++++++++++
 2 files changed, 80 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/powerpc/syscalls/spr_fork.c

diff --git a/tools/testing/selftests/powerpc/syscalls/Makefile b/tools/testing/selftests/powerpc/syscalls/Makefile
index 291ba45..55969f3 100644
--- a/tools/testing/selftests/powerpc/syscalls/Makefile
+++ b/tools/testing/selftests/powerpc/syscalls/Makefile
@@ -1,4 +1,4 @@
-TEST_PROGS := ipc_unmuxed spr_exec
+TEST_PROGS := ipc_unmuxed spr_exec spr_fork
 
 CFLAGS += -I../../../../../usr/include
 
@@ -6,6 +6,7 @@ all: $(TEST_PROGS)
 
 $(TEST_PROGS): ../harness.c
 spr_exec: ../utils.c
+spr_fork: ../utils.c
 
 include ../../lib.mk
 
diff --git a/tools/testing/selftests/powerpc/syscalls/spr_fork.c b/tools/testing/selftests/powerpc/syscalls/spr_fork.c
new file mode 100644
index 0000000..1a351a6
--- /dev/null
+++ b/tools/testing/selftests/powerpc/syscalls/spr_fork.c
@@ -0,0 +1,78 @@
+/*
+ * Copyright 2016, Cyril Bur, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * This test checks that the TAR register (an SPR) is correctly preserved
+ * across a fork()
+ */
+#include <asm/cputable.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/auxv.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "utils.h"
+
+static int fork_spr(void)
+{
+	int child_ret;
+	unsigned long tar;
+	pid_t pid;
+	int i;
+
+
+	/* Do it a few times as there is a chance that one might luckily pass */
+	i = 0;
+	while (i < 10) {
+		/* What are the odds... */
+		tar = 0x123456;
+		asm __volatile__(
+				"mtspr 815, %[tar]"
+				:
+				: [tar] "r" (tar)
+				);
+
+		pid = fork();
+		FAIL_IF(pid == -1);
+		asm __volatile__(
+				"mfspr %[tar], 815"
+				: [tar] "=r" (tar)
+				);
+
+		FAIL_IF(tar != 0x123456);
+
+		if (pid == 0)
+			exit(0);
+
+		FAIL_IF(waitpid(pid, &child_ret, 0) == -1);
+
+		/* Child haddn't exited ? */
+		FAIL_IF(!WIFEXITED(child_ret));
+
+		/* Child detected a bad tar */
+		FAIL_IF(WEXITSTATUS(child_ret));
+
+		/* Reset it */
+		tar = 0;
+		asm __volatile__(
+				"mtspr 815, %[tar]"
+				:
+				: [tar] "r" (tar)
+				);
+
+		i++;
+	}
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	SKIP_IF(!have_hwcap2(PPC_FEATURE2_TAR));
+	return test_harness(fork_spr, "spr_fork");
+}
-- 
2.7.4