5 files changed, 129 insertions, 0 deletions
diff --git a/tools/testing/selftests/powerpc/Makefile b/tools/testing/selftests/powerpc/Makefile
index b08f77cbe31b..4ca83fe80654 100644
--- a/tools/testing/selftests/powerpc/Makefile
+++ b/tools/testing/selftests/powerpc/Makefile
@@ -14,6 +14,7 @@ export CFLAGS
 
 SUB_DIRS = benchmarks 		\
 	   copyloops		\
+	   context_switch	\
 	   dscr			\
 	   mm			\
 	   pmu			\
diff --git a/tools/testing/selftests/powerpc/context_switch/.gitignore b/tools/testing/selftests/powerpc/context_switch/.gitignore
new file mode 100644
index 000000000000..c1431af7b51c
--- /dev/null
+++ b/tools/testing/selftests/powerpc/context_switch/.gitignore
@@ -0,0 +1 @@
+cp_abort
diff --git a/tools/testing/selftests/powerpc/context_switch/Makefile b/tools/testing/selftests/powerpc/context_switch/Makefile
new file mode 100644
index 000000000000..e164d1466466
--- /dev/null
+++ b/tools/testing/selftests/powerpc/context_switch/Makefile
@@ -0,0 +1,10 @@
+TEST_PROGS := cp_abort
+
+all: $(TEST_PROGS)
+
+$(TEST_PROGS): ../harness.c ../utils.c
+
+include ../../lib.mk
+
+clean:
+	rm -f $(TEST_PROGS)
diff --git a/tools/testing/selftests/powerpc/context_switch/cp_abort.c b/tools/testing/selftests/powerpc/context_switch/cp_abort.c
new file mode 100644
index 000000000000..5a5b55afda0e
--- /dev/null
+++ b/tools/testing/selftests/powerpc/context_switch/cp_abort.c
@@ -0,0 +1,110 @@
+/*
+ * Adapted from Anton Blanchard's context switch microbenchmark.
+ *
+ * Copyright 2009, Anton Blanchard, IBM Corporation.
+ * Copyright 2016, Mikey Neuling, Chris Smart, IBM Corporation.
+ *
+ * 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 program tests the copy paste abort functionality of a P9
+ * (or later) by setting up two processes on the same CPU, one
+ * which executes the copy instruction and the other which
+ * executes paste.
+ *
+ * The paste instruction should never succeed, as the cp_abort
+ * instruction is called by the kernel during a context switch.
+ *
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include "utils.h"
+#include <sched.h>
+
+#define READ_FD 0
+#define WRITE_FD 1
+
+#define NUM_LOOPS 1000
+
+/* This defines the "paste" instruction from Power ISA 3.0 Book II, section 4.4. */
+#define PASTE(RA, RB, L, RC) \
+	.long (0x7c00070c | (RA) << (31-15) | (RB) << (31-20) | (L) << (31-10) | (RC) << (31-31))
+
+int paste(void *i)
+{
+	int cr;
+
+	asm volatile(str(PASTE(0, %1, 1, 1))";"
+			"mfcr %0;"
+			: "=r" (cr)
+			: "b" (i)
+			: "memory"
+		    );
+	return cr;
+}
+
+/* This defines the "copy" instruction from Power ISA 3.0 Book II, section 4.4. */
+#define COPY(RA, RB, L) \
+	.long (0x7c00060c | (RA) << (31-15) | (RB) << (31-20) | (L) << (31-10))
+
+void copy(void *i)
+{
+	asm volatile(str(COPY(0, %0, 1))";"
+			:
+			: "b" (i)
+			: "memory"
+		    );
+}
+
+int test_cp_abort(void)
+{
+	/* 128 bytes for a full cache line */
+	char buf[128] __cacheline_aligned;
+	cpu_set_t cpuset;
+	int fd1[2], fd2[2], pid;
+	char c;
+
+	/* only run this test on a P9 or later */
+	SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_3_00));
+
+	/*
+	 * Run both processes on the same CPU, so that copy is more likely
+	 * to leak into a paste.
+	 */
+	CPU_ZERO(&cpuset);
+	CPU_SET(pick_online_cpu(), &cpuset);
+	FAIL_IF(sched_setaffinity(0, sizeof(cpuset), &cpuset));
+
+	FAIL_IF(pipe(fd1) || pipe(fd2));
+
+	pid = fork();
+	FAIL_IF(pid < 0);
+
+	if (!pid) {
+		for (int i = 0; i < NUM_LOOPS; i++) {
+			FAIL_IF((write(fd1[WRITE_FD], &c, 1)) != 1);
+			FAIL_IF((read(fd2[READ_FD], &c, 1)) != 1);
+			/* A paste succeeds if CR0 EQ bit is set */
+			FAIL_IF(paste(buf) & 0x20000000);
+		}
+	} else {
+		for (int i = 0; i < NUM_LOOPS; i++) {
+			FAIL_IF((read(fd1[READ_FD], &c, 1)) != 1);
+			copy(buf);
+			FAIL_IF((write(fd2[WRITE_FD], &c, 1) != 1));
+		}
+	}
+	return 0;
+
+}
+
+int main(int argc, char *argv[])
+{
+	return test_harness(test_cp_abort, "cp_abort");
+}
diff --git a/tools/testing/selftests/powerpc/utils.h b/tools/testing/selftests/powerpc/utils.h
index 175ac6ad10dd..3b370deafb62 100644
--- a/tools/testing/selftests/powerpc/utils.h
+++ b/tools/testing/selftests/powerpc/utils.h
@@ -6,6 +6,8 @@
 #ifndef _SELFTESTS_POWERPC_UTILS_H
 #define _SELFTESTS_POWERPC_UTILS_H
 
+#define __cacheline_aligned __attribute__((aligned(128)))
+
 #include <stdint.h>
 #include <stdbool.h>
 #include <linux/auxvec.h>
@@ -54,4 +56,9 @@ do {								\
 #define _str(s) #s
 #define str(s) _str(s)
 
+/* POWER9 feature */
+#ifndef PPC_FEATURE2_ARCH_3_00
+#define PPC_FEATURE2_ARCH_3_00 0x00800000
+#endif
+
 #endif /* _SELFTESTS_POWERPC_UTILS_H */