selftests/powerpc: Add TM test to check if TAR is corrupted

If the transaction is aborted, the TAR should be rolled back to the
checkpointed value before the transaction began. The value written to the
TAR when the transaction is suspended should only remain there if the
transaction completes successfully.

Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/tm/.gitignore

@@ -4,3 +4,4 @@ tm-signal-msr-resv
 tm-signal-stack
 tm-vmxcopy
 tm-fork
+tm-tar

tools/testing/selftests/powerpc/tm/Makefile

@@ -1,4 +1,4 @@
-TEST_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack tm-vmxcopy tm-fork
+TEST_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack tm-vmxcopy tm-fork tm-tar
 
 all: $(TEST_PROGS)
 

tools/testing/selftests/powerpc/tm/tm-tar.c

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2015, Michael Neuling, IBM Corp.
+ * Licensed under GPLv2.
+ * Original: Michael Neuling 19/7/2013
+ * Edited: Rashmica Gupta 01/12/2015
+ *
+ * Do some transactions, see if the tar is corrupted.
+ * If the transaction is aborted, the TAR should be rolled back to the
+ * checkpointed value before the transaction began. The value written to
+ * TAR in suspended mode should only remain in TAR if the transaction
+ * completes.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "tm.h"
+#include "utils.h"
+
+int	num_loops	= 10000;
+
+int test_tar(void)
+{
+	int i;
+
+	SKIP_IF(!have_htm());
+
+	for (i = 0; i < num_loops; i++)
+	{
+		uint64_t result = 0;
+		asm __volatile__(
+			"li	7, 1;"
+			"mtspr	%[tar], 7;"	/* tar = 1 */
+			"tbegin.;"
+			"beq	3f;"
+			"li	4, 0x7000;"	/* Loop lots, to use time */
+			"2:;"			/* Start loop */
+			"li	7, 2;"
+			"mtspr	%[tar], 7;"	/* tar = 2 */
+			"tsuspend.;"
+			"li	7, 3;"
+			"mtspr	%[tar], 7;"	/* tar = 3 */
+			"tresume.;"
+			"subi	4, 4, 1;"
+			"cmpdi	4, 0;"
+			"bne	2b;"
+			"tend.;"
+
+			/* Transaction sucess! TAR should be 3 */
+			"mfspr  7, %[tar];"
+			"ori	%[res], 7, 4;"  // res = 3|4 = 7
+			"b	4f;"
+
+			/* Abort handler. TAR should be rolled back to 1 */
+			"3:;"
+			"mfspr  7, %[tar];"
+			"ori	%[res], 7, 8;"	// res = 1|8 = 9
+			"4:;"
+
+			: [res]"=r"(result)
+			: [tar]"i"(SPRN_TAR)
+			   : "memory", "r0", "r4", "r7");
+
+		/* If result is anything else other than 7 or 9, the tar
+		 * value must have been corrupted. */
+		if ((result != 7) && (result != 9))
+			return 1;
+	}
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	/* A low number of iterations (eg 100) can cause a false pass */
+	if (argc > 1) {
+		if (strcmp(argv[1], "-h") == 0) {
+			printf("Syntax:\n\t%s [<num loops>]\n",
+			       argv[0]);
+			return 1;
+		} else {
+			num_loops = atoi(argv[1]);
+		}
+	}
+
+	printf("Starting, %d loops\n", num_loops);
+
+	return test_harness(test_tar, "tm_tar");
+}