[PATCH v2 1/4] powerpc test_emulate_step: enhancement to test negative scenarios

[Balamuruhan S <bala24@linux.ibm.com>]

add provision to declare test is a negative scenario, verify
whether emulation fails and avoid executing it.

Signed-off-by: Balamuruhan S <bala24@linux.ibm.com>
---
 arch/powerpc/lib/test_emulate_step.c | 30 +++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/lib/test_emulate_step.c b/arch/powerpc/lib/test_emulate_step.c
index 0ca2b7cc8d8c..7c30a69c174f 100644
--- a/arch/powerpc/lib/test_emulate_step.c
+++ b/arch/powerpc/lib/test_emulate_step.c
@@ -118,6 +118,7 @@
 #define IGNORE_GPR(n)	(0x1UL << (n))
 #define IGNORE_XER	(0x1UL << 32)
 #define IGNORE_CCR	(0x1UL << 33)
+#define NEGATIVE_TEST	(0x1UL << 63)
 
 static void __init init_pt_regs(struct pt_regs *regs)
 {
@@ -1202,8 +1203,10 @@ static struct compute_test compute_tests[] = {
 };
 
 static int __init emulate_compute_instr(struct pt_regs *regs,
-					struct ppc_inst instr)
+					struct ppc_inst instr,
+					bool negative)
 {
+	int analysed;
 	extern s32 patch__exec_instr;
 	struct instruction_op op;
 
@@ -1212,13 +1215,17 @@ static int __init emulate_compute_instr(struct pt_regs *regs,
 
 	regs->nip = patch_site_addr(&patch__exec_instr);
 
-	if (analyse_instr(&op, regs, instr) != 1 ||
-	    GETTYPE(op.type) != COMPUTE) {
-		pr_info("execution failed, instruction = %s\n", ppc_inst_as_str(instr));
+	analysed = analyse_instr(&op, regs, instr);
+	if (analysed != 1 || GETTYPE(op.type) != COMPUTE) {
+		if (negative)
+			return -EFAULT;
+		pr_info("emulation failed, instruction = %s\n", ppc_inst_as_str(instr));
 		return -EFAULT;
 	}
-
-	emulate_update_regs(regs, &op);
+	if (analysed == 1 && negative)
+		pr_info("negative test failed, instruction = %s\n", ppc_inst_as_str(instr));
+	if (!negative)
+		emulate_update_regs(regs, &op);
 	return 0;
 }
 
@@ -1256,7 +1263,7 @@ static void __init run_tests_compute(void)
 	struct pt_regs *regs, exp, got;
 	unsigned int i, j, k;
 	struct ppc_inst instr;
-	bool ignore_gpr, ignore_xer, ignore_ccr, passed;
+	bool ignore_gpr, ignore_xer, ignore_ccr, passed, rc, negative;
 
 	for (i = 0; i < ARRAY_SIZE(compute_tests); i++) {
 		test = &compute_tests[i];
@@ -1270,6 +1277,7 @@ static void __init run_tests_compute(void)
 			instr = test->subtests[j].instr;
 			flags = test->subtests[j].flags;
 			regs = &test->subtests[j].regs;
+			negative = flags & NEGATIVE_TEST;
 			ignore_xer = flags & IGNORE_XER;
 			ignore_ccr = flags & IGNORE_CCR;
 			passed = true;
@@ -1284,8 +1292,12 @@ static void __init run_tests_compute(void)
 			exp.msr = MSR_KERNEL;
 			got.msr = MSR_KERNEL;
 
-			if (emulate_compute_instr(&got, instr) ||
-			    execute_compute_instr(&exp, instr)) {
+			rc = emulate_compute_instr(&got, instr, negative) != 0;
+			if (negative) {
+				/* skip executing instruction */
+				passed = rc;
+				goto print;
+			} else if (rc || execute_compute_instr(&exp, instr)) {
 				passed = false;
 				goto print;
 			}
-- 
2.24.1