selftests/powerpc: Add test for strlen()

This patch adds a test for strlen()

string.c contains a copy of strlen() from lib/string.c

The test first tests the correctness of strlen() by comparing
the result with libc strlen(). It tests all cases of alignment.

It them tests the duration of an aligned strlen() on a 4 bytes string,
on a 16 bytes string and on a 256 bytes string.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Drop change log from copy of string.c]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/stringloops/Makefile

@@ -6,7 +6,7 @@ EXTRA_SOURCES := ../harness.c
 
 build_32bit = $(shell if ($(CC) $(CFLAGS) -m32 -o /dev/null memcmp.c >/dev/null 2>&1) then echo "1"; fi)
 
-TEST_GEN_PROGS := memcmp_64
+TEST_GEN_PROGS := memcmp_64 strlen
 
 $(OUTPUT)/memcmp_64: memcmp.c
 $(OUTPUT)/memcmp_64: CFLAGS += -m64 -maltivec
@@ -18,6 +18,8 @@ $(OUTPUT)/memcmp_32: CFLAGS += -m32
 TEST_GEN_PROGS += memcmp_32
 endif
 
+$(OUTPUT)/strlen: strlen.c string.c
+
 ASFLAGS = $(CFLAGS)
 
 include ../../lib.mk

tools/testing/selftests/powerpc/stringloops/string.c

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copied from linux/lib/string.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+#include <stddef.h>
+
+/**
+ * strlen - Find the length of a string
+ * @s: The string to be sized
+ */
+size_t test_strlen(const char *s)
+{
+	const char *sc;
+
+	for (sc = s; *sc != '\0'; ++sc)
+		/* nothing */;
+	return sc - s;
+}

tools/testing/selftests/powerpc/stringloops/strlen.c

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <malloc.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "utils.h"
+
+#define SIZE 256
+#define ITERATIONS 1000
+#define ITERATIONS_BENCH 100000
+
+int test_strlen(const void *s);
+
+/* test all offsets and lengths */
+static void test_one(char *s)
+{
+	unsigned long offset;
+
+	for (offset = 0; offset < SIZE; offset++) {
+		int x, y;
+		unsigned long i;
+
+		y = strlen(s + offset);
+		x = test_strlen(s + offset);
+
+		if (x != y) {
+			printf("strlen() returned %d, should have returned %d (%p offset %ld)\n", x, y, s, offset);
+
+			for (i = offset; i < SIZE; i++)
+				printf("%02x ", s[i]);
+			printf("\n");
+		}
+	}
+}
+
+static void bench_test(char *s)
+{
+	struct timespec ts_start, ts_end;
+	int i;
+
+	clock_gettime(CLOCK_MONOTONIC, &ts_start);
+
+	for (i = 0; i < ITERATIONS_BENCH; i++)
+		test_strlen(s);
+
+	clock_gettime(CLOCK_MONOTONIC, &ts_end);
+
+	printf("len %3.3d : time = %.6f\n", test_strlen(s), ts_end.tv_sec - ts_start.tv_sec + (ts_end.tv_nsec - ts_start.tv_nsec) / 1e9);
+}
+
+static int testcase(void)
+{
+	char *s;
+	unsigned long i;
+
+	s = memalign(128, SIZE);
+	if (!s) {
+		perror("memalign");
+		exit(1);
+	}
+
+	srandom(1);
+
+	memset(s, 0, SIZE);
+	for (i = 0; i < SIZE; i++) {
+		char c;
+
+		do {
+			c = random() & 0x7f;
+		} while (!c);
+		s[i] = c;
+		test_one(s);
+	}
+
+	for (i = 0; i < ITERATIONS; i++) {
+		unsigned long j;
+
+		for (j = 0; j < SIZE; j++) {
+			char c;
+
+			do {
+				c = random() & 0x7f;
+			} while (!c);
+			s[j] = c;
+		}
+		for (j = 0; j < sizeof(long); j++) {
+			s[SIZE - 1 - j] = 0;
+			test_one(s);
+		}
+	}
+
+	for (i = 0; i < SIZE; i++) {
+		char c;
+
+		do {
+			c = random() & 0x7f;
+		} while (!c);
+		s[i] = c;
+	}
+
+	bench_test(s);
+
+	s[16] = 0;
+	bench_test(s);
+
+	s[8] = 0;
+	bench_test(s);
+
+	s[4] = 0;
+	bench_test(s);
+
+	s[3] = 0;
+	bench_test(s);
+
+	s[2] = 0;
+	bench_test(s);
+
+	s[1] = 0;
+	bench_test(s);
+
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(testcase, "strlen");
+}