selftests/powerpc: Add {read,write}_{long,ulong}

Add helper functions to read and write (unsigned) long values directly
from/to files. One of the kernel interfaces uses hex strings, so we need
to allow passing a base too.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230203003947.38033-5-bgray@linux.ibm.com

tools/testing/selftests/powerpc/dscr/dscr.h

@@ -65,26 +65,21 @@ inline void set_dscr_usr(unsigned long val)
 unsigned long get_default_dscr(void)
 {
 	int err;
-	char buf[16] = {0};
 	unsigned long val;
 
-	err = read_file(DSCR_DEFAULT, buf, sizeof(buf) - 1, NULL);
+	err = read_ulong(DSCR_DEFAULT, &val, 16);
 	if (err) {
 		perror("read() failed");
 		exit(1);
 	}
-	sscanf(buf, "%lx", &val);
 	return val;
 }
 
 void set_default_dscr(unsigned long val)
 {
 	int err;
-	char buf[16];
 
-	sprintf(buf, "%lx\n", val);
-
-	err = write_file(DSCR_DEFAULT, buf, strlen(buf));
+	err = write_ulong(DSCR_DEFAULT, val, 16);
 	if (err) {
 		perror("write() failed");
 		exit(1);

tools/testing/selftests/powerpc/dscr/dscr_sysfs_test.c

@@ -12,16 +12,16 @@
 
 static int check_cpu_dscr_default(char *file, unsigned long val)
 {
-	char buf[10] = {0};
-	int rc;
+	unsigned long cpu_dscr;
+	int err;
 
-	rc = read_file(file, buf, sizeof(buf) - 1, NULL);
-	if (rc)
-		return rc;
+	err = read_ulong(file, &cpu_dscr, 16);
+	if (err)
+		return err;
 
-	if (strtol(buf, NULL, 16) != val) {
+	if (cpu_dscr != val) {
 		printf("DSCR match failed: %ld (system) %ld (cpu)\n",
-					val, strtol(buf, NULL, 16));
+					val, cpu_dscr);
 		return 1;
 	}
 	return 0;

tools/testing/selftests/powerpc/include/utils.h

@@ -42,6 +42,10 @@ int parse_ulong(const char *buffer, size_t count, unsigned long *result, int bas
 
 int read_file(const char *path, char *buf, size_t count, size_t *len);
 int write_file(const char *path, const char *buf, size_t count);
+int read_long(const char *path, long *result, int base);
+int write_long(const char *path, long result, int base);
+int read_ulong(const char *path, unsigned long *result, int base);
+int write_ulong(const char *path, unsigned long result, int base);
 int read_debugfs_file(const char *debugfs_file, char *buf, size_t count);
 int write_debugfs_file(const char *debugfs_file, const char *buf, size_t count);
 int read_debugfs_int(const char *debugfs_file, int *result);

tools/testing/selftests/powerpc/pmu/lib.c

@@ -192,15 +192,8 @@ bool require_paranoia_below(int level)
 {
 	int err;
 	long current;
-	char buf[16] = {0};
 
-	err = read_file(PARANOID_PATH, buf, sizeof(buf) - 1, NULL);
-	if (err) {
-		printf("Couldn't read " PARANOID_PATH "?\n");
-		return false;
-	}
-
-	err = parse_long(buf, sizeof(buf), &current, 10);
+	err = read_long(PARANOID_PATH, &current, 10);
 	if (err) {
 		printf("Couldn't parse " PARANOID_PATH "?\n");
 		return false;

tools/testing/selftests/powerpc/utils.c

@@ -245,6 +245,87 @@ int parse_ulong(const char *buffer, size_t count, unsigned long *result, int bas
 	return err;
 }
 
+int read_long(const char *path, long *result, int base)
+{
+	int err;
+	char buffer[32] = {0};
+
+	err = read_file(path, buffer, sizeof(buffer) - 1, NULL);
+	if (err)
+		return err;
+
+	return parse_long(buffer, sizeof(buffer), result, base);
+}
+
+int read_ulong(const char *path, unsigned long *result, int base)
+{
+	int err;
+	char buffer[32] = {0};
+
+	err = read_file(path, buffer, sizeof(buffer) - 1, NULL);
+	if (err)
+		return err;
+
+	return parse_ulong(buffer, sizeof(buffer), result, base);
+}
+
+int write_long(const char *path, long result, int base)
+{
+	int err;
+	int len;
+	char buffer[32];
+
+	/* Decimal only for now: no format specifier for signed hex values */
+	if (base != 10) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	len = snprintf(buffer, sizeof(buffer), "%ld", result);
+	if (len < 0 || len >= sizeof(buffer)) {
+		err = -EOVERFLOW;
+		goto out;
+	}
+
+	err = write_file(path, buffer, len);
+
+out:
+	errno = -err;
+	return err;
+}
+
+int write_ulong(const char *path, unsigned long result, int base)
+{
+	int err;
+	int len;
+	char buffer[32];
+	char *fmt;
+
+	switch (base) {
+	case 10:
+		fmt = "%lu";
+		break;
+	case 16:
+		fmt = "%lx";
+		break;
+	default:
+		err = -EINVAL;
+		goto out;
+	}
+
+	len = snprintf(buffer, sizeof(buffer), fmt, result);
+	if (len < 0 || len >= sizeof(buffer)) {
+		err = -errno;
+		goto out;
+	}
+
+	err = write_file(path, buffer, len);
+
+out:
+	errno = -err;
+	return err;
+}
+
 void *find_auxv_entry(int type, char *auxv)
 {
 	ElfW(auxv_t) *p;