selftests/powerpc: Add generic read/write file util

File read/write is reimplemented in about 5 different ways in the
various PowerPC selftests. This indicates it should be a common util.

Add a common read_file / write_file implementation and convert users
to it where (easily) possible.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230203003947.38033-2-bgray@linux.ibm.com

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

@@ -64,48 +64,31 @@ inline void set_dscr_usr(unsigned long val)
 /* Default DSCR access */
 unsigned long get_default_dscr(void)
 {
-	int fd = -1, ret;
-	char buf[16];
+	int err;
+	char buf[16] = {0};
 	unsigned long val;
 
-	if (fd == -1) {
-		fd = open(DSCR_DEFAULT, O_RDONLY);
-		if (fd == -1) {
-			perror("open() failed");
-			exit(1);
-		}
-	}
-	memset(buf, 0, sizeof(buf));
-	lseek(fd, 0, SEEK_SET);
-	ret = read(fd, buf, sizeof(buf));
-	if (ret == -1) {
+	err = read_file(DSCR_DEFAULT, buf, sizeof(buf) - 1, NULL);
+	if (err) {
 		perror("read() failed");
 		exit(1);
 	}
 	sscanf(buf, "%lx", &val);
-	close(fd);
 	return val;
 }
 
 void set_default_dscr(unsigned long val)
 {
-	int fd = -1, ret;
+	int err;
 	char buf[16];
 
-	if (fd == -1) {
-		fd = open(DSCR_DEFAULT, O_RDWR);
-		if (fd == -1) {
-			perror("open() failed");
-			exit(1);
-		}
-	}
 	sprintf(buf, "%lx\n", val);
-	ret = write(fd, buf, strlen(buf));
-	if (ret == -1) {
+
+	err = write_file(DSCR_DEFAULT, buf, strlen(buf));
+	if (err) {
 		perror("write() failed");
 		exit(1);
 	}
-	close(fd);
 }
 
 double uniform_deviate(int seed)

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

@@ -12,24 +12,13 @@
 
 static int check_cpu_dscr_default(char *file, unsigned long val)
 {
-	char buf[10];
-	int fd, rc;
+	char buf[10] = {0};
+	int rc;
 
-	fd = open(file, O_RDWR);
-	if (fd == -1) {
-		perror("open() failed");
-		return 1;
-	}
-
-	rc = read(fd, buf, sizeof(buf));
-	if (rc == -1) {
-		perror("read() failed");
-		close(fd);
-		return 1;
-	}
-	close(fd);
+	rc = read_file(file, buf, sizeof(buf) - 1, NULL);
+	if (rc)
+		return rc;
 
-	buf[rc] = '\0';
 	if (strtol(buf, NULL, 16) != val) {
 		printf("DSCR match failed: %ld (system) %ld (cpu)\n",
 					val, strtol(buf, NULL, 16));

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

@@ -33,6 +33,8 @@ void *get_auxv_entry(int type);
 
 int pick_online_cpu(void);
 
+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_debugfs_file(char *debugfs_file, int *result);
 int write_debugfs_file(char *debugfs_file, int result);
 int read_sysfs_file(char *debugfs_file, char *result, size_t result_size);

tools/testing/selftests/powerpc/nx-gzip/gzfht_test.c

@@ -146,49 +146,37 @@ int gzip_header_blank(char *buf)
 /* Caller must free the allocated buffer return nonzero on error. */
 int read_alloc_input_file(char *fname, char **buf, size_t *bufsize)
 {
+	int err;
 	struct stat statbuf;
-	FILE *fp;
 	char *p;
 	size_t num_bytes;
 
 	if (stat(fname, &statbuf)) {
 		perror(fname);
-		return(-1);
-	}
-	fp = fopen(fname, "r");
-	if (fp == NULL) {
-		perror(fname);
-		return(-1);
+		return -1;
 	}
+
 	assert(NULL != (p = (char *) malloc(statbuf.st_size)));
-	num_bytes = fread(p, 1, statbuf.st_size, fp);
-	if (ferror(fp) || (num_bytes != statbuf.st_size)) {
+
+	err = read_file(fname, p, statbuf.st_size, &num_bytes);
+	if (err) {
 		perror(fname);
-		return(-1);
+		goto fail;
 	}
+
+	if (num_bytes != statbuf.st_size) {
+		fprintf(stderr, "Actual bytes != expected bytes\n");
+		err = -1;
+		goto fail;
+	}
+
 	*buf = p;
 	*bufsize = num_bytes;
 	return 0;
-}
 
-/* Returns nonzero on error */
-int write_output_file(char *fname, char *buf, size_t bufsize)
-{
-	FILE *fp;
-	size_t num_bytes;
-
-	fp = fopen(fname, "w");
-	if (fp == NULL) {
-		perror(fname);
-		return(-1);
-	}
-	num_bytes = fwrite(buf, 1, bufsize, fp);
-	if (ferror(fp) || (num_bytes != bufsize)) {
-		perror(fname);
-		return(-1);
-	}
-	fclose(fp);
-	return 0;
+fail:
+	free(p);
+	return err;
 }
 
 /*
@@ -399,7 +387,7 @@ int compress_file(int argc, char **argv, void *handle)
 	assert(FNAME_MAX > (strlen(argv[1]) + strlen(FEXT)));
 	strcpy(outname, argv[1]);
 	strcat(outname, FEXT);
-	if (write_output_file(outname, outbuf, dsttotlen)) {
+	if (write_file(outname, outbuf, dsttotlen)) {
 		fprintf(stderr, "write error: %s\n", outname);
 		exit(-1);
 	}

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

@@ -190,38 +190,23 @@ int parse_proc_maps(void)
 
 bool require_paranoia_below(int level)
 {
+	int err;
 	long current;
-	char *end, buf[16];
-	FILE *f;
-	bool rc;
-
-	rc = false;
-
-	f = fopen(PARANOID_PATH, "r");
-	if (!f) {
-		perror("fopen");
-		goto out;
-	}
+	char *end;
+	char buf[16] = {0};
 
-	if (!fgets(buf, sizeof(buf), f)) {
+	err = read_file(PARANOID_PATH, buf, sizeof(buf) - 1, NULL);
+	if (err) {
 		printf("Couldn't read " PARANOID_PATH "?\n");
-		goto out_close;
+		return false;
 	}
 
 	current = strtol(buf, &end, 10);
 
 	if (end == buf) {
 		printf("Couldn't parse " PARANOID_PATH "?\n");
-		goto out_close;
+		return false;
 	}
 
-	if (current >= level)
-		goto out_close;
-
-	rc = true;
-out_close:
-	fclose(f);
-out:
-	return rc;
+	return current < level;
 }
-

tools/testing/selftests/powerpc/ptrace/core-pkey.c

@@ -348,15 +348,11 @@ static int parent(struct shared_info *info, pid_t pid)
 
 static int write_core_pattern(const char *core_pattern)
 {
-	size_t len = strlen(core_pattern), ret;
-	FILE *f;
+	int err;
 
-	f = fopen(core_pattern_file, "w");
-	SKIP_IF_MSG(!f, "Try with root privileges");
-
-	ret = fwrite(core_pattern, 1, len, f);
-	fclose(f);
-	if (ret != len) {
+	err = write_file(core_pattern_file, core_pattern, strlen(core_pattern));
+	if (err) {
+		SKIP_IF_MSG(err == -EPERM, "Try with root privileges");
 		perror("Error writing to core_pattern file");
 		return TEST_FAIL;
 	}
@@ -366,8 +362,8 @@ static int write_core_pattern(const char *core_pattern)
 
 static int setup_core_pattern(char **core_pattern_, bool *changed_)
 {
-	FILE *f;
 	char *core_pattern;
+	size_t len;
 	int ret;
 
 	core_pattern = malloc(PATH_MAX);
@@ -376,22 +372,14 @@ static int setup_core_pattern(char **core_pattern_, bool *changed_)
 		return TEST_FAIL;
 	}
 
-	f = fopen(core_pattern_file, "r");
-	if (!f) {
-		perror("Error opening core_pattern file");
-		ret = TEST_FAIL;
-		goto out;
-	}
-
-	ret = fread(core_pattern, 1, PATH_MAX - 1, f);
-	fclose(f);
-	if (!ret) {
+	ret = read_file(core_pattern_file, core_pattern, PATH_MAX - 1, &len);
+	if (ret) {
 		perror("Error reading core_pattern file");
 		ret = TEST_FAIL;
 		goto out;
 	}
 
-	core_pattern[ret] = '\0';
+	core_pattern[len] = '\0';
 
 	/* Check whether we can predict the name of the core file. */
 	if (!strcmp(core_pattern, "core") || !strcmp(core_pattern, "core.%p"))