1 files changed, 131 insertions, 181 deletions

diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 82f53d81a7a7..edec23406dbc 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <assert.h>
 #include <ctype.h>
 #include <errno.h>
 #include <limits.h>
@@ -10,10 +11,12 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <pthread.h>
 #include <unistd.h>
 #include <sys/mount.h>
 
 #include "fs.h"
+#include "../io.h"
 #include "debug-internal.h"
 
 #define _STR(x) #x
@@ -43,7 +46,7 @@
 #define BPF_FS_MAGIC           0xcafe4a11
 #endif
 
-static const char * const sysfs__fs_known_mountpoints[] = {
+static const char * const sysfs__known_mountpoints[] = {
 	"/sys",
 	0,
 };
@@ -86,87 +89,89 @@ static const char * const bpf_fs__known_mountpoints[] = {
 };
 
 struct fs {
-	const char		*name;
-	const char * const	*mounts;
-	char			 path[PATH_MAX];
-	bool			 found;
-	bool			 checked;
-	long			 magic;
-};
-
-enum {
-	FS__SYSFS   = 0,
-	FS__PROCFS  = 1,
-	FS__DEBUGFS = 2,
-	FS__TRACEFS = 3,
-	FS__HUGETLBFS = 4,
-	FS__BPF_FS = 5,
+	const char *		 const name;
+	const char * const *	 const mounts;
+	char			*path;
+	pthread_mutex_t		 mount_mutex;
+	const long		 magic;
 };
 
 #ifndef TRACEFS_MAGIC
 #define TRACEFS_MAGIC 0x74726163
 #endif
 
-static struct fs fs__entries[] = {
-	[FS__SYSFS] = {
-		.name	= "sysfs",
-		.mounts	= sysfs__fs_known_mountpoints,
-		.magic	= SYSFS_MAGIC,
-		.checked = false,
-	},
-	[FS__PROCFS] = {
-		.name	= "proc",
-		.mounts	= procfs__known_mountpoints,
-		.magic	= PROC_SUPER_MAGIC,
-		.checked = false,
-	},
-	[FS__DEBUGFS] = {
-		.name	= "debugfs",
-		.mounts	= debugfs__known_mountpoints,
-		.magic	= DEBUGFS_MAGIC,
-		.checked = false,
-	},
-	[FS__TRACEFS] = {
-		.name	= "tracefs",
-		.mounts	= tracefs__known_mountpoints,
-		.magic	= TRACEFS_MAGIC,
-		.checked = false,
-	},
-	[FS__HUGETLBFS] = {
-		.name	= "hugetlbfs",
-		.mounts = hugetlbfs__known_mountpoints,
-		.magic	= HUGETLBFS_MAGIC,
-		.checked = false,
-	},
-	[FS__BPF_FS] = {
-		.name	= "bpf",
-		.mounts = bpf_fs__known_mountpoints,
-		.magic	= BPF_FS_MAGIC,
-		.checked = false,
-	},
-};
+static void fs__init_once(struct fs *fs);
+static const char *fs__mountpoint(const struct fs *fs);
+static const char *fs__mount(struct fs *fs);
+
+#define FS(lower_name, fs_name, upper_name)		\
+static struct fs fs__##lower_name = {			\
+	.name = #fs_name,				\
+	.mounts = lower_name##__known_mountpoints,	\
+	.magic = upper_name##_MAGIC,			\
+	.mount_mutex = PTHREAD_MUTEX_INITIALIZER,	\
+};							\
+							\
+static void lower_name##_init_once(void)		\
+{							\
+	struct fs *fs = &fs__##lower_name;		\
+							\
+	fs__init_once(fs);				\
+}							\
+							\
+const char *lower_name##__mountpoint(void)		\
+{							\
+	static pthread_once_t init_once = PTHREAD_ONCE_INIT;	\
+	struct fs *fs = &fs__##lower_name;		\
+							\
+	pthread_once(&init_once, lower_name##_init_once);	\
+	return fs__mountpoint(fs);			\
+}							\
+							\
+const char *lower_name##__mount(void)			\
+{							\
+	const char *mountpoint = lower_name##__mountpoint();	\
+	struct fs *fs = &fs__##lower_name;		\
+							\
+	if (mountpoint)					\
+		return mountpoint;			\
+							\
+	return fs__mount(fs);				\
+}							\
+							\
+bool lower_name##__configured(void)			\
+{							\
+	return lower_name##__mountpoint() != NULL;	\
+}
+
+FS(sysfs, sysfs, SYSFS);
+FS(procfs, procfs, PROC_SUPER);
+FS(debugfs, debugfs, DEBUGFS);
+FS(tracefs, tracefs, TRACEFS);
+FS(hugetlbfs, hugetlbfs, HUGETLBFS);
+FS(bpf_fs, bpf, BPF_FS);
 
 static bool fs__read_mounts(struct fs *fs)
 {
-	bool found = false;
 	char type[100];
 	FILE *fp;
+	char path[PATH_MAX + 1];
 
 	fp = fopen("/proc/mounts", "r");
 	if (fp == NULL)
-		return NULL;
+		return false;
 
-	while (!found &&
-	       fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
-		      fs->path, type) == 2) {
+	while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
+		      path, type) == 2) {
 
-		if (strcmp(type, fs->name) == 0)
-			found = true;
+		if (strcmp(type, fs->name) == 0) {
+			fs->path = strdup(path);
+			fclose(fp);
+			return fs->path != NULL;
+		}
 	}
-
 	fclose(fp);
-	fs->checked = true;
-	return fs->found = found;
+	return false;
 }
 
 static int fs__valid_mount(const char *fs, long magic)
@@ -188,8 +193,9 @@ static bool fs__check_mounts(struct fs *fs)
 	ptr = fs->mounts;
 	while (*ptr) {
 		if (fs__valid_mount(*ptr, fs->magic) == 0) {
-			fs->found = true;
-			strcpy(fs->path, *ptr);
+			fs->path = strdup(*ptr);
+			if (!fs->path)
+				return false;
 			return true;
 		}
 		ptr++;
@@ -227,43 +233,26 @@ static bool fs__env_override(struct fs *fs)
 	if (!override_path)
 		return false;
 
-	fs->found = true;
-	fs->checked = true;
-	strncpy(fs->path, override_path, sizeof(fs->path) - 1);
-	fs->path[sizeof(fs->path) - 1] = '\0';
+	fs->path = strdup(override_path);
+	if (!fs->path)
+		return false;
 	return true;
 }
 
-static const char *fs__get_mountpoint(struct fs *fs)
+static void fs__init_once(struct fs *fs)
 {
-	if (fs__env_override(fs))
-		return fs->path;
-
-	if (fs__check_mounts(fs))
-		return fs->path;
-
-	if (fs__read_mounts(fs))
-		return fs->path;
-
-	return NULL;
+	if (!fs__env_override(fs) &&
+	    !fs__check_mounts(fs) &&
+	    !fs__read_mounts(fs)) {
+		assert(!fs->path);
+	} else {
+		assert(fs->path);
+	}
 }
 
-static const char *fs__mountpoint(int idx)
+static const char *fs__mountpoint(const struct fs *fs)
 {
-	struct fs *fs = &fs__entries[idx];
-
-	if (fs->found)
-		return (const char *)fs->path;
-
-	/* the mount point was already checked for the mount point
-	 * but and did not exist, so return NULL to avoid scanning again.
-	 * This makes the found and not found paths cost equivalent
-	 * in case of multiple calls.
-	 */
-	if (fs->checked)
-		return NULL;
-
-	return fs__get_mountpoint(fs);
+	return fs->path;
 }
 
 static const char *mount_overload(struct fs *fs)
@@ -278,52 +267,36 @@ static const char *mount_overload(struct fs *fs)
 	return getenv(upper_name) ?: *fs->mounts;
 }
 
-static const char *fs__mount(int idx)
+static const char *fs__mount(struct fs *fs)
 {
-	struct fs *fs = &fs__entries[idx];
 	const char *mountpoint;
 
-	if (fs__mountpoint(idx))
-		return (const char *)fs->path;
-
-	mountpoint = mount_overload(fs);
+	pthread_mutex_lock(&fs->mount_mutex);
 
-	if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
-		return NULL;
+	/* Check if path found inside the mutex to avoid races with other callers of mount. */
+	mountpoint = fs__mountpoint(fs);
+	if (mountpoint)
+		goto out;
 
-	return fs__check_mounts(fs) ? fs->path : NULL;
-}
+	mountpoint = mount_overload(fs);
 
-#define FS(name, idx)				\
-const char *name##__mountpoint(void)		\
-{						\
-	return fs__mountpoint(idx);		\
-}						\
-						\
-const char *name##__mount(void)			\
-{						\
-	return fs__mount(idx);			\
-}						\
-						\
-bool name##__configured(void)			\
-{						\
-	return name##__mountpoint() != NULL;	\
+	if (mount(NULL, mountpoint, fs->name, 0, NULL) == 0 &&
+	    fs__valid_mount(mountpoint, fs->magic) == 0) {
+		fs->path = strdup(mountpoint);
+		mountpoint = fs->path;
+	}
+out:
+	pthread_mutex_unlock(&fs->mount_mutex);
+	return mountpoint;
 }
 
-FS(sysfs,   FS__SYSFS);
-FS(procfs,  FS__PROCFS);
-FS(debugfs, FS__DEBUGFS);
-FS(tracefs, FS__TRACEFS);
-FS(hugetlbfs, FS__HUGETLBFS);
-FS(bpf_fs, FS__BPF_FS);
-
 int filename__read_int(const char *filename, int *value)
 {
 	char line[64];
 	int fd = open(filename, O_RDONLY), err = -1;
 
 	if (fd < 0)
-		return -1;
+		return -errno;
 
 	if (read(fd, line, sizeof(line)) > 0) {
 		*value = atoi(line);
@@ -341,7 +314,7 @@ static int filename__read_ull_base(const char *filename,
 	int fd = open(filename, O_RDONLY), err = -1;
 
 	if (fd < 0)
-		return -1;
+		return -errno;
 
 	if (read(fd, line, sizeof(line)) > 0) {
 		*value = strtoull(line, NULL, base);
@@ -372,53 +345,24 @@ int filename__read_ull(const char *filename, unsigned long long *value)
 	return filename__read_ull_base(filename, value, 0);
 }
 
-#define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
-
 int filename__read_str(const char *filename, char **buf, size_t *sizep)
 {
-	size_t size = 0, alloc_size = 0;
-	void *bf = NULL, *nbf;
-	int fd, n, err = 0;
-	char sbuf[STRERR_BUFSIZE];
+	struct io io;
+	char bf[128];
+	int err;
 
-	fd = open(filename, O_RDONLY);
-	if (fd < 0)
+	io.fd = open(filename, O_RDONLY);
+	if (io.fd < 0)
 		return -errno;
-
-	do {
-		if (size == alloc_size) {
-			alloc_size += BUFSIZ;
-			nbf = realloc(bf, alloc_size);
-			if (!nbf) {
-				err = -ENOMEM;
-				break;
-			}
-
-			bf = nbf;
-		}
-
-		n = read(fd, bf + size, alloc_size - size);
-		if (n < 0) {
-			if (size) {
-				pr_warn("read failed %d: %s\n", errno,
-					strerror_r(errno, sbuf, sizeof(sbuf)));
-				err = 0;
-			} else
-				err = -errno;
-
-			break;
-		}
-
-		size += n;
-	} while (n > 0);
-
-	if (!err) {
-		*sizep = size;
-		*buf   = bf;
+	io__init(&io, io.fd, bf, sizeof(bf));
+	*buf = NULL;
+	err = io__getdelim(&io, buf, sizep, /*delim=*/-1);
+	if (err < 0) {
+		free(*buf);
+		*buf = NULL;
 	} else
-		free(bf);
-
-	close(fd);
+		err = 0;
+	close(io.fd);
 	return err;
 }
 
@@ -428,7 +372,7 @@ int filename__write_int(const char *filename, int value)
 	char buf[64];
 
 	if (fd < 0)
-		return err;
+		return -errno;
 
 	sprintf(buf, "%d", value);
 	if (write(fd, buf, sizeof(buf)) == sizeof(buf))
@@ -503,15 +447,22 @@ int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
 
 int sysfs__read_bool(const char *entry, bool *value)
 {
-	char *buf;
-	size_t size;
-	int ret;
+	struct io io;
+	char bf[16];
+	int ret = 0;
+	char path[PATH_MAX];
+	const char *sysfs = sysfs__mountpoint();
 
-	ret = sysfs__read_str(entry, &buf, &size);
-	if (ret < 0)
-		return ret;
+	if (!sysfs)
+		return -1;
+
+	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
+	io.fd = open(path, O_RDONLY);
+	if (io.fd < 0)
+		return -errno;
 
-	switch (buf[0]) {
+	io__init(&io, io.fd, bf, sizeof(bf));
+	switch (io__get_char(&io)) {
 	case '1':
 	case 'y':
 	case 'Y':
@@ -525,8 +476,7 @@ int sysfs__read_bool(const char *entry, bool *value)
 	default:
 		ret = -1;
 	}
-
-	free(buf);
+	close(io.fd);
 
 	return ret;
 }