14 files changed, 765 insertions, 0 deletions

diff --git a/tools/lib/api/Build b/tools/lib/api/Build
new file mode 100644
index 000000000..3653965cf
--- /dev/null
+++ b/tools/lib/api/Build
@@ -0,0 +1,2 @@
+libapi-y += fd/
+libapi-y += fs/
diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
new file mode 100644
index 000000000..8bd960658
--- /dev/null
+++ b/tools/lib/api/Makefile
@@ -0,0 +1,43 @@
+include ../../scripts/Makefile.include
+include ../../perf/config/utilities.mak		# QUIET_CLEAN
+
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(shell pwd)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+#$(info Determined 'srctree' to be $(srctree))
+endif
+
+CC = $(CROSS_COMPILE)gcc
+AR = $(CROSS_COMPILE)ar
+
+MAKEFLAGS += --no-print-directory
+
+LIBFILE = $(OUTPUT)libapi.a
+
+CFLAGS := $(EXTRA_WARNINGS) $(EXTRA_CFLAGS)
+CFLAGS += -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fPIC
+CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
+
+RM = rm -f
+
+build  := -f $(srctree)/tools/build/Makefile.build dir=. obj
+API_IN := $(OUTPUT)libapi-in.o
+
+export srctree OUTPUT CC LD CFLAGS V
+
+all: $(LIBFILE)
+
+$(API_IN): FORCE
+	@$(MAKE) $(build)=libapi
+
+$(LIBFILE): $(API_IN)
+	$(QUIET_AR)$(RM) $@ && $(AR) rcs $@ $(API_IN)
+
+clean:
+	$(call QUIET_CLEAN, libapi) $(RM) $(LIBFILE); \
+	find $(if $(OUTPUT),$(OUTPUT),.) -name \*.o | xargs $(RM)
+
+FORCE:
+
+.PHONY: clean FORCE
diff --git a/tools/lib/api/fd/Build b/tools/lib/api/fd/Build
new file mode 100644
index 000000000..605d99f6d
--- /dev/null
+++ b/tools/lib/api/fd/Build
@@ -0,0 +1 @@
+libapi-y += array.o
diff --git a/tools/lib/api/fd/array.c b/tools/lib/api/fd/array.c
new file mode 100644
index 000000000..0e636c433
--- /dev/null
+++ b/tools/lib/api/fd/array.c
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2014, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
+ *
+ * Released under the GPL v2. (and only v2, not any later version)
+ */
+#include "array.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+void fdarray__init(struct fdarray *fda, int nr_autogrow)
+{
+	fda->entries	 = NULL;
+	fda->priv	 = NULL;
+	fda->nr		 = fda->nr_alloc = 0;
+	fda->nr_autogrow = nr_autogrow;
+}
+
+int fdarray__grow(struct fdarray *fda, int nr)
+{
+	void *priv;
+	int nr_alloc = fda->nr_alloc + nr;
+	size_t psize = sizeof(fda->priv[0]) * nr_alloc;
+	size_t size  = sizeof(struct pollfd) * nr_alloc;
+	struct pollfd *entries = realloc(fda->entries, size);
+
+	if (entries == NULL)
+		return -ENOMEM;
+
+	priv = realloc(fda->priv, psize);
+	if (priv == NULL) {
+		free(entries);
+		return -ENOMEM;
+	}
+
+	fda->nr_alloc = nr_alloc;
+	fda->entries  = entries;
+	fda->priv     = priv;
+	return 0;
+}
+
+struct fdarray *fdarray__new(int nr_alloc, int nr_autogrow)
+{
+	struct fdarray *fda = calloc(1, sizeof(*fda));
+
+	if (fda != NULL) {
+		if (fdarray__grow(fda, nr_alloc)) {
+			free(fda);
+			fda = NULL;
+		} else {
+			fda->nr_autogrow = nr_autogrow;
+		}
+	}
+
+	return fda;
+}
+
+void fdarray__exit(struct fdarray *fda)
+{
+	free(fda->entries);
+	free(fda->priv);
+	fdarray__init(fda, 0);
+}
+
+void fdarray__delete(struct fdarray *fda)
+{
+	fdarray__exit(fda);
+	free(fda);
+}
+
+int fdarray__add(struct fdarray *fda, int fd, short revents)
+{
+	int pos = fda->nr;
+
+	if (fda->nr == fda->nr_alloc &&
+	    fdarray__grow(fda, fda->nr_autogrow) < 0)
+		return -ENOMEM;
+
+	fda->entries[fda->nr].fd     = fd;
+	fda->entries[fda->nr].events = revents;
+	fda->nr++;
+	return pos;
+}
+
+int fdarray__filter(struct fdarray *fda, short revents,
+		    void (*entry_destructor)(struct fdarray *fda, int fd))
+{
+	int fd, nr = 0;
+
+	if (fda->nr == 0)
+		return 0;
+
+	for (fd = 0; fd < fda->nr; ++fd) {
+		if (fda->entries[fd].revents & revents) {
+			if (entry_destructor)
+				entry_destructor(fda, fd);
+
+			continue;
+		}
+
+		if (fd != nr) {
+			fda->entries[nr] = fda->entries[fd];
+			fda->priv[nr]	 = fda->priv[fd];
+		}
+
+		++nr;
+	}
+
+	return fda->nr = nr;
+}
+
+int fdarray__poll(struct fdarray *fda, int timeout)
+{
+	return poll(fda->entries, fda->nr, timeout);
+}
+
+int fdarray__fprintf(struct fdarray *fda, FILE *fp)
+{
+	int fd, printed = fprintf(fp, "%d [ ", fda->nr);
+
+	for (fd = 0; fd < fda->nr; ++fd)
+		printed += fprintf(fp, "%s%d", fd ? ", " : "", fda->entries[fd].fd);
+
+	return printed + fprintf(fp, " ]");
+}
diff --git a/tools/lib/api/fd/array.h b/tools/lib/api/fd/array.h
new file mode 100644
index 000000000..45db01818
--- /dev/null
+++ b/tools/lib/api/fd/array.h
@@ -0,0 +1,46 @@
+#ifndef __API_FD_ARRAY__
+#define __API_FD_ARRAY__
+
+#include <stdio.h>
+
+struct pollfd;
+
+/**
+ * struct fdarray: Array of file descriptors
+ *
+ * @priv: Per array entry priv area, users should access just its contents,
+ *	  not set it to anything, as it is kept in synch with @entries, being
+ *	  realloc'ed, * for instance, in fdarray__{grow,filter}.
+ *
+ *	  I.e. using 'fda->priv[N].idx = * value' where N < fda->nr is ok,
+ *	  but doing 'fda->priv = malloc(M)' is not allowed.
+ */
+struct fdarray {
+	int	       nr;
+	int	       nr_alloc;
+	int	       nr_autogrow;
+	struct pollfd *entries;
+	union {
+		int    idx;
+	} *priv;
+};
+
+void fdarray__init(struct fdarray *fda, int nr_autogrow);
+void fdarray__exit(struct fdarray *fda);
+
+struct fdarray *fdarray__new(int nr_alloc, int nr_autogrow);
+void fdarray__delete(struct fdarray *fda);
+
+int fdarray__add(struct fdarray *fda, int fd, short revents);
+int fdarray__poll(struct fdarray *fda, int timeout);
+int fdarray__filter(struct fdarray *fda, short revents,
+		    void (*entry_destructor)(struct fdarray *fda, int fd));
+int fdarray__grow(struct fdarray *fda, int extra);
+int fdarray__fprintf(struct fdarray *fda, FILE *fp);
+
+static inline int fdarray__available_entries(struct fdarray *fda)
+{
+	return fda->nr_alloc - fda->nr;
+}
+
+#endif /* __API_FD_ARRAY__ */
diff --git a/tools/lib/api/fs/Build b/tools/lib/api/fs/Build
new file mode 100644
index 000000000..6de5a4f0b
--- /dev/null
+++ b/tools/lib/api/fs/Build
@@ -0,0 +1,4 @@
+libapi-y += fs.o
+libapi-y += debugfs.o
+libapi-y += findfs.o
+libapi-y += tracefs.o
diff --git a/tools/lib/api/fs/debugfs.c b/tools/lib/api/fs/debugfs.c
new file mode 100644
index 000000000..8305b3e9d
--- /dev/null
+++ b/tools/lib/api/fs/debugfs.c
@@ -0,0 +1,118 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <sys/vfs.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mount.h>
+#include <linux/kernel.h>
+
+#include "debugfs.h"
+
+#ifndef DEBUGFS_DEFAULT_PATH
+#define DEBUGFS_DEFAULT_PATH		"/sys/kernel/debug"
+#endif
+
+char debugfs_mountpoint[PATH_MAX + 1] = DEBUGFS_DEFAULT_PATH;
+
+static const char * const debugfs_known_mountpoints[] = {
+	DEBUGFS_DEFAULT_PATH,
+	"/debug",
+	0,
+};
+
+static bool debugfs_found;
+
+bool debugfs_configured(void)
+{
+	return debugfs_find_mountpoint() != NULL;
+}
+
+/* find the path to the mounted debugfs */
+const char *debugfs_find_mountpoint(void)
+{
+	const char *ret;
+
+	if (debugfs_found)
+		return (const char *)debugfs_mountpoint;
+
+	ret = find_mountpoint("debugfs", (long) DEBUGFS_MAGIC,
+			      debugfs_mountpoint, PATH_MAX + 1,
+			      debugfs_known_mountpoints);
+	if (ret)
+		debugfs_found = true;
+
+	return ret;
+}
+
+/* mount the debugfs somewhere if it's not mounted */
+char *debugfs_mount(const char *mountpoint)
+{
+	/* see if it's already mounted */
+	if (debugfs_find_mountpoint())
+		goto out;
+
+	/* if not mounted and no argument */
+	if (mountpoint == NULL) {
+		/* see if environment variable set */
+		mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
+		/* if no environment variable, use default */
+		if (mountpoint == NULL)
+			mountpoint = DEBUGFS_DEFAULT_PATH;
+	}
+
+	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
+		return NULL;
+
+	/* save the mountpoint */
+	debugfs_found = true;
+	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
+out:
+	return debugfs_mountpoint;
+}
+
+int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename)
+{
+	char sbuf[128];
+
+	switch (err) {
+	case ENOENT:
+		if (debugfs_found) {
+			snprintf(buf, size,
+				 "Error:\tFile %s/%s not found.\n"
+				 "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
+				 debugfs_mountpoint, filename);
+			break;
+		}
+		snprintf(buf, size, "%s",
+			 "Error:\tUnable to find debugfs\n"
+			 "Hint:\tWas your kernel compiled with debugfs support?\n"
+			 "Hint:\tIs the debugfs filesystem mounted?\n"
+			 "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
+		break;
+	case EACCES:
+		snprintf(buf, size,
+			 "Error:\tNo permissions to read %s/%s\n"
+			 "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
+			 debugfs_mountpoint, filename, debugfs_mountpoint);
+		break;
+	default:
+		snprintf(buf, size, "%s", strerror_r(err, sbuf, sizeof(sbuf)));
+		break;
+	}
+
+	return 0;
+}
+
+int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name)
+{
+	char path[PATH_MAX];
+
+	snprintf(path, PATH_MAX, "tracing/events/%s/%s", sys, name ?: "*");
+
+	return debugfs__strerror_open(err, buf, size, path);
+}
diff --git a/tools/lib/api/fs/debugfs.h b/tools/lib/api/fs/debugfs.h
new file mode 100644
index 000000000..455023698
--- /dev/null
+++ b/tools/lib/api/fs/debugfs.h
@@ -0,0 +1,23 @@
+#ifndef __API_DEBUGFS_H__
+#define __API_DEBUGFS_H__
+
+#include "findfs.h"
+
+#ifndef DEBUGFS_MAGIC
+#define DEBUGFS_MAGIC          0x64626720
+#endif
+
+#ifndef PERF_DEBUGFS_ENVIRONMENT
+#define PERF_DEBUGFS_ENVIRONMENT "PERF_DEBUGFS_DIR"
+#endif
+
+bool debugfs_configured(void);
+const char *debugfs_find_mountpoint(void);
+char *debugfs_mount(const char *mountpoint);
+
+extern char debugfs_mountpoint[];
+
+int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename);
+int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name);
+
+#endif /* __API_DEBUGFS_H__ */
diff --git a/tools/lib/api/fs/findfs.c b/tools/lib/api/fs/findfs.c
new file mode 100644
index 000000000..49946cb6d
--- /dev/null
+++ b/tools/lib/api/fs/findfs.c
@@ -0,0 +1,63 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <sys/vfs.h>
+
+#include "findfs.h"
+
+/* verify that a mountpoint is actually the type we want */
+
+int valid_mountpoint(const char *mount, long magic)
+{
+	struct statfs st_fs;
+
+	if (statfs(mount, &st_fs) < 0)
+		return -ENOENT;
+	else if ((long)st_fs.f_type != magic)
+		return -ENOENT;
+
+	return 0;
+}
+
+/* find the path to a mounted file system */
+const char *find_mountpoint(const char *fstype, long magic,
+			    char *mountpoint, int len,
+			    const char * const *known_mountpoints)
+{
+	const char * const *ptr;
+	char format[128];
+	char type[100];
+	FILE *fp;
+
+	if (known_mountpoints) {
+		ptr = known_mountpoints;
+		while (*ptr) {
+			if (valid_mountpoint(*ptr, magic) == 0) {
+				strncpy(mountpoint, *ptr, len - 1);
+				mountpoint[len-1] = 0;
+				return mountpoint;
+			}
+			ptr++;
+		}
+	}
+
+	/* give up and parse /proc/mounts */
+	fp = fopen("/proc/mounts", "r");
+	if (fp == NULL)
+		return NULL;
+
+	snprintf(format, 128, "%%*s %%%ds %%99s %%*s %%*d %%*d\n", len);
+
+	while (fscanf(fp, format, mountpoint, type) == 2) {
+		if (strcmp(type, fstype) == 0)
+			break;
+	}
+	fclose(fp);
+
+	if (strcmp(type, fstype) != 0)
+		return NULL;
+
+	return mountpoint;
+}
diff --git a/tools/lib/api/fs/findfs.h b/tools/lib/api/fs/findfs.h
new file mode 100644
index 000000000..b6f5d05ac
--- /dev/null
+++ b/tools/lib/api/fs/findfs.h
@@ -0,0 +1,23 @@
+#ifndef __API_FINDFS_H__
+#define __API_FINDFS_H__
+
+#include <stdbool.h>
+
+#define _STR(x) #x
+#define STR(x) _STR(x)
+
+/*
+ * On most systems <limits.h> would have given us this, but  not on some systems
+ * (e.g. GNU/Hurd).
+ */
+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
+
+const char *find_mountpoint(const char *fstype, long magic,
+			    char *mountpoint, int len,
+			    const char * const *known_mountpoints);
+
+int valid_mountpoint(const char *mount, long magic);
+
+#endif /* __API_FINDFS_H__ */
diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
new file mode 100644
index 000000000..128ef6332
--- /dev/null
+++ b/tools/lib/api/fs/fs.c
@@ -0,0 +1,199 @@
+/* TODO merge/factor in debugfs.c here */
+
+#include <ctype.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/vfs.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "debugfs.h"
+#include "fs.h"
+
+static const char * const sysfs__fs_known_mountpoints[] = {
+	"/sys",
+	0,
+};
+
+static const char * const procfs__known_mountpoints[] = {
+	"/proc",
+	0,
+};
+
+struct fs {
+	const char		*name;
+	const char * const	*mounts;
+	char			 path[PATH_MAX + 1];
+	bool			 found;
+	long			 magic;
+};
+
+enum {
+	FS__SYSFS  = 0,
+	FS__PROCFS = 1,
+};
+
+static struct fs fs__entries[] = {
+	[FS__SYSFS] = {
+		.name	= "sysfs",
+		.mounts	= sysfs__fs_known_mountpoints,
+		.magic	= SYSFS_MAGIC,
+	},
+	[FS__PROCFS] = {
+		.name	= "proc",
+		.mounts	= procfs__known_mountpoints,
+		.magic	= PROC_SUPER_MAGIC,
+	},
+};
+
+static bool fs__read_mounts(struct fs *fs)
+{
+	bool found = false;
+	char type[100];
+	FILE *fp;
+
+	fp = fopen("/proc/mounts", "r");
+	if (fp == NULL)
+		return NULL;
+
+	while (!found &&
+	       fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
+		      fs->path, type) == 2) {
+
+		if (strcmp(type, fs->name) == 0)
+			found = true;
+	}
+
+	fclose(fp);
+	return fs->found = found;
+}
+
+static int fs__valid_mount(const char *fs, long magic)
+{
+	struct statfs st_fs;
+
+	if (statfs(fs, &st_fs) < 0)
+		return -ENOENT;
+	else if ((long)st_fs.f_type != magic)
+		return -ENOENT;
+
+	return 0;
+}
+
+static bool fs__check_mounts(struct fs *fs)
+{
+	const char * const *ptr;
+
+	ptr = fs->mounts;
+	while (*ptr) {
+		if (fs__valid_mount(*ptr, fs->magic) == 0) {
+			fs->found = true;
+			strcpy(fs->path, *ptr);
+			return true;
+		}
+		ptr++;
+	}
+
+	return false;
+}
+
+static void mem_toupper(char *f, size_t len)
+{
+	while (len) {
+		*f = toupper(*f);
+		f++;
+		len--;
+	}
+}
+
+/*
+ * Check for "NAME_PATH" environment variable to override fs location (for
+ * testing). This matches the recommendation in Documentation/sysfs-rules.txt
+ * for SYSFS_PATH.
+ */
+static bool fs__env_override(struct fs *fs)
+{
+	char *override_path;
+	size_t name_len = strlen(fs->name);
+	/* name + "_PATH" + '\0' */
+	char upper_name[name_len + 5 + 1];
+	memcpy(upper_name, fs->name, name_len);
+	mem_toupper(upper_name, name_len);
+	strcpy(&upper_name[name_len], "_PATH");
+
+	override_path = getenv(upper_name);
+	if (!override_path)
+		return false;
+
+	fs->found = true;
+	strncpy(fs->path, override_path, sizeof(fs->path));
+	return true;
+}
+
+static const char *fs__get_mountpoint(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;
+}
+
+static const char *fs__mountpoint(int idx)
+{
+	struct fs *fs = &fs__entries[idx];
+
+	if (fs->found)
+		return (const char *)fs->path;
+
+	return fs__get_mountpoint(fs);
+}
+
+#define FS__MOUNTPOINT(name, idx)	\
+const char *name##__mountpoint(void)	\
+{					\
+	return fs__mountpoint(idx);	\
+}
+
+FS__MOUNTPOINT(sysfs,  FS__SYSFS);
+FS__MOUNTPOINT(procfs, FS__PROCFS);
+
+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;
+
+	if (read(fd, line, sizeof(line)) > 0) {
+		*value = atoi(line);
+		err = 0;
+	}
+
+	close(fd);
+	return err;
+}
+
+int sysctl__read_int(const char *sysctl, int *value)
+{
+	char path[PATH_MAX];
+	const char *procfs = procfs__mountpoint();
+
+	if (!procfs)
+		return -1;
+
+	snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
+
+	return filename__read_int(path, value);
+}
diff --git a/tools/lib/api/fs/fs.h b/tools/lib/api/fs/fs.h
new file mode 100644
index 000000000..6caa2bbc6
--- /dev/null
+++ b/tools/lib/api/fs/fs.h
@@ -0,0 +1,17 @@
+#ifndef __API_FS__
+#define __API_FS__
+
+#ifndef SYSFS_MAGIC
+#define SYSFS_MAGIC            0x62656572
+#endif
+
+#ifndef PROC_SUPER_MAGIC
+#define PROC_SUPER_MAGIC       0x9fa0
+#endif
+
+const char *sysfs__mountpoint(void);
+const char *procfs__mountpoint(void);
+
+int filename__read_int(const char *filename, int *value);
+int sysctl__read_int(const char *sysctl, int *value);
+#endif /* __API_FS__ */
diff --git a/tools/lib/api/fs/tracefs.c b/tools/lib/api/fs/tracefs.c
new file mode 100644
index 000000000..e4aa9688b
--- /dev/null
+++ b/tools/lib/api/fs/tracefs.c
@@ -0,0 +1,78 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <sys/vfs.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mount.h>
+#include <linux/kernel.h>
+
+#include "tracefs.h"
+
+#ifndef TRACEFS_DEFAULT_PATH
+#define TRACEFS_DEFAULT_PATH		"/sys/kernel/tracing"
+#endif
+
+char tracefs_mountpoint[PATH_MAX + 1] = TRACEFS_DEFAULT_PATH;
+
+static const char * const tracefs_known_mountpoints[] = {
+	TRACEFS_DEFAULT_PATH,
+	"/sys/kernel/debug/tracing",
+	"/tracing",
+	"/trace",
+	0,
+};
+
+static bool tracefs_found;
+
+bool tracefs_configured(void)
+{
+	return tracefs_find_mountpoint() != NULL;
+}
+
+/* find the path to the mounted tracefs */
+const char *tracefs_find_mountpoint(void)
+{
+	const char *ret;
+
+	if (tracefs_found)
+		return (const char *)tracefs_mountpoint;
+
+	ret = find_mountpoint("tracefs", (long) TRACEFS_MAGIC,
+			      tracefs_mountpoint, PATH_MAX + 1,
+			      tracefs_known_mountpoints);
+
+	if (ret)
+		tracefs_found = true;
+
+	return ret;
+}
+
+/* mount the tracefs somewhere if it's not mounted */
+char *tracefs_mount(const char *mountpoint)
+{
+	/* see if it's already mounted */
+	if (tracefs_find_mountpoint())
+		goto out;
+
+	/* if not mounted and no argument */
+	if (mountpoint == NULL) {
+		/* see if environment variable set */
+		mountpoint = getenv(PERF_TRACEFS_ENVIRONMENT);
+		/* if no environment variable, use default */
+		if (mountpoint == NULL)
+			mountpoint = TRACEFS_DEFAULT_PATH;
+	}
+
+	if (mount(NULL, mountpoint, "tracefs", 0, NULL) < 0)
+		return NULL;
+
+	/* save the mountpoint */
+	tracefs_found = true;
+	strncpy(tracefs_mountpoint, mountpoint, sizeof(tracefs_mountpoint));
+out:
+	return tracefs_mountpoint;
+}
diff --git a/tools/lib/api/fs/tracefs.h b/tools/lib/api/fs/tracefs.h
new file mode 100644
index 000000000..da780ac49
--- /dev/null
+++ b/tools/lib/api/fs/tracefs.h
@@ -0,0 +1,21 @@
+#ifndef __API_TRACEFS_H__
+#define __API_TRACEFS_H__
+
+#include "findfs.h"
+
+#ifndef TRACEFS_MAGIC
+#define TRACEFS_MAGIC          0x74726163
+#endif
+
+#ifndef PERF_TRACEFS_ENVIRONMENT
+#define PERF_TRACEFS_ENVIRONMENT "PERF_TRACEFS_DIR"
+#endif
+
+bool tracefs_configured(void);
+const char *tracefs_find_mountpoint(void);
+int tracefs_valid_mountpoint(const char *debugfs);
+char *tracefs_mount(const char *mountpoint);
+
+extern char tracefs_mountpoint[];
+
+#endif /* __API_DEBUGFS_H__ */