4 files changed, 85 insertions, 2 deletions
diff --git a/tools/lib/api/fs/debugfs.c b/tools/lib/api/fs/debugfs.c
index a74fba6d774..d2b18e88707 100644
--- a/tools/lib/api/fs/debugfs.c
+++ b/tools/lib/api/fs/debugfs.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -67,7 +68,7 @@ int debugfs_valid_mountpoint(const char *debugfs)
 
 	if (statfs(debugfs, &st_fs) < 0)
 		return -ENOENT;
-	else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
+	else if ((long)st_fs.f_type != (long)DEBUGFS_MAGIC)
 		return -ENOENT;
 
 	return 0;
@@ -98,3 +99,45 @@ char *debugfs_mount(const char *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
index f19d3df9609..0739881a989 100644
--- a/tools/lib/api/fs/debugfs.h
+++ b/tools/lib/api/fs/debugfs.h
@@ -26,4 +26,7 @@ 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/fs.c b/tools/lib/api/fs/fs.c
index c1b49c36a95..128ef6332a6 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -7,6 +7,10 @@
 #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"
@@ -75,7 +79,7 @@ static int fs__valid_mount(const char *fs, long magic)
 
 	if (statfs(fs, &st_fs) < 0)
 		return -ENOENT;
-	else if (st_fs.f_type != magic)
+	else if ((long)st_fs.f_type != magic)
 		return -ENOENT;
 
 	return 0;
@@ -163,3 +167,33 @@ const char *name##__mountpoint(void)	\
 
 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
index cb7049551f3..6caa2bbc6ce 100644
--- a/tools/lib/api/fs/fs.h
+++ b/tools/lib/api/fs/fs.h
@@ -11,4 +11,7 @@
 
 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__ */